Research by the U.S. Geological Survey documents 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 report, “Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009” and its accompanying map is available online.

The press release explains why the loss of ice shelves is so significant:

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.

The press release also quotes 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 Antarctic Peninsula’s southern section 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.

Ice-front retreat of the Wilkins Ice Shelf from 1947 to 2009

Last year Post Carbon Oregon had a series of posts documenting the disintegration of the ice bridge connecting the Wilkins ice shelf to Charcot Island, featuring photos from the European Space Agency’s Webcam in Space. Pretty spectacular stuff.

Following the collapse on April 4 of a narrow ice bridge that had connected the Wilkins ice shelf with a small island off the Antarctic Peninsula, the northern ice front of the ice sheet is beginning to disintegrate.

On 24 April, the satellite data showed that the first icebergs had started to break away from the fragile ice shelf. A very rough estimate suggests that, so far, about 700 sq km of ice has been lost from the Wilkins Ice Shelf. Scientists expect up to 3370 sq km of the ice shelf will be lost.

David Vaughan from the British Antarctic Survey explains what’s happening:

The retreat of Wilkins Ice Shelf is the latest and the largest of its kind. Eight separate ice shelves along the Antarctic Peninsula have shown signs of retreat over the last few decades. There is little doubt that these changes are the result of atmospheric warming on the Antarctic Peninsula, which has been the most rapid in the Southern Hemisphere.

How the situation will evolve remains to be seen. A new stable ice front may form between Latady Island, Petrie Ice Rises and Dorsey Island. But If the connection to Latady Island is lost, the loss of ice could be much more than anticipated.

The European Space Agency reports that icebergs have begun to calve from the northern front of the Wilkins Ice Shelf – indicating that the huge shelf has become unstable. This follows the collapse three weeks ago of the ice bridge that had previously linked the Antarctic mainland to Charcot Island.

The ice bridge, which effectively formed a barrier pinning back the northern ice front of the central Wilkins Ice Shelf, collapsed on 5 April removing about 330 sq km of ice. As a consequence of the collapse, the rifts, which had already featured along the northern ice front, widened and new cracks formed as the ice adjusted in the days that followed.

On 24 April, the satellite data showed that the first icebergs had started to break away from the fragile ice shelf. A very rough estimate suggests that, so far, about 700 sq km of ice has been lost from the Wilkins Ice Shelf.

In contrast to the ice bridge, which shattered very quickly, it is expected that the discharge of ice will continue for some weeks. The icebergs are calving as a result of fracture zones that have formed over the last 15 years and which turned Wilkins into a fragile and vulnerable ice shelf.

Below are two satellite photos showing the breakup of the ice bridge pinning the Wilkins ice shelf in place. The first was taken on April 8, the second a week earlier. The photos are from the European Space Agency’s webcam from space.

It’s a cautionary tale: things that have been stable for thousands or even hundreds of thousands of years can change in an instant, the world never to be the same. When it comes to the climate change game, we’re playing for keeps, and at stake is humanity’s fate.

The big news over the weekend was the collapse of the ice bridge which pinned the Wilkins Ice Shelf in place since the beginning of recorded history.

The context of that event is the warming of Antarctia.

Antarctic ice is melting far faster than believed possible. Updated scientific modeling on global warming projects up to one-third of all Antarctic sea ice is likely to melt by the end of the century and that ice melts in the Antarctic Peninsula and Western Ice Shelf will be greater and more rapid than expected, contributing significantly to dangerous sea level rises.

Ice shelves float on the water, so breakages will not directly raise sea levels. But when ice shelves break up, the glaciers and landed ice behind them then slide towards the ocean more rapidly, thus raising sea levels.

The West Antarctic Ice Sheet (WAIS) is fundamentally far less stable than the Greenland ice sheet because most of it is grounded far below sea level. The WAIS rests on bedrock as deep as two kilometers underwater. The collapse of ice shelves provides exit routes for ice from further inland.

Joseph Romm sees this as a potentially catastrophic feedback loop:

The warmer it gets, the more unstable WAIS outlet glaciers will become. Since so much of the ice sheet is grounded underwater, rising sea levels may have the effect of lifting the sheets, allowing more – and increasingly warmer – water underneath, leading to further bottom melting, more ice shelf disintegration, accelerated glacial flow, and further sea level rise, and so on and on, another vicious cycle. The combination of global warming and accelerating sea level rise from Greenland could be the trigger for catastrophic collapse in the WAIS.

You can see the ice bridge and how it pins the Wilkins ice sheet together on this map.

The ice bridge supporting the Wilkins ice shelf shattered yesterday (Saturday, April 4).

The last photo on the European Space Agency’s animated “webcam from space” shows the disintegrating ice.

David Vaughan, a glaciologist with the British Antarctic Survey, told Reuters:

It’s amazing how the ice has ruptured. Two days ago it was intact. We’ve waited a long time to see this.

