Arctic Sea Ice : Forum

Cryosphere => Antarctica => Topic started by: FredBear on February 06, 2018, 02:49:42 PM

Title: Antarctic Icebergs
Post by: FredBear on February 06, 2018, 02:49:42 PM
Have been looking at the icebergs, particularly around the Weddell Sea recently.

a68a (82*25nm) hit the headlines when it calved in 2017 but there is also a23a (44*40nm) which has been grounded to the SE for many years, although it does seem to have moved slightly NW since January 2017. (Also I wonder if a23a is accumulating snow faster than it is melting - the Brunt ice shelf to the NE accumulates about 1.5 m per year?).

Some other 'bergs are heading off from the Weddell Sea in the direction of South Georgia - b15z (15*7nm), b15t (25*6nm), c28b (21*14nm) and b09f (20*8nm) are fairly clear.

A new recruit has been b15aa (11*6nm) which came round the bend from the east above the Brunt ice shelf (about October 24 2017) and has been drifting round in small circles all this summer season, rather than going south towards Brunt.


Don't know if this is of interest to other readers or if there is anything to add?
Title: Re: Antarctic Icebergs
Post by: Tealight on February 07, 2018, 09:20:57 PM
I keep a look on icebergs as well because they are the main mechanism for ice loss of the continent apart from subsurface melting. Typically ice-shelfs are getting thinner towards the edge and icebergs are the thinnest parts so i assume A23a is losing mass as well. Once it floats freely in the Weddell Sea it doesn't matter anyway, because it can leave Antarctic waters in a few month and melt in the South Atlantic.

The icebergs B15z, B15t,C28b and B09f you mentioned have drifted from the center of the Weddell Sea to the current position in just 12 month ( see image and NASA link). A23a might follow the same path.

Same icebergs 12 month ago:
https://go.nasa.gov/2EP1APk

My focus is more on West-Antarctica particularly B22a (44X24 nm) which blocks Thwaites Glacier from the open sea. If this beast becomes loose all the icebergs behind can drift out as well.

Title: Re: Antarctic Icebergs
Post by: AbruptSLR on February 07, 2018, 10:39:12 PM
Linked is a regularly updated list of the locations of large Antarctic icebergs:

http://www.scp.byu.edu/current_icebergs.html
Title: Re: Antarctic Icebergs
Post by: gerontocrat on February 24, 2018, 02:23:43 PM
The quote is from Johnm33 - he was answering

Quote
In order to move north bergs have to be accelerated eastward by about 5kph for every 20k travelled [needs checking], or their inertia will press them against the peninsular. So they need to get caught up in a powerful current or tidal movement to 'escape' antarctica. If you look at the 600 s lat. you'll see that for practical purposes a berg, going n, is moving directly away from the axis of rotation, and that the 600lat. is approx half the distance the equator is from that axis, thus the surface speed is approx half that at the equator. We know there's a powerful clockwise tidal flow through Weddel. 
https://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp/azimuthal_equidistant
The icebergs escaping but not from Weddel look more like rare events, but worth looking into, given their similarities, as/when time permits.

"We know there's a powerful clockwise tidal flow through Weddell" - you knew,  I did not.  During Antarctica's brief summer, drift seemed to slow down a lot. Does that tidal current diminish in summer?

Tor Bejnar also posted this link on the Larsen C thread. I have copied it so I can remember where it is.
Quote
The Antarctic Iceberg Tracking Database (http://www.scp.byu.edu/data/iceberg/)shows where icebergs have traveled.

What a super image
Title: Re: Antarctic Icebergs
Post by: johnm33 on February 24, 2018, 03:08:55 PM
gerontocrat
Here's (https://www.esr.org/research/polar-tide-models/movies/) a link to polar tidal animations. You'll see that there's some limited action where the other bergs get energised to escape. Tides are seasonal to the extent that they're generally more extreme, high/low, when the Sun's over the equator rather than the tropics cancer/capricorn, but the extremes are really driven by the the moons position relative to the sun and also by mslp, so a lower pressure means higher tides. Then there's winds, currents and resonances ... 
Title: Re: Antarctic Icebergs
Post by: FredBear on June 07, 2018, 11:56:23 AM
I see that Susan Anderson has found the latest EO pictures of B-15Z breaking up:-

https://earthobservatory.nasa.gov/IOTD/view.php?id=92238&src=eoa-iotd

A link to a 27 October 2017 from EO:-

https://earthobservatory.nasa.gov/IOTD/view.php?id=91181
Title: Re: Antarctic Icebergs
Post by: FredBear on December 13, 2018, 02:13:58 AM
Iceberg B15AA (12/12/2018 Lng -39.49, Lat -65.06 approx) is still moving NW, but more slowly than the thinner sea ice floes that have been passing it. However, recently the surrounding sea ice floes have been breaking up rapidly and the iceberg is now approaching the inner edge of the 'goodbye waves'. It could soon be floating free in the southern ocean?

A23A is still grounded (top NE corner has only moved from Lng -40.52 Lat -76.06 [2000 Mar 05] to Lng -39.86 Lat -75.66 [2018 Dec 05] over 18.75 years!). It has had a tendency block ice flow to the south and east of the Weddell Sea over this time. The Brunt ice shelf to the NE accumulates 1.5m snow/year (which has been burying the BAS Halley stations), so it might be possible that A23A is growing in thickness rather than melting? This iceberg could affect any break-up of the Brunt ice shelf & where the resulting icebergs move, as the natural flow is to the south and west.
Title: Re: Antarctic Icebergs
Post by: FredBear on December 13, 2018, 02:25:36 AM
I notice that BYU have not updated iceberg positions for some time, more up-to-date positions can be found at:-   

https://www.natice.noaa.gov/pub/icebergs/Iceberg_Tabular.pdf
Title: Re: Antarctic Icebergs
Post by: Tealight on January 08, 2019, 02:00:38 PM
Over the last year Iceberg B22A has moved a few kilometer north-west opening up more space for Thwaites Glacier and soon the Crosson Ice Shelf to clear out all icebergs and thick multi-year sea ice that has been stuck behind it for years. Perhaps some of the larger icebergs can finally begin their journey around Antarctica this year.

Link to current conditions:
https://go.nasa.gov/2FdzdNV
Title: Re: Antarctic Icebergs
Post by: FredBear on January 09, 2019, 02:50:30 AM
B22A and many surrounding icebergs in this area seem to have a raft-type structure composed of smaller "logs" of ice which move as together as units. Eventually many of the "logs" break away forming the smaller bergs littering this part of the sea.
To me this seems to be quite different behaviour from most calvings, for example the Pine Island Icebergs which start off large and planar (with their designation) and then break up into smaller pieces, or calvings from other ice shelves.
Is this an example of ice-cliff failure in the Thwaites Glacier, just a feature of the speed of calving, or because any outward flow from the coast is not constrained by fjord walls?

(In the northern hemisphere I suspect that Jakobshaven has a high surface flow which washes it's icebergs downstream rapidly so that they do not build up in the fjord.)
Title: Re: Antarctic Icebergs
Post by: FredBear on January 16, 2019, 02:35:51 AM
Looking at    http://www.arctic.io/explorer/   top right drop down  Antarctica-true color

B22 broke clear from Thwaites between 2002.02.13 and 2002.03.13 and joined the ice peninsular (which often formed) by about 2012.03.20.
Another major calving from the Thwaites tongue occurred in the dark before 2012.09.01 and headed north east of B22 towards the open sea. It drifted westwards, then back towards the coast, onwards towards the northern Ross Sea, where it was breaking up on 2018.03.14 (long153.9, lat 67.8 )
This shows that Thwaites is fairly free to calve even if B22A does not move (and the ice tongue that B22A joined at the base is more often present than not.) but some of the other 'bergs are trapped to the west of Thwaites.

There was more sea ice around Pine Island/Thwaites last year than usual but it is breaking up a bit more this year   .   .   .   watching with interest to see what will transpire.
Title: Re: Antarctic Icebergs
Post by: Tealight on January 17, 2019, 11:46:51 AM
Looking at    http://www.arctic.io/explorer/   top right drop down  Antarctica-true color

B22 broke clear from Thwaites between 2002.02.13 and 2002.03.13 and joined the ice peninsular (which often formed) by about 2012.03.20.
Another major calving from the Thwaites tongue occurred in the dark before 2012.09.01 and headed north east of B22 towards the open sea. It drifted westwards, then back towards the coast, onwards towards the northern Ross Sea, where it was breaking up on 2018.03.14 (long153.9, lat 67.8 )
This shows that Thwaites is fairly free to calve even if B22A does not move (and the ice tongue that B22A joined at the base is more often present than not.) but some of the other 'bergs are trapped to the west of Thwaites.

If you only look at ice edge glacier definitions it is true that Thwaites could calve freely the last few years. Especially the sub-region of Thwaites Ice Tongue where several other icebergs came from. I meant more the whole Thwaites area. Haynes Glacier is really just a sub glacier of Thwaites. Even the Crosson ice shelf is connected to Thwaites over Pope/Smith glacier.
Title: Re: Antarctic Icebergs
Post by: steve s on January 17, 2019, 06:37:29 PM
The Thwaites' bergs seem to require time -- years -- losing depth in warm water before they are free to drift out to sea. I wish I had a better picture of the undersea topography relative to the existing sea ice and bergs. 
Title: Re: Antarctic Icebergs
Post by: Tealight on February 20, 2019, 10:45:37 PM
A small part of A68A completly disintegrated instead of breaking off in one piece. Previous images are in the "Rift in Larsen C" topic which really isn't fitting anymore.

https://forum.arctic-sea-ice.net/index.php/topic,1175.msg186956.html#msg186956
Title: Re: Antarctic Icebergs
Post by: interstitial on February 21, 2019, 02:58:45 PM
https://www.polarview.aq/

In under 16 hours another chunk came off iceberg A68a
Title: Re: Antarctic Icebergs
Post by: b_lumenkraft on February 21, 2019, 04:34:14 PM
Isn't this where it is suspected to be grounded due to the pivoting around this place?

Maybe it's the ocean current pulling so hard, it has to give somewhere.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 21, 2019, 04:37:07 PM
That's my guess. [Edit:  lots of historical images of A68-A in the Rift in the Larsen C (https://forum.arctic-sea-ice.net/index.php/topic,1175.msg120454.html#msg120454) thread.  First reported as 'detached' in linked post.]
Title: Re: Antarctic Icebergs
Post by: FredBear on February 26, 2019, 12:50:55 PM
Re:- Reply 14.
All the bits of A68A seem to be moving - just not very much?
Title: Re: Antarctic Icebergs
Post by: Shared Humanity on February 26, 2019, 08:46:17 PM
If you look at the first image, fractures in A68 propagate from the calving area across the berg. Wouldn't surprise me to see this calving to continue and eventually cause the berg to separate into two large pieces.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 26, 2019, 09:33:16 PM
Today (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201902/S1B_IW_GRDH_1SSH_20190226T080124_1907_S_1.8bit.jp2)'s PolarView (https://www.polarview.aq/antarctic) shows no (significant) breakage since the 20th (unlike before then!).

[It sure looks like a bite: teeth marks and all!]
Title: Re: Antarctic Icebergs
Post by: b_lumenkraft on March 03, 2019, 06:16:53 PM
The 180 is completed!
Title: Re: Antarctic Icebergs
Post by: Andreas T on March 03, 2019, 09:52:26 PM
on the other side of the Wedell sea there is an ice berg drifting towards the Brunt ice shelf. Maybe another "Pooh stick" (as in the Milne books) to watch.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on March 20, 2019, 08:43:26 PM
Ice Island A68-A appears to have not moved 'much at all' since March 3rd.  (PolarView (https://www.polarview.aq/antarctic) image from today (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201903/S1B_EW_GRDM_1SDH_20190320T081712_169E_S_1.8bit.jp2).  WorldView image [insert] from gif recently posted [above].) [two images are not quite to same scale.]
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on April 03, 2019, 07:15:28 PM
A68-A has moved since the previous post.  As of April 2, it has moved northward (NNW) (parallel to the local coast) about 30 km. It's got to go due east, then northeastwards to stay away from land.  I think the 'bluish tinged' coast due north (upper left corner) is Robertson Island.  PolarView (https://www.polarview.aq/antarctic) image from 2019-04-02 (https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20190402T080951_B493_S_1.final.jpg) [map credit (http://cdn.antarcticglaciers.org/wp-content/uploads/2012/06/Antarctic_peninsula1.jpg)]
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on April 08, 2019, 09:10:32 PM
A68-A have move north about 12 km in 6 days, per today's PolarView (https://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SDH_20190408T000619_3C86_S_1.final.jpg) (and the image above).

[Note: as 1º latitude = 110 km, the 'waist' of A68-A is about 27 km wide.]
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on April 16, 2019, 04:40:06 PM
During this week (as of March 15), A68-A has moved 6 km northwards (measuring at the side of the ice island closest to the point just north of Larsen C Ice Shelf, and the south end has moved (rotated) about 7 km eastward (away from Larsen C).  (Image is stitched from two Polar View (https://www.polarview.aq/antarctic) images [north (https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20190415T080059_9443_S_1.final.jpg) and south (https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20190415T080124_E8AF_S_1.final.jpg)].)  I'm guessing the ice island will continue its slow counterclockwise spin and will thus not get stuck south of Robertson Island, although I expect the ice to bump into the island (in 3 weeks, at the current rate).
Title: Re: Antarctic Icebergs
Post by: b_lumenkraft on April 16, 2019, 05:07:23 PM
Will it make a 360?  ;D
Title: Re: Antarctic Icebergs
Post by: Tealight on May 03, 2019, 08:18:24 PM
Now A68-A is just 5.5km away from the islands. I wonder if it's actually going to collide with the island itself. According to the Bedrock map the area is quite shallow, but it might be wrong. The small part that broke off early (A68-B) is currently in 40-50m deep waters.
Title: Re: Antarctic Icebergs
Post by: interstitial on May 03, 2019, 08:51:17 PM
I was looking at that yesterday and thinking the front end was grounded or nearly so. It looks to me like the back end has started to roll around towards the front because of this. On the other hand that could just be the way the currents are pushing the iceberg around.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on May 14, 2019, 09:39:50 PM
A68A is mostly rotating between April 15 and May 14: today's PolarView (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201905/S1B_EW_GRDM_1SSH_20190514T080911_87F3_S_1.8bit.jp2) compared with last month's composite.
Title: Re: Antarctic Icebergs
Post by: Tealight on May 28, 2019, 10:11:01 PM
A68A rotation continues in the same spot. Animation beween 3rd May and 28th May.
Title: Re: Antarctic Icebergs
Post by: Adam Ash on May 29, 2019, 02:17:18 PM
...tho its rotation is around a point away from the berg.  Thus it is floating free of restraining points beneath it, IMHO.
Title: Re: Antarctic Icebergs
Post by: IceConcerned on June 10, 2019, 03:10:07 PM
As seen on Polarview SAR imagery : https://www.polarview.aq/images/105_S1jpgfull/S1A_IW_GRDH_1SSH_20190608T080144_5C66_S_1.final.jpg,
it appears the rotation of the iceberg is going on.

