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FredBear

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Re: Rift in Larsen C
« Reply #250 on: February 01, 2018, 10:03:54 PM »
The ice edge is growing outwards to the south of Gipps ice rise and has filled the bay (where the ice is shown overlaid in grey in the following picture).

https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=1175.0;attach=54638;image

To me it looks like the large rift could grow to create a calving but because the ice has been growing beyond the accepted margin it may be inhibited/prevented from happening? Anyway, these rifts can grow slowly for many years before breaking (c.f. A68).

Tor Bejnar

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Re: Rift in Larsen C
« Reply #251 on: February 05, 2018, 04:39:03 PM »
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gerontocrat

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Re: Rift in Larsen C
« Reply #252 on: February 05, 2018, 07:55:13 PM »
Wind and Sea Ice drift in the SW Weddell sea has been zilch for months. But when winter comes things are often very very different. (as a typical image from HYCOM last May shows)

So I guess 68a ain't gonna move much until then.
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #253 on: February 05, 2018, 09:51:59 PM »
Ice Island A-68A 'drifted' north about 20 km during the past week.
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gerontocrat

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Re: Rift in Larsen C
« Reply #254 on: February 05, 2018, 11:34:53 PM »
Ice Island A-68A 'drifted' north about 20 km during the past week.
is that a lot, or is it a little ? I confess I have no knowledge at all about how fast large bergs can move around.
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magnamentis

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Re: Rift in Larsen C
« Reply #255 on: February 05, 2018, 11:44:26 PM »
Ice Island A-68A 'drifted' north about 20 km during the past week.
is that a lot, or is it a little ? I confess I have no knowledge at all about how fast large bergs can move around.

an example from the Harbour Authority Of Twillingate   Twillingate, NL A0G 4M0
An iceberg drifts at about 0.2 m/s or 0.7 k/hr. The speed that an iceberg drifts depend on various factors such as, size, shape, currents, waves and wind.

i think this is very individually different, up there they move relatively fast due to the labrador current while on the other hand the 20km for that huge and specific berg is faster than it has travelled before that. it's all relative :-)


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johnm33

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Re: Rift in Larsen C
« Reply #256 on: February 06, 2018, 12:05:06 AM »
Ice Island A-68A 'drifted' north about 20 km during the past week.
Tides have been huge this last few days.

gerontocrat

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Re: Rift in Larsen C
« Reply #257 on: February 06, 2018, 12:27:16 AM »
Ice Island A-68A 'drifted' north about 20 km during the past week.
Tides have been huge this last few days.
Supermoon effect?
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johnm33

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Re: Rift in Larsen C
« Reply #258 on: February 06, 2018, 11:18:46 AM »
'supermoon?' I guess so

gerontocrat

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Re: Rift in Larsen C
« Reply #259 on: February 06, 2018, 02:09:48 PM »
Ice Island A-68A 'drifted' north about 20 km during the past week.
is that a lot, or is it a little ? I confess I have no knowledge at all about how fast large bergs can move around.
20 km in 7 days is not a lot, it is a little.

The little table below says if that 20 km took 7 days, the average speed was 0.033 metres per second, as opposed to average speed of icebergs subject to the Labrador current of 0.2 metres per second. On the one hand, 68A is huge as is its inertia. But once moving, somewhat difficult to stop. 20 km movement is an impressive performance by the supermoon.

The first images below show how the SW Weddell Sea is currently a dead spot for cyclones, as it has been for most days in the summer. This seems to me why the sea ice theere is more or less stuck.

Winter seems to be very different. The last image shows a typical sea ice drift image from JAXA in winter (September) caused by cyclones forming between the circumpolar vortex and the coast of the Weddell Sea. Ice is pushed West and then North right alongside Larsen C. Methinks in a few months we will see real northward drift of Larsen C as this is the normal and persistent weather pattern. "That is my theory and it belongs to me!" (pace Monty Python)
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #260 on: February 06, 2018, 03:29:48 PM »
Ice Island A-68A 'drifted' north about 20 km during the past week.
is that a lot, or is it a little ? I confess I have no knowledge at all about how fast large bergs can move around.
I reported on January 30 that the ice island had moved about 200 meters during the previous 5 days.  From mid July to January 30 (6.5 months), the ice island moved a net (through more of a wolf pattern than a crow pattern) 50 km, so the recent movement is relatively fast.

