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Event Details

Glacier Melting event report

Category: Glacier Melting
Observation: 28.12.2011
Continent: South Pole
Country: Antarctica
State:
Area: Pine Island Glacier
Location:
Severity: Hight
Event details
The Pine Island Glacier in West Antarctica, a large ice stream flowing west-northwest along the south side of the Hudson Mountains, is melting 50 percent faster than it has 15 years earlier, an international team of scientists from Lamont-Doherty Earth Observatory and British Antarctic Survey says. The melting is the result of an increased volume of warm water reaching the cavity beneath the ice. The glacier is currently sliding into the sea at a rate of 2.5 miles (4 kilometers) per year, while its ice shelf (the part that floats on the ocean) is melting at about 80 cubic kilometers per year. British Antarctic Survey, Pine Island Glacier“More warm water from the deep ocean is entering the cavity beneath the ice shelf, and it is warmest where the ice is thickest,” said lead author Stan Jacobs, an oceanographer at Columbia University’s Lamont-Doherty Earth Observatory. In 2009, Jacobs sailed to the Amundsen Sea aboard the icebreaking ship Nathaniel B. Palmer to study the region’s thinning ice shelves - floating tongues of ice where land bound glaciers meet the sea. One goal was to study oceanic changes near Pine Island Glacier, which they had visited in an earlier trip in 1994. The researchers discovered that melting beneath the ice shelf had risen by about 50 percent. While regional ocean temperatures had also warmed slightly by around 0.2 degrees Centigrade, the temperature increase was not enough to account for the jump. The local geology offered one explanation. On the same cruise, a group led by Adrian Jenkins, a glaciologist at British Antarctic Survey (BAS) and co-author of the paper, sent an automated submarine called Autosub3 under the ice shelf, which revealed an underwater ridge (mountain) on the sea floor. The team concluded that the ridge had once slowed the glacier like a giant retaining wall. When the receding glacier detached from the ridge, some time before the 1970s, the warm deep water gained access to deeper parts of the glacier. Over time, the inner cavity grew, more warm deep water flowed in, more melt water flowed out, and the ice thinned. With less friction between the ice shelf and seafloor, the land-bound glacier accelerated its move into the sea. Other glaciers in the Amundsen region have also thinned or widened, including the Thwaites Glacier and the much larger Getz Ice Shelf. “Our research shows that the glacier melt rate has increased significantly because more warm water is circulating beneath it,” said Jenkins. “It appears that the thinning of the ice shelf that has resulted from the higher melt rates is what has allowed the circulation to strengthen. It’s evidence of a complex feedback between glacier dynamics, seabed topography and ocean circulation that we need to understand if we are to say how Pine Island Glacier will evolve in the future. The glaciers from the Amundsen Sea region are contributing more to sea level rise than any other part of Antarctica, so it’s imperative we understand the processes involved.”
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