I am wondering besides, with such a big bloc at the outlet of the gulf, will there be no effect (through tides, diverged currents...) on the remains of Larsen B ? I have the impression that the cracks around the islets in particular are growing wider and longer ? (maybe just an illusion). To be noted, there was a minor calving at the norther junction with the meninsula a few days ago (with the resulting iceberg still visible in the gulf, oriented more or less N-S)
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on June 10, 2019, 05:55:58 PM
A68-A is rotating around a different center now.  I thought it would be closer to the island/peninsula, but it is also 'moving out'.  New PolarView (https://www.polarview.aq/antarctic) image ('added' to the previous GIF) is from June 8 (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201906/S1A_IW_GRDH_1SSH_20190608T080144_5C66_S_1.8bit.jp2).
Title: Re: Antarctic Icebergs
Post by: b_lumenkraft on June 10, 2019, 06:33:07 PM
Something is there beneath the surface. I'd guess it'll lose it's nose.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on June 26, 2019, 09:36:06 PM
A68-A is amazingly close to Robertson Island.  From the last published image just above, the ice island has rotated a little (counterclockwise as always) and snuggled up close to the island.  At the surface, the ice island is about 300 meters from the thin white line that approximates the edge of the island.  (yellow lines approximate the gap) PolarView (https://www.polarview.aq/antarctic) image from today (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201906/S1B_IW_GRDH_1SSH_20190626T080103_45CF_S_1.8bit.jp2)
Title: Re: Antarctic Icebergs
Post by: magnamentis on June 26, 2019, 11:23:45 PM
A68-A is amazingly close to Robertson Island.  From the last published image just above, the ice island has rotated a little (counterclockwise as always) and snuggled up close to the island.  At the surface, the ice island is about 300 meters from the thin white line that approximates the edge of the island.  (yellow lines approximate the gap) PolarView (https://www.polarview.aq/antarctic) image from today (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201906/S1B_IW_GRDH_1SSH_20190626T080103_45CF_S_1.8bit.jp2)

i suspect that there is contact under water ?
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on July 05, 2019, 05:06:15 PM
Ice Island A68-A continues to move back and forth (tides? wind?) as it approaches the end of its 2nd year as a free agent  (https://forum.arctic-sea-ice.net/index.php/topic,1175.msg120454.html#msg120454)- no pesky fast ice will hold it in place.  It has actually slid back, or to the 'left' or westward, a spot from the June 26 image (above), but has rotated a hair counterclockwise (as always).
Title: Re: Antarctic Icebergs
Post by: gerontocrat on July 12, 2019, 08:55:06 PM
The BBC have got a movie on A68-A's progress over the last 2 years.

https://www.bbc.co.uk/news/science-environment-48920168

I suppose if I was clever I could filch it from the web-page, but I am not (sigh)
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on July 19, 2019, 06:55:33 PM
A68-A is (slowly) escaping from the clutches of Robertson Island [blue-highlighted blob on the left in new image] in the dark of night.  July 3 image from above; July 16 image (https://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SSH_20190716T233400_D970_S_1.final.jpg) from PolarView (https://www.polarview.aq/antarctic).  Rotation during these two weeks is about 10º - pretty fast! Near Robertson Island, A68-A slid southwestwards a bit.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on August 09, 2019, 07:05:20 PM
A68-A has rotated another 15 or so degrees, plus a piece broke off on the 'left' side …  PolarView (https://www.polarview.aq/antarctic) image from 2019-08-08 (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201908/S1B_EW_GRDM_1SDH_20190808T075248_9F33_S_1.8bit.jp2)

Interesting icy feature at the 'top' end of the ice island.   [my guess: ] Caused by the sea ice moving 'north' faster than the ice island?
Title: Re: Antarctic Icebergs
Post by: blumenkraft on August 09, 2019, 07:22:26 PM
Interesting icy feature at the 'top' end of the ice island.

I see them all the time. I think it's caused by wind.

For example at the Brunt shelf (Pic1) or PIG (Pic2).
Title: Re: Antarctic Icebergs
Post by: Stephan on August 09, 2019, 10:19:25 PM
I just realized a new little crack on the very W tip of the PIG, where (behind it) a minor calving occurred in June (https://forum.arctic-sea-ice.net/index.php/topic,429.msg205693.html#msg205693).
Title: Re: Antarctic Icebergs
Post by: DrTskoul on August 09, 2019, 11:27:43 PM
A68-A has rotated another 15 or so degrees, plus a piece broke off on the 'left' side …  PolarView (https://www.polarview.aq/antarctic) image from 2019-08-08 (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201908/S1B_EW_GRDM_1SDH_20190808T075248_9F33_S_1.8bit.jp2)

Interesting icy feature at the 'top' end of the ice island.   [my guess: ] Caused by the sea ice moving 'north' faster than the ice island?

Looks the sea is rushing away....
Title: Re: Antarctic Icebergs
Post by: blumenkraft on September 06, 2019, 08:42:39 AM
I think A68A is on the move now.

08 - 11 - 15.09. and 03.09.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on September 06, 2019, 12:31:50 PM
Yesterday Sentinel took a beautiful pic btw.

Yes, we can haz light!
Title: Re: Antarctic Icebergs
Post by: blumenkraft on September 09, 2019, 08:25:21 AM
A68A from 4th without 1 cloudy day.
Title: Re: Antarctic Icebergs
Post by: Stephan on September 13, 2019, 07:22:33 PM
A68 is now really on the move.
I compared its position between Aug 03 and Sep 12, 2019. Its northern tip has moved ca. 80 km northward whereas its southern tip made a journey of ca. 37 km in NE direction. Combined with this movement it has also turned counterclockwise and is now more oriented (but not yet parallel) to the Antarctic Peninsula. It looks like it wants to leave Weddell Sea to see something different...
80 or 37 km means a movement of ca. 2 km/day (northern tip) or 1 km/day (southern end).

See attached pictures.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on September 13, 2019, 08:25:55 PM
Interestingly, it also moves along with the tides.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on September 20, 2019, 07:38:57 PM
Because of A68-A is moving and Sentinel-hub-playground (https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-65.05678718833466&lng=-57.66105651855469&zoom=10&preset=CUSTOM&layers=B01,B02,B03&maxcc=100&gain=1.0&gamma=1.0&time=2019-03-01%7C2019-09-20&atmFilter=&showDates=true&evalscript=cmV0dXJuIFtCOEEqMixCMDMqMSxCMDIqMV0%3D) 'daily' images don't always give complete coverage, we have, in one screenprint, evidence of the ice island's movement over time.  I believe the added yellow arrow shows 12 km movement between September 5 and 12.  Edit: larger area shows the Sept. 5, 11 and 12 images in context 'better'  (the ice island is circled).
Title: Re: Antarctic Icebergs
Post by: blumenkraft on September 25, 2019, 10:08:07 PM
New iceberg!

Big claving at Amery!

Further west we might lose A68-A to the ocean this year?

Click to play!
Title: Re: Antarctic Icebergs
Post by: blumenkraft on October 01, 2019, 09:26:16 AM
As reported in the Thwaites glacier thread, B22-A has moved a little.

This GIF is showing 21st vs 28th of September.
Title: Re: Antarctic Icebergs
Post by: crandles on October 01, 2019, 11:13:58 AM
https://www.bbc.co.uk/news/science-environment-49885450

Quote
The Amery Ice Shelf in Antarctica has just produced its biggest iceberg in more than 50 years.

The calved block covers 1,636 sq km in area - a little smaller than Scotland's Isle of Skye - and is called D28.

(https://ichef.bbci.co.uk/news/660/cpsprodpb/B48F/production/_109032264_body-nc.png)

Oops better covered at https://forum.arctic-sea-ice.net/index.php/topic,2578.msg560 (The Amery Ice Shelf Thread)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on October 01, 2019, 11:19:08 AM
Belongs here too, Crandles. :)
Title: Re: Antarctic Icebergs
Post by: Stephan on October 01, 2019, 11:28:13 AM
As reported in the Thwaites glacier thread, B22-A has moved a little.

This GIF is showing 21st vs 28th of September.
Thanks blumenkraft for this animation.
Interestingly, most of the floating smaller icebergs move synchronously to B-22-A. But some icebergs, mainly at the western edge are immobile and seem to be grounded. Will they act as barrier to prevent B-22-A from further moving westward?
Title: Re: Antarctic Icebergs
Post by: charles_oil on October 02, 2019, 10:06:10 AM
BBC article on it as well
https://www.bbc.com/news/science-environment-49885450 (https://www.bbc.com/news/science-environment-49885450)



Title: Re: Antarctic Icebergs
Post by: blumenkraft on October 06, 2019, 09:20:07 AM
Will they act as barrier to prevent B-22-A from further moving westward?

Welcome Stephan :)

I think they are getting crushed if they are in its way. They are so tiny and B-22-A is so huge.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on October 06, 2019, 09:21:37 AM
A68-A made quite some way...
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on October 23, 2019, 09:06:57 PM
Again, we have parts of A-68A imaged on two dates both showing in Sentinel-hub Playground (https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-65.10177760829487&lng=-57.57282257080078&zoom=11&preset=92_NDWI&layers=B01,B02,B03&maxcc=100&gain=1.0&gamma=1.0&time=2019-04-01%7C2019-10-23&atmFilter=&showDates=true).
A-68A moved about 8.2 km in 7 days.  The two triangular icebergs in the 'fast ice' appear to have moved about 8.4 km.  Has the ice island rotated anticlockwise a bit, too?
Title: Re: Antarctic Icebergs
Post by: blumenkraft on October 23, 2019, 09:31:21 PM
Yep!
Title: Re: Antarctic Icebergs
Post by: Stephan on October 27, 2019, 10:58:14 AM
As reported in the Thwaites glacier thread, B22-A has moved a little.

I analysed the Sentinel pictures from Oct 03 and Oct 26, 2019.
B22-A moved around 300 m in NNW direction. This is a movement of 13m/day.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on October 29, 2019, 03:43:55 PM
13 m/day for B-22A and 650 m/day for A-68A (e.g., 28 km during recent 43 day period). Sentinel-hup Playground imagery (https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-64.42659403500943&lng=-58.49395751953125&zoom=8&preset=92_NDWI&layers=B01,B02,B03&maxcc=100&gain=1.0&gamma=1.0&time=2019-04-01%7C2019-10-29&atmFilter=&showDates=true) [click to run 2-frame GIF]
Title: Re: Antarctic Icebergs
Post by: Stephan on October 29, 2019, 07:22:44 PM
OK Tor, "your" berg is faster than "mine"  ;)
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on October 29, 2019, 08:00:10 PM
Is this where I say "Nana-nana-boo-boo (https://www.urbandictionary.com/define.php?term=nana%20nana%20boo%20boo)"? ::)  I'll admit to having never heard 'the rest of the taunt' that the link provides.  :-[  We only ever said "Nana-nana-boo-boo" to each other in games of chase when an attempt to catch failed.

But the race is on!  Should we check in every few months?  Are there other contestants?
 :)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on October 29, 2019, 08:17:42 PM
Guys, my berg is D-26. At the end, i might win! :P
Title: Re: Antarctic Icebergs
Post by: grixm on October 30, 2019, 10:48:36 AM
A68a is on the move. In the last week it has drifted around 10 km NNE.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on November 10, 2019, 05:00:53 PM
Is it expected for such a huge iceberg to move just as fast as the sea ice surrounding it?

Click to play.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on November 12, 2019, 07:04:08 PM
Another fine SAR shot came in today.

This is 07.11. vs. 12.11.
Title: Re: Antarctic Icebergs
Post by: gerontocrat on November 12, 2019, 08:25:43 PM
Is it expected for such a huge iceberg to move just as fast as the sea ice surrounding it?

Click to play.
I've forgotten what it's freeboard is. 20 metres? Wind speed at 25 metres always higher than at the surface. 180 metres below the water ? Effect of currents ?

Lots of inertia but once on its way vey slow to stop.
Title: Re: Antarctic Icebergs
Post by: baking on November 13, 2019, 12:41:14 AM
It's moving about 88 meters per hour.  It is most likely pulling/pushing the sea ice with it.  If it became grounded, the sea ice might move faster.  But if there is no grounding, there is no reason for it to move slower or faster than the surrounding sea ice except for inertia (or waves in open water.)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on November 19, 2019, 04:54:55 PM
Still having the impression it moves at sea ice speed (ish?). I was Gerontocrat on this one. I expected different outcomes with different forces affecting it. But this assumption might be wrong. There must be one dominant driving force which is ... what?

Anyway, it now moves away from the shallow waters. This is 12. vs. 18. Nov.
Title: Re: Antarctic Icebergs
Post by: gerontocrat on November 19, 2019, 05:55:27 PM
Still having the impression it moves at sea ice speed (ish?). I was Gerontocrat on this one. I expected different outcomes with different forces affecting it. But this assumption might be wrong. There must be one dominant driving force which is ... what?

Anyway, it now moves away from the shallow waters. This is 12. vs. 18. Nov.
Helluva big ice-breaker.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on November 19, 2019, 07:22:03 PM
Helluva big ice-breaker.

Nah, i would see that in the satellite pictures. ;)
Title: Re: Antarctic Icebergs
Post by: gerontocrat on November 19, 2019, 07:31:43 PM
Helluva big ice-breaker.

Nah, i would see that in the satellite pictures. ;)
Stealth technology (if the Klingons can do it, so can we).
Title: Re: Antarctic Icebergs
Post by: blumenkraft on November 19, 2019, 08:09:20 PM
Wow, this is uncanny. I just talked about Klingons with a friend.  :o

PS: Not in Klingon though.  ;D
Title: Re: Antarctic Icebergs
Post by: blumenkraft on November 23, 2019, 05:52:54 PM
4 beautiful cloud-free days in a row.
Title: Re: Antarctic Icebergs
Post by: FredBear on November 30, 2019, 12:39:50 AM
Looking back to the initial post I thought it might be interesting to have a current "fix" on all numbered icebergs so that future movements can be defined more accurately. This might be particularly useful for A23A and B22A which have been grounded for years but move slightly?