From above (0.2 km/hr) and from the internet (0.7 km/hr), I get 33 to 115 km per week movement 'doable'.
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gerontocrat

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Re: Rift in Larsen C
« Reply #261 on: February 06, 2018, 04:06:32 PM »
HYCOM's snapshot archive from 2017 suggests that active cyclones and strong sea ice drift could start as early as late Feb or early March. Winter comes early at 70 degrees south.
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SteveMDFP

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Re: Rift in Larsen C
« Reply #262 on: February 12, 2018, 07:15:19 PM »
Here's a very interesting article about research on the sea and sea floor underneath A68:

UK team set for giant Antarctic iceberg expedition
http://www.bbc.com/news/science-environment-43008058
Quote
British Antarctic Survey marine biologist Dr Katrin Linse, who is leading the mission, said that the calving of the iceberg, which has been named A68, provides researchers with "a unique opportunity to study marine life as it responds to a dramatic environmental change".

Sleepy

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Re: Rift in Larsen C
« Reply #263 on: February 13, 2018, 05:30:03 PM »
A nice and closer view of that little ice cube:
https://twitter.com/emm_pearce/status/963167751018827776
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gerontocrat

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Re: Rift in Larsen C
« Reply #264 on: February 20, 2018, 04:30:10 PM »
Here's a very interesting article about research on the sea and sea floor underneath A68:

UK team set for giant Antarctic iceberg expedition
http://www.bbc.com/news/science-environment-43008058
Quote
British Antarctic Survey marine biologist Dr Katrin Linse, who is leading the mission, said that the calving of the iceberg, which has been named A68, provides researchers with "a unique opportunity to study marine life as it responds to a dramatic environmental change".
The expedition ship leaves port on Wednesday. But which port ? The article does not say, of course. Long way from UK to Larsen C

https://www.theguardian.com/environment/2018/feb/20/scientists-race-to-explore-antarctic-marine-life-revealed-by-giant-iceberg
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Sleepy

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Re: Rift in Larsen C
« Reply #265 on: February 20, 2018, 04:48:14 PM »
Omnia mirari, etiam tritissima.
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #266 on: February 20, 2018, 07:44:27 PM »
Since February 1, A68-A moved about 19 km (in 18 days), so about 7 km/week.  Screen print from yesterday's PolarView.  However, most of the movement happened before February 5 (1 km/week).
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gerontocrat

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Re: Rift in Larsen C
« Reply #267 on: February 20, 2018, 07:56:21 PM »
A68-A moved about 19 km (in 18 days), so about 7 km/week.  Screen print from However, most of the movement happened before February 5 (1 km/week).

How many Kms to escape the peninsula? is it likely to get trapped by winter ice, or will winds help it on its way. " I want to know!", or will I have to just wait and see.
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #268 on: February 20, 2018, 08:54:08 PM »
If A68-A continues northeastward along the Antarctic Peninsula, its leading end needs to travel about 600 km to pass Joinville Island (just off the northern tip of the peninsula).  It has traveled about 70 km in 7 months.  At this rate, it will take about 5 more years for the leading end to emerge north of the peninsula.  Although A68-A is about 200 km long, when the ice island gets that far north, I suspect it will be caught by the Antarctic Circumpolar Current and will not take an additional year or two to be clear of the peninsula.  (I'll probably break into significant smaller ice islands before then, and the pieces will travel separately.)

The Polar View screen shot shows a snap shot (showing most of A68-A) of the frame highlighted in yellow.  The tip of the Antarctic Peninsula (land is outlined in purple) is in the 3rd frame northeast of this one.

The Antarctic Iceberg Tracking Database shows where icebergs have traveled.

(Disclaimer:  I am not an ice expert.)
Edit:  a couple typos fixed.



« Last Edit: February 23, 2018, 07:59:37 PM by Tor Bejnar »
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Susan Anderson

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Re: Rift in Larsen C
« Reply #269 on: February 23, 2018, 06:47:18 PM »
@Tor Bejnar, that is a fantastic resource.

disclaimer: I'm even less expert than you.

gerontocrat

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Re: Rift in Larsen C
« Reply #270 on: February 23, 2018, 07:25:27 PM »
If A68-A continues northeastward along the Antarctic Peninsula, its leading end needs to travel about 600 km to pass Joinville Island (just off the northern tip of the peninsula).  It has traveled about 70 km in 7 months.  At this rate, it will take about 5 more years for the leading end to emerge north of the peninsula. 

