The Petermann Glacier covers some 1,295 square kilometers (500 square miles) along the northwestern coast of Greenland, and its floating ice tongue is the Northern Hemisphere’s largest. It has occasionally calved large icebergs. On this map from the Environment Canada website we see the exact location of the glacier:
Back in 2008 Pelto wrote a guest commentary for RealClimate, stating the following:
The Petermann Glacier lost a substantial area, 29 km2 due to calving this summer, and a crack well back of the calving front indicates another 150 km2 is in danger. The volume of the ice lost is much less than that from the loss of a comparable area by Jakobshavn because the ice is an order of magnitude thinner. Once again the key to this glacier’s second major ice loss this decade after limited retreat in the last century, is thinning of the floating tongue, which weakens the glacier. The loss of this ice should then lead to acceleration, developing more crevassing and glacier retreat. The crack seen in the image of Petermann Glacier (ASTER image provided by Ian Howat of Ohio State) is more of a rift, like those on Larsen Ice Shelf, than a crevasse. This transverse rift is further connected to longitudinal-marginal rifts. Illustrating the poor connection of the Petermann Glacier to its margin and lack of a stabilizing force this margin has, even 15 km behind the calving front. This is not the only rift of its kind on the glacier. Also note that like on Larsen Ice Shelf the rift crosscuts surface streams.
Allow me to first show this small animation I've made of the breaking off of the sea ice in front of the glacier these past few days (click for a slightly larger image):
And now compare it to previous years. For instance 2008, shown in this image from the Glacier Change blog (please notice on the lower, bigger picture that Manhattan Island has been drawn in to give a sense of proportion):
The sea ice seems to break off just a few days earlier this year.
Here's a little animation that compares 2010 to 2009:
By this time in 2009 the sea ice had already broken off a week earlier, on day 172 to be precise. Judging from the snow surrounding the glacier 2010 appears to be a little warmer.
Obviously this is just the start and some more sea ice has to break off to approach 2008 circumstances. Whether the warm conditions in the Canadian Archipelago, the lack of ice bridges in Nares Strait and the transport of ice floes from the Lincoln Sea have any influence on the big rift halfway the glacier leading to major calving off this summer, remains to be seen. But keep an eye on it and give a shout in the comments if and when it happens.
For more detailed pictures of the big rift have a look at NASA's Image of the Day from September 12th 2008.
I don't think the tongue material is properly referred to as sea ice.
Posted by: Steve Bloom | July 02, 2010 at 23:23
"I do not approve of appealing to authority, but there's nothing wrong with sucking up to authority, is there?"
Neven: you really made me laugh out loud with that one! Nice! :-)
Steve: the tongue is, of course, glacial ice. Until recent decades it extended right up to Nares Strait. It then receded, but the bay was filled with melange - not exactly sea ice. Last year the area around the end of the tongue seemed filled with more sea ice than melange. I think that the Petermann sea ice/ melange, and the ice from Kane Basin, is holding down SSTs.
Posted by: logicman | July 03, 2010 at 00:05
Just shy of a century break for the prelim for the 2nd. Still the curve appears to have more of an upturn due to the averaging.
Still a race, it would appear.
Posted by: Kevin McKinney | July 03, 2010 at 06:17
I don't think the tongue material is properly referred to as sea ice.
Sure, but what is breaking off isn't tongue material either, is it? In all three pictures/animations you see the same basic shape for 2008, 2009 and 2010. I would guess that that's the glacier and the stuff in front of it is ice that froze there during winter.
Posted by: Neven | July 03, 2010 at 08:18
I agree Neven that the glacier ice front did not change in 2009 and yes what is disappearing is just the sea ice in front of the glacier tongue. The reason this tongue is vulnerable is that it is only on the order of 70 meters thick at the end with less than 10 m of free board. This is typical for a small ice shelf not a big Greenland outlet glacier. I do expect a notable calving retreat this summer. The reduced snowcover indicates a more advanced stage of melting in the region this year, which was the case in 2008 as well.
Posted by: Glacierchange.wordpress.com | July 03, 2010 at 13:17
Thanks, Mauri! A 'notable calving retreat' should make for some spectacular pictures. That's the only fun thing about it, though.
Posted by: Neven | July 03, 2010 at 14:30
Neven
I really like your animations.
Can you share some details on how you make them?
I use ImageJ, what software do you use?
How do you label your individual images with year and day of year. I find that very helpful in following time sequence.
Posted by: Chartsgraphs.wordpress.com | July 03, 2010 at 15:59
Can you share some details on how you make them?
Sure. I use Photoshop to put the dates on images, by making templates first. I then copy the MODIS image into the template, change the date and save the image. I do it for all images, which is a bit of a hassle, but I don't how to do it otherwise yet.
For this image for Petermann glacier I figured out yesterday how to use guide lines so I can make templates that make it easier to cut out the part that I need from the high resolution (250m) images.
I then use the program Easy GIF Animator to make the animations. It's a great little program that allows you to resize the image or change saved animations (like I'm doing with the McClure Strait animation that is updated every day for the time being).
Posted by: Neven | July 03, 2010 at 16:14
Neven: not yet in today's mosaic as I write this, but I picked it up in a near-real-time image.
It's a biggy!
http://www.science20.com/chatter_box/arctic_newsflash_petermann_ice_tongue_loses_huge_chunk
Posted by: logicman | August 05, 2010 at 17:01
Holy Mary, that is HUGE! That has to be the most impressive image of this melting season so far.
Everyone, check that out. Now.
Posted by: Neven | August 05, 2010 at 17:10
I'm too worn out to make any sort of accurate estimate of size. 300km2 maybe, or is that too much?
Help! Pixel counters wanted. No pay, just kudos. :-)
Posted by: logicman | August 05, 2010 at 17:32
The main lump is 250 km2. There's an additional 20km2 diffuse white patch between the main piece and the west shore of the fjord, which may or may not be attached to the shore and/or the floating ice. There's probably an additional 10 km2 or so of loose ice floating around the margins.
So, somewhere between 250 to 280 km2. Pretty close to your estimate!
Posted by: me.yahoo.com/a/OoZSnzoSgsZAqZRMd5eHntQ.HVlUqjgbqI0- | August 05, 2010 at 18:21
Grateful to you for those figures, friend.
Posted by: logicman | August 05, 2010 at 18:47
Petermann's glacier have broken my heart.its because lol too long followed this rip apart
Posted by: meelis | August 07, 2010 at 04:18
Hey Patrick. Well done on being way ahead of mass media.
BBC covered it today. 260 sq/km is their estimate of the size of it.
http://www.bbc.co.uk/news/science-environment-10900235
Posted by: Jim Dowling | August 07, 2010 at 09:26