Antarctic Icebergs

[baking]

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.

[blumenkraft]

A68A update.

[Stephan]

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.

[blumenkraft]

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.

[baking]

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.

[blumenkraft]

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.

[Stephan]

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.

[blumenkraft]

A68A drift update.

[blumenkraft]

A68A drift update.

[blumenkraft]

There was a calving in the north-west facing side. Not a big one, but way bigger than recent ones.

[oren]

Thanks for these updates blumenkraft.

[FredBear]

A68A still drifting northwards, notice the sea ice (the "goodbye waves") drifting up to the south-east edge now.

[blumenkraft]

Very welcome, Oren.

'Goodbye wave' is nicely said, Fred. I like that.

[blumenkraft]

Annamaria Luongo
@annamaria_84 on Twitter

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

[Tor Bejnar]

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]).

[FredBear]

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

[Tealight]

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.

[blumenkraft]

Hey, Tealight! Nice to see you around!

[blumenkraft]

Who says an ice island cannot turn on a dime.

It did it again! A68A update.

(GIF showing movement from 25.03 to today)

[interstitial]

A big chunk broke off of A68.

[blumenkraft]

You beat me to it, Interstitial! 

Here is the GIF with bathymetry (from 07.04. to 22.04.). I had to switch satellites mid-GIF because the sun went off.

[interstitial]

Yeah but you took the time to make a better presentation of it. 

[blumenkraft]

Thanks!

[blumenkraft]

Between the 23th and today, A68A almost made no way at all. The sea ice is catching up with it.

[bairgon]

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.

[baking]

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.

[blumenkraft]

A68A is stuck. This is a GIF showing movement between 29.04 and 06.05.

[FredBear]

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

[blumenkraft]

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.

[FredBear]

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?)"

[blumenkraft]

Looks like A68C made it over the underwater mountain. A68A still stuck behind it.

[blumenkraft]

A68C very much on the move. A68A still snaking along the underwater mountain in north-east direction.

[oren]

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.

[blumenkraft]

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.

[blumenkraft]

Interesting, A68C came back south.

A68A slowly in northeast direction still.

[FredBear]

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

[blumenkraft]

29.05. vs. 03.06.

A68A is making it over the underwater mountain as it seems.

[blumenkraft]

Almost.

[FredBear]

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?).

[blumenkraft]

Soon!

[interstitial]

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.

[blumenkraft]

That seems about right, Interstitial.

This is today's radar imagery.

Click to play.

[blumenkraft]

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.

[interstitial]

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.

[Eco-Author]

thanks!!  need to bounce around this site more often!!  Great call! <3

[blumenkraft]

Boom!

[paolo]

Another image of calving
For the surface of the larger iceberg I did not take into account the fast ice attached.

[interstitial]

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.

[interstitial]

The pinning point is the island on the lower right.

[paolo]

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