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Author Topic: Halley base shut down and new crack in Brunt shelf  (Read 24002 times)

solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #50 on: October 29, 2018, 03:44:56 AM »
Here's a snip from the latest Polarview.  Looks like Chasm 1 has joined up with the Halloween crack, but hard to say for certain.  I find the straightness of the new crack section to be a concern, perhaps a data glitch in that area? Of course we just saw the rectangular bergs.  Even if it is all the way through, it still may not move significantly.  It also looks to me like there is also a crack extension heading to the coast, but perhaps I need to clean my glasses.
Original image 34 mb
https://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SDH_20181027T231436_AC7B_S_1.final.jpg
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solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #51 on: October 30, 2018, 06:25:12 AM »
Okay, so that's two in a row, but it still looks weird.  Original 10 mb
https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20181029T234745_234F_S_1.final.jpg
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solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #52 on: October 30, 2018, 05:29:29 PM »
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iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #53 on: October 30, 2018, 06:03:18 PM »
Here's a view switching between the 7th and the 27th Oct - you can clearly see the crack has extended and checking here https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-75.53564672956175&lng=-26.096477508544922&zoom=13&preset=1_NATURAL_COL0R&layers=B01,B02,B03&maxcc=85&gain=0.4&gamma=1.0&time=2015-01-01%7C2018-10-27&atmFilter=&showDates=true
at the crack tip shows this to be about 1 km over the 20 days.

i think we could be looking at a differently shaped ice shelf before xmas...

solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #54 on: November 05, 2018, 06:57:14 PM »
Very nice animation from July 30, 2016 to Oct 30 2018

https://adrianluckman.wordpress.com/2018/10/31/
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FrostKing70

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #55 on: November 05, 2018, 07:43:29 PM »
Interesting animations!   Does any one have access to information on how big (area and volume) the calving events would be from Chasm 1 and the Halloween Crack (when they eventually go, although I believe one or both will happen this summer)?

FrostKing70

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #56 on: November 06, 2018, 08:27:35 PM »
I have done some poking around on the internet and have not been able to find any indication of the potential size of the calving events.   Can any one point me towards to good source?

solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #57 on: November 07, 2018, 07:45:35 AM »
Here is a wider view of the Brunt Ice Shelf showing the other side of the Halloween Crack.  Looks like there is a chance for a significant  calving there.
Original image 53 mb https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20181106T233049_C2BC_S_1.final.jpg

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iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #58 on: November 20, 2018, 03:46:54 PM »
SolarTim27,

I think you are right, here's this month's animation showing the MIR area.
you can see that in the area above the widening Halloween crack there is another crack starting up across the area of the shelf that you have highlighted.

No sign of Crevasse 1 at this scale yet but my guess is that it won't be long.


FredBear

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #59 on: November 24, 2018, 10:39:09 PM »

FredBear

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #60 on: December 12, 2018, 06:34:56 PM »
  .   .   and Halley opened up again by BAS   .    . 

https://www.bas.ac.uk/media-post/summer-fieldwork-begins-at-halley

iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #61 on: December 13, 2018, 05:35:37 PM »
Looks like Chasm 1 has advanced some more - very close to calving now...

FredBear

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #62 on: December 21, 2018, 02:58:21 PM »
Just found this on the British Antarctic Survey site:-


SteveMDFP

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #63 on: December 26, 2018, 08:17:04 PM »
Turns out, the Halley crew doesn't just spend all their time dodging new cracks in the ice shelf.
They also monitor electronic signals related to space weather.
Some of these are low-frequency radio waves, corresponding to audio wavelengths.
So, they can just hook up the electronic signals directly into an audio recorder.
So, for your aural pleasure,

Listen to the Creepy Noises Picked Up at a Space Weather Station in Antarctica
https://gizmodo.com/listen-to-the-creepy-noises-picked-up-at-a-space-weathe-1831234519

solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #64 on: December 31, 2018, 03:55:45 AM »
Looks to me like there is significant crack development right to the left of the Longitude line.  That doesn't mean that if it does go all the way that the berg will move anywhere, or any time soon, but I feel there is a non-zero chance that Brunt could break apart this summer.
Snip from https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20181230T233130_2AC8_S_1.final.jpg   (31 MB)
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solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #65 on: December 31, 2018, 04:04:15 AM »
Here's a worldview GIF from the end of November to the end of December. Hard to say if the crack really expanded that much, or if it's just surface snow melting, blowing, or something to make it more visible.  A nice Sentinel shot would be nice around now.
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solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #66 on: December 31, 2018, 05:24:21 PM »
There was an almost clear Sentinel shot of Brunt on the 29th.  Here's a gif from September until then from the playground in natural color, and a 2nd shot in the same area with the NDWI band selected. ( Note the 3 km scale bar in the lower right corner )
« Last Edit: December 31, 2018, 05:35:38 PM by solartim27 »
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iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #67 on: January 11, 2019, 02:42:16 PM »
Well, there was a clear image on the 8th Jan so here's the new year's animation.

