Are the ice fields of Antarctica increasing or decreasing? How do we know?
U.S. Geological Survey released a study of the change in glaciation in Antarctica between 1947 and 2009. Serious student of climate change will heed what the maps show — better bookmark the site. The study and publication were done in a joint effort of USGS, the British Antarctic Survey, the Scott Polar Research Institute, and the Bundesamt für Kartographie und Geodäsie (same page, in English, here).
Coastal-Change and Glaciological Map of the Palmer Land Area, Antarctica: 1947—2009
By Jane G. Ferrigno,1 Alison J. Cook,2 Amy M. Mathie,3 Richard S. Williams, Jr.,4 Charles Swithinbank,5 Kevin M. Foley,1 Adrian J. Fox,2 Janet W. Thomson,6 and Jörn Sievers
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), 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.
Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council (1986), in subsequent recommendations by the Scientific Committee on Antarctic Research (SCAR) (1989, 1993), and by the National Science Foundation’s (1990) Division of Polar Programs. On the basis of these recommendations, the U.S. Geological Survey (USGS) decided that the archive of early 1970s Landsat 1, 2, and 3 Multispectral Scanner (MSS) images of Antarctica and the subsequent repeat coverage made possible with Landsat and other satellite images provided an excellent means of documenting changes in the cryospheric coastline of Antarctica (Ferrigno and Gould, 1987). The availability of this information provided the impetus for carrying out a comprehensive analysis of the glaciological features of the coastal regions and changes in ice fronts of Antarctica (Swithinbank, 1988; Williams and Ferrigno, 1988). The project was later modified to include Landsat 4 and 5 MSS and Thematic Mapper (TM) images (and in some areas Landsat 7 Enhanced Thematic Mapper Plus (ETM+) images), RADARSAT images, aerial photography, and other data where available, to compare changes that occurred during a 20- to 25- or 30-year time interval (or longer where data were available, as in the Antarctic Peninsula). The results of the analysis are being used to produce a digital database and a series of USGS Geologic Investigations Series Maps (I-2600) (Williams and others, 1995; Swithinbank and others, 2003a,b, 2004; Ferrigno and others, 2002, 2005, 2006, 2007, 2008, and in press; and Williams and Ferrigno, 2005) (available online at http://www.glaciers.er.usgs.gov).
The paper version of this map is available for purchase from the USGS Store.
What’s the condition of glaciers in Antarctica? Now you can look it up.
The pamphlet accompanying the maps says under “Discussion”:
The most noticeable and dramatic changes that can be seen on the Palmer Land area map are the retreat of George VI, Wilkins, Bach, and northern Stange Ice Shelves. The northern ice front of George VI Ice Shelf was at its farthest extent during our period of observation between 1966 and 1974. It retreated, losing 906 km2 between 1974 and 1992 and 87 km2 between 1992 and 1995. After 1995, it retreated an additional 1 km to more than 6 km by 2001. The southern George VI ice front retreated considerably from 1947 to the late 1960s. From the late 1960s to 1973, there was additional substantial retreat, the greatest during the period of measurements. From 1973 to 2001, there was overall noticeable retreat.
Wilkins Ice Shelf had four ice fronts up till 2009; all retreated during the time period of our study, but Wilkins “a” and “b” have had the most dramatic change, including extensive calving in 2009 that eliminated ice front “b” and threatened the future of the ice shelf. During the period of observation, the Bach Ice Shelf front maintained a fairly consistent profile, and advanced or retreated at the same time along the entire ice front. The overall trend of Bach Ice Shelf is retreat. On the northern Stange Ice Shelf during the period of observation, the 1947, 1965–66, 1973, and 1986 ice fronts were more advanced, and the 1997 and 2001 ice fronts were more in retreat. However, the earlier data are less accurate geographically, and it is difficult to quantitatively analyze them. The later satellite images are more accurate, and it is possible to measure overall advance from 1986 to 1989, then retreat from 1989 to 1997 and from1997 to 2001; the net result was retreat.
The three coastal-change and glaciological maps of the Antarctic Peninsula (I–2600–A, –B, and –C) portray one of the most rapidly changing areas on Earth. The changes exhibited in the region are widely regarded as among the most profound and unambiguous examples of the effects of global warming yet seen on the planet.