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Author Topic: Rift in Larsen C  (Read 107498 times)

Shared Humanity

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Re: Rift in Larsen C
« Reply #350 on: November 08, 2018, 08:08:44 PM »
What are all of the gray spots on the ice berg? Those can't be melt ponds.

Tor Bejnar

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Re: Rift in Larsen C
« Reply #351 on: November 08, 2018, 09:29:59 PM »
Definitely not melt ponds!  It is very cold (from a human perspective) there, I'm sure.  PolarView doesn't create visual-light-like images, but uses other parts of the electro-magnetic spectrums. (These details are not my forte.)  I like these because they "see" through clouds and night's (and winter's) darkness.
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #352 on: November 21, 2018, 05:49:47 PM »
The Ice Island A68-A has rotated about 115º in 6 months, but the pivot end hasn't moved diddlysquat. 

The largest iceberg in the area (current, lower, image) has, in the meantime, moved about 125 km northwards, squeezing through what I'll call an ice-strait.  (1st image from a May 18 post by johnm33 [conveniently at the top of this thread's page 7]; 2nd image from PolarView on November 20.) 

I'm going to postulate, now, that intermittent grounding keeps A68-A where it is; no point is clearly 'actually' stuck in one place for any length of time.  A GIF covering multiple images might show if any spot does get stuck (becoming a fixed (if temporary) pivot point).
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FredBear

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Re: Rift in Larsen C
« Reply #353 on: November 30, 2018, 09:33:37 PM »
The Ice Island A68-A continues to inch(!?) northwards over the last 10 days, with the narrower 'tail' getting further from the coastal ice shelf.

Perhaps more importantly for the region, there is now a blue tint to the remains of the Larsen A & B shelves and also the ice further off-shore (From arctic.io 2018-11-30). Caused by adiabatic winds from the peninsula melting snow from the surface (+insolation)?

Tor Bejnar

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Re: Rift in Larsen C
« Reply #354 on: December 17, 2018, 06:11:58 PM »
A-68A has move about 20 km northward this past month.  I'm guessing it will escape the shoals near Bawden Ice Rise soon (if it hasn't already).
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litesong

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Re: Rift in Larsen C
« Reply #355 on: December 17, 2018, 06:42:31 PM »
A-68A has move about 20 km northward this past month.  I'm guessing it will escape the shoals near Bawden Ice Rise soon (if it hasn't already).
........ as the yearly Antarctic sea ice decrease loses its ability to hold onto A-68A.

FredBear

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Re: Rift in Larsen C
« Reply #356 on: December 18, 2018, 01:49:40 PM »
So far the sea ice has been building to the south and east of A68A (which seems to be blocking the gyre) , but dispersing to the NW.
On 13/12/2018 A68B had drifted in line with the point of the peninsular between Larsens A & B, just SE of a large sea ice floe. Also appears about level with the north of A68A.

The iceberg B15AA has been drifting across the Weddell Sea, but it is moving more slowly than the surrounding sea ice (which is now breaking up quite rapidly.). This demonstrates that icebergs can impede the movement of the  thinner sea ice.

FrostKing70

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Re: Rift in Larsen C
« Reply #357 on: December 18, 2018, 04:35:14 PM »
I wonder if it will break into at least 3 chunks soon, especially if the bottom end stays grounded....

johnm33

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Re: Rift in Larsen C
« Reply #358 on: December 18, 2018, 06:29:06 PM »
Wouldn't be surprised if it 1/2 rotated again before breaking.

Tor Bejnar

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Re: Rift in Larsen C
« Reply #359 on: December 18, 2018, 10:56:05 PM »
From an enlargement of the left side of A-68A (PolarView) dated 2018-12-17@23:41:58 (just over 18 minutes before midnight), I don't see current support for the cracks propagating in the suggested manner. Am I missing something?  But for sure, we'll see one way or another.  I do see the possibility of a ~2 x ~10 km scab braking off in this area. (sea ice on the left; A-68A on the right and top)
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #360 on: December 27, 2018, 04:41:28 PM »
The southern end of Bawden Ice Rise has a rim of open water now, per this Sentinel-hub image from December 19. The first image (of mp4) is the NDWI rendering of bands (to identify the setting), and the second image is the 'Natural Color' rendering (exact same area).
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Tealight

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Re: Rift in Larsen C
« Reply #361 on: January 21, 2019, 09:51:18 PM »
A nice view of A-68A today showing the rifts in a lot more detail than usual. A small part even broke off since the last picture posted here in December.

IceConcerned

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Re: Rift in Larsen C
« Reply #362 on: February 04, 2019, 02:59:41 PM »
Apparently new cracks appeared recently on the shelf, a big chunk seems ready to get loose.

Shared Humanity

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Re: Rift in Larsen C
« Reply #363 on: February 04, 2019, 05:43:26 PM »
Those fractures are getting dangerously close to the Bawden Ice Rise. Would hate to see the ice shelf lose this pinning point.

Tor Bejnar

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Re: Rift in Larsen C
« Reply #364 on: February 21, 2019, 02:16:23 AM »
IceConcerned,
You will notice the cracks are little changed from one and two years ago, see here, for example.  Yes, they look ready to let loose!
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #365 on: February 25, 2019, 05:06:49 PM »
I'll probably start posting A68A images in the Antarctic Icebergs thread (after this one).  I estimate (with the assistance of a small protractor) the ice island has rotated 175º since forming.  That's quite a bite where it is (was?) grounded.  PolarView image from yesterday.
« Last Edit: February 25, 2019, 05:14:12 PM by Tor Bejnar »
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FredBear

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Re: Rift in Larsen C
« Reply #366 on: February 25, 2019, 11:26:25 PM »
If A68A drifts into the bay it could replace the old Larsen B ice shelf!?? - no, the ice in the shelf area still seems to flush out.
This berg hasn't moved much this summer (but more than last year) - maybe it will move more in the winter.
The sea ice/icebergs in the Weddell Sea have been concentrated on the western & southern sides (apart from the lee of A68A) this year, but their location is very variable from year to year. Rather less total ice than recent years?