Guest commentary by David Vaughan
The recent retreat of ice shelves on the Antarctic Peninsula has been widely attributed to warming atmospheric temperatures. There is, however, little published work describing the response of glacier margin positions to this regional climate change. In the paper Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century published this week in Science, we presented new data describing trends in 244 marine glacier fronts on the Antarctic Peninsula over the last 50 years. The data come from matching archives of over 2000 aerial photographs of the Antarctic Peninsula to satellite images, and represent about three years of work by Alison Cook. The work was carried out at British Antarctic Survey, but was funded by the US Geological Survey, as part of a larger programme to map change in the coastline of all Antarctica.
Analysis of the data reveals that 87% of glaciers have retreated (click on the image for a more detailed figure) and that the change from advance to retreat has occurred progressively with latitude. In 1950s only the most northerly glaciers appeared to be retreating, but a transition from advance to retreat appeared to move down the Antarctic Peninsula over a period of about 10 to 20 years, broadly in line with what we would expect if this was a consequence of the warming that has been measured in this area. However, there are features of the pattern of change that we find difficult to explain by atmospheric warming alone. In particular, there was a period in the late-1980s and early-1990s when retreat slowed down along most of the coast, and we don’t see any cause for this in the temperature records – so there may be some other factors at work, perhaps ocean temperature.
The retreat of these glaciers in itself will have a negligible effect on sea level, since most of the ice that has retreated was in the water already. However, if as a consequence of shortening, the glaciers are also flowing faster, then we would be seeing another (small) contribution to sea level rise. This is the next line of work and we will report in the near future.
Reference: Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century A. J. Cook, A. J. Fox, D. G. Vaughan, J. G. Ferrigno, Science, Vol 308, Issue 5721, 541-544 , 22 April 2005 [DOI: 10.1126/science.1104235]
See also the earlier RealClimate post on Antarctic temperature change.