Not a lot of changes -
expansion of the crack above the halloween crack radiating from the MIR
Movement around the MIR

There's been a suggestion on the SAR images of chasm 1 forking towards the tip, not really seeing anything in the visual images though.

I do like the NDWI band as a way to highlight the cracks.
 

solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #68 on: January 18, 2019, 07:38:07 PM »
World view is nice and clear today, hopefully we can get a visual shot this weekend.  Looks like the cracks might have joined up right upstream of the ice rise.
https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20190118T002007_76A0_S_1.final.jpg  (32 MB)
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solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #69 on: January 18, 2019, 07:51:44 PM »
Worldview shows lots of development over the last four weeks, but the resolution is not high enough to see for certain.
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solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #70 on: January 19, 2019, 01:52:25 AM »
Sentinel came through today, gif from 29 Nov to 18 Jan, NDWI band.  Not quite there yet.
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iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #71 on: January 21, 2019, 05:26:34 PM »
 :o

getting very close now - maybe 5km between the cracks at this stage.

and an interesting article published in October - read it now before it becomes outdated news.
https://www.the-cryosphere.net/12/3361/2018/tc-12-3361-2018.pdf

solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #72 on: January 31, 2019, 09:58:46 PM »
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Stephan

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #73 on: February 10, 2019, 10:33:09 PM »
I just visited Sentinel images of the Brunt Ice Shelf. The Chasm 1 crack has lengthened about 2 km between Dec 29, 2018 and Feb 07, 2019. Its distance to the tip of the Halloween Crak is now only around 8 km. I wonder when these two cracks will meet and what happens thereafter...

iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #74 on: February 11, 2019, 01:51:21 PM »
Indeed, taking a look at the recent polarview IW image it's getting very close now.

It looks like chasm 1 will not meet the Halloween crack but just end with the calved section below the MIR on the image below.

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #75 on: February 13, 2019, 02:29:16 AM »
I found this image of the brunt ice shelf looking at the new thread of Antarctic expeditions.
https://www.bas.ac.uk/project/moving-halley/

It looks like some of what I thought was new growth is harder to see on some days.

Andreas T

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #76 on: February 14, 2019, 07:47:19 PM »
This paper looks interesting and has not been linked to before it seems:
https://www.the-cryosphere-discuss.net/tc-2018-206/tc-2018-206.pdf
one small quote:
Quote
However, the DEM surface topography (and ICESat data) shows large variations in the distribution of
the incorporated icebergs (Fig. 5), and the ice shelf draft upstream of the MIR (Fig. 6) which can be used to
determine if grounding will be maintained. For example, there are currently portions of the ice shelf, due to pass
over MIR 4-12 years from 2017 that may have insufficient draft to ground, with no keels extending below -200
m. At this time the ice shelf might be more prone to reduced, or loss of, contact (Fig. 6b).

solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #77 on: February 20, 2019, 04:28:54 PM »
Latest Polarview shot. Have some clear skies on Worldview, so hopefully there's a Sentinel nearby.  31 MB link  https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20190219T235547_542C_S_1.final.jpg
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iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #78 on: February 20, 2019, 05:49:01 PM »
It's been noticed by Nasa and there's a post on the earth observatory today

https://earthobservatory.nasa.gov/images/144563/countdown-to-calving-at-brunt-ice-shelf


Stephan

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #79 on: February 20, 2019, 10:09:58 PM »
Thank you for that link.

FredBear

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« Last Edit: February 28, 2019, 09:25:43 PM by FredBear »

Jim Hunt

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #81 on: February 28, 2019, 09:52:00 PM »
Thank you for those links Fred!
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Stephan

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #82 on: March 01, 2019, 06:45:07 PM »
On Feb 27 a new clear Sentinel picture was available. It shows that the crack "Chasm1" has grown into NNW direction by about 2 km (compared to Jan 24). So the distance to the western end of the Halloween crack has reduced to about 7 km, the distance to the 2nd crack west of McDonnell Ice Rise is about 6,5 km.

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #83 on: March 02, 2019, 05:33:40 AM »
Brunt Ice shelf Feb 27th @ 3:49 am UTC
The crack is hard to see but shows up better in the original 53mb file. 

