Melting ice in Arctic and Antarctica
Worrisome signs re ice melting at both poles.
From Nat Geo:
An "alarming rate" of melting in the Antarctic Peninsula has finally snapped the ice bridge that held the Wilkins Ice Shelf in place, experts say.The 25-mile-long (40-kilometer-long) ribbon of sea ice that secured the Jamaica-size ice shelf (which is just out of view in the above pictures) to Antarctica had been "hanging by a thread" since August 2008 (above, top, in November 2008 in a European Space Agency satellite image).
On Saturday, April 4, the bridge broke at its weakest point (bottom)—at about 1,640 feet (500 meters) wide—and shattered into hundreds of small icebergs. The ice shelf, which is now exposed to the open ocean, is more vulnerable to breaking up, experts say.
"We've been watching it all summer, waiting for it to go, and bang—now it's gone," David Vaughan, a glaciologist for the British Antarctic Survey, told National Geographic News.
"It's the culmination of yet another ice shelf retreat that's been driven by [warming] climate," Vaughan said.
The Antarctic Peninsula has warmed 3 degrees Celsius (5.4 degrees Fahrenheit) since the 1950s, he said—"something that people should take note of."
Jamaica-Size Ice Shelf Breaks Free
and from BBC:
Arctic ice reached a larger maximum area this winter than in the last few years, scientists say, but the long-term trend still shows it declining.The 30-year trend shows the maximum annual sea-ice cover, usually seen in March, is shrinking by 2.7% per decade.
Only 10% of the cover consists of relatively durable ice that has formed over more than two years, a record low.
Scientists from the US National Snow and Ice Data Center (NSIDC), say the thin ice is prone to summer melting.
"Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover," said NSIDC scientist Walt Meier.
"As the ice cover in the Arctic grows thinner, it grows more vulnerable to melting in the summer."
In the 1980s, thick multi-year ice made up 30-40% of the cover, the scientists say.
The summer minimum area is changing much faster than the winter maxima, shrinking by about 0.7% per year. Last year UK researchers showed that the ice has also markedly thinned in recent years.
Press release from US Geological Survey:
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.
Research by the U.S. Geological Survey 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.
The report, “Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009” and its accompanying map is available online.
The other completed reports in the Coastal Change and Glaciological Maps of Antarctica series can be viewed online.
From the Guardian:
Arctic sea ice has melted to a level not recorded since satellite observations started in 1972 – and almost certainly not experienced for at least 8,000 years, say polar scientists.Daily satellite sea-ice maps released by Bremen university physicists show that with a week's more melt expected this year, the floating ice in the Arctic covered an area of 4.24 million square kilometres on 8 September. The previous one-day minimum was 4.27m sq km on 17 September 2007.
...Arctic temperatures have risen more than twice as fast as the global average over the past half century.
Separate, less reliable, research suggests that Arctic ice is in a downward spiral, declining in area but also thinning. Using records of air, wind and sea temperature, scientists from the Polar Science Centre of the University of Washington, Seattle, announced last week that the Arctic sea-ice volume reached its lowest ever level in 2010 and was on course to set more records this year.
...Further evidence of dramatic change in the Arctic came last week from Alan Hubbard, a Welsh glaciologist at Aberystwyth University, who has been studying the Petermann glacier in northern Greenland for several years.
The glacier, which covers about 6% of the icecap, is 186 miles (300km) long and up to 3,280ft (1km) high. In August last year, a 100 square-mile (260 sq km) block of ice calved from the glacier. Photographs show that by July this year it had melted and disappeared.
"I was gobsmacked. It [was] like looking into the Grand Canyon full of ice and coming back two years later to find it full of water," said Hubbard.
WWF release: