While the rest of world has warmed, Antarctica has grown chillier, scientists say. According to a new study, air temperature on the southernmost continent fell by 0.7 degree Celsius per decade between 1986 and 2000 - a cooling trend that has come with ecological consequences.
The findings may come as a surprise to climate researchers. Conventional wisdom holds that the polar regions should be the first to show the effects of global warming. And previous work has indeed detected increased temperatures in Antarctica. But those studies, Peter T. Doran of the University of Illinois and colleagues note, used data collected from the Antarctic Peninsula, which extends north toward South America. Doran and his team, in contrast, analyzed a 14-year continuous weather station record from a cold, snow-less desert known as the dry valleys region—the continent’s largest ice-free area. The results of that analysis, in combination with a 35-year continental temperature compilation, suggest that temperature readings from the more numerous Peninsula stations have misrepresented the situation. "Our approach," Doran remarks, "shows that if you remove the Peninsula from the data set and look at the spatial trend, the majority of the continent is cooling."
Furthermore, the observed cooling is seasonal, affecting summer and fall temperatures the most. Summer cooling can have an especially dramatic impact on the organisms in Antarctica’s fragile terrestrial ecosystems, where liquid water is of limited availability. In fact, the continent’s cooling trend already appears to have affected life in the dry valleys, the researchers note. Decreased productivity of the region’s lakes may well stem from a climate-induced increase in lake ice thickness, which cuts down on the amount of light that reaches the resident phytoplankton. Changes in the abundance of soil-dwelling invertebrates have occurred as well, the team reports, declining in some cases by 10 percent per year. Prolonged summer cooling, the investigators thus propose, "will diminish aquatic and soil biological assemblages throughout the valleys and possibly in other terrestrial Antarctic ecosystems."
Kate Wong | Scientific American
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16.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
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