(Disclaimer:  I am not an ice expert.)

I am not an ice expert.  -anybody who knows more than me is, in my eyes, an expert. So I will ask the expert two questions.

To the casual eye the iceberg tracker says the majority of icebergs originate from the shores of the Weddell Sea (or  pushed along the shore from the East?). True or false?

During the last winter HYCOM (and even the JAXA Sea Ice Drift Images) showed really strong movement along the Weddell Sea from East to West and then North up along the coast until exiting the peninsula into the Westerlies. It looked as if strong cyclones often developed between the west to east circumpolar vortex and the shore with strong easterlies along the shoreline. Could this not hurry the Larsen C beastie on its way?

ps: I am with Ms Anderson - what a super resource. Every day my environment folder bulges more and more at the seams.
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #271 on: February 23, 2018, 08:15:30 PM »
Replying just to be polite...
True or False?  No idea.
Hurrying the beastie?  No idea, except that I think Ice Shelf Larsen C and Ice Island A68 (now A68-A - whatever happened to A68-B  :'() got a divorce and that A68 would like folks to use its chosen name, A68-A.  (I don't like the idea of old acquaintances calling me my ex's beastie  >:([I guess I am an expert at junior high humor.  The year I left junior high school they closed it down and former 7th grades went to the expanding middle school, with the 8th and 9th graders going into the high school.  Therefore, I do not have to apologize to current junior high school students, for there are none where I came from.]
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Susan Anderson

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Re: Rift in Larsen C
« Reply #272 on: February 23, 2018, 08:42:08 PM »
@
Here's a very interesting article about research on the sea and sea floor underneath A68:

UK team set for giant Antarctic iceberg expedition
http://www.bbc.com/news/science-environment-43008058
Quote
British Antarctic Survey marine biologist Dr Katrin Linse, who is leading the mission, said that the calving of the iceberg, which has been named A68, provides researchers with "a unique opportunity to study marine life as it responds to a dramatic environmental change".
The expedition ship leaves port on Wednesday. But which port ? The article does not say, of course. Long way from UK to Larsen C

https://www.theguardian.com/environment/2018/feb/20/scientists-race-to-explore-antarctic-marine-life-revealed-by-giant-iceberg

New Zealand or southern Chile? My New Yorker (favorite resource) had a terrific article about Worsley's expeditions, including a centennial Shackleton one, that describes the process of getting out there and resources available to them. The quote below is a very small part of a 25 page special with great pix. I know they allow 5 articles a month free. https://www.newyorker.com/magazine/2018/02/12/the-white-darkness

Quote
the new expedition would be composed of descendants of men who had explored alongside Shackleton. They would try to reach Shackleton’s farthest point on January 9, 2009—exactly a hundred years after he did—and then press on to the South Pole, completing, in Gow’s words, “unfinished family business.”

Worsley listened in amazement. Here was the chance of a lifetime.
....
Worsley, Gow, and Adams planned to begin their journey south of New Zealand, on Ross Island. The island is bound by the Ross Ice Shelf, which extends over the Ross Sea and is the largest body of floating ice in the world—more than 180,000 square miles and, on average, more than a thousand feet thick. Because the Ross Ice Shelf is easier to reach by sea during the summer than other parts of the continent, and because it is relatively smooth and stretches nearly 600 miles toward the heart of Antarctica, it was the starting point for expeditions to the South Pole during the golden age of Antarctic exploration. Shackleton and Scott and Amundsen all began their expeditions on the shelf.
....
On October 30, 2008, Worsley, Gow, and Adams arrived in Punta Arenas, on the southern tip of Chile. They went to a warehouse owned by a company named Antarctic Logistics & Expeditions. During the summer, between 30,000 and 40,000 tourists visit the continent, nearly all of them travelling on small cruise ships. Worsley’s party had hired A.L.E. to provide logistical support, which included transporting them by airplane to their starting point on Ross Island.