The scale bar is approximate but should be close enough. I don't have the exact pixel resolution for the image so I used the latitude lines on the picture. I couldn't find the exact distance between the 75th and 76th southern latitude. I did find the distance is 110.567 at the equator and 111.699 at the poles so interpolated and came up with 111.5209 km between the 75th and 76th parallel. I measured the number of pixels using imageJ and used that to scale the image.

iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #84 on: March 06, 2019, 03:54:01 PM »
In a reminder to sit back and take a look at the bigger picture a fairly large iceberg approaches the Brunt Ice shelf caught in the currents around the coast.

So the final event may not be determined by the gradual progression of the crack but by the shock of an external impact...

« Last Edit: March 06, 2019, 04:12:12 PM by iwantatr8 »

b_lumenkraft

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #85 on: March 06, 2019, 04:33:29 PM »
That would be fascinating actually...

b_lumenkraft

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b_lumenkraft

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #87 on: March 07, 2019, 04:23:22 PM »

So do you guys think the iceberg hit the shelf?

It looks like some pieces chipped off of the iceberg (marked).

crandles

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #88 on: March 07, 2019, 04:38:19 PM »
Looks like crack might be complete at resolution shown.

Zooming in a little more, I am not even sure of the cracks marked with lines drawn above and or right of feature. Is interpreting more cracks justified?

iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #89 on: March 08, 2019, 03:28:12 PM »
Well looking at the latest images it looks very much like the shelf has calved to me.

And fortunately below the MIR so this should help ensure the shelf stays stable.

as to if the Iceberg hit, it's possible but I guess we may never know.


b_lumenkraft

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #90 on: March 18, 2019, 08:34:16 AM »
Yesterday we finally got a new clear Sentinel 2 shot.

Crandles got it right, the crack has not completed yet.

Susan Anderson

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #91 on: March 29, 2019, 06:36:44 PM »
Reporting in the New York Times 28 March:
An Iceberg Twice the Size of New York City Is About to Split From Antarctica: Two rifts on the Brunt Ice Shelf in Antarctica are close to creating an iceberg over 560 square miles in size. Scientists say the calving event could happen any day now.
https://www.nytimes.com/interactive/2019/03/28/climate/antarctica-brunt-iceberg.html

brief but good graphical presentation ...

I think A68 calved in winter. Is it a thing, that as it gets colder the calving potential continues? If so, for how long? Might be, answer is, nobody really knows, just sayin' ... [ocean temps lag a lot, for example in Boston it's just beginning to warm up a tiny bit, over 3 months later]

b_lumenkraft

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #92 on: March 29, 2019, 06:41:31 PM »
Wow, what a great visualisation (even though this is weirdly projected)! This is how you do it!

Thanks for the link, Susan.

b_lumenkraft

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #93 on: March 31, 2019, 09:02:33 PM »
Chasm1 has made it's way to McDonald ice rumples (now for real (i think)).

Link >> https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20190330T233046_A43B_S_1.final.jpg


crandles

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #94 on: April 05, 2019, 03:21:53 AM »
https://www.bbc.co.uk/news/science-environment-47817510

Quote
Antarctic: No role for climate in Halley iceberg splitting

Jan De Rydt and Hilmar Gudmundsson have built a model to describe the behaviour of the floating ice platform, which is known as the Brunt Ice Shelf.
he Brunt is essentially an amalgam of glacier ice that's flowed off land and pushed out to sea at a rate of about 400m per year.

Incorporating satellite and surface-gathered data, the team's model reveals how stress is distributed across the 150-250m-thick structure. And it predicts accurately where cracks are likely to develop and the path they will take.

"It all fits together; it's a very compelling piece of work," says Prof Gudmundsson.

"It shows that the chasm started to grow because of the stresses building up, and they built up because of the natural growth of the ice shelf. The ice shelf itself created this chasm."

...

"The chasm's been growing at about 1-2km a year and we haven't really seen any slow-down in winter. It's almost through already, but I would say it should happen within a year."

Susan Anderson

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #95 on: April 06, 2019, 09:45:56 AM »
@crandles

Useful and fascinating, makes sense.

Trouble is, headlines are all too often oversimplifications. I get it, but in fact global warming and climate will play a part in ice breakoffs as time goes on. Perhaps more after the break (the stress explanation makes sense) in terms of where the ice ends up, and how much the surrounding area will be degraded (if it is).

Stephan

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #96 on: April 12, 2019, 06:14:12 PM »
In the same sense as BBC (posting above) Wetteronline in Germany presented a short information about the expected calving of parts of the Brunt Ice Shelf:
https://www.wetteronline.de/klimawandel/antarktis-schelfeis-hat-risse-riesen-eisberg-droht-abzubrechen-2019-04-12-aa
The main claim is that this is a natural process as this part of Antarctica has not seen a relevant warming in the past decades (but only air temperature mentioned; no information about increasing sea temperatures)