My feeling is that we will lose more of the ice, but there will be a remnant to the south.

We believe the warming on the Antarctic Peninsula is related to global climate change, though the links are not entirely clear.

Temperatures on the Antarctic Peninsula, which snakes up toward South America, have risen by up to about 3 Celsius (5.4 Fahrenheit) in the past 50 years, the fastest rate of warming in the Southern Hemisphere.

Nine other shelves have receded or collapsed around the Antarctic Peninsula in the past 50 years, often abruptly like the Larsen A in 1995 or the Larsen B in 2002 further north.

The loss of the ice bridge, which was almost 100 km wide in 1950 and had been in place for hundreds of years at least, could allow ocean currents to wash away more of the Wilkins.

Great timing. On Monday the United States will be hosting a “polar conference” with representatives of 47 of the world’s governments. Climate change is to be a major focus of the talks, which are preparatory to the global talks in Copenhagen scheduled for December.

A new analysis of changing conditions in the region published in Friday’s edition of the journal Geophysical Research Letters concludes Arctic sea ice is melting so fast most of it could be gone in 30 years.

The new report by Muyin Wang of the Joint Institute for the Study of Atmosphere and Ocean and James E. Overland of the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory, projects the area covered by summer sea ice to decline from about 2.8 million square miles normally to 620,000 square miles within 30 years.

Last year’s summer minimum was 1.8 million square miles in September, second lowest only to 2007 which had a minimum of 1.65 million square miles, according to the National Snow and Ice Data Center (NSIDC).

A change in the amount of ice is important because the white surface reflects sunlight back into space. When ice is replaced by dark ocean water that sunlight can be absorbed, warming the water and increasing the warming of the planet. Wang explained in a statement:

The Arctic is often called the Earth’s refrigerator because the sea ice helps cool the planet by reflecting the sun’s radiation back into space. With less ice, the sun’s warmth is instead absorbed by the open water, contributing to warmer temperatures in the water and the air.

The extent of winter sea ice is also declining. NSIDC reports Arctic sea ice reached its winter maximum for this year at 5.8 million square miles on Feb. 28. That was 278,000 square miles below the 1979-2000 average, the fifth lowest on record. The six lowest maxima since 1979 have all occurred in the last six years.

There’s hot news from the Antarctic, too. The European Space Agency reports collapse of the ice bridge supporting Wilkins Ice Shelf appears imminent.

The Wilkins Ice Shelf is at risk of partly breaking away from the Antarctic Peninsula as the ice bridge that connects it to Charcot and Latady Islands looks set to collapse. The beginning of what appears to be the demise of the ice bridge began this week when new rifts forming along its center axis resulted in a large block of ice breaking away.

Many changes occurred to the ice shelf in 2008, as witnessed by Envisat. In late February, 425 sq km of ice calved away, narrowing the ice bridge down to a 6-km strip. At the end of May a 160-sq-km chunk of ice broke away and reduced the ice bridge to just 2.7 km, leaving it only 900 m wide at its narrowest location.

The Wilkins Ice Shelf had been stable for most of the last century before it began retreating in the 1990s.

The Wilkins isn’t the only ice shelf at risk. The Wordie Ice Shelf has been disintegrating since the 1960s and is now gone, and the northern part of the Larsen Ice Shelf no longer exists. More than 3,200 square miles (8,300 square km) have broken off from the Larsen shelf since 1986.

Climate change is to blame, according to the report from the U.S. Geological Survey and the British Antarctic Survey, available at pubs.usgs.gov/imap/2600/B. During the past 50 years, the Antarctic Peninsula has warmed by 2.5°C – far more than the global average.

The European Space Agency reports new rifts have developed on the Wilkins Ice Shelf that could lead to the opening of the ice bridge that has been preventing the ice shelf from disintegrating and breaking away from the Antarctic Peninsula.

As Antarctica summer is about to begin, the Wilkins Ice Shelf is experiencing significant changes which could lead to a new break-up. The ESA site has posted animated photos showing the gradual opening of fractures during the last days, in particular on 26 November 2008.

In the past 20 years, seven ice shelves along the Antarctic Peninsula have retreated or disintegrated, including the most spectacular break-up of the Larsen B Ice Shelf in 2002.

Wilkins is the size of the state of Connecticut, or about half the area of Scotland. It is the largest ice shelf on the Antarctic Peninsula yet to be threatened. The ice shelf had been stable for most of the past century before it began retreating in the 1990s.

Even in the depths of the Southern Hemispheric winter, the Wilkins Ice Shelf is experiencing further disintegration.  The ice bridge connecting the shelf to Charcot Island is poised to collapse – and since the connection to the island helps to stabilize the ice shelf, the break-up of the bridge could put the remainder of the ice shelf at risk.

click to enlarge image

The breakup of the Wilkins ice shelf in Antarctica first became apparent from satellite images. I came across this flyover footage from a Twin Otter at the blog Climate Feedback: