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Author Topic: Rift in Larsen C  (Read 67541 times)

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
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
Omnia mirari, etiam tritissima.

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
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.

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.]
Arctic ice is healthy for children and other living things.

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
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

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.