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When will an ice island completely (definitively) break from the Petermann Ice Shelf (including the mid-tongue crevasse)?

before poll closes (before ~ August 19, 2019, GMT)
1 (1.6%)
rest of August 2019
3 (4.9%)
September 1 - 15, 2019
5 (8.2%)
September 16 - 30, 2019
10 (16.4%)
October 2019
10 (16.4%)
November - December 2019
8 (13.1%)
January - March 2020
9 (14.8%)
April - June 2020
5 (8.2%)
July - August 2020
5 (8.2%)
after August 2020
5 (8.2%)

Total Members Voted: 34

Voting closed: August 19, 2019, 04:22:10 AM

Author Topic: Poll: Petermann Glacier's next major calving event  (Read 4599 times)

Tor Bejnar

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Poll: Petermann Glacier's next major calving event
« on: August 05, 2019, 04:22:10 AM »
Background:
...
Also, from the July 3 post:
Quote
Furthermore, a new sophisticated computer model of Petermann Gletscher reveals that the loss of this large “still attached” ice island is already gone from the glacier in terms of the friction that it provides along the sidewalls. Another way of putting this, all it takes is a little wiggle or bump and the separation will become visible. Dr. Martin Rueckamp just published this study in the Journal of Geophysical Research.
JGR link
My Petermann posts here and here show the mid-tongue (or mid-shelf or mid-glacier) lateral crevasse extending southwestward and crevasses extending from the SW edge extending into the tongue during the past year.  Thomas Barlow showed the mid-tongue crevasse definitively connected to a crevasse coming from the NE edge of the tongue (although it was apparent in January with other sensors).  Other posts in the Petermann thread show the various crevasses widening.

So, when will an ice island completely (definitively) break from the Petermann Ice Shelf at the mid-tongue crevasse?

A calving boundary that does not include the mid-tongue crevasse doesn't count.  By "definitive" I mean clear satellite imagery that shows a continuous crevasse between the shelf and the new ice island in the area southwest of the mid-tongue crevasse reaching the SW edge of the tongue.  (There is one already northeast of the mid-tongue crevasse.)

(Just in case there are any questions about where I mean, tomorrow I'll post an annotated image of the Petermann Ice Shelf.)

The less sure you are of when the event will happen the more bins you can choose, up to 3.  As it is all a guess (unless it cracks within a fortnight), we should all probably choose 3 bins! Votes can be changed.  Of course, kudos to the person who votes only one bin and correctly!  In case it breaks at a bin edge, time is GMT (with which some satellite images are tied).
« Last Edit: August 05, 2019, 05:37:40 PM by Tor Bejnar »
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #1 on: August 05, 2019, 05:26:33 PM »
Here is the promised map of the Petermann Glacier tongue and the general vicinity of where a crevasse must open to qualify for this poll.

Universal suffrage:  please vote!  (in up to 3 bins)
« Last Edit: August 05, 2019, 05:38:01 PM by Tor Bejnar »
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blumenkraft

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Re: Petermann Glacier's next major calving event
« Reply #2 on: August 05, 2019, 05:37:59 PM »
As mentioned in the Petermann thread, i think it's going to happen in winter.

There are holes and ponds with freezing and expanding water in winter. Perhaps this gives it the needed last push.
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #3 on: August 06, 2019, 08:20:10 PM »
Two frame GIF shows crevasses lengthening between May and August this year.  Sentinel-hub Playground images from May and August.  The apparent gap between growing crevasse ends decreased by around 1.0 - 1.5 km these past three months.  How long to crack the remaining 4 km of ice shelf?

Remember, you can vote in up to three bins if you are less sure or more tentative. 
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oren

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Re: Poll: Petermann Glacier's next major calving event
« Reply #4 on: August 06, 2019, 10:21:10 PM »
I voted for Jan-Aug 2020. Just a hunch. Petermann is a huge but slow beast.

petm

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Re: Poll: Petermann Glacier's next major calving event
« Reply #5 on: August 06, 2019, 11:56:32 PM »
Well that's quite a glacier and quite a crack!

Probably way too optimistic (pessimistic?), but I chose the first 3 bins.

I really have no idea, but my reasoning is: The crack should grow faster now both due to a non-linear response of increased stress over a decreased remaining distance, and due to faster ice dynamics this time of year (exacerbated by the recent surge of heat into Greenland).

If I remember, I'll strategically shift my 'before end of poll' vote to the next bin just before the poll closes. ;)

By the way, Google Maps (satellite) has quite an interesting collage of Petermann (att).

Thomas Barlow

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Re: Poll: Petermann Glacier's next major calving event
« Reply #6 on: August 10, 2019, 02:56:47 PM »
I think will be stabilised a little in winter, and it is so slow to change, I put it at after August 2020, but what do I know.
« Last Edit: August 10, 2019, 08:44:41 PM by Thomas Barlow »

FishOutofWater

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Re: Poll: Petermann Glacier's next major calving event
« Reply #7 on: August 13, 2019, 03:05:27 AM »
I voted 3 bins October through March. The thick central area is going to take a little time to break through but it's going to happen inevitably.

Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #8 on: August 13, 2019, 06:00:42 PM »
Here is a 4-frame GIF showing crevasse development from July 3 to August 12.  Click is required.

