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Posts Tagged ‘ice shelves’

The Great Antarctic Peninsula Ice Shelf Extinction

Posted by feww on February 23, 2010

Public Release: USGS

Ice shelves disappearing on Antarctic Peninsula

Glacier retreat and sea level rise are possible consequences

Ice shelves are retreating in the southern section of the Antarctic Peninsula due to climate change. This could result in glacier retreat and sea-level rise if warming continues, threatening coastal communities and low-lying islands worldwide.

Click Images to Enlarge!


Southern Portion of Antarctic Peninsula. This image identifies the southern portion of the Antarctic Peninsula, which is one area studied as part of this project. Research on the southern Antarctic Peninsula is summarized in the USGS report, “Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009” (map I—2600—C). Source: U.S. Geological Survey


Multi-year ice. ARCTIC OCEAN – A multi-year ice floe slides down the starboard side of the Coast Guard Cutter Healy Aug. 11, 2009, as the ship heads north into even thicker ice. “You can tell that this is a multi-year ice floe by the light blue melt ponds that have formed on top of the floe,” said Pablo Clemente-Colón, chief scientist at the U.S. National Ice Center. Credit: Patrick Kelley, U.S. Coast Guard


Southern Antarctic Peninsula. This image shows ice-front retreat in part of the southern Antarctic Peninsula from 1947 to 2009. The southern portion of the Antarctic Peninsula is one area studied as part of this project, and is summarized in the USGS report, “Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009” (map I—2600—C). Source: U.S. Geological Survey

U.S. Geological Survey says its research is the first to document that every ice front in the southern part of the Antarctic Peninsula has been retreating overall from 1947 to 2009, with the most dramatic changes occurring since 1990. The USGS previously documented that the majority of ice fronts on the entire Peninsula have also retreated during the late 20th century and into the early 21st century.

The ice shelves are attached to the continent and already floating, holding in place the Antarctic ice sheet that covers about 98 percent of the Antarctic continent. As the ice shelves break off, it is easier for outlet glaciers and ice streams from the ice sheet to flow into the sea. The transition of that ice from land to the ocean is what raises sea level.

“This research is part of a larger ongoing USGS project that is for the first time studying the entire Antarctic coastline in detail, and this is important because the Antarctic ice sheet contains 91 percent of Earth’s glacier ice,” said USGS scientist Jane Ferrigno. “The loss of ice shelves is evidence of the effects of global warming. We need to be alert and continually understand and observe how our climate system is changing.”

The Peninsula is one of Antarctica’s most rapidly changing areas because it is farthest away from the South Pole, and its ice shelf loss may be a forecast of changes in other parts of Antarctica and the world if warming continues.

Retreat along the southern part of the Peninsula is of particular interest because that area has the Peninsula’s coolest temperatures, demonstrating that global warming is affecting the entire length of the Peninsula.

The Antarctic Peninsula’s southern section as described in this study contains five major ice shelves: Wilkins, George VI, Bach, Stange and the southern portion of Larsen Ice Shelf. The ice lost since 1998 from the Wilkins Ice Shelf alone totals more than 4,000 square kilometers, an area larger than the state of Rhode Island.

The USGS is working collaboratively on this project with the British Antarctic Survey, with the assistance of the Scott Polar Research Institute and Germany’s Bundesamt fűr Kartographie und Geodäsie. The research is also part of the USGS Glacier Studies Project, which is monitoring and describing glacier extent and change over the whole planet using satellite imagery.

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Contact: Jessica Robertson
jrobertson@usgs.gov
United States Geological Survey

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Posted in Antarctic Peninsula, Antarctica, Ice Shelf, Larsen Ice Shelf | Tagged: , , , , , , , | Leave a Comment »

Canada’s Ice Shelves Lose Quarter of their Cover

Posted by feww on September 3, 2008

Canada’s Ice Shelves Disappearing Much Faster than Previously Thought

The Markham Ice Shelf break-up animated using cloud-free MODIS images. The animation shows an area that is approximately 40 km wide. MODIS image from the Rapid Response Project at NASA/GSFC. Animation courtesy Derek Mueller, Trent University.

[Kudos to Derek Mueller for his plain, yet revealing animations. See  below also for Serson Ice Shelf break-up and Ward Hunt Ice Shelf break-up animations.]

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Markham Ice Shelf, a massive 50 square km ice shelf, almost the land size of Manhattan Island, in Canada’s northern Arctic broke away in August. The remaining shelves are shrinking at a “massive and disturbing” rate, as a result of of accelerating climate change, scientists reported.

The Markham Ice Shelf, one of just five remaining ice shelves in the Canadian Arctic, calved from Ellesmere Island in early August. Additionally, two other large chunks measuring a total of about 122 square km calved from Serson Ice Shelf, reducing its size by nearly two-thirds.


Chunk of ice are drifting away after calving from the Ward Hunt Ice Shelf off the north coast of Ellesmere Island in Canada’s far north. Photo: AP. Image may be subject to copyright.

“The changes … were massive and disturbing,” said Warwick Vincent, at Laval University in Quebec.

