USGS Reports Dramatic Retreat of Ice Shelves in Southern Antarctic Peninsula

The U.S. Geological Survey (USGS) reported today (22 February 2010) 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 finding comes on the heels of the warmest January on record for the Southern Hemisphere.

The USGS presented the findings in a map and a pamphlet (Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009 [PDF]), results of a collaborative project with the British Antarctic Survey, assisted by the Scott Polar Research Institute and Germany’s Bundesamt fűr Kartographie und Geodäsie.  In the pamphlet's introduction, the authors put the findings in context:

Reduction in the area and volume of the two polar ice sheets is intricately linked to changes in global climate, and the resulting rise in sea level could severely impact the densely populated coastal regions on Earth. Antarctica is Earth’s largest reservoir of glacial ice. Melting of the West Antarctic part alone of the Antarctic ice sheet would cause a sea-level rise of approximately 6 meters (m) [20 feet], and the potential sea-level rise after melting of the entire Antarctic ice sheet is estimated to be 65 m [213 feet] (Lythe and others, 2001) to 73 m [240 feet] (Williams and Hall, 1993).

Data from the  Gravity Recovery and Climate Experiment (GRACE) satellite for 2002 to 2005 indicate that the mass of the Antarctic ice sheet decreased during that time, and that most of the reduction was from the West Antarctic ice sheet. 

In a press release (Ice Shelves Disappearing on Antarctic Peninsula) the USGS explains that the area covered by the 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 says.

Above: Southern Portion of Antarctic Peninsula. 

Above: Southern Antarctic Peninsula.  This image shows ice-front retreat in part of the southern Antarctic Peninsula from 1947 to 2009. Source: USGS.

In its press release the USGS adds:

"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.... 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 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." 

According to NASA data, after the warmest year on record in 2009, the Southern Hemisphere started 2010 with a record-shattering January. 

Online Resources:

• Ice Shelves Disappearing on Antarctic Peninsula.  Press release (22 February 2010) from USGS.
• USGS Podcast. Scientist Jane Ferrigno discusses the USGS project that is for the first time studying the entire Antarctic coastline in detail. 
• Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009.  
  • Palmer Land Area Map I-2600-C PDF (23.1 MB)
  • Pamphet to Accompany Map: Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009 [PDF].  By Jane G. Ferrigno et al.  Prepared in cooperation with the British Antarctic Survey, the Scott Polar Research Institute, and the Bundesamt für Kartographie und Geodäsie.  Dated 2009. 
• Antarctica Losing More than 24 cubic Miles of Ice Annually -- and the Pace is Accelerating.  WWF Climate Blog, 15 January 2010.
• NASA: After Warmest Year on Record, Southern Hemisphere Starts 2010 With Record-Shattering January.  WWF Climate Blog, 17 January 2010.
• Southern Hemisphere in 2009 Saw Warmest Year on Record. WWF Climate Blog, 16 January 2010.