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Artful Dodger

Neven: the impression I get is whenever an ice floe collides with a larger object, whether coast or a larger floe, then instead of getting compaction, we see a fracture of the floe. The relative shape of the resulting floe tends to become more elliptical with successive collisions, so that shape becomes a proxy for elapsed time since the floe separated from the pack ice. New floes are geometric, older floes are more rounded.


It does seem to have slowed down recently - if you look at the PIPS 2.0 animation on your update 26 you can see the displacement is across or away from the archipelago for the last week.

Cloud made it difficult to tell, but I think some large floes were also blocking movement somewhat. That seems to have cleared as there now appears to be plenty of movement deeper in the NWP; one of the biggest free floes around is currently zipping down M'Clintock Channel at a good rate, smashing up the last of the ice pressed against the east coast of Victoria Island, and there is still quite bit of ice moving between Bathurst and Melville Islands into Viscount Melville Sound (the southern exit of Prince Gustav Adolf).

Todays forecast (for 26/8) shows much stronger displacement towards this area, especially towards Prince Gustav Adolph - the most effective channel for export through the archipelago (and the most open, I think). I'm no expert on reading PIPS maps, but I would expect from the prediction for 26/8 that tomorrows prediction will show even stronger displacement in this direction.

Ballantyne Strait doesn't really lead anywhere much, and ice passage through there will always be pretty hit and miss.

Artful Dodger

Huge ice chunk breaks off Ellesmere Island

"A large parcel of ice has fractured from a massive ice shelf on Ellesmere Island, marking the third known case of Arctic ice loss this summer alone.

The chunk of ice, which scientists estimate is roughly the size of Bermuda, broke away from the Ward Hunt Ice Shelf on the island's northern coast around Aug. 18, according to NASA satellite imagery."

Read more: http://www.cbc.ca/canada/north/story/2010/08/24/ellesmere-ward-hunt-ice-shelf.html


Well its not trivial - 50 sq kms out of the 400 or so sq kms left of the Ward Hunt Ice Shelf - but its not that huge when you note that just down the coast, there is a 900 sq km floe (~38 x 23 kms) of compacted seaice on the move. Its probably not as thick, but I'll bet it has more volume overall. Its heading WSW along the coast of Ellesmere and will probably head into the Sverdrup/Peary channels.

Meanwhile, the ice is moving more freely now. Today (Day 237 - 25/8/10) the ice advanced about 6 kms* down Prince Gustav Adolf, and a similar distance (eyeball, I didn't measure) in Peary/Sverdrup. PGA has a front of ~90 kms, so that would be 500 sq kms down this channel. With the other outlet channels, that would be about 1000 sq kms per day exiting the Arctic Basin through the archipelago, on top of any other losses.

*measured against a large floe in the middle of the channel. Its less in the west and more in the east, so the average is probably about right.


"A large parcel of ice has fractured from a massive ice shelf on Ellesmere Island, marking the third known case of Arctic ice loss this summer alone."

BTW - called it, before the MODIS pix were posted:
"BTW - if anyone wants to watch the demise of a couple of the four remaining Arctic iceshelves, have an optic at the north coast of Ellesmere Island. At the time of year that the high latitudes are supposed to be firming up, one of the few remaining solid areas of ice is falling apart. Ward Hunt - the biggest - has a big crack from 2008, and it looks to me like the eastern end is going to be toast in a few days."

Well, okay, it didn't completely fall apart, but close enough for a Kryten moment: "Ahhhh, smug mode...."

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