Scientists today are using past climatic changes as a proxy for today's to help them understand the changes that are presently occurring and those that will occur in the future. Evidence shows that within the Pleistocene, many rapid climatic fluctuations in which global sea level rose and fell occurred. Geologists believe that the rapid fluctuations were due to the advancement and retreat of the West Antarctic Ice Sheet (WAIS) and ultimately to global climate changes. By studying the ice sheet evolution today, geologists can attempt to uncover a modern or even a future analog for processes that occurred during the Pleistocene. In this way, the anthropogenic effects on climate and current/future sea level changes can be understood. Antarctic ice volume during the Pleistocence has been recorded through evidence such as deep sea oxygen isotope records and geomorphic data including coral reef data and loess deposits.

WAIS ice sheet instability stems from changes in climate and from the fact that it lies on bedrock that is 1000ft below sea level. Storm clouds deliver snow to the ice sheet where it is then compacted into the glacier (see figure 2). Most often, it returns to ice shelves at the base of the glacier through ice streams. The ice shelves detach an thus add to the sea level. With a rise in global temperature this process is enhanced.

Greenland (G1SP2) ice core data shows that during the last 8, 000 years the climate has been "friendly" to humans because we are in an interglacial period. However, the cores also show that rapid climatic changes from glacial to interglacial may have occurred in as little as 1-3 years in the 100,000 years prior (Figure 3). The size of the Antarctic ice sheet has changed according to these climatic events. Deep sea oxygen isotope records show at least 20 glacial periods within the Pleistocene . Coral data in the Carribean Sea and around the world depict several highstands in a short period of time. Loess deposits that accumulated in nonglaciated areas during glacial periods also show evidence of Pleistocene climate fluctuations.

Figure 3: Core data showing accumulation rates during the Pleistocene.

Ice volume estimates for the WAIS during times of greatest retreat show that the ice sheet may have contributed between 6.1-13.1 meters of water to the oceans, all of which was part of the glacier during the Last Glacial Maximum. Figure 4 shows the time intervals of greatest sea level change due to the WAIS retreat.

If the WAIS were to melt away at a constant rate, it could add as much as 20 meters to the sea level within a few centuries. This could drown coastal areas such as Florida and completely drown small island communities. Understanding the WAIS and its past effects on climate and eustatic sea level change will allow for a better understanding of current and future climate and eustatic sea level changes.

Figure 4: Computer simulation of Antarctic ice during the present, and the last glacial maximum.

References Cited

Bentley, M. J., 1999, Volume fo Antarctic ice at the last glacial maximum, and its impacts on global sea level change: Quaternary Science Reviews, v. 18, p. 1569-1595.

Bindschadler, R. A., 1991, WAIS Initiative Science and Implementation Plan: National Aeronautics and Space Administration Conference Publication. Preprint.

Bindschadler, R. A., 1998, Future of the West Antarctic Ice Sheet: West Antarctic Ice Sheet Home Page. http://igloo.gsfc.nasa.gov/science/perspective.html (accessed 24 April 2001).

Bindshcadler, R. A, et al., 1998, "What is happening to the West Antarctic Ice Sheet?" Eos, v.79 n. 22.

Jacobs, S. S., and Comiso, J. C., 1993, A recent sea-ice retreat west of te Antarctic Penninsula: Geophysical Research Letters, v. 20 n. 12, p. 1171-1174.

Lambeck, K. et al., 2000, Global ice volumes at the Last Glacial Maximum and early Late Glacial: Earth and Planetary Science Letters, v. 181, p. 513-527.