Ice-front retreat in part of the southern Antarctic Peninsula from 1947 to 2009. Source: USGS. Click to enlarge.

The research 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 20^th century and into the early 21^st century.

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), and the potential sea-level rise after melting of the entire Antarctic ice sheet is estimated to be 65 m (Lythe and others, 2001) to 73 m (Williams and Hall, 1993). The mass balance (the net volumetric gain or loss) of the Antarctic ice sheet is highly complex, responding differently to different climatic and other conditions in each region (Vaughan, 2005).

In a review paper, Rignot and Thomas (2002) concluded that the West Antarctic ice sheet is probably becoming thinner overall; although it is known to be thickening in the west, it is thinning in the north. The mass balance of the East Antarctic ice sheet is thought by Davis and others (2005) to be positive on the basis of the change in satellite-altimetry measurements made between 1992 and 2003.

—Ferrigno et al.

The ice shelves are attached to the continent and already floating, holding in place the Antarctic ice sheet that covers about 98% 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. 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

—USGS scientist Jane Ferrigno

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 research is part of the USGS Glacier Studies Project, which is monitoring and describing glacier extent and change over the whole planet using satellite imagery.

Resources

• Ferrigno, J.G., Cook, A.J., Mathie, A.M., Williams, R.S., Jr., Swithinbank, Charles, Foley, K.M., Fox, A.J., Thomson, J.W., and Sievers, Jörn, 2009, Coastal-change and glaciological map of the Palmer Land area, Antarctica: 1947–2009: US Geological Survey Geologic Investigations Series Map I–2600–C, 1 map sheet, 28-p. text