Heat-driven expansion not a major source of sea level rise
With the power to drown low-lying nations, destroy infrastructure, and seriously affect sensitive coastal ecosystems, sea level rise may be one of the most readily apparent consequences of global warming that is already under way. However, the sources of the rising waters, and the dynamics driving them, are not so clear. Melting land-locked glaciers, shrinking ice sheets over Greenland and Antarctica, and the ocean’s thermal expansion will all play a part, but the expected contribution from each of these sources is still up for debate. Previous studies have suggested that thermal expansion driven by rising sea surface temperatures will account for up to 70 percent of sea level rise in the near future, but research by McKay et al. suggests this may be a drastic overestimate.
The authors draw on paleoclimate records and model simulations of the last interglacial period, when the sea level rose by more than 6 meters (19.7 feet), to isolate the contribution of thermal expansion to sea level rise during a previous period of global warming. The authors found that during the last interglacial period, between 130,000 and 120,000 years ago, the global average sea surface temperature changed between .4 and 1.3 degrees Celsius (-0.7 and 2.3 degrees Fahrenheit). On the basis of research into the temperature sensitivity of thermal expansion, the authors suggest that between .2 and 0.7 m (-0.66 and 2.29 ft) of ocean rise would have been attributable to thermal expansion. With thermal expansion playing such a small role in the pronounced sea level rise during the last interglacial, the authors suggest that the Greenland and, in particular, Antarctic ice sheets may be more sensitive to increasing temperatures than previously thought, with important implications for estimates of future sea level rise.
Geophysical Research Letters, doi:10.1029/2011GL048280, 2011
Title: The role of ocean thermal expansion in Last Interglacial sea level rise
Authors: Nicholas P. McKay: Department of Geosciences, University of Arizona, Tucson, Arizona, USA;
Jonathan T. Overpeck: Department of Geosciences, Institute of the Environment, and Department of Atmospheric Science, University of Arizona, Tucson, Arizona, USA;
Bette L. Otto-Bliesner: National Center for Atmospheric Research, Boulder, Colorado, USA.