 The positions are at 11/29/2019
Title: Re: Antarctic Icebergs
Post by: grixm on December 05, 2019, 08:05:01 PM
Moved about 20 km since Nov. 23, no signs of slowing down
Title: Re: Antarctic Icebergs
Post by: Stephan on December 05, 2019, 10:41:49 PM
Are there any bumps or shallow waters on its way NE that would prevent iceberg A-68-A to continue its journey?
Title: Re: Antarctic Icebergs
Post by: baking on December 06, 2019, 03:50:09 PM
Are there any bumps or shallow waters on its way NE that would prevent iceberg A-68-A to continue its journey?

Tierra del Fuego?  The Falklands?  A cruise ship?
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 06, 2019, 04:40:58 PM
LOL  ;D

Yes, Stephan, there are shallow waters ahead. But i think the ice island is tall enough to not get grounded there but snaking along as it does at the moment. We'll see i guess.

(https://www.researchgate.net/profile/Michael_Meredith2/publication/314024970/figure/fig1/AS:482987130265601@1492164513787/Bathymetry-of-the-Antarctic-Peninsula-shelf-with-selected-place-names-marked-Also-shown.png)

Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 16, 2019, 04:15:56 PM
This Polar View (https://www.polarview.aq/antarctic) image of A68-A (2019-12-16 (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201912/S1B_EW_GRDM_1SSH_20191216T080817_10A5_S_1.8bit.jp2)) shows some surface structure particularly well.  Some of the islands (made of rock) near the Antarctic Peninsula are labeled (and two bodies of water).  Joinville Island is the slightly boomerang-shaped island east ("above") the Antarctic Peninsula.  (This image is pretty much oriented so that NE is 'up' and NW to the left). The map just above shows there is shallow water (<250 m) between A68-A and Joinville Island.  [Place names from Wikipedia (https://en.wikipedia.org/wiki/File:Wfm_antarctic_peninsula_islands.png).]  -  Click for enlargement or go to link  (2019-12-16 (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201912/S1B_EW_GRDM_1SSH_20191216T080817_10A5_S_1.8bit.jp2)) for a much larger image.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 16, 2019, 04:22:09 PM
So what do you guys think about the thickness of this big boi?

Assuming it's >300m it will likely not get grounded, rather bouncing back from the underwater mountains, right?

If it's <250m, a grounding in the north is rather likely?
Title: Re: Antarctic Icebergs
Post by: baking on December 16, 2019, 04:28:40 PM
It's managed to bump into a couple of islands already without getting grounded, but if one end of it does get grounded I see it breaking up.  It's too long and unstable and too close to ocean currents to take the stress of being partially grounded.  But that's just my guess.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 16, 2019, 04:31:54 PM
Quote
It measured 1,000 feet (300 metres) thick
per this article (https://www.sciencealert.com/antarctica-iceberg-a68-location-map-animation-one-year-on-2018-7)
or
Quote
1,100 feet thick [= 335 m]

per this article (https://www.atlasobscura.com/articles/how-big-is-larsen-c-new-iceberg-a68-size-comparisons)
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 16, 2019, 04:39:09 PM
A68-A was grounded (apparently) for a while in September 2018, per discussion on the ASIF here (https://forum.arctic-sea-ice.net/index.php/topic,1175.msg173091.html#msg173091).  It seems a piece broke off that was at the (or a major) pinning point.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 16, 2019, 04:50:56 PM
Picture of A68-A from a ship on 2019-12-09 (link to Wikipedia JPGs (https://en.wikipedia.org/wiki/Iceberg_A-68))
(https://en.wikipedia.org/wiki/Iceberg_A-68#/media/File:Closeup_of_the_iceburg_A-68_on_9th_December_2019.jpg)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 16, 2019, 04:51:59 PM
Quote
It measured 1,000 feet (300 metres) thick
per this article (https://www.sciencealert.com/antarctica-iceberg-a68-location-map-animation-one-year-on-2018-7)
or
Quote
1,100 feet thick [= 335 m]

per this article (https://www.atlasobscura.com/articles/how-big-is-larsen-c-new-iceberg-a68-size-comparisons)

Amazing, Tor. Thanks so much!
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 16, 2019, 05:07:13 PM
A68-A was grounded (apparently)

Looks more like a bouncing against rocks to me.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 16, 2019, 06:51:28 PM
B_,
Check out this  (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg189602.html#msg189602)contemporary comment re "pinned" (possibility) (and posts just above it).

For "bouncing off the rocks", look here (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg208548.html#msg208548).
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 16, 2019, 09:42:58 PM
Haha, good find! Thanks for the hint, Tor.  ;)
Title: Re: Antarctic Icebergs
Post by: baking on December 16, 2019, 11:53:06 PM
First off, "pivots" are not necessarily due to grounding.  It is so large that currents pushing on one end could cause it to rotate just because the force would be so far away from the center of inertia.

Second, I was the first to say it "bounced" off the island, but it is more like a "skim."   But the point is that it didn't "hang" as it passed closely by the area so it was was not getting grounded in what might be relatively shallow water.
Title: Re: Antarctic Icebergs
Post by: baking on December 17, 2019, 03:16:23 PM
Yesterday's Sentinel-1 image of A68A shows a significant increase in speed.  The GIF below is in six day increments.

Also, I've drawn in the rough location of the shallows at the end of the Antarctic Peninsula.  There are two grounded icebergs circled in red.

Click first image to play GIF
Title: Re: Antarctic Icebergs
Post by: baking on December 18, 2019, 04:51:07 PM
Click below for a detailed GIF showing the approach of iceberg A68A over the last three days to a large number of grounded icebergs in the shallows off the end of the Antarctic Peninsula.  Two larger grounded iceberg can be seen in the upper left which were identified in the previous post, but on closer inspection there are many more smaller icebergs that are also grounded and are much closer to A68A.

Given the current speed and trajectory, A68A will hit the shallows in two days time.  Clearly, if these relatively tiny icebergs are grounded, A68A will certainly hit bottom if this motion continues.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 18, 2019, 04:57:21 PM
We might see it pivot again. Another 180 makes it square, so to say.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 18, 2019, 05:42:22 PM
Great GIF, Baking!  The rock under the grounded iceberg that is closest to A68-A has to be so shallow that the ice island will hit and bounce off of it (or split, or course), and not get stuck.  Going about due north (per Baking's GIF) though, A68-A is headed straight for it!

The map B_ posted on Dec. 6 (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg239753.html#msg239753) indicates a 'deep current' just beyond these shallows.  Will the current drag A68-A to safety - off to the northeast (until the next islands, anyway)?

Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 18, 2019, 09:17:53 PM
First of all, sorry for the big file size.

Here is from 06.09 to today, 104 frames, daily increments, fast-playing to obscure the clouds.
Title: Re: Antarctic Icebergs
Post by: oren on December 19, 2019, 01:59:19 AM
baking and blumenkraft - love the GIFs.
Title: Re: Antarctic Icebergs
Post by: baking on December 20, 2019, 05:10:27 AM
I've added a couple more images to the GIF of A68A, roughly at 24 hour increments, the last just before midnight UTC.

Movement had been due North up until 24 hours ago when it shifted dramatically to the East, just short of the grounded smaller icebergs.

Is it just luck that it avoided grounding, or has it made contact with the sides of a much shallower rise and is sliding past?  And if it is sliding, will the irregular sides of the iceberg eventually get hung up?

Edit:  Also note the medium size berg (broken off from A68A) that has successfully maneuvered to the East of the grounded ice showing the shallow area is really quite small.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 20, 2019, 08:29:38 AM
The RAMMB is cloudy but it looks to me as if a tidal wave pushed it east. It lost a small piece at what's now the tale btw. I think here it hit the bottom.
Title: Re: Antarctic Icebergs
Post by: baking on December 20, 2019, 03:50:28 PM
The latest Sentinel-1 image shows that A68A hasn't moved much in the last 8 hours.
Title: Re: Antarctic Icebergs
Post by: baking on December 21, 2019, 03:51:09 PM
Latest GIF from Sentinel-1 images shows many small pieces of iceberg A68-A breaking off at the grounding point.  No question that it has hit ground, but what will happen next is anyone's guess.

Click image below to see animation.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 22, 2019, 03:02:40 PM
GIF 1: The crash Baking mentioned.

GIF 2: A comparison of 01.12. and 21.12. to see the grounded icebergs.

GIF 3: Beautiful, very old ice.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 22, 2019, 03:12:31 PM
BTW, the thickness, at least at this part of the iceberg, is nowhere near the 300-335m figure.
Title: Re: Antarctic Icebergs
Post by: gerontocrat on December 22, 2019, 05:53:13 PM
BTW, the thickness, at least at this part of the iceberg, is nowhere near the 300-335m figure.
When A-68 first broke away, the size was said to be 5,800 km2, and the mass 1 trillion tons, i.e. an average thickness of just over 170m. On average freeboard is about 10%, i.e. 17 metres, meaning on average around 155 metres is below the sea surface.

The iceberg is also very flat, so maybe the average is pretty close to the thickness at the edge.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 22, 2019, 06:39:26 PM
OK, but this is the side that was facing the ocean once it was a shelf still. So we can assume it's thinner on this side than the other, right?

If that's a correct assumption, the 170m must be wrong.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 22, 2019, 07:01:36 PM
Amazing, how you can see layers of different ice.

I get why it's white on top, but why has it this darker blue middle layer?
Title: Re: Antarctic Icebergs
Post by: HapHazard on December 22, 2019, 09:54:04 PM
Perhaps that bit has pretty much always been underwater? (From past flips.) Anyway, definitely neat.
Title: Re: Antarctic Icebergs
Post by: gerontocrat on December 22, 2019, 10:09:18 PM
OK, but this is the side that was facing the ocean once it was a shelf still. So we can assume it's thinner on this side than the other, right?

If that's a correct assumption, the 170m must be wrong.
My ignorance on the extent of thinning on the ocean side of an ice shelf is profound. The edges are also chipped and bashed from is journey, presumably mostly on its underside.

So who knows?
Title: Re: Antarctic Icebergs
Post by: vox_mundi on December 22, 2019, 11:37:33 PM
Quote
... I get why it's white on top, but why has it this darker blue middle layer? 
The clearer (darker) the ice - the fewer trapped air bubbles.

Perphaps those clearer layers represent periods (... tens of thousands of years) of lighter (or heavier snowfall) when that portion of the glacier was much further inland.

This ice shelf has been traveling towards the coast for many 21,000 and 41,000 year precessional and orbital cycles and probably a few 100,000 year cycles. Things change.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 23, 2019, 06:27:09 AM
Thanks, Hap and Vox! Fascinating stuff. :)

So who knows?

We are here to find out, aren't we? ;) :)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 24, 2019, 10:24:01 PM
A-68A still marching!

23. vs 24.
Title: Re: Antarctic Icebergs
Post by: FredBear on December 25, 2019, 12:08:18 AM
Do I see the tail of A-68A (southern end ) breaking up? (arctic.io.   2019-12-24, antarctic true color)
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 25, 2019, 02:40:57 AM
Here's the latest available PolarView (https://www.polarview.aq/antarctic) image of A68-A from 12/23 (https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20191223T080038_3242_S_1.final.jpg) showing the tail looking just fine.  (I look forward to seeing the next 'radar' image => 12/24.)

Over half the world is into 12/25, so Merry Christmas, y'all!  (I have to wait three and a half hours for the soot-repellent-suit wearing elf to fly down our imaginary chimney and fill the oversized stockings presumptuously laid out on the sofa, eager to be filled with minor loot. [The stockings have a mercurial mind of their own!  They're so calm most of the year.])

Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 25, 2019, 11:59:11 AM
Do I see the tail of A-68A (southern end ) breaking up?

Nope. Today's Sentinel-1 just came in.

But looks like it had another bump on the side.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 25, 2019, 04:08:08 PM
Between yesterday and today, A-68A has moved ~ 10km north-east.

Surprising to me is that it's turning clockwise!  :o
Title: Re: Antarctic Icebergs
Post by: baking on December 25, 2019, 09:42:15 PM
Surprising to me is that it's turning clockwise!

Not all that surprising considering the Northeastern end has run aground.  But it also means a strong likelihood that the Southwestern end will also be grounded.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 25, 2019, 09:50:24 PM
I find it hard to wrap my head around this massive thing being stoped by grounding though. That kind of momentum needs a lot of friction to slow down. Likely it will rather break in pieces, would you agree Baking?
Title: Re: Antarctic Icebergs
Post by: baking on December 25, 2019, 10:00:42 PM
I'm not sure how strong the currents are there, but I do know they would be much stronger than anything it experienced in the past two years.  Also, icebergs that are much longer than they are wide tend to breakup pretty readily.  And there is lots of evidence of cracks and other weaknesses.  If it stays grounded for more than a few days at both ends I think a breakup is likely.
Title: Re: Antarctic Icebergs
Post by: baking on December 25, 2019, 10:29:08 PM
Here is a 48-hour GIF of the movement of the SW end of A68-A.  It looks like there may be a possibility of it getting by without grounding.
Title: Re: Antarctic Icebergs
Post by: baking on December 25, 2019, 11:07:12 PM
On the other hand, today's Sentinel-1 image of the NE grounding point of A68-A shows that it may have already moved away from that grounding point after a lot of smaller icebergs calved off of the larger one.  (Can the force of calving force the larger berg away from the grounding point?)  See the GIF below.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 26, 2019, 06:32:46 PM
Today's Sentinel 3 shows it pivoting clockwise furthermore.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 28, 2019, 06:00:52 PM
More of the same.

The iceburg moved north-east, even though way more east than north, and is rotating clockwise still.

I think it's snaking along.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 28, 2019, 06:15:23 PM
B_,
With undated images, I cannot tell which is older. 

I've always wondered about "clockwise", because from the clock's perspective, the hands go from the top of the dial to the left and downwards.  Now I'm wondering which way time goes:  numbers go up as we increase years before the present.  The future is just a belief.
 :D
Documentation would keep my mind from wondering.  :o :P ::) :-X
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 28, 2019, 06:23:25 PM
Oh dear, that poor confused mind of yours and it's all my fault. :-/

I will do better my friend. :)

To help you out with this one, the older one is the one where the iceburg is further on the left. Since this is via EO-Browser, north is up.

With the clockwise thing, you confused me btw!
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 29, 2019, 08:39:03 PM
With timestamp, i promised. :)

More of the same i guess. No signs of grounding.
Title: Re: Antarctic Icebergs
Post by: FredBear on December 29, 2019, 08:49:45 PM
Still think that the tail (SE corner, lower left in above images) has lost lumps of ice recently!
(Possibly only sea ice sticking to the 'berg?)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 29, 2019, 09:19:21 PM
Yes, it lost almost all the fast-ice and a few small pieces at its tail(ish) around the 24th.
Title: Re: Antarctic Icebergs
Post by: baking on December 29, 2019, 11:41:01 PM
Yes, it lost almost all the fast-ice and a few small pieces at its tail(ish) around the 24th.

