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Stephan

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Re: PIG has calved
« Reply #950 on: February 17, 2019, 12:02:11 PM »
A new Sentinel picture of PIIS is available. I checked the actual rifts and didn't find any relevant lengthening or widening. Only a very little calving must have taken place this week (500m x 150m of ice is missing) close to the junction of PIIS and the SW tributary glacier at the same place where another calving event took place two weeks earlier.
I looked at three different features of PIIS and compared their NW-ward drift between Jan 27 and Feb 16 (=20 days). The movement of the ice was 272m, 263m and 270m, respectively, which results in a speed of ~13-14 m/day, which is in the upper range of what has been calculated earlier.

The small rift in the SW tributary has moved north by about 36 m in the same time, which shows a much smaller speed (ca. 2 m/day).
« Last Edit: February 17, 2019, 02:01:57 PM by Stephan »

b_lumenkraft

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Re: PIG has calved
« Reply #951 on: February 17, 2019, 02:03:27 PM »
Hey Stephan, thanks so much for your meticulous updates! :)

I wonder when this sucker is due. I take bets!  8)

Stephan

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Re: PIG has calved
« Reply #952 on: February 17, 2019, 02:16:37 PM »
I went back in Sentinel around 25 months ago, and at that time this rift looked almost the same as it does now.
So the answer to your bet may take a while  ;)

b_lumenkraft

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Re: PIG has calved
« Reply #953 on: February 17, 2019, 02:36:08 PM »
Oh, i didn't realize it's there for so long.

I'd say you are right, but that would be lame. So i say it's gone before the sun is gone.

Stephan

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Re: PIG has calved
« Reply #954 on: February 17, 2019, 10:27:33 PM »
I just compared PIG February 2018 with February 2019. The western flank of it shows much more cracks and bergs within a frozen sea in 2019 compared to 2018. The area where these features appear, has grown longer and wider (circled in blue). I see this as the beginning of a further dis-integration and a preparation of more and more frequent calving events in the coming years.

I also want to correct my statement from earlier this day: One of the cracks has widened by about 50% since early January 2019. It is marked in yellowish green.

See attached pictures. And please compare the calving front which has massively moved inland.

Andreas T

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Re: PIG has calved
« Reply #955 on: February 17, 2019, 11:03:04 PM »
Here are some pictures of research in Pine island bay happening now. I had not realised that there are parts which get free of snow in the summer.
https://www.facebook.com/thwaitesglaciercollaboration/?fref=mentions&__tn__=K-R

I assume these were taken on the Lindsay islands mentioned in an earlier post
http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=apollodata/data_polarview_apollodata/ahf/S2B_MSIL2A_20190206T151259_N0211_R139_T13CEU_20190206T182919.3031.crop.8bit.jp2

maga

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Re: PIG has calved
« Reply #956 on: February 19, 2019, 10:34:34 PM »
There seem to be some cracks which will be very important and interesting to watch in the future that nobody seems to have noticed so far. I tried to highlight them together with the bigger known ones. To be clear: I'm talking about the small ones that are the most retreated. Probably you have to watch the original Sentinel pic yourself in order to see them properly.


Stephan

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Re: PIG has calved
« Reply #958 on: February 20, 2019, 10:15:00 PM »
There seem to be some cracks which will be very important and interesting to watch in the future that nobody seems to have noticed so far. I tried to highlight them together with the bigger known ones. To be clear: I'm talking about the small ones that are the most retreated. Probably you have to watch the original Sentinel pic yourself in order to see them properly.
Please look at my postings #917, #921 and #930 in this thread.
PS: I noticed the three short parallel cracks which are the southermost of them, buit I didn't yet mention them in one of my postings.

