New Rifts on Wilkins Ice Shelf
28 November 2008
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, according to the European Space Agency.
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| New rifts on the Wilkins Ice Shelf that developed from 10 August to 26 November 2008. These rifts joined previously existing rifts (denoted by blue-dotted line). Credits: A. Humbert, Münster University, Germany (based on ESA Envisat images) Click to enlarge. |
The ice bridge connects the Wilkins Ice Shelf to two islands, Charcot and Latady. As seen in the Envisat image to the right acquired on 26 November 2008, new rifts (denoted by colored lines and dates of the events) have formed to the east of Latady Island and appear to be moving in a northerly direction. Dr Angelika Humbert from the Institute of Geophysics, Münster University, and Dr Matthias Braun from the Center for Remote Sensing, University of Bonn, spotted the newly formed rifts during their daily monitoring activities of the ice sheet via Envisat Advanced Synthetic Aperture Radar (ASAR) acquisitions.
These new rifts, which have joined previously existing rifts on the ice shelf (blue dotted line), threaten to break up the chunk of ice located beneath the 21 July date, which would cause the bridge to lose its stabilization and collapse. These recent changes are happening slower and more continuously than the events we saw earlier this year.
—Angelika Humbert
In February 2008 an area of about 400 km2 broke off from the ice shelf, narrowing the ice bridge down to a 6 km strip. At the end of May 2008 an area of about 160 km2 broke off, reducing the ice bridge to just 2.7 km. Between 30 May and 9 July 2008, the ice shelf experienced further disintegration and lost about 1,350 km2. (Earlier post.)
The Wilkins Ice Shelf, a broad plate of floating ice south of South America on the Antarctic Peninsula, had been stable for most of the last century before it began retreating in the 1990s. The peninsula has been experiencing extraordinary warming in the past 50 years of 2.5°C.
If the ice shelf breaks away from the peninsula, it will not cause a rise in sea level since it is already floating. However, ice shelves on the Antarctic Peninsula are sandwiched by extraordinarily raising surface air temperatures and a warming ocean, making them important indicators for on-going climate change.
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.
The West Antarctic Ice Sheet is often described as the world's most unstable ice sheet. As the Wilkins shows and warming predicts, the WAIS is disintegrating and may disappear altogether in a warmer future. In a paper to test the hypotheses of past disintegration of the WAIS published in Geo-Marine Letters. 22: 51-59, the authors studied the nature and history of glaciomarine deposits contained in sediment cores recovered from the West Antarctic continental margin in the Amundsen Sea.
http://tinyurl.com/5zw8ua
All proxies regarded as sensitive to a WAIS collapse, according to the authors, changed markedly during the global climatic cycles of the past 1.8 million years, "but do not confirm a complete disintegration of the WAIS during the Pleistocene" at a place where "dramatic environmental changes linked to such an event should be documented." In fact, they say their results "suggest relative stability rather than instability of the WAIS during the Pleistocene climatic cycles."
The authors noted that their study did not rule out the possibility of WAIS future melt, but that the data was "consistent with only a minor reduction of the WAIS during the last interglacial period (Huybrechts, 1990; Cuffey and Marshall, 2000; Huybrechts, 2002), which was slightly warmer than the Holocene."
Interestingly all four of the interglacials that preceded the current interglacial were warmer than the Holocene, by an average of more than 2°C.
Posted by: sulleny | 29 November 2008 at 11:11 AM
Wilkins Ice Shelf is small ice shelf situated at Antarctic PENINSULA:
http://en.wikipedia.org/wiki/Image:20080325_wilkins_figure1.jpg
This is great difference between Antarctica and Antarctic Peninsula. Antarctic Peninsula represents about 3% of Antarctica landmass, and is warming (unlike mainland Antarctica) at very high rate for last 50 years. Most scientists attribute such warming of Antarctic Peninsula to periodic changes in ocean current patterns.
Posted by: Andrey Levin | 30 November 2008 at 03:03 AM