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mitch

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Re: Antarctic Icebergs
« Reply #150 on: January 05, 2020, 09:38:41 PM »
Westward drift? Antarctic Circumpolar Current flows west to east. 

Stephan

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Re: Antarctic Icebergs
« Reply #151 on: January 05, 2020, 10:29:05 PM »
Thank you Mitch, I meant the drift west to east, of course. Got it fixed.
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blumenkraft

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Re: Antarctic Icebergs
« Reply #152 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.)

blumenkraft

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Re: Antarctic Icebergs
« Reply #153 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.

blumenkraft

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Re: Antarctic Icebergs
« Reply #154 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.

blumenkraft

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Re: Antarctic Icebergs
« Reply #155 on: January 12, 2020, 06:26:32 PM »
A68A from the end of October to today, daily increments, fast-playing to obscure the clouds.

grixm

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Re: Antarctic Icebergs
« Reply #156 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?

blumenkraft

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Re: Antarctic Icebergs
« Reply #157 on: January 12, 2020, 07:26:32 PM »
I wouldn't say that quite yet. Perhaps there are more underwater mountains in its way.

« Last Edit: January 12, 2020, 07:40:49 PM by blumenkraft »

blumenkraft

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Re: Antarctic Icebergs
« Reply #158 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.

baking

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Re: Antarctic Icebergs
« Reply #159 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.

oren

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Re: Antarctic Icebergs
« Reply #160 on: January 14, 2020, 03:33:17 AM »
I think at this stage it's safe from grounding.
Blumenkraft thanks for the animations.

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Re: Antarctic Icebergs
« Reply #161 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. ;)

baking

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Re: Antarctic Icebergs
« Reply #162 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.

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Re: Antarctic Icebergs
« Reply #163 on: January 14, 2020, 03:24:01 PM »
OK, that's a good point, Baking.

Tor Bejnar

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Re: Antarctic Icebergs
« Reply #164 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.
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blumenkraft

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Re: Antarctic Icebergs
« Reply #165 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.

nanning

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Re: Antarctic Icebergs
« Reply #166 on: January 19, 2020, 06:36:55 PM »
You have become good at this blumenkraft :)
"It is preoccupation with possessions, more than anything else, that prevents us from living freely and nobly" - Bertrand Russell
"It is preoccupation with what other people from your groups think of you, that prevents you from living freely and nobly" - Nanning
Why do you keep accumulating stuff?

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Re: Antarctic Icebergs
« Reply #167 on: January 19, 2020, 06:57:49 PM »
Thank you so much, Nanning. :)

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Re: Antarctic Icebergs
« Reply #168 on: January 21, 2020, 04:18:29 PM »
We will soon know if A68A fits. :)

FredBear

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Re: Antarctic Icebergs
« Reply #169 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?).

blumenkraft

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Re: Antarctic Icebergs
« Reply #170 on: January 23, 2020, 07:34:09 AM »
Looking at Tor's map posted above, i think it's entirely possible, Fred.

blumenkraft

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Re: Antarctic Icebergs
« Reply #171 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.

baking

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Re: Antarctic Icebergs
« Reply #172 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.

Tor Bejnar

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Re: Antarctic Icebergs
« Reply #173 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
It'd be bad luck to get stuck on one of the named (rocky) islands!
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FredBear

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Re: Antarctic Icebergs
« Reply #174 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

gerontocrat

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Re: Antarctic Icebergs
« Reply #175 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?
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blumenkraft

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Re: Antarctic Icebergs
« Reply #176 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

blumenkraft

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Re: Antarctic Icebergs
« Reply #177 on: January 25, 2020, 04:42:58 PM »
The pivoting goes on.

From 21th to today plus bathymetry map.

blumenkraft

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Re: Antarctic Icebergs
« Reply #178 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. :)

blumenkraft

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Re: Antarctic Icebergs
« Reply #179 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.

baking

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Re: Antarctic Icebergs
« Reply #180 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.

blumenkraft

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Re: Antarctic Icebergs
« Reply #181 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

gerontocrat

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Re: Antarctic Icebergs
« Reply #182 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.

"Para a Causa do Povo a Luta Continua!"
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blumenkraft

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Re: Antarctic Icebergs
« Reply #183 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.

FredBear

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Re: Antarctic Icebergs
« Reply #184 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?

blumenkraft

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Re: Antarctic Icebergs
« Reply #185 on: February 06, 2020, 07:28:37 PM »
No pivoting or rotating between yesterday's and today's shot but north-west movement.

Tor Bejnar

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Re: Antarctic Icebergs
« Reply #186 on: February 07, 2020, 09:29:29 PM »
Using Polar View images from Feb. 6 and Feb. 7 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.  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.
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blumenkraft

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Re: Antarctic Icebergs
« Reply #187 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.

Tor Bejnar

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Re: Antarctic Icebergs
« Reply #188 on: February 10, 2020, 07:54:36 PM »
I've had some fun.  I made screenshots of PolarView '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 (with the trunk) and neighboring islands. Shackleton was here 104 years ago.
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blumenkraft

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Re: Antarctic Icebergs
« Reply #189 on: February 10, 2020, 08:16:10 PM »
Nice, Tor! :)

New poll? Will A68A hit Shackleton or the Elephant? ;)

baking

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Re: Antarctic Icebergs
« Reply #190 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. ;)

blumenkraft

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Re: Antarctic Icebergs
« Reply #191 on: February 11, 2020, 04:35:32 PM »
Yeah, i regret not naming my cat after him, Baking. ;)

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Re: Antarctic Icebergs
« Reply #192 on: February 11, 2020, 04:37:04 PM »
A68A update. We had multiple cloud-free days in a row! <3

gerontocrat

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Re: Antarctic Icebergs
« Reply #193 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?
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blumenkraft

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Re: Antarctic Icebergs
« Reply #194 on: February 11, 2020, 08:58:55 PM »
Oh great. Yet another feedback loop. :-[

gerontocrat

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Re: Antarctic Icebergs
« Reply #195 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.
"Para a Causa do Povo a Luta Continua!"
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blumenkraft

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Re: Antarctic Icebergs
« Reply #196 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.

Stephan

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Re: Antarctic Icebergs
« Reply #197 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.
It is too late just to be concerned about Climate Change

blumenkraft

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Re: Antarctic Icebergs
« Reply #198 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.

blumenkraft

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Re: Antarctic Icebergs
« Reply #199 on: February 17, 2020, 08:51:05 PM »
The bigger picture.