I-Mockery Forum - Largest Arctic Ice Shelf Melting

Arctic ice shelf melting, tearing itself apart
First casualty was lake containing both fresh, saltwater

By STEPHEN STRAUSS, Toronto Globe and Mail
September 24, 2003

The largest Arctic ice shelf is beginning to rip itself apart, 4,500 years after it began forming.

As it does so, it has begun to destroy a unique ecosystem that was starting to tell scientists both how life might have survived periods in which the Earth was frozen and how it might exist elsewhere in the solar system.

During the past two years, scientists at the University of Laval and the University of Alaska have begun to measure huge fissures tearing apart Ward Hunt Ice Shelf.

The shelf, which is more than 270 square miles, has "snapped in two," said Warwick Vincent, a professor of ecology at Laval.

According to images taken by Canada's Radarsat satellite, the fracture occurred sometime between 2000 and 2002.

In a paper soon to be published in the journal Geophysical Research Letters, the researchers report that the first casualty of the breakup was a unique lake.

Scientists believe it had existed in back of the ice shelf since Ward Hunt first started forming off the northern flank of Ellesmere Island.

The upper part of the lake was freshwater, and the lower part was salty seawater that had seeped under the ice shelf. Together they created an ecosystem in which freshwater and saltwater versions of the same small animals existed.

The sudden draining of this lake through the new crack produced a flood into the Arctic Ocean of no small consequence.

"My graduate student has estimated that the amount of water lost would have been equivalent to the water that flows over Niagara Falls in a month," Vincent said.

The appearance of a rift, miles long and more than 200 feet wide in some places, is also causing scientists to rethink their notions of the effect of global warming, both human-induced and natural, on the Eastern Arctic.

The area had been seen as an island of relative stability in a northern cold zone, despite notable warming in Siberia and Alaska.

Going back over the historical temperature records, scientists see an accelerated increase in the air temperature over the now-dry lake bed since 1967.

Some of the rise is related to a general warming since what is known as the Little Ice Age froze things on Earth in the middle of the 19th century. Higher temperatures since then have melted about 90 percent of the ice banks first reported in the area by early European explorers.

However, the scientific consensus is that the warming is likely to be the result of man-made processes as well.

While only relatively small portions of the ice field have broken off and drifted out to sea, scientists believe that the entire field is now unglued from its moorings.

The disappearance of the shelf would take with it a unique ecosystem. Each year, on top of the ice, a bright orange patch appears. It is composed of a tangled mat of algae, bacteria and single-celled animals that are reborn after being frozen for most of the year.

The ecosystem's existence has been used by proponents of the so-called Snowball Earth hypothesis to explain how life could have continued to exist when geological records suggest that much or all of the planet was icebound during periods 500 million to 700 million years ago.

The resilience of the ice-field ecosystem also could explain how microscopic life might exist on cold places such as Jupiter's moon Europa. Astronomers now believe underground water or "warm ice" might harbor what is called "extreme life."

Source: http://www.knoxnews.com/kns/science/...292204,00.html