Slide 16: Thermal indicators: Sea ice
Comprehensive Antarctic sea ice records date from the 1970s, although there is considerable data prior to this point for the Arctic.
A considerable decrease in sea ice thickness over the 1978-1996 period has been observed (Parkinson et al., 1999).
Satellite data has shown a considerable decrease in the extent of sea ice.
This is particularly evident in the collapse of the Larsen B ice shelf in 2002, which lost 3250 sq. km. In total the shelf has lost 5700 sq km, and is 40% of its previous stable size.
Four other major ice shelves have retreated (Vaughan and Doake, 1996). The total area of sea ice lost (barring that expected to calve under normal conditions) is 13 500 sq km since 1974!
Sea ice melt does not contribute to sea-level rise, since it is already in the ocean. However, it does have other effects such as reducing the salinity and albedo of the polar regions that both accelerate global warming.
Vaughan, D.G. and C.S.M. Doake, 1996: Recent atmospheric warming and retreat of ice shelves on the Antarctic Peninsula. Nature, 379, 328-331
Parkinson, C.L., 2000: Variability of Arctic sea ice. The view from space, an 18-year record. Arctic, 53, 341-358.
Parkinson, C.L., D.J. Cavalieri, P. Gloersen, H.J. Zwally and J.C. Comiso, 1999: Arctic sea ice extents, areas, and trends, 1978-1996. J. Geophys. Res., 104(C9), 20837-20856.