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Author Topic: Pine Island Glacier (PIG) Calving and Discussion  (Read 440067 times)

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2500 on: August 27, 2020, 05:29:29 PM »
I have a little more analysis of the shifting of Point2 and why it is happening now.

First image is a 6-day GIF with all motion relative to Point2.  You can see which pieces of ice are moving attached or along with Point2, and which pieces are moving away.

The second image is my reading of where the middle piece of Cork3 is caught between the prominence on the Southern Ice Shelf and icebergs attached to Point2.  Also shown are they previous contact points from June which demonstrates that shifting ice can result in different binding points that can raise or lower the risk of a major calving.

Third image is from a posting I made on June 16 showing the dynamics at that time.

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2501 on: August 31, 2020, 01:29:22 PM »
Some low-resolution clearing of the melange in the Northern Shear Margin today.  One-day GIF.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2502 on: September 02, 2020, 08:12:05 PM »
What had to happen, happened  ;)

Almond, goodbye
The outermost piece of Cork3 (relative to the SIS) follows him.

Tomorrow's image will be interesting to see the latecomers who will follow them.

NB: The image is from the 02, but we don't have any images from the 01/09.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2503 on: September 02, 2020, 08:19:21 PM »
PS: what is interesting is that the base of the Almond has been projected (hence a rotation of 90° degrees clockwise) which shows that a tension existed before calving.

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2504 on: September 03, 2020, 12:23:36 AM »
Yesterday's image came late today so a 1-day comparison is now available.  Don't read too much into what you see in the melange since the middle piece of Cork3 has apparently not moved, I don't think any significant has happened behind it.  It's merely an artifact of the different orbits and resolutions.

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2505 on: September 03, 2020, 06:08:15 PM »
Thank you baking and paolo,
almost no week passes by without a mini calving at either NSM or SSM. When will this stop? Until both zones of destruction are emptied??
It is too late just to be concerned about Climate Change

interstitial

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2506 on: September 03, 2020, 11:30:00 PM »
Thank you baking and paolo,
almost no week passes by without a mini calving at either NSM or SSM. When will this stop? Until both zones of destruction are emptied??
When eastern Antarctica returns to a chain of islands? This may temporarily slow but I don't expect it to stop or slow much until that ice river is mostly depleted to the source. Their is some historical evidence of order of magnitude or two faster motion in this glacier.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2507 on: September 04, 2020, 12:51:45 PM »
For the moment no new developments, but the extension and widening of the "new rift", which seems to connect to the cR1 (central rift 1), as well as an extension of the cR1 towards the front, which seems to be becoming clearer, seem to indicate that the calving of P2, as well as Cork3b, should not be long in coming.
Indeed, the iceberg stacking upstream of Cork3c has recently reactivated and, as a consequence, its action of destabilising the PIG, with extension and widening of the "new rift" and smR2.

Moreover, the two rifts cR1 and smR2 have extended and are to be followed very closely. In the not too distant future, they could lead to a significant calving of the PIG.

Click to zoom in

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2508 on: September 07, 2020, 10:05:48 PM »
P2 and Cork3b detachment underway

Click to zoom in

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2509 on: September 08, 2020, 11:35:49 AM »
Cork3b has detached itself, waiting for P2 ...

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2510 on: September 08, 2020, 08:19:45 PM »
so now the last named pieces in the SZD are on their way out.
Wonder how long the NW piece of PIIS with P2 will stay in place.
It is too late just to be concerned about Climate Change

Bernard

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2511 on: September 12, 2020, 12:27:27 AM »
Sorry to ask if it's a dumb question.

I've been following this destruction story for months (years?). Correct me if I am wrong, but it is currently just the end of winter in Antarctica. Should not the surroundings of PIG be stuck with sea ice at this time of the year? How comes all those calved icebergs seem able to float off freely and quite quickly?

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2512 on: September 12, 2020, 07:27:46 AM »
A very short answer:
It is not about air temperatures and missing insolation during the Austral winter, but about sea water temperatures which are high enough to allow a continuous melting of the ice shelf from below.
Pine Island Bay partly has polynyas, which means that "warmer" (0, 1, 2, 3°C) waters upwell close to the calving front.
It is too late just to be concerned about Climate Change

oren

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2513 on: September 12, 2020, 09:48:35 AM »
I think the question was how come there is a polynya in Pine Island Bay. I think it's not just upwelling but also about winds typically blowing offshore? (Maybe this is from the stupid answers department)

charles_oil

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2514 on: September 12, 2020, 11:10:42 AM »
I think also that the bergs are several orders of magnitude more massive (could be 100's of metres) than surrounding new sea ice (few m thick), so I imagine they can move around and displace / crush the sea ice if, as is likely, the winds / currents act differently on them.

