Canadian Arctic nearly loses entire ice shelf from global warming

Author: 
Charmaine Noronha
Source: 
Globe and Mail
Date published: 
Fri, 2011-09-30

Luke Copland is an associate professor in the geography department at the University of Ottawa who co-authored the research published on Carleton University’s website. He said the Serson Ice Shelf shrank from 205 square kilometres to two remnant sections five years ago, and was further diminished this past summer.

Prof. Copland said the shelf went from a 42-square-km floating glacier tongue to 25 square km, and the second section from 35 square km to 7 square km, off Ellesmere Island’s northern coastline.

This past summer, Ward Hunt Ice Shelf’s central area disintegrated into drifting ice masses, leaving two separate ice shelves measuring 227 and 74 square km respectively, reduced from 340 square km the previous year.

“It has dramatically broken apart in two separate areas and there’s nothing in between now but water,” said Prof. Copland.

Prof. Copland said those two losses are significant, especially since the Ward Hunt Ice Shelf has always been the biggest, the farthest north and the one scientists thought might have been the most stable.

“Recent [ice shelf] loss has been very rapid, and goes hand-in-hand with the rapid sea ice decline we have seen in this decade and the increasing warmth and extensive melt in the Arctic regions,” said Ted Scambos, lead scientist at the National Snow and Ice Data Center at the University of Colorado, remarking on the research.

Prof. Copland, who uses satellite imagery and who has conducted field work in the Arctic every May for the past five years, said since the end of July, pieces equalling one and a half times the size of Manhattan Island have broken off. Co-researcher Derek Mueller, an assistant professor at Carleton University’s geography and environmental studies department, said the loss this past summer equals up to three billion tonnes. Prof. Copland said their findings have not yet been peer reviewed since the research is new, but a number of scientists contacted by The Associated Press reviewed the findings, agreeing the loss in volume of ice shelves is significant.

Mr. Scambos said the loss of the Arctic shelves is significant because they are old and their rapid loss underscores the severity of the warming trend scientists see now relative to past fluctuations such as the Medieval Warm Period or the warmer times in the pre-current era.

Ice shelves, which began forming at least 4,500 years ago, are much thicker than sea ice, which is typically less than a few metres thick and survives up to several years.

Canada has the most extensive ice shelves in the Arctic along the northern coast of Ellesmere Island. These floating ice masses are typically 40 metres thick (equivalent to a 10-storey building), but can be as much as 100 metres thick. They thickened over time with snow and sea ice accumulation, along with glacier inflow in certain places.

The northern coast of Ellesmere Island contains the last remaining ice shelves in Canada, with an estimated area of 1,043 square km, said Prof. Mueller.

Between 1906 and 1982, there has been a 90-per-cent reduction in the areal extent of ice shelves along the entire coastline, according to data published by W.F. Vincent at Quebec’s Laval University. The former extensive “Ellesmere Island Ice Sheet” was reduced to six smaller, separate ice shelves: Serson, Petersen, Milne, Ayles, Ward Hunt and Markham. In 2005, the Ayles Ice Shelf whittled almost completely away, as did the Markham Ice Shelf in 2008 and the Serson this year.

“The impact is significant and yet only a piece of the ongoing and accelerating response to warming of the Arctic,” said Dr. Robert Bindschadler, emeritus scientist at the Hydrospheric and Biospheric Sciences Laboratory at the NASA Goddard Space Flight Center in Maryland.

Dr. Bindschadler said the loss is an indication of another threshold being passed, as well as the likely acceleration of buttressed glaciers able to flow faster into the ocean, which accelerates their contribution to global sea level.

Prof. Copland said mean winter temperatures have risen by about 1 degree Celsius a decade for the past five to six decades on northern Ellesmere Island.

            

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