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Posts tagged Ice Stream

Start of Iceberg Calving Off Pine Island Glacier, Antarctica – February 6th, 2012

75.1S 100W

February 6th, 2012 Category: Climate Change, Glaciers and Ice Caps

Pine Island Glacier - January 28th, 2012

The Pine Island Glacier, visible at the center of this image, is a large ice stream flowing west-northwest along the south side of the Hudson Mountains into Pine Island Bay, Amundsen Sea, Antarctica. The image focuses on a floating ice shelf at the downstream end of Pine Island Glacier. The crack shows the start of a large iceberg calving.

The area drained by Pine Island Glacier comprises about 10 percent of the West Antarctic Ice Sheet. Satellite measurements have shown that the Pine Island Glacier Basin has a greater net contribution of ice to the sea than any other ice drainage basin in the world and this has increased due to recent acceleration of the ice stream.

The Pine Island and Thwaites Glaciers are two of Antarctica’s five largest ice streams. Scientists have found that the flow of these ice streams has accelerated in recent years, and suggested that if they were to melt, global sea levels would rise by 0.9 to 1.9 m (2 ft 10 in to 6 ft 3 in), destabilising the entire West Antarctic Ice Sheet and perhaps sections of the East Antarctic Ice Sheet.

Melting Glaciers in Antarctica

April 30th, 2009 Category: Climate Change

Fires in Nepal - April 24th, 2009

Fires in Nepal - April 24th, 2009

Close-up

Close-up

In the full image, glaciers and ice streams can be seen south of the Kemp Peninsula, in Palmer Land on the eastern coast of the Antarctica Peninsula. The close-up shows icebergs breaking off the glacier.

Glaciers in Antarctica are melting faster and across a much wider area than previously thought, scientists say, a development that threatens to raise sea levels worldwide and force millions of people to flee low-lying areas, reports USA Today.

Researchers once believed that the melting was limited to areas like the one visible here on the Antarctic Peninsula, a narrow tongue of land pointing toward South America. However, satellite data and automated weather stations now indicate it is more widespread, even extending all the way down to west Antarctica near the South Pole.

By the end of the century, the accelerated melting could cause sea levels to climb by 3 to 5 feet — levels substantially higher than predicted by a major scientific group just two years ago.

Making matters worse, scientists said, ice shelves, such as the Wilkins Ice Shelf, that hold the glaciers back from the sea are also weakening.

The biggest of the western glaciers, the Pine Island Glacier, is moving 40% faster than it was in the 1970s, discharging water and ice more rapidly into the ocean. The Smith Glacier, also in west Antarctica, is moving 83% faster than in 1992.

The glaciers are slipping into the sea faster because the floating ice shelf that would normally stop them, which is usually 650 to 980 feet thick, is melting. Together, all the glaciers in west Antarctica are losing a total of around 114 billion tons per year because the melting is much greater than the new snowfall.

The glaciers’ discharge is making a significant contribution to increasing sea levels. Some people fear that this is the first signs of a collapse of the west Antarctic ice sheet, which would cause a sea level rise of between 1 and 1.5 meters (about 3.5 to 5 feet).

Trail of Ice Stream in Antarctica

April 3rd, 2009 Category: Snapshots

Antarctica - March 23rd, 2009

Antarctica - March 23rd, 2009

In this radar (ASAR) image, an ice stream appears as a bright white trail through the surrounding Antarctic terrain.

An ice stream is a region of an ice sheet that moves significantly faster than the surrounding ice. They are significant features of the Antarctic where they account for 10% of the volume of the ice. They are up to 50 km wide, 2 km thick, can stretch for hundreds of kilometres, and account for most of the ice leaving the ice sheet.

The speed of an ice stream can be over 1,000 meters per year, an order of magnitude faster than the surrounding ice. The shear forces at the edge of the ice stream cause deformation and recrystallization of the ice, making it softer, and concentrating the deformation in narrow bands or shear margins. Crevasses form, particularly around the shear margins.

Most ice streams have some water at their bases, which lubricates the flow. The type of bedrock also is significant. Soft, deformable sediments result in faster flow than hard rock.

It has been suggested that the Antarctic ice sheet is losing mass. The past and ongoing acceleration of ice streams and outlet glaciers is considered to be a significant, if not the dominant cause of this recent imbalance.

Glacier on West Coast of Greenland

February 1st, 2009 Category: Snapshots

Glacier melting on west coast of Greenland - November 30th, 2008

Glacier melting on west coast of Greenland - November 30th, 2008

Here we can see a large glacier off the western coast of Greenland, seemingly fed by three ice streams.

The largest glaciers are continental glaciers, enormous masses of ice that are not visibly affected by the landscape and that cover the entire surface beneath them, except possibly on the margins where they are thinnest.

Antarctica and Greenland are the only places where continental ice sheets currently exist. These regions contain vast quantities of fresh water.

The volume of ice is so large that if the Greenland ice sheet melted, it would cause sea levels to rise some six meters (20 ft) all around the world.

These ice sheets are further divided into sections based on characteristics. Ice shelves are areas of an ice sheet that are at the margin and are afloat. As a result they are thinner, have limited slopes and reduced velocities.

Ice streams, like the three visible in the image, are fast moving sections of an ice sheet.

source Wikipedia

Ice Dunes in Antarctica

January 30th, 2009 Category: Snapshots

Antarctica - January 25th, 2009

Antarctica - January 25th, 2009

This radar (ASAR) images shows several different features of the ice in Antarctica.

The ice in the lower part of the image has many deep grooves.

An ice stream can be seen moving northward into the freezing waters off the coast, where many icebergs are floating.

Further north, particularly in the full image, many ripples are visible in the ice. These may actually be “megadunes” of ice.

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