Late last year and early this year, various news stories reported the demise of the Ayles Ice Shelf, Ellesmere Island. On Dec. 29, 2006, National Geographic reported Giant Ice Shelf Breaks Off in Canadian Arctic and on Jan 4, 2007, CNN reported the story. The catastrophe actually occurred in August 2005, but no one
noticed reported it until 16 months later.
From the story:
The mass of ice broke clear 16 months ago from the coast of Ellesmere Island, about 800 kilometers (497 miles) south of the North Pole, but no one was present to see it in Canada’s remote north. Scientists using satellite images later noticed that it became a newly formed ice island in just an hour and left a trail of icy boulders floating in its wake. (Watch the satellite images that clued in ice watchers) ..
The event registered as a small earthquake on instruments stationed 150 miles (250 kilometers) away, Warwick Vincent of Quebec’s Laval University told the CanWest News Service.
The Washington Post reported the story here showing the following picture from NASA. The Ayles ice shelf is visible in the center of the photograph at the lower part of the open water. They reported:
Within days of breaking free, the Ayles Ice Shelf drifted about 30 miles offshore before freezing into the sea ice.
Here is a jpg showing the break-up (thanks , Mark – also see link in Mark’s post below):
A specialist scientist (Vincent) said that such an event was unprecedented in the tennnnnnnnnn years that he had been studying the area.
Interestingly, Hattersley-Smith 1967 (Arctic Circular 17, 13-14 noted up in Jeffries 1986) had previously observed that the Ayles Ice Shelf no longer existed. Jeffries 1986:
In 1966 only scattered ice islands and slivers of ice shelf were observed in Ayles Fjord (Hattersley-Smith 1967). Hattersley-Smith concluded that Ayles Ice Shelf no longer existed,
Jeffries 1986 went on to say that, as of 1986, it was known that the Ayles Ice shelf had actually moved 5 km out of Ayles Fjord, a position that it still occupied in 1984 (and presumably up to August 2005):
but this is now known not to be the case. Much of Ayles Ice Shelf, an area of about 100 km2, remains in the mouth of Ayles Fjord, but in a much more exposed position than in 1959.
So the calving of the Ayles Ice Shelf appears to have been at least a two-stage process – breaking off of its connection to land in the early 1960s and the most recent move into the polar ice pack.
Jeffries 1986 speculated that the cause of the original calving in the early 1960s coincided with a massive calving at the Ward Hunt ice shelf attributed to a coincidence of tidal and seismic events:
The cause of the massive calving of ice from Ward Hunt ice shelf has been attributed to the coincidence of tidal and seismic events in February 1962 that created a critical condition in the ice shelf and ultimately caused the calving event (Holdsworth 1971) …
Jeffries 2002 reports that, in some cases, multiyear landfast sea ice (MLSI) has re-occupied areas formerly occupied by ice shelves and may be incipient ice shelves.
Jeffries, Martin O., 1986. Ice Island Calvings and Ice Shelf Changes, Milne Ice Shelf and Ayles Ice Shelf, Ellesmere Island, N.W.T.. Arctic 39 (1) (March 1986) http://pubs.aina.ucalgary.ca/arctic/Arctic39-1-15.pdf
Jeffries MO. 2002. Ellesmere Island ice shelves and ice islands. In Satellite Image Atlas of Glaciers of the World: North America, Williams RS, Ferrigno JG (eds). United States Geological Survey: Washington, DC; J147–J164. http://pubs.usgs.gov/prof/p1386j/iceshelves/iceshelves-lores.pdf (This is an interesting account of ice shelves).