Stephan

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Re: PIG has calved
« Reply #959 on: February 21, 2019, 07:11:58 PM »
I analysed the cracks on PIIS on Feb 20 and compared them with Feb 06, 2019.
Some cracks have relevantly widened (marked in dark red), one has grown longer (marked in orange) and a new very thin crack appeared very close to the calving front (marked in yellowish green). [Edit: I just discovered a new thin crack, also marked in yellowish green, which is roughly the continuation of the bigger crack in the centre of the image (marked in blue) and N of the four short parallel cracks mentioned two postings above (circled in pale magenta)]
See attached picture.
« Last Edit: February 21, 2019, 09:45:03 PM by Stephan »

IceConcerned

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Re: PIG has calved
« Reply #960 on: February 22, 2019, 05:57:08 PM »
Same analysis on the Western cracks. The new thin one is approx. 1km long, and is doubled by the prolongation of the longer one a little further downstream
On the eastern side, the crack appears to have significantly widened and lengthened (2km?)

b_lumenkraft

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Re: PIG has calved
« Reply #961 on: March 02, 2019, 01:06:44 PM »
PIGs snout is moving fast!

Comparison  A: 2019-03-02, B: 2019-02-16

Corrected Reflectance (True Color)
Suomi NPP / VIIRS

Stephan

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Re: PIG has calved
« Reply #962 on: March 03, 2019, 08:27:30 PM »
The clean-up of Pine Island Bay from fast sea ice continues. After about two weeks of cloudiness EOSDIS offered a very clear view on Pine Island Bay.
I marked the missing (comparison with Feb. 04, 2019) areas of fast sea ice in red.
Please also note the big "crack" at the eastern shore of Thwaites Ice tongue. It is no crack, it is just the gap between the ice tongue and the sea ice/iceberg mélange that was pushed towards the ice tongue the last days.
The "green" iceberg in the centre is the biggest remain of the last calving event (Oct 2018). It has moved slightly inland the last days and rotated by around 300° compared to a month ago.
I wonder whether "this will be it" for this melting season, we're approaching equinox in a few weeks.

See attached picture.

Stephan

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Re: PIG has calved
« Reply #963 on: March 10, 2019, 09:09:34 PM »
Finally a new Sentinel Picture from March 02 is available. Unfortunately it is not as clear as the 20 Feb or 01 Jan picture. Nevertheless I took the chance to compare it with previous ones.
Main findings:
1. The Pine Island Ice Shelf continues its WNW movement, the SW Tributary moves northward
2. The cracks are almost the same as on Feb 20 or Jan 21.
3. New little cracks are highlighted in yellow.
4. A minor calving has taken place at the merger of PIIS and the SW tributary. The area lost was about 0.3 x 0.1 km, not much of a deal (circled in red)
I took several features and measured their movement. The speed differs from place to place. I calculated them (March 2 minus Dec 28 to have a longer time distance) and wrote them into the picture. Unfortunately the central and eastern part does not present useful features which can be followed easily, therefore there is no data in that region.

See attached picture.

oren

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Re: PIG has calved
« Reply #964 on: March 10, 2019, 10:14:12 PM »
Thank you Stephan. This is of course worrying as the PIG's flow speed is considered to be 4000 m/year, translating to 11 m/day. So you measurements seem to indicate a speedup of around 10%.

Stephan

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Re: PIG has calved
« Reply #965 on: March 19, 2019, 06:39:13 PM »
I can report about a little calving event (ca. 2 * 1 km) on the central front of PIIS, marked in brown.
Unfortunately the actual Sentinel picture (March 18) is so cloudy that I cannot use it for demonstration purposes. So I decided to take the last clear picture (March 2) of PIIS and marked the position of ice that was lost during the last days.
The gap south of the calving front has not widened the last weeks, so the speed of both parts must be roughly the same.
See attached picture.

Susan Anderson

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Re: PIG has calved
« Reply #966 on: April 10, 2019, 04:48:08 AM »
Earth Observatory has a nice animation and summary: The Wide View of a Shrinking Glacier: Retreat at Pine Island. It's longish and presents a range of information.
https://earthobservatory.nasa.gov/features/pine-island

IceConcerned

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Re: PIG has calved
« Reply #967 on: April 11, 2019, 12:06:29 PM »
Good image from Worldview today
New cracks on the eastern side (circled)
And I have the impression that the big central cracked have lengthened (see the white lines). Or is it just a visual artifact ?

