Lakes Showing Signs
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The gradual effects of global warming on the earth’s ecological systems make it challenging to study. But UNL hydroclimatologist John Lenters believes he’s witnessing its impact in action.
Lenters studies how lakes respond to climate change. Whether a lake is frozen in the Arctic or fed by water percolating up from an aquifer in Nebraska’s Sandhills, Lenters is finding the influences of a warming climate.
As the planet warms, the consequences to lakes often mean decreasing water supplies for people, wildlife and ecosystems.
Normally, sediments on lake bottoms draw heat out of the water during the summer and release it in the winter in a heat-flux equilibrium. In the Arctic, however, Lenters found lakes drawing heat into the permafrost most of the year. The National Science Foundation funds this study of changes in Arctic lake dynamics.
"We are witnessing the thawing of permafrost in action in just a year’s worth of data," Lenters said. "As the climate warms, the lake sediments take a lot longer to respond and are out of whack. They’re trying to readjust."
In the Sandhills, lakes draw water from the High Plains Aquifer. Sunny, windy and dry conditions increase evaporation, further taxing the aquifer, a vital resource for agriculture, communities and wildlife.
"We’re measuring the highest evaporation rates of any of the lakes we’re looking at," Lenters said of the Sandhills research. "It seems like this region could potentially be very sensitive to slight variations in climate."
On an island in Lake Superior, Lenters is beginning to measure evaporation rates on the world’s largest freshwater lake.
Although Lenters is primarily collecting field data, he’s also combining lake measurements, such as ice thickness in the Arctic and salinity in Nebraska, with weather and other climatic data to create models to help predict global warming’s impacts on lakes over long time periods.