One of those larger pieces is an iceberg that was visible on December 23 in the GIF from my reply #119 and is probably not from A68-A.  Not sure about the other one, or whether it is an iceberg or sea ice.

Edit:  Here is an image from Dec. 18 showing where the iceberg in question broke off of A68-A.  Still searching for the other one.

Edit2:  I found the other piece in the Dec. 23-25 GIF, to the right of the first piece on Dec 23 and above it to the left on Dec. 25, but I can't find it either loose or attached on Dec. 18, but I am now convinced it did break off because it has a dark line across it visible to radar showing it has broken off from old ice.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 30, 2019, 04:21:45 PM
Yes Baking, totally forgot about that tale one. Thanks for adding.

A68-A is still not grounded. WestEastwards movement, seemingly circumventing shallow waters.
Title: Re: Antarctic Icebergs
Post by: baking on December 30, 2019, 05:43:09 PM
Westwards movement

Eastward.  A68-A is almost halfway past the grounding point.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 30, 2019, 05:56:53 PM
Fixed, thank you, Baking! :)

What now? Can we declare it free now? ;)
Title: Re: Antarctic Icebergs
Post by: gerontocrat on December 30, 2019, 06:44:19 PM
Being lazy, I am asking you lot for the exact lat/long of A-68.

By the looks of it, recently there was a strong wind assisting A-68's northward movement. That is now dead calm or even in reverse. (see gif)

Presumably the prevailing currents will still help to nudge it north, though how strong those currents are I do not know. (see Weddell Gyre and Antarctic Currents images).

Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 30, 2019, 06:48:18 PM
Iceberg A68A
Size: 82X26 nm
Coordinates: -54.82, -64.08
Remarks: belle
Date recorded: 2019-12-27
Source: US National Ice Center
Title: Re: Antarctic Icebergs
Post by: baking on December 30, 2019, 07:41:31 PM
Coordinates: -54.82, -64.08
Date recorded: 2019-12-27

Based on this morning's radar image, I don't think I would change those coordinates too much, although it has moved a little to the East.  The problem is in finding the center of mass or whatever they are targeting.  The iceberg itself actually stretches from 56W to 53W so maybe 54.5W is more current estimate.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on December 30, 2019, 07:54:35 PM
Back on December 16 (annotated image) (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg240909.html#msg240909), the leading edge of A68-A was just south of Joinville Island (functionally the 'northern' tip - actually eastern tip - of the Antarctic Peninsula).

Baking's image (just above) (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg242512.html#msg242512) includes parts of Joinville Island ('above') and Dundee Island ('below' - North is towards the upper left corner of the image).  About 2/3rds of A68-A is east of Joinville Island.

Attached image (map from here (http://cdn.antarcticglaciers.org/wp-content/uploads/2012/06/Antarctic_peninsula1.jpg)) has approximate July 2018 ice island location and approximate December 2019 location.  (The shaps of the ice island are approximate, and have changed some over these 18 months.) 

Gerontocrat, your green circle on the wind map is way far from where the ice island floats.  ;)
Title: Re: Antarctic Icebergs
Post by: gerontocrat on December 30, 2019, 08:16:21 PM
Good heavens. I had no idea it was almost at the open sea. I thought it would take years and years to meander north.

It would be a hoot if it went across the Weddell Sea a bit too far south and got caught by the gyre  and sent south go around the whole coastline.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 31, 2019, 05:05:45 PM
The trajectory of A68A has clearly changed now. We are headed east (~7km since yesterday), the clockwise rotation seems to have stopped.
Title: Re: Antarctic Icebergs
Post by: gerontocrat on December 31, 2019, 06:04:26 PM
I wonder how much of the movement of A-68 is determined by wind and how much by ocean currents.

The wind is currently from the North at A68's location
Title: Re: Antarctic Icebergs
Post by: blumenkraft on December 31, 2019, 06:32:00 PM
Since it's pretty constantly snaking along the (underwater) coastline i would assume the wind has only a little influence. My humble opinion based on observation only, no knowledge of the physics involved.
Title: Re: Antarctic Icebergs
Post by: Stephan on January 01, 2020, 09:48:15 PM
What about B-22 in Amundsen Sea?

I chose five different remarkable points A, B, C, D, and E and calculated the changes of their position between 10.01.2019 and 27.09.2019 (Shift 1) as well as the changes between 10.01.2019 and 25.12.2019 (Shift 2) from clear Sentinel images.
B-22 lies north of Haynes/Smith Glacier and NW of Thwaites Ice Tongue, from which it broke off almost 10 years ago. It is not perfectly grounded, but almost stuck in shallow waters. But it moves slowly into NW direction. I present the position changes in the following table (numbers in km, direction indicated)

Point  Shift 1 [km]  - Shift 2 [km]
A       2,7 W 2,0 N  -  3,6 W 2,5 N
B       2,5 W 1,9 N  -  4,4 W 2,9 N
C       2,7 W 1,6 N  -  3,8 W 4,6 N
D       2,9 W 1,6 N  -  2,7 W 4,1 N
E       2,8 W 1,8 N  -  3,3 W 3,3 N
_____________________________
F       0,7 W 2,2 N  -  7,9 W 7,7 N (the "cork", see text below)

The westward movement, predominant in the first part (Shift 1) has turned into a more northward movement in the latter part (Shift 2), especially at the eastern end of B-22.
The western end is slowly eroding by calving. It loses maybe 100 m per year at some points. B-22`s length is around 85 km - please calculate by yourself how long it might take for a complete calving...

South of B-22 the compact sea ice has opened (area circled in blue). One of the larger icebergs south of B-22 has floated into NW direction (8 km in Shift 2). Now it seems to be stuck in shallow waters. It blocks the outflow of the sea ice in the blue circled region. Therefore it acts as a cork. I have no idea whether it will stay there for longer or whether it will be pushed through by the currents. Until that happens a complete clear-out of sea ice south of B-22 seems unlikely.

See attached picture.
Title: Re: Antarctic Icebergs
Post by: baking on January 01, 2020, 11:02:09 PM
it broke off almost 10 years ago.

Actually, 2002.
Title: Re: Antarctic Icebergs
Post by: Stephan on January 01, 2020, 11:23:16 PM
OK, thank you. I should have checked that...
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 02, 2020, 03:41:36 PM
Yesterdays Sentinel 3 came in very late, so i didn't manage to make a GIF.

Here is 3 days instead.

Note the stranded icebergs in the north.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 03, 2020, 06:00:59 PM
Another 7/8 km of dodging underwater mountains.

Click to play.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 04, 2020, 03:46:48 PM
A68A 'only' made 4-5 km between the two shots. This can either mean a different time frame than usual between the shots, or it has slowed down. I would guess the further.

The trajectory is still eastwards.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on January 04, 2020, 11:12:10 PM
Further to my post on December 30 (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg242529.html#msg242529) (with Antarctic Peninsula map), here is a Polar View (https://www.polarview.aq/antarctic) image from 18 hours ago (https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20200103T231129_A640_S_1.final.jpg) showing A68-A (lower right, mostly off the image, darker grey - 64S and 54W go through the ice island) in relation to the tip of the Antarctic Peninsula (actually, the islands just east of the tip (in blue) - Joinville Island in the middle.  (North is to the upper left. 56N goes through the land islands; 63S brushes the northern one. Lines are every 1 degree N-S and 2 degrees E-W.)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 05, 2020, 04:02:37 PM
3-4 km eastwards movement only between yesterdays shot and today. That makes it two slow(ish) days. Also, we have a counter-clockwise movement.

I suspect we are scratching along an underwater mountain.
Title: Re: Antarctic Icebergs
Post by: Stephan on January 05, 2020, 05:57:31 PM
I wonder whether A-68 will be able to join the westeastward drift around Antarctica or whether it will be caught by the Weddell gyreand remain in that area for a while.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 05, 2020, 06:04:08 PM
Yeah, me too! That will be interesting to watch. :)
Title: Re: Antarctic Icebergs
Post by: mitch on January 05, 2020, 09:38:41 PM
Westward drift? Antarctic Circumpolar Current flows west to east. 
Title: Re: Antarctic Icebergs
Post by: Stephan on January 05, 2020, 10:29:05 PM
Thank you Mitch, I meant the drift west to east, of course. Got it fixed.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 06, 2020, 05:31:10 PM
~3-4 km between yesterday's and today's shot.

A68A moving further east. Rotation seems to have stopped.

(Oops forgot the timestamps. The iceburg is moving to the right.)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 07, 2020, 08:48:35 PM
5km eastwards movement between yesterday's and today's picture.

Yesterday's pic is the one where the iceburg is further to the left.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 12, 2020, 09:55:12 AM
Here is A68A from 07th to 11th.

Slowly marching eastwards. In the last frame, you can see a) fast ice detachment and b) pivoting counterclockwise.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 12, 2020, 06:26:32 PM
A68A from the end of October to today, daily increments, fast-playing to obscure the clouds.
Title: Re: Antarctic Icebergs
Post by: grixm on January 12, 2020, 07:23:09 PM
So is it fair to say that it is now past any danger of grounding and is basically in the open sea?
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 12, 2020, 07:26:32 PM
I wouldn't say that quite yet. Perhaps there are more underwater mountains in its way.

(https://www.researchgate.net/profile/Maria_Kavanaugh2/publication/280286415/figure/fig2/AS:667643585499139@1536190043694/Bathymetry-along-the-Western-Antarctic-Peninsula-continental-shelf-Spatial-resolution-is.jpg)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 13, 2020, 03:37:35 PM
I think this one makes it clearer with what i mean with 'underwater mountains in its way'.

This is the NASA Marple layer and yesterday's SNPP Day&Night band.
Title: Re: Antarctic Icebergs
Post by: baking on January 13, 2020, 04:39:48 PM
A68-A recently passed through 300 meters deep water without issues, only running aground at about 200 meters deep.  I don't think that 600 meter deep water will present a problem.
Title: Re: Antarctic Icebergs
Post by: oren on January 14, 2020, 03:33:17 AM
I think at this stage it's safe from grounding.
Blumenkraft thanks for the animations.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 14, 2020, 09:29:55 AM
Very welcome, Oren.

But i disagree, somewhere out there it could get stranded IMHO. I base this assumption on a) there are more underwater mountains, no matter which way it takes (despite south of course, but i don't think it's headed south) and b) possibly inaccurate bathymetry maps. ;)
Title: Re: Antarctic Icebergs
Post by: baking on January 14, 2020, 03:05:09 PM
b) possibly inaccurate bathymetry maps. ;)

At depths yes, but a shallow that could be a hazard to shipping or snag a fishing net will be on every chart and has been for ages.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 14, 2020, 03:24:01 PM
OK, that's a good point, Baking.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on January 14, 2020, 03:33:22 PM
Well, if A68-A, per the attached tracking map of icebergs released from Antarctica, goes north or northeast it could get grounded.  (There are rock islands along the extension of the Antarctic Peninsula - the submarine ridge - the last being the South Orkney Islands.) Many of the tracked icebergs have wandered in these occasionally shallow waters.

New location:  The Antarctic Iceberg Tracking Database (https://www.scp.byu.edu/data/iceberg/ ) shows where icebergs have traveled.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 19, 2020, 03:48:06 PM
That's a most useful map, Tor. Thanks for posting.

Here is A68A from 15th to today plus bathymetry.

It is clearly snaking along this underwater mountain. Shallow waters ahead.
Title: Re: Antarctic Icebergs
Post by: nanning on January 19, 2020, 06:36:55 PM
You have become good at this blumenkraft :)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 19, 2020, 06:57:49 PM
Thank you so much, Nanning. :)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 21, 2020, 04:18:29 PM
We will soon know if A68A fits. :)
Title: Re: Antarctic Icebergs
Post by: FredBear on January 23, 2020, 04:22:22 AM
Looking at    arctic.io   antarctic-true color for 19 January:-

In 2019 there are 2 icebergs visible to the 'north-east' of the Antarctic peninsular:-
B15AA  @ long. -40.178, lat. -64.994  (all values approximate)
B16      @ long. -43.930, lat. -62.662
Both icebergs are still moving northward into the south Atlantic now.

In 2020 the northern tip of A68A is @ long. -51.457, lat. -63.473
                 southern end is around @ long. -53.751,  lat. -64.314

It may be that because A68A is more westerly it will get a faster tow northwards than the other 'bergs (if it doesn't ground on any shallow areas). Therefore I expect that A68A will be melting in the South Atlantic this time next year (comments?).
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 23, 2020, 07:34:09 AM
Looking at Tor's map posted above, i think it's entirely possible, Fred.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 23, 2020, 04:37:06 PM
OK! This looks like we are passing.

I'm still cautious. A68A moves slightly differently from the track the bathymetry map implies. I don't trust this Marple layer.
Title: Re: Antarctic Icebergs
Post by: baking on January 23, 2020, 08:02:05 PM
A68A moves slightly differently from the track the bathymetry map implies.

Whoosh!  I think it is easily clearing any obstacles that remain.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on January 23, 2020, 09:10:53 PM
Ice Island A68-A on January 10 [I think] and 20 with a map of islands/peninsula - Sentinel-hub Playground (https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-61.42826064821461&lng=-60.029296875&zoom=5&preset=CUSTOM&layers=B01,B02,B03&maxcc=100&gain=1.0&gamma=1.0&time=2019-07-01%7C2020-01-20&atmFilter=&showDates=true&evalscript=cmV0dXJuIFtCMDMqMi41LEIwMSoxLEIwMioxXQ%3D%3D)
It'd be bad luck to get stuck on one of the named (rocky) islands!
Title: Re: Antarctic Icebergs
Post by: FredBear on January 24, 2020, 09:15:23 PM
Britih Antarctic Survey estimates the thickness of A68A as 190 metres thick, with 30 metres above sea-level, so it only needs 160m. sea depth to float?

https://www.bas.ac.uk/data/our-data/publication/larsen-c-ice-shelf
Title: Re: Antarctic Icebergs
Post by: gerontocrat on January 24, 2020, 10:28:06 PM
Britih Antarctic Survey estimates the thickness of A68A as 190 metres thick, with 30 metres above sea-level, so it only needs 160m. sea depth to float?

https://www.bas.ac.uk/data/our-data/publication/larsen-c-ice-shelf
That is average thickness. The top is flat - the bottom?

Below surface melting was likely uneven, channels funneling incoming warm water etc, and perhaps generally thicker on the land side c.f. the ocean side.. Maybe even big lumps sticking down here and there? Who knows?
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 25, 2020, 06:05:57 AM
Fred, a piece broke off and turned to the side. It's ~220m thick.

