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 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
Lead author Dr Hamish Pritchard from British Antarctic Survey (BAS) said:
We were surprised to see such a strong pattern of thinning glaciers across such large areas of coastline — it’s widespread and in some cases thinning extends hundreds of kilometres inland. We think that warm ocean currents reaching the coast and melting the glacier front is the most likely cause of faster glacier flow. This kind of ice loss is so poorly understood that it remains the most unpredictable part of future sea level rise.
The authors conclude that this ‘dynamic thinning’ of glaciers now reaches all latitudes in Greenland, has intensified on key Antarctic coastlines, is penetrating far into the ice sheets’ interior and is spreading as ice shelves thin by ocean-driven melt. Ice shelf collapse has triggered particularly strong thinning that has endured for decades.
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.
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.
The latest photos of the Wilkens ice sheet from the European Space Agency’s “webcam in space” show that the ice bridge is just . . . gone.
Stunning.
New research being published in Nature says at the end of the last interglacial (the Eemian) sea levels rose five centimeters a year for 50 years. The Eemian was some 2°C warmer than current global temperatures, but we’re well on track to hit that mark again, soon. Glaciers and ice sheets are already melting, and sea levels rising, as a result.
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.