FredBear

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Re: Rift in Larsen C
« Reply #273 on: February 24, 2018, 06:21:13 AM »
gerontocrat, on: February 23, 2018, 07:25:27 PM you asked where the icebergs in the Weddell sea started out. In the topic "Antarctic Icebergs" I said:-

"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."

b15 was a huge berg from the Ross Sea, so its remains (b15z, b15t) have travelled in a westerly direction 3/4 of the way round Antarctica before heading north into the South Atlantic Ocean.

b15aa was doing cart-wheels round the coast last year, and after being freed from the winter pack, was continuing but stalled. It is now drifting away from the shore - is it going to take a short cut towards the Antarctic Peninsular, drift north, or continue south round the Weddell Sea? Time will tell!


Sleepy

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Re: Rift in Larsen C
« Reply #274 on: February 24, 2018, 10:49:36 AM »
@
Here's a very interesting article about research on the sea and sea floor underneath A68:

UK team set for giant Antarctic iceberg expedition
http://www.bbc.com/news/science-environment-43008058
Quote
British Antarctic Survey marine biologist Dr Katrin Linse, who is leading the mission, said that the calving of the iceberg, which has been named A68, provides researchers with "a unique opportunity to study marine life as it responds to a dramatic environmental change".
The expedition ship leaves port on Wednesday. But which port ? The article does not say, of course. Long way from UK to Larsen C

https://www.theguardian.com/environment/2018/feb/20/scientists-race-to-explore-antarctic-marine-life-revealed-by-giant-iceberg

New Zealand or southern Chile?
Susan, I posted a link dírectly after gerontocrat's question above with the exact (and live) location of RRS James Clark Ross:
RRS James Clark Ross (ZDLP) is in Port Stanley:
https://www.marinetraffic.com/en/ais/details/ships/shipid:780940/mmsi:740339000/vessel:ZDLP

So, on Feb 20:th the ship was still in Port Stanley, Falkland Islands.
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gerontocrat

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Re: Rift in Larsen C
« Reply #275 on: February 24, 2018, 11:44:51 AM »

b15 was a huge berg from the Ross Sea, so its remains (b15z, b15t) have travelled in a westerly direction 3/4 of the way round Antarctica before heading north into the South Atlantic Ocean.


perhaps this post should be in the Antarctic Icebergs thread, for as Sleepy remarked, A68-A is now divorced from Larsen C.

travelled in a westerly direction 3/4 of the way round Antarctica - Watching Antarctica weather and sea ice drift over the last year I was struck how the West to East polar vortex was consistently well off shore, and from it often strong lows developed between it and the shore, often with strong Easterlies along the coast. Perhaps most of the time only when icebergs reach the peninsula at the SW corner of the Weddell Sea is the drift forced north until the Vortex can pick them up and send them out to their slow death.

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johnm33

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Re: Rift in Larsen C
« Reply #276 on: February 24, 2018, 01:33:28 PM »
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.

gerontocrat

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Re: Rift in Larsen C
« Reply #277 on: February 24, 2018, 02:14:13 PM »
hullo Johnm33,

putting my answer to your most informative post in the Antarctic Icebergs thread. A68-A is now divorced from Larsen C

cheers

Gerontocrat
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Re: Rift in Larsen C
« Reply #278 on: February 24, 2018, 10:23:39 PM »
@Sleepy, thanks, that's an interesting link. (Out of my depth here, but I was intrigued by the Worsley story.)

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Re: Rift in Larsen C
« Reply #279 on: February 25, 2018, 09:42:44 AM »
Susan, the ships name was mentioned in the BBC article that Steve posted. If you know the ships name, you can often find their call sign, in this case: ZDLP.
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Re: Rift in Larsen C
« Reply #280 on: March 02, 2018, 01:02:13 PM »
I see the Larsen C expedition to explore the newly cleared sea bed has been abandoned for this year.

http://www.bbc.co.uk/news/science-environment-43257289

The RRS James Clark Ross (ZDLP) seemed to head for the western side of the Antarctic Peninsular earlier, so I did wonder whether it would send scientists across by air as the sea ice did not look good (or was too good?) in satellite images of the East this year.

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Re: Rift in Larsen C
« Reply #281 on: March 02, 2018, 03:45:34 PM »
https://www.telegraph.co.uk/news/2018/03/02/penguin-super-colony-discovered-antarctic-danger-islands-pictures/

When i read this article the first thing I thought "A-68 will probably hit the island and wipe-out the colony..."

and then I thought, what happens when A-68 will hit an island like that, will it even be noticed on such an island because it won't hit the island but it will get grounded near the island probably, and will it stay grounded for a long time?

Tor Bejnar

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Re: Rift in Larsen C
« Reply #282 on: March 19, 2018, 05:16:25 PM »
Looks like A68-A has moved about 4 km in 4 weeks. (Polar View - today's image)
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Re: Rift in Larsen C
« Reply #283 on: March 19, 2018, 08:44:47 PM »
So how close is A68 to the Bawden ice rise? What effect if any could A68 have on this crucial pinning point for Larsen C?

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Re: Rift in Larsen C
« Reply #284 on: March 19, 2018, 09:56:49 PM »
reference

They've been closer. 

To your question, "What effect?",  I don't know, but I'm watching!
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Re: Rift in Larsen C
« Reply #285 on: March 20, 2018, 01:46:30 AM »
Thanks. So a little under 2 km.

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Re: Rift in Larsen C
« Reply #286 on: March 20, 2018, 01:54:58 AM »
That reference link shows A68 closer to Larsen C but that is not the Bawden ice rise. The ice rise is the step feature that is just north of A68 on the picture you just posted. A little less than 2 km separates them. This island serves to pin the Larsen C glacier, providing essential stability to the entire shelf. There is a 2nd, the Gipps Ice Rise (Island) further south that performs the same function.

Sleepy

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Re: Rift in Larsen C
« Reply #287 on: March 20, 2018, 08:50:05 AM »
So what's the time frame here until Bawden and Gipps doesn't do their job anymore and A68 leaves port without doing damage. A few more years, or less? If the future resembles Larsen B, it might collapse down to Kenyon Peninsula rather quickly after they fail, maybe even down to a lesser straight line between Kenyon and Churchill:

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Tor Bejnar

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Re: Rift in Larsen C
« Reply #288 on: March 30, 2018, 07:53:41 PM »
A68-A has move south a bit since I last posted.
full image link
Polar View (Antarctica)

Still about 800 meters separate ice shelf from ice island.
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #289 on: April 20, 2018, 03:25:21 PM »
Not much movement lately...
Today's PolarView image
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #290 on: April 25, 2018, 05:34:15 PM »
Did something go 'bump in the night'? (less than 100 m separation)
From today's Polar View image.
Okay, not quite 'night', per Worldview.
« Last Edit: April 25, 2018, 05:42:12 PM by Tor Bejnar »
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Re: Rift in Larsen C
« Reply #291 on: April 25, 2018, 09:08:48 PM »
I am not familiar enough with this area to understand the bottom picture.   Would you kindly explain what it shows?

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Re: Rift in Larsen C
« Reply #292 on: April 25, 2018, 09:51:09 PM »
This help? EOSDIS WorldView link (Enlarging from this linked view will show more clearly the features roughly outlined below.)
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Re: Rift in Larsen C
« Reply #293 on: April 25, 2018, 09:59:26 PM »
Thank you, with that I can now tie it together!

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Re: Rift in Larsen C
« Reply #294 on: May 02, 2018, 08:27:08 PM »
With climate change coming the Larsen C ice shelf is a dead-man walking:

Title: "‘Foehn winds’ causing Antarctica’s Larsen C ice shelf to melt in winter"

https://www.carbonbrief.org/foehn-winds-causing-antarcticas-larsen-c-ice-shelf-to-melt-in-winter

Extract: "Parts of Antarctica’s Larsen C ice shelf are melting in the depths of winter, when temperatures typically stay well below freezing, research finds.

Between 2015 and 2017, around 23% of the annual surface melt across the ice shelf occured in the winter months, according to results taken from field and satellite observations."
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #295 on: May 14, 2018, 05:35:32 PM »
Icebergs have broken off A68-A (I'm curious why/how) and image showing the least distance I've seen between ice island and shelf (since the original separation).  Today's PolarView image from PolarView Antarctica.
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Re: Rift in Larsen C
« Reply #296 on: May 14, 2018, 05:50:50 PM »
Looking at this image, I am very concerned about the condition of Larsen C where it is attached to the Bawden ice rise. Those pronounced troughs (melt streams?) on the northern half of the island suggests the shelf is losing its grip on the rise, a crucial pinning point that stabilizes the entire shelf. The southern half looks bad as well with the dark portion of the ice shelf that runs parallel to the island.

When the shelf breaks free, I expect to see a rapid collapse of this portion of the shelf.

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Re: Rift in Larsen C
« Reply #297 on: May 14, 2018, 07:04:39 PM »
The 'fingers' at (or north of) the Bawden Ice Rise in today's image look like the image Tealight posted in December dated 2017-12-09 (reproduced here).
These looked similar in a ProjectMIDAS lower-resolution image dated 2017-07-12 (partial screen print below).

Shared Humanity's concern may be the apparent weakness on the 'left' side of the Bawden Ice Rise which may be more developed than it was 5 months ago.

For educational purposes:
Quote
An ice rise is a clearly defined elevation of the otherwise totally flat ice shelf, typically dome-shaped and rising 100 to 200 metres above the surrounding ice shelf. An ice rise forms where the ice shelf touches the rocky seabed because of an elevation in the seabed that remains below sea level.
Quote
Bawden Ice Rise (66°59′S 60°50′WCoordinates: 66°59′S 60°50′W) is an ice rise, 8 nautical miles (15 km) long and 2 nautical miles (4 km) wide, near the edge of the Larsen Ice Shelf, 41 nautical miles (76 km) east-southeast of Cape Alexander, Graham Land. The feature, which may consist of more than one ice rise, was mapped on a British Antarctic Survey (BAS) radio echo sounding flight from Adelaide Island in February 1975, and named by the UK Antarctic Place-Names Committee in 1985 after John Bawden, who was with BAS from 1971 and was Finance Officer, 1973–78.

I wonder if the bit of A68-A that recently broke off got stuck on (submerged) rocks...
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Shared Humanity

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Re: Rift in Larsen C
« Reply #298 on: May 14, 2018, 07:19:17 PM »
The 'fingers' at (or north of) the Bawden Ice Rise in today's image look like the image Tealight posted in December dated 2017-12-09 (reproduced here).
These looked similar in a ProjectMIDAS lower-resolution image dated 2017-07-12 (partial screen print below).

Shared Humanity's concern may be the apparent weakness on the 'left' side of the Bawden Ice Rise which may be more developed than it was 5 months ago.

For educational purposes:
Quote
An ice rise is a clearly defined elevation of the otherwise totally flat ice shelf, typically dome-shaped and rising 100 to 200 metres above the surrounding ice shelf. An ice rise forms where the ice shelf touches the rocky seabed because of an elevation in the seabed that remains below sea level.
Quote
Bawden Ice Rise (66°59′S 60°50′WCoordinates: 66°59′S 60°50′W) is an ice rise, 8 nautical miles (15 km) long and 2 nautical miles (4 km) wide, near the edge of the Larsen Ice Shelf, 41 nautical miles (76 km) east-southeast of Cape Alexander, Graham Land. The feature, which may consist of more than one ice rise, was mapped on a British Antarctic Survey (BAS) radio echo sounding flight from Adelaide Island in February 1975, and named by the UK Antarctic Place-Names Committee in 1985 after John Bawden, who was with BAS from 1971 and was Finance Officer, 1973–78.

I wonder if the bit of A68-A that recently broke off got stuck on (submerged) rocks...

Not talking about the fingers of ice north of Bawden. I'm looking at where the ice is in contact with the island. There are very visible troughs/depressions/rifts which come into contact with the island.

IMHO, the very dark portions of the ice shelf that run the entire length of the island are evidence of thinning and the 4 pronounced dark spots on the northern half that terminate each of the 4 troughs that run towards the island are due to melt or rifting.

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Re: Rift in Larsen C
« Reply #299 on: May 14, 2018, 10:42:59 PM »
"I'm curious why/how"
 It's worth considering the tides rotating clockwise through Weddel, being inhibited by the island, and forcing the island north. The islands cliffs are what 200ft high?, the warmer waters passing through are going to find the shallowest way through at the north end of the island, eventually cutting a deep gouge on the underside, maybe? It does look like some of the ice directly north of the island is new which may indicate deeper warm waters surfacing and briefly clearing the ice.