Link >> https://forum.arctic-sea-ice.net/index.php/topic,2245.msg241647.html#msg241647
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 25, 2020, 04:42:58 PM
The pivoting goes on.

From 21th to today plus bathymetry map.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 28, 2020, 05:20:49 PM
No, A68A, don't turn left, it's a trap!

Today we see in a nice north/south alignment. :)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on January 30, 2020, 05:11:55 PM
Anyhow, A68A is pivoting around something that's not in the NASA bathymetry map.

Click to play.
Title: Re: Antarctic Icebergs
Post by: baking on January 30, 2020, 06:02:27 PM
A68A is pivoting

Turning just means the currents are pushing on a profile that is off center to the center of mass.  Any iceberg that is much longer than it is wide is going to be subject to this.  It's already turned 360 from when it calved.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 03, 2020, 05:02:13 PM
I think it's taking the left turn - right into the fishnet where a grounding is likely (IMHO).

Click to play
Title: Re: Antarctic Icebergs
Post by: gerontocrat on February 05, 2020, 08:50:47 PM
The Beeb has something to say about A-68 & a couple of others

https://www.bbc.co.uk/news/science-environment-51389690
World's biggest iceberg makes a run for it
Quote
The world's biggest iceberg is about to enter the open ocean.

A68, a colossus that broke free from the Antarctic in 2017, has pushed so far north it is now at the limit of the continent's perennial sea-ice.

When it calved, the berg had an area close to 6,000 sq km (2,300 sq mi) and has lost very little of its bulk over the past two and a half years.

But scientists say A68 will struggle to maintain its integrity when it reaches the Southern Ocean's rougher waters. "With a thickness to length ratio akin to five sheets of A4, I am astonished that the ocean waves haven't already made ice cubes out of A68," said Prof Adrian Luckman from Swansea University, UK. "If it survives for long as one piece when it moves beyond the edge of the sea-ice, I will be very surprised," he told BBC News.

When it pops above the tip of the peninsula, the massive block should be swept northwards towards the Atlantic - a path researchers refer to as "Iceberg Alley". Many of Antarctica's greatest bergs even make it as far - and beyond - the British Overseas Territory of South Georgia at roughly 54 degrees South.

The biggest ever recorded iceberg in the modern era was the 12,000-sq-km block called B15, which calved from the Ross Ice Shelf in 2000. One of its last remnants, now measuring "just" 200 sq km, is halfway to the South Sandwich Islands, east of South Georgia.

While they keep an eye on A68, scientists are also watching for two other, soon-to-birth bergs.

One is about to come off the front of Pine Island Glacier in the West Antarctic. This will be a little over 300 sq km when it calves. The block is already riven with many cracks. "I expect that the new iceberg will break into many pieces soon after it calves," said Prof Luckman.

The other imminent large berg is forming in eastern Antarctica, on the edge of the Brunt Ice Shelf. This should be about 1,500 sq km - roughly the area of Greater London. The putative berg has garnered a lot of attention because Britain's Halley research station had to be moved to make sure it wasn't in harm's way.

Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 05, 2020, 09:08:35 PM
I might follow Baking and say it's now rotating. The forward movement is curbed as it seems.
Title: Re: Antarctic Icebergs
Post by: FredBear on February 06, 2020, 12:18:52 PM
In 2018 there were 3 big icebergs among the islands just off the north-western tip of the Antarctic Peninsular - the closest was about the length of A68A from A68A's current position. Those 'bergs drifted around for quite a while before they traveled away northwards. I am wondering if A68A is going to get trapped in eddies in this area as the western end seems to have stalled its travels - or has it grounded somewhere along its length?
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 06, 2020, 07:28:37 PM
No pivoting or rotating between yesterday's and today's shot but north-west movement.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 07, 2020, 09:29:29 PM
Using Polar View (https://www.polarview.aq/antarctic) images from Feb. 6 (https://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SDH_20200206T073512_4D03_S_1.final.jpg) and Feb. 7 (https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20200207T072752_9333_S_1.final.jpg) and an approximate outline of A68-A (from one of B_'s posts), I superimposed the outline on size-adjusted copies of the two PolarView images, approximately aligned them and created this gif with ezgif (https://ezgif.com/).  The ice island is moving nearly due northwards (towards the upper left corner).  The lat-long that is closest to A68A is 52ºW-63ºS.
Edit:  I could have aligned the outline with the Feb. 7 image better, but I hope I've not distorted the conclusion:  no stuckness.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 09, 2020, 07:45:54 PM
A68A!

I'm thinking the ice melange accumulating on the west side could be stuff it's losing on the bottom as it's scratching along something hard down there.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 10, 2020, 07:54:36 PM
I've had some fun.  I made screenshots of PolarView (https://www.polarview.aq/antarctic) 'image location plots' for three periods of time, highlighting images from February 6, 8 and 9, and screenshots of each 'image preview' and image description.  I pasted these screenshots onto Word documents, aligned the topography (and size) as best I could, plopped on the 'image previews' and date info, and a resized and rotated ice island outline, before making this GIF.

Of note: A68-A appears to be headed towards Elephant (https://en.wikipedia.org/wiki/Elephant_Island) (with the trunk) and neighboring islands. Shackleton (https://en.wikipedia.org/wiki/Ernest_Shackleton) was here 104 years ago.
(https://www.dictionary.com/e/wp-content/uploads/2018/04/Kilroy-was-here-300x300.jpg)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 10, 2020, 08:16:10 PM
Nice, Tor! :)

New poll? Will A68A hit Shackleton or the Elephant? ;)
Title: Re: Antarctic Icebergs
Post by: baking on February 11, 2020, 05:33:39 AM
Nice, Tor! :)

New poll? Will A68A hit Shackleton or the Elephant? ;)
I will bet any amount of money it won't hit Shackleton.  He's been dead since 1922. ;)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 11, 2020, 04:35:32 PM
Yeah, i regret not naming my cat after him, Baking. ;)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 11, 2020, 04:37:04 PM
A68A update. We had multiple cloud-free days in a row! <3
Title: Re: Antarctic Icebergs
Post by: gerontocrat on February 11, 2020, 08:51:34 PM
The Chill Factor
From what I have read on AbruptSLR's thread, and elsewhere, of significance is the chill factor. 5000 sq km of very cold ice slowly thawing and chilling a lot of surface water and the air at somewhat low latitudes. Must be some local weather effects.

Add an Armada of the beasties and you get very cold surface water turning to ice as winter comes, blocking warmer deeper water from the surface which then increases its flow to attack ice shelves & marine terminating glaciers from below.

The shape of things to come?
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 11, 2020, 08:58:55 PM
Oh great. Yet another feedback loop. :-[
Title: Re: Antarctic Icebergs
Post by: gerontocrat on February 11, 2020, 09:08:19 PM
Oh great. Yet another feedback loop. :-[
A good many studies are saying this is happening now, though due to increased submarine & surface melting, including preliminary results from the project that dug a hole in Thwaites Glacier at the grounding line.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 13, 2020, 05:55:25 PM
Yesterday's Sentinel 3 was too cloudy to include.

I think A68A is still losing mass on the bottom, this bright blue ice on its westside isn't going away. It should though, this is warmer water up here in the north. Therefore i assume it's getting replenishment from the bottom.
Title: Re: Antarctic Icebergs
Post by: Stephan on February 15, 2020, 08:37:31 PM
My "pet Iceberg" B-22 in Amundsen Sea (NW of Thwaites Gl.) is on the move again. In the last two weeks it moved by approx. 1.5 km in WNW direction (identified on its S edge). A full evaluation of its movement (at all edges of B-22) is not possible, because the latest Sentinel picture is partly cloudy.
Anyway, this WNW movement increases the area of open water between it and the ice mélange further south. Sea ice in that area also slowly erodes, but this erosion process is much too slow to reach Thwaites Ice Tongue in this fading austral summer.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 17, 2020, 08:28:38 PM
I changed the color scheme (before it was true color, now it's RGB (17,5,2)). I think this one makes ice/snow and clouds more distinguishable.

Next A68A GIF will include Shackleton and Elephant Island i guess. We are coming close.

We lost the mushy stuff.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 17, 2020, 08:51:05 PM
The bigger picture.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 21, 2020, 10:02:58 AM
Looks like A68A bumped into something.

In today's SAR picture, you can see new small icebergs.

The GIF is showing yesterday's position with bathymetry.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 21, 2020, 04:01:46 PM
Polar View (https://www.polarview.aq/antarctic) image from February 20 (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_202002/S1A_EW_GRDM_1SSH_20200220T231128_E3AE_S_1.8bit.jp2) - two views (11% and 100% enlargement ["en-small-ment"].  11% view includes Elephant Island (etc.).  100% view is 'close up' of the 'calving'.  I agree it probably hit something.  GIF's bathymetry map from Researchgate (https://www.researchgate.net/figure/Map-showing-the-core-location-fronts-of-the-ocean-current-system-and-bathymetric_fig6_249868689).
Title: Re: Antarctic Icebergs
Post by: baking on February 21, 2020, 04:12:25 PM
Looks like A68A bumped into something.
A two and a half year old iceberg can break apart without bumping into anything.  Bathymetry without depth measurements isn't really bathymetry.  I doubt there is anything at that location shallow enough to cause a grounding.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 21, 2020, 05:20:27 PM
Baking, your opinion, your knowledge is very valuable to me.

But here i'm pretty sure you are wrong. It's snaking along this underwater mountain for weeks and months now. It's amazingly obvious to me that it had a big say in the route the iceburg was taking.

Of course, you are right the iceberg can lose parts at any time, but look at this debris. It's not just one part breaking up randomly. It's multiple parts as if it hit something.

Quote
Bathymetry without depth measurements isn't really bathymetry

Could you elaborate on that one, please? Not sure i understand. Is the NASA bathymetry map wrong?
Title: Re: Antarctic Icebergs
Post by: baking on February 21, 2020, 11:55:15 PM
Could you elaborate on that one, please? Not sure i understand. Is the NASA bathymetry map wrong?
It's not wrong, it's just not labeled with any depth measurements.  The area where the break-off occurred was in water more than 800 meters deep.  There is no way that any part of the iceberg is much deeper than 300 meters, or it never would have left the shelf.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 22, 2020, 08:05:48 AM
Yes, A68A is thinner than 300m. According to turned over icebergs it lost it's rather 200-250 meters thick. (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg241647.html#msg241647)

And you are also right, the waters there are deeper in the east. But on it's western side, where the breakoff occurred there is an underwater mountain in the map.

How do you rule out that it can have peaks that are, say 200m below the surface?

Sorry, Baking, i honestly don't understand where you are coming from. I clearly see an underwater mountain in the bathymetry map and really don't understand your opposition.

Given the track the iceberg took, the alignment if the bathymetry map must be wrong, but only by a smidgeon. If you move the bathymetry map only a little to the right, all the movement of A68A makes total sense.

Title: Re: Antarctic Icebergs
Post by: baking on February 22, 2020, 03:49:45 PM
How do you rule out that it can have peaks that are, say 200m below the surface?
Unless I completely misunderstand how bathymetry charts work, when it says 800 meters or more deep, that is what I assume.  If there is a peak, it is still 800 meters or more deep, not 200.  Yes if you move the map a little it will be shallower, but that isn't where the iceberg is.  Find a single chart with depth measurements that supports your conclusion.  I cannot.

Bathymetry maps are designed for sailors who might want to stay away from shallow water or for fishing boats who don't want to lose their nets on underwater formations.  Or maybe even submarines.  If a chart says 800 meters or deep there isn't an asterisk that says "on average" or some such nonsense.  The users of those charts want to know the minimum depth in the area.  That is their primary purpose.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 22, 2020, 04:03:58 PM
Baking, thanks for your answer.

Here is a bathymetry map with a deepness scale (we don't have that with the NASA Blue Marple layer on EO-Browser). The track of the iceburg was following that red dotted line (ocean current) quite accurately. And this map claims 0-250m water depth for the western side of A68A. This fits my theory quite well IMHO.

(https://www.researchgate.net/profile/Michael_Meredith2/publication/314024970/figure/fig1/AS:482987130265601@1492164513787/Bathymetry-of-the-Antarctic-Peninsula-shelf-with-selected-place-names-marked-Also-shown.png)
Title: Re: Antarctic Icebergs
Post by: baking on February 22, 2020, 04:53:33 PM
Unfortunately, the iceberg is well off that map so it is useless.  The map I used is below.

EDIT:  Added bonus, the map below uses the same projection as PolarView so you only need to scale the images to overlay them.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 22, 2020, 05:06:04 PM
Baking, i saw this map when i googled bathymetry maps. I dismissed it because the 0-400m scale tells us absolutely nothing since the iceberg wouldn't go that deep, even if we assume maximum thickness.
Title: Re: Antarctic Icebergs
Post by: oren on February 22, 2020, 05:29:14 PM
Interesting argument.
Baking and BL, are you able to put the iceberg's contour overlaid on any of these maps? I'm afraid I am clueless as to its current location.
Title: Re: Antarctic Icebergs
Post by: baking on February 22, 2020, 06:21:40 PM
Interesting argument.
Baking and BL, are you able to put the iceberg's contour overlaid on any of these maps? I'm afraid I am clueless as to its current location.
It is a huge PITA to scale these maps, but here it is on the day of the break-off.  The point in question is the Northwestern corner.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 22, 2020, 06:30:41 PM
are you able to put the iceberg's contour overlaid on any of these maps

Hell no!  ;D

Just tried my Gimp luck. It's not my lucky day i guess.

I will try again, but no guarantee.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 22, 2020, 06:34:37 PM
Just curious if I'm on "Ignore", 'cause my GIF in Post 201 (above) (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg250668.html#msg250668) attempted to overlay a ice island PolarView image with a 'bathymetry' map (albeit there are better maps to be had - I just didn't find one).
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 22, 2020, 06:36:32 PM
Could you do it with the map i provided above, Tor?
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 22, 2020, 06:56:51 PM
I'd do it on Baking's map too, but I don't have the technology at home (same map projection, per Baking). 

I also want to compare ice island shape 'before' and 'after'.  The February 21 PolarView image shows very distinct edges.  Attempting to do this with the Feb. 20 image suggested smaller calvings in other areas than the obvious one (forward left corner), but that image doesn't have such sharp edges delineated.  Also, comparing 3 or 4 PolarView images in a GIF might suggest the ice island's movement was 'adjusted' by [what I'm convinced was] the impact with a seamount (or shoal). 