Vincent’s team have recorded peak temperatures of about  20 degrees Celsius (°C), some 12 degrees (250%) higher than the average of about 8°C. The team’s estimate that the shelves would lose 22 square km of ice this summer proved to be highly optimistic. The actual figure was closer to 220 square km—ten times higher than their estimate.

Before


A MODIS image of the Markham Ice Shelf (2006 extent outlined in red) on July 28, 2008 prior to calving. Note the open water in Markham Fiord south of the ice shelf. MODIS image from the Rapid Response Project at NASA/GSFC. Map courtesy Derek Mueller, Trent University.

After


A MODIS image of Markham Fiord on August 12, 2008 following the loss of the Markham Ice Shelf (2006 extent outlined in red). MODIS image from the Rapid Response Project at NASA/GSFC. Map courtesy Derek Mueller, Trent University.


The Serson Ice Shelf break-up animated using cloud-free MODIS images. The animation shows an area that is approximately 80 km wide. MODIS image from the Rapid Response Project at NASA/GSFC. Animation courtesy Derek Mueller, Trent University.

Scientists believe that global warming is increasing the temperatures in the Arctic far faster than the global average in the last 30 years.

“These substantial calving events underscore the rapidity of changes taking place in the Arctic,” said Derek Mueller, a specialist at Trent University in Ontario.


Markham Fiord in August 2008 after the Markham Ice Shelf broke away. Compare with the photograph above. Photo courtesy of Denis Sarrazin, Laval University.

“These changes are irreversible under the present climate and indicate that the environmental conditions that have kept these ice shelves in balance for thousands of years are no longer present,” he said.


The Ward Hunt Ice Shelf break-up animated using cloud-free MODIS images. The animation shows an area that is approximately 75 km wide. NB: The events displayed here were already widely reported at the end of July. MODIS image from the Rapid Response Project at NASA/GSFC. Animation courtesy Derek Mueller, Trent University.
According to Mueller a totl of about 215 square km of ice was lost from the shelves along Ellesmere Island this summer.

“Reduced sea ice conditions and unusually high air temperatures have facilitated the ice shelf losses,” said Luke Copland of the University of Ottawa.

“Extensive new cracks across remaining parts of the largest remaining ice shelf, the Ward Hunt, mean that it will continue to disintegrate in the coming years,” he said.


Calving of the Ward Hunt Ice Shelf into Disraeli Fiord during August 2008. Photo courtesy of Denis Sarrazin, ArcticNet/Centre d’Etudes Nordiques.

Ellesmere Island previously home to a single giant ice shelf measuring about 10,000 square km, now has four very small shelves covering only about 800 square km—less than a tenth of the original size!

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Posted in Climate Change, energy, environment, food, Global Warming, health, Tourism, Travel | Tagged: , , , , | 1 Comment »

Arctic ice cover second-lowest on record

Posted by feww on August 28, 2008

The extent of Arctic ice is now 10 percent lower than the 1997-2000 period

Arctic sea ice cover shrank to its second-lowest level ever and could set a new low by the and of this year’s melt season. The worst affected area is the Chukchi Sea, home to one of the world’s largest polar bear populations, as well as large oil and gas fields.


Daily Arctic sea ice extent for August 26, 2008, fell below the 2005 minimum, which was 5.32 million square kilometers (2.05 million square miles). The orange line shows the 1979 to 2000 average extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. —Credit: National Snow and Ice Data Center.

Arctic sea ice extent has declined 2.06 million sq km since the beginning of August. On August 26 sea ice extent stood at 5.26 million sq km, below the 2005 minimum of 5.32 sq km set on September 21 of that year, the second-lowest extent observed by satellite, said National Snow and Ice Data Center (NSIDC) in Boulder, Colorado.

In 2007 the ice cover melt to its lowest recorded minimum of 4.12 million sq km opening the the Northwest Passage  for the first time on record.

“No matter where we stand at the end of the melt season it’s just reinforcing this notion that Arctic ice is in its death spiral,” said Mark Serreze, a scientist at NSIDC.

Loss of summer Arctic ice could have far-reaching implications for wildlife, especially the polar bear and walrus, which depend on ice shelves to hunt for food.

With more Arctic ice melting, the bears have to swim farther to find suitable ice shelves for hunting. The longer they swim in open waters, despite being capable swimmers, the more likely they get into trouble. A number of bears are known to have been drowned in the recent years.


A polar bear is seen in the water during an aerial survey off the Alaska coast in this photo taken August 15, 2008. Arctic sea ice shrank to its second-lowest level ever, U.S. scientists said on Wednesday, with particular melting in the Chukchi Sea, where at least 12 polar bears were recently seen swimming far off the Alaskan coast. REUTERS/Geoff York/World Wildlife Fund/Handout.

Interestingly, the state of Alaska is suing the federal government because it says listing polar bears as a threatened species is hurting Alaskan oil and gas exploration and development, commercial fisheries, transportation and tourism. In other words, the polar bears had no right to be there!

“We believe that … decision to list the polar bear was not based on the best scientific and commercial data available,” said Alaska Gov. Sarah Palin.

Will 2008 also break the standing record low set in 2007? We will know soon—there are still a few weeks left to the end of melt season!

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Posted in Climate Change, energy, environment, food, Global Warming, health, politics, Tourism, Travel | Tagged: , , , , , , , , , | 4 Comments »