Bernard

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2515 on: September 12, 2020, 01:34:32 PM »
Thanks for the answers, all making sense - for me at least.  :)

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2516 on: September 12, 2020, 02:06:56 PM »
One thing that hasn't been mentioned is that the glacier keeps moving no matter the season.  It pushes "smaller" icebergs and breaks off parts of the neighboring ice shelf as it goes.  When icebergs "float off" they don't usually go gently, but with a massive release of energy.

That said, the recent icebergs have not gone far.  Even in Pine Island Bay which is usually ice free for for large parts of the year, the sea ice is thick enough right now to keep them from floating away.  September is usually considered to be the time of maximum ice extent in Antarctica.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2517 on: September 12, 2020, 04:29:49 PM »
Some elements to complete and finalize this discussion:

Dimension at stake :
Sea ice: ~1m (the last place in the bay where the sea ice stabilizes and is no longer carried away, neither by the bay's current (turning clockwise) nor by the winds, being precisely the front of the PIG and it has only recently stabilized. The outgoing current, see below, can probably explain this.

Icebergs/Glacier: ~400m

Translated: an elephant and a small beetle

Clearly there is no possible comparison: when an iceberg is " ejected " by calving (expression of the existing tensions before calving which are released almost instantaneously), for it the sea ice does not exist.
Similarly, given its dimensions, if, following calving, it is no longer in static equilibrium and turns over.

On the other hand :
> the presence of sea ice can stop the movement of an iceberg more quickly than sea water alone
> a free iceberg surrounded by sea ice can be retained, even in the presence of currents or winds, if these are not too strong.


Warm current CDW :this enters the bay at depth (< -700m), reaches the grounding line, melts the PIG and comes out, passing under the glacier (and continuing to melt it), with water, whose temperature has dropped, but which is still warmer than sea water, which explains the formation of polynyas especially where it is stronger as in correspondence of the NSM, of the SSM and of the centre of the front (after the last big calving in February a new site appeared in correspondence of the Shear Margin between the SWT and the SIS).
This current is at its peak in autumn, but this is of no importance in relation to calvings. In fact its action, melting of the PIG, clearly has an influence on the dynamics of the glacier, but over the long term and not on a seasonal level.

To conclude, I would like to remind you, as Baking has already done, that the dynamics of the PIG is not currently linked to the seasons!

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2518 on: September 14, 2020, 01:58:22 PM »
Today's high-resolution image of the Southern Shear Margin shows a calving of the Southern Ice Shelf at the prominence where the "almond" was previously attached.  The remains of the "cork" pushing on the ice shelf just upstream probably contributed to the calving.  First image of the GIF is from 18 days ago, second is 6 days ago, and last is today.

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2519 on: September 14, 2020, 02:28:00 PM »
The eye likes to play tricks on you, and sometimes you see things that are not there.  Also, the data compression of JPEGs can take random noise and turn it into a pattern.  But I'm seeing today an extension of rifts on both sides of the PIG and possible cracks joining them, spreading across the entire glacier.  All motion in the GIF (click to view) is relative to the glacier.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2520 on: September 14, 2020, 02:42:25 PM »
I confirm Baking's impression, it's been several days, that I've been following the development of a fracture pattern over the entire glacier from nmR1 (in the north) to cR1 and smR2 (in the south), but for the moment lacks a clear and indisputable image, that's why I haven't published anything.

In any case we are already in two to have more than one impression!

To be monitored !!

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2521 on: September 14, 2020, 02:57:39 PM »
PS: The only difference is that I have the impression that there is also a system of fractures a little further upstream. We are eagerly awaiting the first Sentinel2 clean image...

grixm

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2522 on: September 14, 2020, 04:36:33 PM »
PS: The only difference is that I have the impression that there is also a system of fractures a little further upstream.

This one?

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2523 on: September 14, 2020, 05:23:07 PM »
Exactly

This was already visible a week ago.

PS: It's a pity, but the season will be interesting.

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #2524 on: September 14, 2020, 06:25:25 PM »
Maybe we will have the answer in a few days, when (hopefully) clear Sentinel VIS pictures will be available.
It is too late just to be concerned about Climate Change