A 100 m deep (shallow) rock would not affect the navigation of any boat, I would think, so not a big issue for shipping concerns, not that there is any 'shipping' in these waters...
Title: Re: Antarctic Icebergs
Post by: baking on February 22, 2020, 07:07:04 PM
Just curious if I'm on "Ignore", 'cause my GIF in Post 201 (above) (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg250668.html#msg250668) attempted to overlay a ice island PolarView image with a 'bathymetry' map (albeit there are better maps to be had - I just didn't find one).
Different projections, not triangulated, the scale looked off from what I had done on my own, and no depth measurements.  In short, I didn't trust it and it provided no new information.  Sorry.
Title: Re: Antarctic Icebergs
Post by: Shared Humanity on February 22, 2020, 07:18:04 PM
Odd we can have such a contentious discussion about something that is just the "tip of an iceberg".  ;)
Title: Re: Antarctic Icebergs
Post by: baking on February 22, 2020, 07:27:38 PM
Could you do it with the map i provided above, Tor?
If you really must do it with that projection, at least use the map below which extends to the area where the iceberg actually is and has more detailed bathymetry.

But you are going to need to scale it AND rotate it and it will STILL be wrong because of the different projection.  You will however get the same result as I did.

Kavanaugh 2015 "Effect of continental shelf canyons on phytoplankton biomass and community composition along the western Antarctic Peninsula"
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 22, 2020, 07:50:13 PM
+1!

This one is better!
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 22, 2020, 07:54:43 PM
Thanks for saying , Baking. 

I agree with the 'different projections' issue, however I wonder if scale makes it somewhat less an issue - but better to use the same map projection, for sure. 

As to triangulation, the two islands show on both map and image, and were aligned on a 3x enlargement of the images, albeit the map had very blurry island corners then, and I'll agree the triangulation points (island locations not 'surrounding' the iceberg location) was less then ideal.  I think I should use a screen print of the PolarView map that shows 'all' the image locations to have many more points to overlap a bathymetry map.

Better, the red ice island outline, also placed on the 3x enlargement, was drawn on a full-computer-screen-width ice island image (from a week ago), and at the size reduction in the final, the differences are a pixel here and there.   
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 22, 2020, 09:23:01 PM
Nautical chart of South Shetland Islands (http://fishing-app.gpsnauticalcharts.com/i-boating-fishing-web-app/fishing-marine-charts-navigation.html?title=South+Shetland+Islands+and+Bransfield+Strait+boating+app#8/-61.377/-54.988) (including Elephant Island)

That "364" spot looks to be about where I place the "point of contact".  What are the units? Feet
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 22, 2020, 09:29:03 PM
There you have it, folks. 128 meters is shallow enough for my theory! \o/  8)
Title: Re: Antarctic Icebergs
Post by: baking on February 22, 2020, 10:34:03 PM
Or fathoms.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 22, 2020, 11:38:19 PM
Baking,
I wondered too, so I searched the website with the nautical map and found (and provided a screen print above) the scale.  Apparently you can purchase the map with the scale in "metres", feet or fathoms.
Title: Re: Antarctic Icebergs
Post by: baking on February 23, 2020, 12:08:40 AM
Baking,
I wondered too, so I searched the website with the nautical map and found (and provided a screen print above) the scale.  Apparently you can purchase the map with the scale in "metres", feet or fathoms.
No, changing that setting doesn't change the map.
Title: Re: Antarctic Icebergs
Post by: baking on February 23, 2020, 12:17:34 AM
Just keep scrolling, down and to the left, down and to the left . . .
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 23, 2020, 01:50:35 AM
Hmmm,
First, when I click on the three-bars button in the upper left corner, it indicates "feet".  That window indicates one can purchase the map in meters, fathoms or feet.  Yes, changing the units drop-down box and clicking "Apply" doesn't change the numbers on the map.

Second, when I scroll the linked map over to New Zealand (or England/France), I note near-shore contours of "98.4" and "164".  These, if in feet, convert to 30 m and 50 m.  But who's to say one part of the world map uses the same scale as another?  (But it is suggestive!)  Some detailed areas of the map show no contours; around Elephant Island there are contours in even thousands, and one at "200".  Around Germany I identified a contour at "65.6" which, if in feet, converts to 20 m.

Scrolling on what gives that paper, Baking?  (Scrolling the map down takes me to mid-Antarctica [and no further], and scrolling left takes me around the world until I'm dizzy.)

Title: Re: Antarctic Icebergs
Post by: baking on February 23, 2020, 05:58:01 AM
Scrolling on what gives that paper, Baking?  (Scrolling the map down takes me to mid-Antarctica [and no further], and scrolling left takes me around the world until I'm dizzy.)

Just follow the East coast of the Antarctic Peninsula.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 23, 2020, 06:56:09 AM
Thanks, Baking; found it!  It seems you have to scroll at the 'right' enlargement to see 'the paper'  The two named islands (Brabant and Adelaide) are on the west side of the Antarctic Peninsula, west (and south) of the area we're interested in.  It does make things confusing, given that water depths are clearly in feet elsewhere.  The area covered by that 'paper' is tiny compared to the world which the map covers.
Title: Re: Antarctic Icebergs
Post by: baking on February 23, 2020, 04:17:05 PM
clearly NOT in feet elsewhere.
FTFY
Title: Re: Antarctic Icebergs
Post by: baking on February 23, 2020, 04:33:26 PM
Look at the shallows surrounding Bransfield Island.  Using standard chartmaking practice, depths less than ten fathoms are shown as fathomsfeet.  E.g. 74 is 7 fathoms and 4 feet, 32 is 3 fathoms and 2 feet, and even 02 which is 0 fathoms and 2 feet.  This is the only time feet are used to show depth on this chart.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 23, 2020, 11:21:12 PM
Thank you, Baking - excellent evidence of fathoms being used, there (and even just NE of d'Urville I.).  This area that includes fathom depths is in a box with a "(see Note-POSITIONS) 225" associated with it.  The Elephant Island area is not in this box.  Just below the right corner of this box is some information about high tides and low tides, duplicated below. (it includes a "bay" which wouldn't normally have any 'above 0' heights; obviously the islands would, but the chart is about tides.)

Please explain the "98.4", "164" and "65.6" contours referenced in Reply #227 (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg250891.html#msg250891)!

And why would A68-A have a calving event right above a seamount whose peak was significantly below the bottom of the ice island?
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 23, 2020, 11:27:12 PM
Here's another information box, identifying tides in meters, whereas the previous one was in feet.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 23, 2020, 11:39:20 PM
Near the South Orkney Islands is an explanation box that includes "Soundings in fathoms" (etc.) but there is a little area in blue with a "656.2" contour. 656.2 feet just happens to equal 200.01 m.

Does anybody know what that pop-up box in upper left corner means? "DEPARE (656.17 ft - 3280.84 ft) [Depth area]" might be associated with areas in blue.  (656.17 feet is 200.000616 meters.  3280.84 is 1000 meters.)
Title: Re: Antarctic Icebergs
Post by: uniquorn on February 23, 2020, 11:54:24 PM
https://www.gmrt.org/GMRTMapTool/sp/
may be helpful, zoom in and hover over location, lat/lon/elevation bottom left
Title: Re: Antarctic Icebergs
Post by: baking on February 24, 2020, 02:53:27 AM
Please explain the "98.4", "164" and "65.6" contours referenced in Reply #227 (https://forum.arctic-sea-ice.net/index.php/topic,2245.msg250891.html#msg250891)!

And why would A68-A have a calving event right above a seamount whose peak was significantly below the bottom of the ice island?
I was not the person who found this website.  It is quite bizarre and I can't explain why they do what they do.  I'm only referencing the depth soundings on this particular source map where we have multiple sources for the bathymetry that agree with the units being fathoms.

I agree there is an underwater peak.  I have posted an image of the peak in a more detailed map shown in my GIF, but as I have said repeatedly:

1.  The peak is too deep to have caused a collision with the Iceberg,

AND

2.  The peak is too far South and is NOT at the site of the break-off.

I explained that the iceberg is 2 and a half years old and will certainly continue to have calving events at any time.  I think it is up to you guys to explain why you think that a peak that is clearly too deep and not even at the location of the supposed collision could be the cause.

I know you guys are stubborn, but this is really too much.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on February 25, 2020, 02:54:16 PM
Below is a more recent bathymetry map as part of a GIF [click required], cobbled together from here (https://webapp-srv1a.awi.de/eBathy/int905/contour_comp_int907_1.jpg) and here (https://webapp-srv1a.awi.de/eBathy/int905/contour_comp_int907_2.jpg).  (Reference site: here (https://apps3.awi.de/eBathy/int905/int905.html).)   Contours are in meters (every 100 to 500, then by 1000s).  Everything in red (circles, arrows, names, depths) were added by me.  A couple spot depths are included to show the contour labels are accurate.  There were no spot depths on the map that included the area of the seamount (alas!); it was just an example of the finished map, or something:
(https://webapp-srv1a.awi.de/eBathy/int905/screenshot3b.jpg)

The seamount's peak is apparently less than 300 meters below the surface.  Could the ice island have hit it?  At approximately 300 meters thic (https://www.sciencealert.com/antarctica-iceberg-a68-location-map-animation-one-year-on-2018-7)k, the seamount's peak would need to be about 270 meters below the surface, so "maybe".  Was the iceberg 'next to' the seamount when it calved?  The GIF below has PolarView images from February 19 and 20 superimposed on the map, pinned by the top of Clarence Island and a peninsula on Jonesville Island (both identified with little red arrows).  The map and images are set to different projections, so there will be distortion.  Is the distortion little enough so that that this demonstrates Baking's contention that the calving shown on February 20 (with a little circle around the main calving) was not due to a collision or is the distortion enough to leave open my hypothesis there was?
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 25, 2020, 03:12:33 PM
Whatever the answer to this question is, this is great work, Tor. Thanks a million! :)

Now i'm eager to see Baking commenting.
Title: Re: Antarctic Icebergs
Post by: baking on February 25, 2020, 04:16:03 PM
OK, you've got one source that says 300 meters, everybody else says closer to 400 but fine.  One problem with your theory is that the iceberg passed over large areas previously that were shallower than 300 meters and only encountered grounding at depths less than 200 meters.

Also you are still combining a Stereographic projection and a Mercator projection.  Probably better to estimate the position in latitude and longitude.

Edit:  Pretty sure those are two different peaks.  The deeper one is further east.  They can be seen in my GIF reproduced below:
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 25, 2020, 04:37:43 PM
My two pence:

In the GIF provided by Tor, you can see a grounded iceberg in supposedly deeper waters.

Also, Baking just confirmed there are differences between different bathymetry maps.

These two points make me trusting these bathymetry maps even less.
Title: Re: Antarctic Icebergs
Post by: baking on February 25, 2020, 05:38:18 PM
In the GIF provided by Tor, you can see a grounded iceberg in supposedly deeper waters.
Deeper than what?  That iceberg is in the 200-300 meter range of shallow water.  A68A is in much deeper water near a few peaks.  Look at my GIF above.

Also, you don't know where that other iceberg came from or where it has been.  It could be much thicker than A68A.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 25, 2020, 06:24:22 PM
Baking, you are right. I got that wrong.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 26, 2020, 04:28:35 PM
Will that be a bump or a miss? I take bets, ladies and gentlemen.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 26, 2020, 04:41:36 PM
Today's position plus NASA Blue Marple bathymetry.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on February 28, 2020, 09:10:28 PM
Today's position of A68A.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 02, 2020, 05:16:38 PM
27th to today, A68A is taking a right turn...
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 02, 2020, 05:18:09 PM
... incidentally following the bathymetry. (i'm saying this even though i can hear you, Baking, opposing ;) )
Title: Re: Antarctic Icebergs
Post by: FredBear on March 06, 2020, 01:58:03 PM
I see that B15AA and B16 are melting/breaking up fast, B16 too small for tracking after 28/2/2020.
Locations @ 28/02/2020:-
B15AA      53°07'S   30°35'W
B16          58°29'S   22°52'W

The positions given for a couple of other moving icebergs of current interest:-
A68A        62°37'S    53°14'W
D28          67°18'S    72°12'E

Source:- https://www.natice.noaa.gov/pub/icebergs/Iceberg_Tabular.pdf
Title: Re: Antarctic Icebergs
Post by: Stephan on March 06, 2020, 03:54:56 PM
Could you please help the newbies here to tell a short history of B15AA and B16 - when did they calve and which glacier/ice shelf did they come from?

Thank you.
Title: Re: Antarctic Icebergs
Post by: baking on March 06, 2020, 04:52:26 PM
https://earthsky.org/earth/iceberg-b15z-antarctica-ross-ice-shelf

B-15 through B-18 broke off from the Ross Ice Shelf in 2000.  B-15 went more than half-way around Antarctica (all the way around East Antarctica) before exiting the Wendell Sea near the Antarctic Peninsula.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 06, 2020, 05:40:28 PM
A68A update.
Title: Re: Antarctic Icebergs
Post by: Stephan on March 06, 2020, 10:49:53 PM
B-15 through B-18 broke off from the Ross Ice Shelf in 2000.  B-15 went more than half-way around Antarctica (all the way around East Antarctica) before exiting the Wendell Sea near the Antarctic Peninsula.

Thank you baking.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 09, 2020, 09:40:02 PM
A68A update.

If it was bumping against this underwater mountain, we should see some debris surrounding the iceburg. There is no debris. I would assume a current has it in its fangs.
Title: Re: Antarctic Icebergs
Post by: baking on March 10, 2020, 05:54:47 AM
There is no debris.
There has been a lot of debris lately.  The whole sea around it, especially down current, has been littered with small icebergs, too numerous to count.  There were a couple of slightly large ones obviously recently calved a few days ago.  I think the most likely explanation is that it is getting caught in stronger currents and is very slowly disintegrating and there is no sign that it is concentrated in any one location.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 13, 2020, 04:22:06 PM
Agreed, Baking! Once in a while you can see some calvings, but they are mini and there is no apparent pattern.

Here is the new update movie.
Title: Re: Antarctic Icebergs
Post by: Stephan on March 17, 2020, 10:29:37 PM
As a follow-up to my reply #140 I used the opportunity to analyse the movement of my "pet iceberg" B-22 northwest of Thwaites Ice Tongue.

I chose five different corners (see picture) and looked at the changes of their positions between Jan 22 and March 15, 2020:

A = 3.5 km, N direction of movement
B = 3.5 km, NE direction of movement
C = 1.1 km, ESE direction of movement
D = 1.7 km, WNW direction of movement
E = 2.0 km, NNW direction of movement

This implies a general N movement with a clockwise turn around a centre close to point C. The highest rates are equivalent to an averaged daily movement of 60-65 m.
In the detailed analysis I found some very minor calvings off of the edge from the western side of B-22.

