Polar regions have long been suggested by climate models to be the parts of the planet most susceptible to CO2-induced global warming, which is projected to melt large portions of the polar ice caps and thereby raise global sea level by several meters, wreaking havoc on low-lying islands and coastal regions of the world. In the frozen wastes of Antarctica, however, recent observations tell a radically different story.
Comiso (2000) examined trends in surface- and satellite-derived temperatures in this region since 1979, finding that both data sets exhibited cooling, 0.008°C per year for the surface record and 0.042°C per year for the satellite record. This cooling, in the words of the author, is "intriguing," especially in light of the fact that all GCMs predict greenhouse gas-induced global warming to be particularly pronounced in polar regions. Could it be that the models are wrong?
Additional observational evidence brings even more bad news for those who cling to the outmoded belief that state-of-the-art GCMs can adequately simulate polar climate. Measurements of the mean position of the Antarctic sea ice edge over the last 18 years reveal an equator-ward expansion of 0.011 degrees of latitude per year (Yuan and Martinson, 2000). Furthermore, the Summary of our Subject Index entry West Antarctic Ice Sheet (WAIS) reveals that the modern-day retreat of the WAIS's grounding line is part of an ongoing recession that has been underway since the early to mid-Holocene, and that this recession is therefore not a consequence of anthropogenic warming or recent sea level rise. Even more striking is the reported likelihood that the entire Antarctic Ice Sheet has probably been in near-perfect balance for the past 1000 years.
Although the vast bulk of Antarctica is either maintaining a near-constant temperature or slightly cooling, the west coast of the Antarctic Peninsula has warmed substantially over the past several decades. Hence, it is only natural to wonder what impact this warming is having on the two plant species that make up the totality of the continent's vascular vegetation: Colobanthus quitensis (a cushion-forming member of the Caryophyllaceae) and Deschampsia antarctica (a prostrate tussock grass). Xiong et al. (2000) report that increases in the size and number of populations of these species have recently been observed along the Peninsula. They also report that the plants experience significant increases in total biomass, number of leaves, and total leaf area as temperatures rise, concluding that "continued warming along the Peninsula will lead to improved vegetative growth of these species."
Other ecological changes are also taking place in response to recent warming on the Antarctic Peninsula. Chinstrap penguins and gentoo penguins have begun to take up residence alongside indigenous Adelie penguins (Smith et al., 1999), thus demonstrating a typical response observed in many parts of the planet, namely, that when the temperature rises, so too do ecosystem primary production and biodiversity increase. To this rule, the western Antarctic Peninsula is no exception.
References
Comiso, J.C. 2000. Variability and trends in Antarctic surface temperatures from in situ and satellite infrared measurements. Journal of Climate 13: 1674-1696.
Elderfield, H. and Rickaby, R.E.M. 2000. Oceanic Cd/P ratio and nutrient utilization in the glacial Southern Ocean. Nature 405: 305-310.
Smith, R.C., Ainley, D., Baker, K., Domack, E., Emslie, S., Fraser, B., Kennett, J., Leventer, A., Mosley-Thompson, E., Stammerjohn, S. and Vernet M. 1999. Marine ecosystem sensitivity to climate change. BioScience 49: 393-404.
Xiong, F.S., Meuller, E.C. and Day, T.A. 2000. Photosynthetic and respiratory acclimation and growth response of Antarctic vascular plants to contrasting temperature regimes. American Journal of Botany 87: 700-710.
Yuan, X. and Martinson, D.G. 2000. Antarctic sea ice extent variability and its global connectivity. Journal of Climate 13: 1697-1717.