Stephan

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Re: PIG has calved
« Reply #968 on: April 11, 2019, 06:50:37 PM »
Could you please zoom out this picture to identify the exact location? Thanks

b_lumenkraft

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Re: PIG has calved
« Reply #969 on: April 11, 2019, 07:03:22 PM »

Stephan

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Re: PIG has calved
« Reply #970 on: April 11, 2019, 07:17:16 PM »
Thank you.
I analysed the picture with the Sentinel images of Feb 20 and March 02, 2019 and couldn't find any difference (apart from the minor calvings I reported some weeks ago). So there was no calving. The floating iceberg must come from somewhere else. With persistent E / NE winds in the last weeks it is likely that it has been driven into the bay close to the calving front of the SW tributary during that time.
_____

Unfortunately there seems to be no (more) EOSDIS and Sentinel pictures of Pine Island Bay or Thwaites area due to the coming Austral winter. So Polarview may remain as only source for changes along the Amundsen Sea calving fronts.

Wipneus

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Re: PIG has calved
« Reply #971 on: April 14, 2019, 06:36:31 PM »
Very late in the season for an optical image but here it is. With a solar elevation of just 1.45 degrees (IIRC that is just three solar disks), the shadowed cracks are shown in exquisite detail.

Notice that the pair of major cracks are getting accompanied by a couple more to the right. This is a new feature, these new ones are not visible on a similar image 9 days older.

Uploaded in the native 15m/pix resolution, you must click the image for the better view.

steve s

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Re: PIG has calved
« Reply #972 on: April 14, 2019, 07:02:40 PM »
I think I see distortions in the fresh snow beyond some of the visible cracks, implying they are growing rapidly.

Stephan

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Re: PIG has calved
« Reply #973 on: April 14, 2019, 08:39:10 PM »
Just for comparison:
This is the latest clear Sentinel image from Feb 20, 2019.
In my opinion the SW crack (the low left one in Sentinel, the right one in Wipneus' post) has grown, widened and lengthened since then. But for a "perfect" comparison the angles of sunlight should be as identical as possible.
With probably no more Sentinel pictures of that area in the coming Austral winter I hope that others will follow this crack, because: If it cracks completely (= calving) it will be the highest ever calving front of PIIS, also exposing the already broken-up western flank of PIIS to open waters with probably even more (minor) calving events to follow.

Big thank you to Wipneus for this wonderful and clear picture.

lifeblack

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Re: PIG has calved
« Reply #974 on: April 15, 2019, 07:01:07 PM »
If it cracks completely (= calving) it will be the highest ever calving front of PIIS, also exposing the already broken-up western flank of PIIS to open waters with probably even more (minor) calving events to follow.

Big thank you to Wipneus for this wonderful and clear picture.

What would be the height above sea level of the exposed ice cliff? 
Also, a question regarding ice-cliff failure....  If the face of the partially complete crack is high enough to fail, could the sides of the crack fail and wedge the crack futher apart?

Stephan

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Re: PIG has calved
« Reply #975 on: April 15, 2019, 09:19:46 PM »
The same question came into my mind. I wonder whether actual altitude measurements exist on PIIS and which height the cliff would have at the actual cracks if it calves at that place, and if this height would meet "MICI criteria".
Please also look at ASLR's fantasic latest news from the WAIS conference (in the multiple meter sea level rise thread).

lifeblack

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Re: PIG has calved
« Reply #976 on: April 16, 2019, 12:45:49 AM »
The same question came into my mind. I wonder whether actual altitude measurements exist on PIIS and which height the cliff would have at the actual cracks if it calves at that place, and if this height would meet "MICI criteria".
Please also look at ASLR's fantasic latest news from the WAIS conference (in the multiple meter sea level rise thread).

looks like per page 32 of this paper:  https://www.the-cryosphere-discuss.net/tc-2018-209/tc-2018-209.pdf
(Ice shelf basal melt rates from a high-resolution DEM record for Pine Island Glacier, Antarctica)
eyeballing the vicinity gives something around 60M above the local sea level

Wipneus

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Re: PIG has calved
« Reply #977 on: April 17, 2019, 11:47:44 AM »

In my opinion the SW crack (the low left one in Sentinel, the right one in Wipneus' post) has grown, widened and lengthened since then.

PS. these Sentinel Images are from identical orbital positions.


Mostly yes. Here is an animation of a month of Sentinel 1 A/B images showing changes in the other crack as well, less pronounced perhaps.

As a result from the 10m/pix resolution, you must click the image for the better view.

b_lumenkraft

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