Sentinel-hub Playground images from July 3, July 18, August 1 and August 12.  First and last frames stay longer.  First frame has a green line just below the mid-glacier crevasse (only the SW end of the crevasse is showing) so you can find it.  Last frame has the end of this crevasse underlined in yellow; two red lines are beneath a streambed (not a crevasse); and a green line is just below the end of the longest crevasse coming from the southwest edge of the shelf (on the left side of the image).

This southwest-edge-of-the-shelf crevasse's ~200m growth appears to have all occurred between the first two frames (basically, the crevasse extension just above the green line).  The mid-glacier crevasse appears to have grown just over 1 km during this 6-week period.

500m scale in lower right corner is half obscured by frame date.  (Sorry about that.)
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #9 on: August 15, 2019, 04:23:28 AM »
As shown by the GIF Espen posted of the Ryder Glacier calving in 2016, a stretch of ice shelf can have no crack then both crack open and separate within a day.

Can someone who follows tidal forecasts report when the next high tide or two will occur at Petermann Glacier?  (I know actual tides have been measured there, but are there forecasts?)  My guess is a high tide or a cyclone nearby (with strong winds blowing down the fjord) will break the future ice island away from the remaining shelf.
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Espen

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Re: Poll: Petermann Glacier's next major calving event
« Reply #10 on: August 15, 2019, 08:45:07 AM »
Full Moon at Petermann Gletscher today at 10.29 AM local (about 4 hours from now)
« Last Edit: August 15, 2019, 09:32:48 AM by Espen »
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johnm33

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Re: Poll: Petermann Glacier's next major calving event
« Reply #11 on: August 16, 2019, 10:13:54 AM »
I chose sept16-30, the frequent stops and starts of ice export in Fram suggest to me that the deep current of Atl. water from the north is balancing most of the demand of the gradient between the Arctic and Baffin. That current I'm guessing enters on the north side of Peterman and leaves on the south side, enhanced by the tides, so since I expect that current to warm until at least mid sept. the best chance of the island breaking free probably comes towards the end of sept as the tides peak.

Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #12 on: August 16, 2019, 06:45:34 PM »
Looking 'closely' at the crevasse northeast of the lateral (transverse) crevasse (where the NE crevasse is about 535-540 meters wide) on August 1 and August 15 suggests it has widened about 5 meters during this fortnight.  GIF from Sentinel-hub Playground images from 2019-08-01 and 2019-08-15.  Shelf image has an oval in the area shown in the GIF.  The yellow line segments offer a reference point 'associated' with the crevasse edge (and are not intended to define either image's edge).

The images were juxtaposed to show the crevasse remaining in place.  The date blocks are fixed on the originals, and show this part of the tongue has moved about 70 meters during the two weeks between images.

Edit:  a day and a half to vote!  Remember, you can vote in up to 3 bins.  The more the merrier!
« Last Edit: August 16, 2019, 06:50:50 PM by Tor Bejnar »
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #13 on: August 20, 2019, 04:29:46 PM »
Well, voting closed while I was busy elsewhere.  The Petermann Glacier is covered by clouds these past few days, so here is a Polar View image of the mid-tongue crevasse from yesterday.  (The mid-tongue transverse (lateral) crevasse is just above the added yellow line.)

No obvious crevasse between the transverse crevasse and the SW (left) margin of the tongue.
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #14 on: September 03, 2019, 05:47:12 AM »
We're into September and I don't see any crack creating this major calving event (today's Sentinel image).  What I 2-weeks ago identified as stream beds (underlined in red here) may be an extension of the mid-glacier transverse crevasse (as someone else has suggested).
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #15 on: October 01, 2019, 08:01:57 PM »
It's October 1 (or later, depending on your longitude) and the most recent image I find for the Petermann Glacial Tongue is from September 29th.  PolarView image screen print below.  No convincing evidence the crack connects to the SW edge of the tongue.  The timing of the 'expected' calving event continues to elude us.
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nukefix

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Re: Poll: Petermann Glacier's next major calving event
« Reply #16 on: October 03, 2019, 10:14:02 AM »
It's October 1 (or later, depending on your longitude) and the most recent image I find for the Petermann Glacial Tongue is from September 29th.  PolarView image screen print below.  No convincing evidence the crack connects to the SW edge of the tongue.  The timing of the 'expected' calving event continues to elude us.
Now would be a good time to do InSAR-analysis of the tongue to see how far the crack really goes. It is not entirely straightforward since the tongue is moving between the image acquisitions. The data and tools to do it are free...if only I had the time..

Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #17 on: October 03, 2019, 07:43:53 PM »
No change, per yesterday's PolarView image, although the circled area is suggestive (as it has been for a year).  I, too, desire the ability to do (or, really, have somebody else get all the glory and do it themselves) interferometry on Petermann's tongue.
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #18 on: October 22, 2019, 04:48:02 PM »
cross post:
Although I expected a real calving in 2019 which obvisously did not happen, the cracks at the port side of the glacier are still extending further towards each others.
The cracks are shown with a red 1. and 2.
Go to Espen's original for a GIF showing September 27 and October 21 (2019) changes in crack width or length.
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #19 on: October 22, 2019, 05:03:59 PM »
Per the votes above, some folks believe the 'real calving' could well still happen in 2019.
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Tor Bejnar

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Re: Poll: Petermann Glacier's next major calving event
« Reply #20 on: November 08, 2019, 02:42:25 PM »
Am I seeing something or just wishful thinking? PolarView image from November 6, 2019  (Okay, my lines could be a little bit better drawn, and there are other possible traces ... and there is a possible connection between the two segments ...)
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