See attached picture.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 20, 2020, 06:34:20 PM
A68A drift update.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 25, 2020, 02:53:14 PM
A68A drift update.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 25, 2020, 02:59:24 PM
There was a calving in the north-west facing side. Not a big one, but way bigger than recent ones.
Title: Re: Antarctic Icebergs
Post by: oren on March 26, 2020, 04:35:51 AM
Thanks for these updates blumenkraft.
Title: Re: Antarctic Icebergs
Post by: FredBear on March 26, 2020, 06:11:53 AM
A68A still drifting northwards, notice the sea ice (the "goodbye waves") drifting up to the south-east edge now.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on March 26, 2020, 07:52:42 AM
Very welcome, Oren. :)

'Goodbye wave' is nicely said, Fred. I like that.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on April 02, 2020, 05:48:25 PM
Annamaria Luongo
@annamaria_84 on Twitter

Quote
The drift of A68 #iceberg, #Antarctica  🇦🇶 continues.
Images acquired by #Sentinel3  🇪🇺🛰️between December 2019 - March2020

Link >> https://twitter.com/annamaria_84/status/1244749026416885760

GIF at link.

I uploaded a mirror here >> https://imgur.com/z8UozKs
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on April 02, 2020, 09:54:48 PM
That GIF is so cool!  Who says an ice island cannot turn on a dime (that's the US's smallest coin, worth ten cents [a 1¢ coin, usually called a 'penny', and a 5¢ 'nickel' are physically larger (https://www.usmint.gov/learn/coin-and-medal-programs/coin-specifications)]).
Title: Re: Antarctic Icebergs
Post by: FredBear on April 05, 2020, 02:42:42 PM

The positions given for a couple of moving icebergs of current interest:-
Locations @ 02/28/2020:-        ->        @04/03/2020
A68A        62°37'S    53°14'W.  ->         61°17'S    50°34'W
D28          67°18'S    72°12'E.   ->        67°01'S    74°04'E. (This is marked as grounded!)

From:-
https://www.natice.noaa.gov/pub/icebergs/Iceberg_Tabular.pdf
Title: Re: Antarctic Icebergs
Post by: Tealight on April 06, 2020, 02:50:08 AM
Ever since A68A left the Antarctic Peninsula behind it moved along the 0C line and with a common North-West wind it gets 3-5C warm. This air is also very humid, more typical to temperate regions than polar air.

The iceberg might never experience a freezing winter again. 50km further North the water is +1C and 250km North it is +4C. At a speed of 30-40km/week it doesn't take to long to get there. All depends on the direction it takes.

The gif is 3 days out for the currently most northern point of the iceberg at 60.5S ,50W.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on April 06, 2020, 07:38:48 AM
Hey, Tealight! Nice to see you around! :)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on April 07, 2020, 04:50:19 PM
Who says an ice island cannot turn on a dime.

It did it again! A68A update.

(GIF showing movement from 25.03 to today)
Title: Re: Antarctic Icebergs
Post by: interstitial on April 23, 2020, 12:07:48 PM
A big chunk broke off of A68.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on April 23, 2020, 12:26:52 PM
You beat me to it, Interstitial!  :D

Here is the GIF with bathymetry (from 07.04. to 22.04.). I had to switch satellites mid-GIF because the sun went off.
Title: Re: Antarctic Icebergs
Post by: interstitial on April 23, 2020, 01:05:25 PM
Yeah but you took the time to make a better presentation of it.  :D
Title: Re: Antarctic Icebergs
Post by: blumenkraft on April 23, 2020, 01:35:01 PM
Thanks! :)
Title: Re: Antarctic Icebergs
Post by: blumenkraft on April 28, 2020, 07:35:50 PM
Between the 23th and today, A68A almost made no way at all. The sea ice is catching up with it.
Title: Re: Antarctic Icebergs
Post by: bairgon on April 29, 2020, 08:21:50 AM
Interesting that the recent calving made so much progress but the main body did not.

Might imply that the main body is grounding; but I would expect the calving to be as deep as the main body. Bathymetry implies that any ridge for grounding is to the north, unless the calving has slipped through a gap.

The calving, being smaller, may be more influenced by wind and current and therefore moved more.
Title: Re: Antarctic Icebergs
Post by: baking on April 29, 2020, 05:40:19 PM
Calving can produce an enormous amount of explosive energy.  Simple physics says that in order for that potential energy to transformed to kinetic energy while conserving momentum, the smaller object must move at a much faster speed than the larger one.  You also see the larger iceberg turning counterclockwise away from the smaller iceberg which would also be consistent.  Obviously a lot of energy would be absorbed by the water, but I think the underlying physics would still dictate the gross motion we are seeing.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on May 07, 2020, 01:15:08 PM
A68A is stuck. This is a GIF showing movement between 29.04 and 06.05.
Title: Re: Antarctic Icebergs
Post by: FredBear on May 09, 2020, 02:37:04 PM
The positions given for a couple of moving icebergs of current interest:-
Locations @ 02/28/2020:-        ->        @04/03/2020               ->08/05/2020
A68A        62°37'S    53°14'W.  ->         61°17'S    50°34'W      ->60°32'S    50°21'W
D28          67°18'S    72°12'E.   ->        67°01'S    74°04'E.      ->66°22'S    71°12'E.

A68A almost stopped moving since A68C broke off - grounding?
D28 is now moving westwards and rotating anticlockwise more rapidly.

From:-
https://www.natice.noaa.gov/pub/icebergs/Iceberg_Tabular.pdf
Title: Re: Antarctic Icebergs
Post by: blumenkraft on May 09, 2020, 04:51:43 PM
grounding?

Well, it moves slightly alongside this underwater mountain. I think it's bouncing off of it, but it's not grounded for how i see it.
Title: Re: Antarctic Icebergs
Post by: FredBear on May 10, 2020, 01:49:21 AM
I have been using an arbitrary 5 week series to show movement:-
Locations @ 02/28/2020:-        ->        @04/03/2020               ->08/05/2020
A68A        62°37'S    53°14'W.  ->         61°17'S    50°34'W      ->60°32'S    50°21'W
But 1 week before the location was given as  60°33'S    50°22'W - only 1' change in the following week. Also A68C calved about time so that may have influenced the main 'berg's recorded position a little?
I see a slight clockwise rotation lately - perhaps I should have said "grounding? (slightly?)"
Title: Re: Antarctic Icebergs
Post by: blumenkraft on May 10, 2020, 08:11:02 PM
Looks like A68C made it over the underwater mountain. A68A still stuck behind it.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on May 21, 2020, 09:26:18 AM
A68C very much on the move. A68A still snaking along the underwater mountain in north-east direction.
Title: Re: Antarctic Icebergs
Post by: oren on May 23, 2020, 05:11:27 PM
Thanks for the updates BL.
It took me a few seconds to realize the aspect of the last animation is reversed from the previous one.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on May 23, 2020, 05:54:42 PM
Welcome, Oren.  :)

Yes, this last one is the JPSS satellite via RAMMB-SLIDER (Day&Night band).

The radar shots via Sentinel are not delivering updates regularly enough.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on May 30, 2020, 02:18:03 PM
Interesting, A68C came back south.

A68A slowly in northeast direction still.
Title: Re: Antarctic Icebergs
Post by: FredBear on May 30, 2020, 06:13:39 PM
A68C has moved relatively much more east than south in the last week (but latitude/longitude angles are not equivalent to distances!):-

Locations @ 05/22/2020:-        ->        @05/29/2020               
A68A        60°24'S    49°42'W.  ->         60°13'S    49°17'W     
A68C        59°28'S    50°31'W.  ->         59°38'S    49°14'W
Title: Re: Antarctic Icebergs
Post by: blumenkraft on June 03, 2020, 05:27:33 PM
29.05. vs. 03.06.

A68A is making it over the underwater mountain as it seems.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on June 10, 2020, 02:32:22 PM
Almost.
Title: Re: Antarctic Icebergs
Post by: FredBear on June 13, 2020, 04:14:50 AM

The positions given for a couple of moving icebergs of current interest:-
Locations @ 02/28/2020:-     ->   @04/03/2020         ->08/05/2020              ->12/06/2020
A68A    62°37'S    53°14'W.  -> 61°17'S    50°34'W   ->60°32'S    50°21'W   -> 59°57'S 48°55'W
A68C                                                    (22/05/2020   -> 59°57'S 48°55'W)-> 59°26'S 47°21'W
D28      67°18'S    72°12'E.   ->   67°01'S    74°04'E. ->66°22'S    71°12'E.  ->66°40'S  64°41'E.

A68A moving more slowly recently, A68C is smaller and moved around much more since it broke off.
D28 has started moving westward relatively rapidly (at last!) with a little southwards movement - probably rotating(?) (but arctic io pictures have disappeared for me so I am now working blind - anyone know how to get those lovely historical records back?).

Title: Re: Antarctic Icebergs
Post by: blumenkraft on June 18, 2020, 08:33:46 PM
Soon!
Title: Re: Antarctic Icebergs
Post by: interstitial on June 21, 2020, 10:16:13 PM
On 6/20  A68a was north of 60 degrees south on worldview. I think that puts it over the underwater ridge but I am not sure because IDK where the ridge is exactly.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on June 22, 2020, 06:23:21 PM
That seems about right, Interstitial. :)

This is today's radar imagery.

Click to play.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on June 24, 2020, 02:46:31 PM
This will be the last one of A68A with bathymetry for a while. Given that it will drift further north, it can now float freely for some time to come. Bon voyage.

Click to play.
Title: Re: Antarctic Icebergs
Post by: interstitial on June 25, 2020, 09:16:53 PM
https://www.newsweek.com/iceberg-larsen-antarctica-ice-shelf-1513096 (https://www.newsweek.com/iceberg-larsen-antarctica-ice-shelf-1513096)


Iceberg the size of Chicago is set to brake off of Larsen D ice shelf. It also could take some very old fast ice with it.
It could also destabilize Larsen C more IMO.
Title: Re: Antarctic Icebergs
Post by: Eco-Author on June 25, 2020, 10:02:31 PM
thanks!!  need to bounce around this site more often!!  Great call! <3
Title: Re: Antarctic Icebergs
Post by: blumenkraft on June 26, 2020, 08:39:06 AM
Boom!
Title: Re: Antarctic Icebergs
Post by: paolo on June 26, 2020, 11:47:33 AM
Another image of calving
For the surface of the larger iceberg I did not take into account the fast ice attached.
Title: Re: Antarctic Icebergs
Post by: interstitial on June 26, 2020, 10:22:54 PM
Another image of calving
For the surface of the larger iceberg I did not take into account the fast ice attached.
1000000 years? IDK that is probably an Island or will be when the ice around it melts.
Title: Re: Antarctic Icebergs
Post by: interstitial on June 26, 2020, 10:26:56 PM
The pinning point is the island on the lower right.
Title: Re: Antarctic Icebergs
Post by: paolo on June 27, 2020, 08:21:13 AM
Interstitial,
I may have expressed myself a bit ambiguously.
Of course, he's an ice raise and not an ice rumple, and is an island.

But the my question was, how long will the ice shelf be there and use it as a pinning point?

PS: thanks for the map, always useful
Title: Re: Antarctic Icebergs
Post by: blumenkraft on June 27, 2020, 05:50:31 PM
So what's the name of the new one? A69?

Here is the progress A68A and A68C made. The sea ice is catching up again. Click to play.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on July 04, 2020, 07:07:59 PM
A68A update.

Note how the sea ice totally caught up with the iceburg. A68C made a good way south north-west.
Title: Re: Antarctic Icebergs
Post by: interstitial on July 05, 2020, 12:56:59 AM
A68A looks like it moved back a bit. Maybe it is still interacting with that ridge.
Title: Re: Antarctic Icebergs
Post by: FredBear on July 05, 2020, 04:01:23 AM
From the locations of the icebergs A68C has moved 1° north in a week, 32' east as well,
but A68A has moved 2' south, 8' east in the same time (to 03 July).
Location of A68C is almost 2° north, 3° east of A68A now.


https://www.natice.noaa.gov/pub/icebergs/Iceberg_Tabular.pdf
Title: Re: Antarctic Icebergs
Post by: blumenkraft on July 05, 2020, 06:18:15 AM
North! Of course. Thanks, Fred. Corrected my post.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on July 05, 2020, 06:26:04 AM
A68A looks like it moved back a bit. Maybe it is still interacting with that ridge.

I have no doubt it is somehow interconnected with it through ocean currents. Not directly over it at the moment though.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on July 13, 2020, 07:36:42 PM
Ladies and gentlemen, the wonder of birth. Meet A68D.
Title: Re: Antarctic Icebergs
Post by: igs on July 13, 2020, 08:43:46 PM
Ladies and gentlemen, the wonder of birth. Meet A68D.

From size it looks more like an abortion [JK]

 ;) ;) ;) ;) ;)

 :D :D :D :D :D
Title: Re: Antarctic Icebergs
Post by: blumenkraft on July 13, 2020, 09:13:24 PM
Well, it's kilometers long, hundreds of meters thick, and kinda heavy. ;)
Title: Re: Antarctic Icebergs
Post by: igs on July 13, 2020, 10:07:36 PM
Well, it's kilometers long, hundreds of meters thick, and kinda heavy. ;)

[JK] means Just Kidding, i thought with all the smilies & smirks it was clear, sorry.

Further just for the sake of it, size of children we see in relation to the size of the parents.

 ;D ;D ;D

My wife calls this kind of kidding [Half Jokes] because a part is true but taken with a good portion of humor just to make fun.
Title: Re: Antarctic Icebergs
Post by: blumenkraft on July 13, 2020, 10:14:21 PM
All good, IGS. No need to be sorry, i was joking as well. Mine was one-tenth of a joke, not even half! ;)
Title: Re: Antarctic Icebergs
Post by: FredBear on July 22, 2020, 02:10:58 AM
       
5 week updated positions given for a couple of moving icebergs of current interest:-
Locations @ 02/28/2020:-     ->08/05/2020              ->12/06/2020           ->17/07/2020
A68A    62°37'S    53°14'W.  ->60°32'S    50°21'W    -> 59°57'S 48°55'W  ->59°30'S 49°13'W
A68C                 (22/05/2020   -> 59°57'S 48°55'W) -> 59°26'S 47°21'W  -> 57°41'S 41°12'W
D28      67°18'S    72°12'E.   ->66°22'S    71°12'E.   ->66°40'S  64°41'E    ->66°35'S  59°59'E

A68A moving more slowly recently (still 0.5° north in 5 weeks, but little in last 4 weeks), A68C is smaller and moved around much more since it broke off, more easterly recently.
D28 has continued moving westward relatively rapidly round the coast (at last!) - probably rotating(?).

arctic io pictures have disappeared for me so I am now working blind - anyone know how to get those lovely historical records back?


