Thursday, September 20, 2012

Glacier drainage

Andy Soos in Environment News Service: Fast-flowing and narrow glaciers have the potential to trigger massive changes in the Antarctic ice sheet and contribute to rapid ice-sheet decay and sea-level rise, a new study has found. These glaciers are suspected to act as a sort of stream that drain off inland ice sheets. Research results published in the journal Proceedings of the National Academy of Sciences reveal in more detail than ever before how warming waters in the Southern Ocean are connected intimately with the movement and thinning of massive ice-sheets deep in the Antarctic interior.

"It has long been known that narrow glaciers on the edge of the Antarctica act as discrete arteries termed ice streams, draining the interior of the ice sheet," says Dr Chris Fogwill, an author of the study and an ARC Future Fellow with the UNSW (University of New South Wales)Climate Change Research Center.

"However, our results have confirmed recent observations suggesting that ocean warming can trigger increased flow of ice through these narrow corridors. This can cause inland sectors of the ice-sheet - some larger than the state of Victoria - to become thinner and flow faster."

The researchers, led by Dr Nicholas Golledge from Victoria University of Wellington, New Zealand, tested high-resolution model simulations against reconstructions of the Antarctic ice sheet from 20,000 years ago, during the last glacial maximum.

They used a new model, capable of resolving responses to ice-streams and other fine- scale dynamic features that interact over the entire ice sheet. This had not previously been possible with existing models. They then used this data to analyze the effects of a warming ocean over time.

The results showed that while glacier acceleration triggered by ocean warming is relatively localized, the extent of the resultant ice-sheet thinning is far more widespread. This observation is particularly important in light of recently observed dynamic changes at the margins of Antarctica. It also highlighted areas that are more susceptible than others to changes in ocean temperatures....

Shackleton's ship, Endurance, trapped in the ice of the Weddell Sea. Frank Hurley took this indelible shot


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