Extreme Heat and Rain Turned These Arctic Lakes Brown

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By Larissa G. Capella, Eos/AGU. 

Excerpt: Jasmine Saros, a lake ecologist at the University of Maine, has been studying Arctic lakes in Kangerlussuaq, Greenland, since 2013, ...in 2023, they returned to find many once-clear lakes had turned brown. ...Lake browning often results from high concentrations of dissolved organic carbon, primarily from decaying vegetation. It can also be caused by an increase in iron, typically resulting from natural processes such as weathering of iron-rich soils and rocks into the water, as well as anthropogenic influences such as agricultural runoff and industrial discharges. Data from the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA5)...showed that nine atmospheric rivers had dumped precipitation over the area between September and October of 2022. Atmospheric rivers are known for transporting moisture, but they can also carry warm air. The ERA data also highlighted that September 2022 was the hottest and wettest September on record in West Greenland since 1940. By early July 2023, when Saros and her colleagues were back on the lake, dissolved organic carbon levels had risen by 22% compared to the 2013–2023 average. Iron concentrations had increased 1,000%. ...“Those atmospheric rivers drove not only record precipitation but also record heat,” Saros said. Higher temperatures caused precipitation to fall as rain instead of snow. The heavy rainfall saturated the landscape, thawed permafrost, and released organic material and iron into the lakes, turning them brown, she explained. The study was published in the Proceedings of the National Academy of Sciences of the United States of America.... 

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