Pacific Spirit Marine Institute

Sentinels of the high Arctic are disappearing from their posts.

Friday, August 1, 2008

It was fairly un-nerving when, a chunk of ice broke loose from the Ward Hunt Ice Shelf off the coast of Ellesmere Island recently, but it had to have been somewhat expected.

The Ward Hunt is near the most northerly point in North America. Located in quttinirpaaq National Park it is the largest of five remnants of a much larger ice shelf discovered by Admiral Peary in 1906.

More than 6 years ago Derek Mueller, then at Universite Laval, Quebec, found the biggest ice shelf in the Arctic was indeed breaking apart.

Canadian RADARSAT images acquired in August 2002 showed a huge crack running North-south down the center of the Ward Hunt Ice Shelf. Secondary fractures running west had fragmented a large area of the shelf into free-floating ice blocks.

At that time the shelf was home to a fresh water lake. These fresh water lakes are known as ehishelf lakes. That fracturing caused the immediate and catastrophic drainage of an ehishelf lake that had called the Ward Hunt Ice Shelf home. Ehishelf lakes are an important link in the ecology chain. This fresh water ‘floats’ on the more dense ocean water. Located in Disraeli Fjord this was the largest and best-understood epishelf lake in the Northern Hemisphere.

The epishelf lake suddenly spilled more than 3 billion cubic meters of fresh water into the Arctic Ocean.

Ice-dependant ecosystems are made vulnerable by the shifting climate. Microbial communities of algae, micro-invertebrates, and bacteria that could withstand near-freezing water temperatures, freezing and thawing cycles and organisms that used pigment changes to withstand ultraviolet radiation were suddenly and forever lost in that 2000-2002 crack-up and with them much information, and probably many untold secrets.

This most recent chunk of ice to separate from the Ward Hunt is 18 square kilometers across.

The Ward Hunt Ice Shelf is estimated to be around 3,000 years old. Ice core climate data and lake sediments indicate the ‘Little Ice Age’ ended about 150 years ago and the climate has been warming since then. Only about 10% of the original ice shelf may be remaining.

They say the precise triggering mechanism for these fractures isn’t known. Although temperature records from Alert which is 175 km east of the Ward Hunt Ice shelf show a significant increase in the annual mean air temperatures during the last 30 years which parallel the thinning and loss of the epishelf lake.

Derek Mueller, now a Trent University researcher says, “We’re in a different climate now.” “It’s not conducive to regrowing them.” [ice sheets] “It’s a one-way process.

In 2003 Mueller wrote of the Ward Hunt Ice Shelf, “…one thing seems clear: it and the other Ellesmere ice shelves are sentinels of high Arctic environmental change…”

Photo Thanks #2 NASA
#1 Canadian Space Agency

Labels: Arctic, Arctic Ice, Canada, Climate Change, Global Warming, North Pole, Quttinirpaaq National Park, Sea Ice, Ward Hunt Ice Shelf, ehishelf lakes