Source:-     https://www.natice.noaa.gov/pub/icebergs/Iceberg_Tabular.pdf
Title: Re: Antarctic Icebergs
Post by: blumenkraft on August 16, 2020, 05:28:10 PM
Nice, A68-A coming into sight of Sentinel 3 soon!
Title: Re: Antarctic Icebergs
Post by: grixm on September 02, 2020, 10:35:10 PM
A68-A twirling around in the same spot for the last month and a half.
Title: Re: Antarctic Icebergs
Post by: Tealight on September 08, 2020, 12:31:07 PM
Iceberg A23A has moved significantly over the winter and is not classified as grounded anymore by the National Ice Center. According to their iceberg tables it happened in Week 28 (between 3rd and 10th July). However since then it hasn't moved much.
Title: Re: Antarctic Icebergs
Post by: FredBear on September 09, 2020, 03:00:39 PM
Looked at the locations of two big "grounded" icebergs - they "wriggle" occasionally but have not moved far over many years, unlikely to have floated free yet?

Brunt ice shelf accumulates significant snow on the surface each winter, I don't know whether the "nearby" A23A does too as that could reduce its chances of floating free? Many other icebergs to the south have drifted west and then north over the years but A23A may be towards the centre of the circulation in the Weddell Sea?

There has been more icebergs break off the edges of B22A over the years and it looks more likely to move out and break up than A23A.

The other big 'berg is the grounded D15A which hasn't moved location in this time frame.

Locations @ 29/11/2019:-     ->14/09/2020             
A23A    75°47'S    41°04'W    ->75°36'S    40°12'W   
B22A    73°59'S  109°13'W    -> 73°58'S 109°20'W
D15A                     66°39'S 81°55'E

Source:-     https://www.natice.noaa.gov/pub/icebergs/Iceberg_Tabular.pdf
Title: Re: Antarctic Icebergs
Post by: Stephan on September 11, 2020, 09:38:41 PM
The sun still does not shine at the South Pole, but Amundsen Sea is north and bright enough to allow EOSDIS to make new pictures.

So the first look I took was on my pet iceberg that has lost parts of its SW tip some months ago (details in the Thwaites Gl. thread).

I took the opportunity and evaluated the movement of B-22A between 15. Nov 2019 and 11. Sept 2020.
It moved slowly in NW direction (around 5 km). I checked different places and spots on this iceberg, measured the distance between the two dates and added them into the attached picture. As far as I evaluated there seems to be no turning around of the iceberg.
Title: Re: Antarctic Icebergs
Post by: Stephan on September 12, 2020, 09:08:37 PM
In addition to my post yesterday I examined the area between B-22 and Bear Peninsula which - even during winter - frequently shows open water (probably of polynya type). The last week saw an extension of open waters (orange arrows) into areas that were sea ice covered before.

In addition I discovered the western tip of B-22 that calved off B-22 some months ago. It lies grounded in shallow seas N of Bear Peninsula (circled in yellow). Size, position, shape and texture reveal that this is the "missing part". It might stay there for a while, I will watch it this melting season.

See attached picture.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on September 14, 2020, 09:24:39 PM
Somebody with the name u/b_lumencraft (now, where did I see a name sort of like that before?  ::) :o ;) ) has posted a couple Antarctic Iceberg-related items at  https://www.reddit.com/r/Fans_Of_Hans_Club


For the record, B_ wrote to me: "Reposts to ASIF are of course fine with me."
Title: Re: Antarctic Icebergs
Post by: Tealight on September 20, 2020, 12:30:44 AM
This week A23A moved another 4km. Compared to it's 81km length and 74km width it's not far, but it's also not grounded. Eventually it will reach the deeper parts of the Weddell Gyre.

https://cryospherecomputing.tk/Icebergs
Title: Re: Antarctic Icebergs
Post by: Stephan on September 21, 2020, 10:11:16 PM
Some recent observations around my pet iceberg B-22 in EOSDIS.

One of the icebergs in the mélange S of B-22 trapped behind grounded icebergs (green) was pushed out by strong currents in WNW direction in the last ten days. It is circled in yellow. The NW movement of B-22 over winter maybe has opened a gate that allows further export of icebergs from the mélange into the polynya. We will see...

A rift in the sea ice has formed (marked in broken lines in black). It appeared much earlier than last year (approx. position broken grey lines) and it is approx. 3-6 km further south than previous year.

Open waters from the polynya slowly crawl in SE direction (blue arrows), but some other parts are newly covered by sea ice (red crosses) that were open ten days ago. It is still quite cold there (Climate Reanalyser says something about -15°C today).

It is a very volatile area and its shape changes within days. See attached picture.
Title: Re: Antarctic Icebergs
Post by: Stephan on October 05, 2020, 10:02:22 PM
It looks like B-22 is losing further pieces.
I analysed the latest picture from Sentinel 2 and found a small soon-to-be breaking off iceberg at the Western edge of B-22, circled in orange. The latest calving is marked by a blue arrow. A much older calving (yellow arrow) is still hanging around, it is grounded.

I also detected a new rift (green line) starting in the SW corner and going almost to the centre of B-22. It was absent last year. Is this a first sign of a more fundamental disintegration of my pet iceberg?

See attached picture.
Title: Re: Antarctic Icebergs
Post by: interstitial on October 05, 2020, 11:36:49 PM
It looks like B-22 is losing further pieces.
I analysed the latest picture from Sentinel 2 and found a small soon-to-be breaking off iceberg at the Western edge of B-22, circled in orange. The latest calving is marked by a blue arrow. A much older calving (yellow arrow) is still hanging around, it is grounded.

I also detected a new rift (green line) starting in the SW corner and going almost to the centre of B-22. It was absent last year. Is this a first sign of a more fundamental disintegration of my pet iceberg?

See attached picture.
It probably is getting ready to break up. If not it has moved a few km towards the ocean this winter. A warm current tends to show up on that end of the northern portion of the iceberg so I am expecting some more change this Antarctic melting season.
Title: Re: Antarctic Icebergs
Post by: Tealight on October 12, 2020, 01:56:46 AM
A68A drifts into sub-Antarctic waters. Over the last week its speed was 15km per day northwards.

The northern tip (56.6S,48W) already touches 2-3°C warm edge currents. Maybe this is its last summer as a giant iceberg.
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on October 12, 2020, 05:03:07 AM
I'm curious, Tealight, why the ice island appears to be so close to the ice edge, or whatever that is 'below' the berg's point.

Below, I've rotated and annotated the Polar View (https://www.polarview.aq/antarctic) image-selection screen (selecting a date range to identify only three images - October 9, 2020).  This shows the location and approximate shape of A68-A.  (I moved the scale [It didn't originally cross 30oW; it crossed 50oS, west of Chile].) [click for clearer image]

I then copied the two Preview images that include A68-A (its actual shape), stitched them together (keeping most of the southern image's area, and not perfectly done), annotated it and rotated it to approximate north being up.
Title: Re: Antarctic Icebergs
Post by: APMartie2 on October 13, 2020, 01:05:33 AM
Really nice graphic Tor. I like seeing the big picture portrayal of A68-A out there adrift and its size in relation to S. Georgia Is.

I am a total ASIF lurker. This is one of my favorite sub-forums.
Title: Re: Antarctic Icebergs
Post by: Tealight on October 14, 2020, 02:12:57 AM
I'm curious, Tealight, why the ice island appears to be so close to the ice edge, or whatever that is 'below' the berg's point.

The island, South Orkney as you correctly identified is simply close to the polar front. The warm pacific waters have to squeeze through the drake passage and mix with the cold Antarctic water at that boundary.

Here is a graphic from wikipedia (Drake Passage article)
(https://upload.wikimedia.org/wikipedia/commons/8/87/Drake-Passage_profile_hg.png)
Title: Re: Antarctic Icebergs
Post by: Stephan on November 02, 2020, 10:45:41 PM
Update from my pet iceberg (B-22) in the Amundsen Sea, NW of Thwaites Glacier.

Finally a relatively clear day allowed another inspection of its NW movement. I took Sep 16, 2020 as reference day. Since then B-22 moved around 2 km into NW direction (black arrow).
This movement direction does not open the gateway for the sea ice south of B-22 at the moment. But if this movement will continue for another 13-15 km then the bottleneck (green lines between B-22 and the sea ice as well as between the sea ice and the fast ice south of it) will finally open.
At the moment the gateway is blocked by several grounded smaller icebergs (orange squares).
When this blocking is ended, the flush of sea ice south of B-22 into the open sea will accelerate, which will have a destabilising effect on the fast ice NW of Thwaites ice tongue.

See attached picture.
Title: Re: Antarctic Icebergs
Post by: baking on November 04, 2020, 05:20:52 AM
https://www.bbc.com/news/science-environment-54798031

A68 iceberg on collision path with South Georgia

"The world's biggest iceberg, known as A68a, is bearing down on the British Overseas Territory of South Georgia.

The Antarctic ice giant is a similar size to the South Atlantic island, and there's a strong possibility the berg could now ground and anchor itself offshore of the wildlife haven.

If that happens, it poses a grave threat to local penguins and seals.

The animals' normal foraging routes could be blocked, preventing them from feeding their young properly."
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on November 04, 2020, 03:11:37 PM
I'm reminded of Ernest Shackleton who, with 5 crew, sailed a 22.5' (6.9 m) lifeboat from Elephant Island to South Georgia Island after the sinking of the Endurance in 1915, "one of the greatest boat journeys ever accomplished". (Wikipedia (https://en.wikipedia.org/wiki/Voyage_of_the_James_Caird) offers a fascinating read.)  A-68A was just south of Elephant Island a while back, 1,300 kilometers southwest of South Georgia.
(https://upload.wikimedia.org/wikipedia/commons/thumb/f/f4/James_Caird_en.svg/310px-James_Caird_en.svg.png)

If A-68A does ground on or near South Georgia, it won't climb over the mountains like Shackleton did.  :P
Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on November 05, 2020, 03:10:21 PM
PolarView (https://www.polarview.aq/antarctic) offers some detail of the leading point as of November 4 (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_202011/S1A_EW_GRDM_1SSH_20201104T071812_3917_S_1.8bit.jp2).

Per PolarView (https://www.polarview.aq/antarctic), the finger is about 20 km wide.
Title: Re: Antarctic Icebergs
Post by: Tealight on November 16, 2020, 04:12:06 PM
It's been over two years since A68 calved from Larsen C. Even though it's length hasn't changed it lost a considerable amount of width in various places.

Here is an image with it's current size overlayed on an Sep 2018 image.

Title: Re: Antarctic Icebergs
Post by: Tor Bejnar on November 16, 2020, 06:02:10 PM
Much appreciated, Tealight!
Here's A-68A in yesterday's context. (Yellow 'square' identifies image preview location. South Georgia Island is to the ice island's northeast.)  Polar View (https://www.polarview.aq/antarctic) image dated Nov. 15 (http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_202011/S1B_EW_GRDM_1SDH_20201115T072536_3C15_S_1.8bit.jp2) [click for clearer images]
Title: Re: Antarctic Icebergs
Post by: HapHazard on November 16, 2020, 08:52:04 PM
Totally reminded me of Glove.

(https://i.pinimg.com/600x315/2e/16/c8/2e16c8e915778fe9200f3852b96bb26f.jpg)
Title: Re: Antarctic Icebergs
Post by: Stephan on November 18, 2020, 09:44:58 PM
Referring to my post #327 I give a short update from B-22.
Since Nov 02 it has further moved into WNW-NW direction by approx. 0.6 km.
It seems B-22 has lost some its contact to underwater ridges or pinning points.
If it continues with this speed, it will open up the gateway as defined in post #327 within this melting season.
Title: Re: Antarctic Icebergs
Post by: baking on November 19, 2020, 05:20:55 PM
Referring to my post #327 I give a short update from B-22.
Since Nov 02 it has further moved into WNW-NW direction by approx. 0.6 km.
It seems B-22 has lost some its contact to underwater ridges or pinning points.
If it continues with this speed, it will open up the gateway as defined in post #327 within this melting season.
Freaky, although I expect those larger icebergs will get stuck.
Title: Re: Antarctic Icebergs
Post by: Stephan on November 20, 2020, 04:58:16 PM

Freaky, although I expect those larger icebergs will get stuck.

Thank you for that animation. B-22's moving direction has changed (more N instead of WNW-NW). Maybe also a rotational aspect of its movement is present.

Concerning the larger icebergs, you may be right. Most of the icebergs west of that red longitude line had moved into that area through that gateway in the last years and got stuck on that underwater ridge.
Title: Re: Antarctic Icebergs
Post by: Stephan on November 22, 2020, 04:02:01 PM
Update from Cork, our hero of last melting season.
He lies still grounded, roughly two thirds between SWT and Thwaites Eastern Ice Shelf. I am not sure whether the smaller bergs around him are Cork's calving products.

See attached picture, the smaller inlay shows his position (orange circle).
Title: Re: Antarctic Icebergs
Post by: APMartie2 on November 24, 2020, 12:19:25 AM
Enjoy clicking on to Worldview on a daily basis to check progress of A68-A's movement east towards S. Georgia I. As of today (Nov. 23) my crude measurement indicates it is about 277 km west of the islands NW tip and has moved about 69 km east (w/ slight clockwise spin) from its location on Nov. 7.                           
                                                                                                                                         
Media (BBC) has reported possible doom and gloom for S. Georgia's foraging sea mammals and penguins but to contrary, wonder if a giant ice island might provide some habitat and feeding opportunities where none existed before. Structure often attracts critters. Looked on internet but not able to track down any information regarding this.
Title: Re: Antarctic Icebergs
Post by: APMartie2 on November 24, 2020, 12:51:50 AM
Having a little trouble getting a jpg image to go along with my previous post. Below is link to Worldview image I wanted to post.

https://worldview.earthdata.nasa.gov/?v=-52.35652539267464,-64.24132657418312,-28.200233639142652,-50.93884732616007&t=2020-11-07-T16%3A00%3A00Z&l=Reference_Labels,Reference_Features,Coastlines,VIIRS_NOAA20_CorrectedReflectance_TrueColor,VIIRS_SNPP_CorrectedReflectance_TrueColor,MODIS_Aqua_CorrectedReflectance_TrueColor,MODIS_Terra_CorrectedReflectance_TrueColor
Title: Re: Antarctic Icebergs
Post by: oren on November 24, 2020, 02:11:49 AM
Hi APMartie2, to do that you need to save the image to your device and then upload it as attachment to your post.
Thanks to your link, here's an even better Worlview output, an animation of the past month (made using the video camera icon on WV, optimized on EZgif to reduce size). Click to animate.