Pleistocene Sea Level and Future Ice Sheet Stability

How certain are we that sea level exceeded modern values during some previous interglacial periods? Where did the extra water come from, and how quickly?

One major consequence of global climate change is a shift in sea level. Melting continental ice sheets cause sea level to rise. Were the Greenland Ice Sheet to melt entirely, sea level would increase by about 6.5 meters; were the West Antarctic Ice Sheet to melt, sea level would rise 8 meters; and were the massive East Antarctic Ice Sheet to melt, sea level would rise by about 65 meters.

A critical source of information about the susceptibility of ice sheets to collapse, and thus about what constitutes 'dangerous anthropogenic interference' with Earth's climate system, is the record of past sea level change. During the Pleistocene (the last 1.8 million years), sea level has reached levels about 130 meters lower than today during peak glaciations. Based on the elevation of fossil reefs and on geomorphological markers, during the Last Interglacial period (about 125 thousand years ago), sea level may have been a few meters higher than today. If it was, then two urgent follow-up questions are: what ice sheet melted to produce those extra meters of water, and how long did it take to melt?

Working with Michael Oppenheimer, Adam Maloof, and Gabrielle Dryfus, I am currently conducting a review of sea level indicators for the Last Interglacial, from high-latitude 'near field' localities as well as from the low-latitude 'intermediate field' and 'far field' sites more commonly examined. By compiling a global database of sea-level indicators with awareness of errors in both space and time, we are assessing the viability of 'fingerprinting' the meltwater source: identifying the ice sheet that collapsed by looking at spatial variability of the sea level perturbation it produced.