The world’s largest High Arctic lake responds rapidly to climate warming

Igor Lehnherr, Vincent L. St. Louis, Martin Sharp, Alex S. Gardner, John P. Smol, Sherry L. Schiff, Derek C. G. Muir, Colleen A. Mortimer, Neil Michelutti, Charles Tarnocai, Kyra A. St. Pierre, Craig A. Emmerton, Johan A. Wiklund, Günter Köck, Scott F. Lamoureux, Charles H. Talbot

Using a whole-watershed approach and a combination of historical, contemporary, modeled and paleolimnological datasets, we show that the High Arctic's largest lake by volume (Lake Hazen) has succumbed to climate warming with only a ~1 °C relative increase in summer air temperatures. This warming deepened the soil active layer and triggered large mass losses from the watershed's glaciers, resulting in a ~10 times increase in delivery of glacial meltwaters, sediment, organic carbon and legacy contaminants to Lake Hazen, a >70% decrease in lake water residence time, and near certainty of summer ice-free conditions. Concomitantly, the community assemblage of diatom primary producers in the lake shifted dramatically with declining ice cover, from shoreline benthic to open-water planktonic species, and the physiological condition of the only fish species in the lake, Arctic Char, declined significantly. Collectively, these changes place Lake Hazen in a biogeochemical, limnological and ecological regime unprecedented within the past ~300 years.