As the Arctic warms nearly four times faster than the rest of the world, glaciers collapse, habitats continue to vanish at a record rate, and a wide range of ecosystems are endangered. Now, a team of researchers led by the University of Florida has identified another major threat: over the past two decades, Arctic lakes have shrunk or dried completely across the pan-Arctic – a region including the northern parts of Canada, Russia, Alaska, Greenland, and Scandinavia. The experts set out to find the causes of this mass drying, together with possible solutions to slow this process.
The Arctic lakes are a critical cornerstone of the Arctic ecosystems, providing important sources of water for local Indigenous communities and industries. Moreover, many threatened animal species, including migratory birds and aquatic creatures, also rely on the habitats these lakes offer.
Since scientists had initially predicted that climate change would expand lakes across the tundra due to land surface changes caused by melting ground ice, the discovery that the lakes are in fact declining came as a surprise. Apparently, the thawing of the permafrost – the frozen soil blanketing the Arctic – has a crucial role in draining the lakes, by creating drainage channels and increasing soil erosion into the lakes.
“Our findings suggest that permafrost thaw is occurring even faster than we as a community had anticipated,” said study lead author Elizabeth Webb, a postdoctoral fellow in Biology at the University of Florida. “It also indicates that the region is likely on a trajectory toward more landscape-scale drainage in the future.”
Besides rising temperatures, increases in autumn rainfall also causes permafrost degradation and lake drainage. “It might seem counterintuitive that increasing rainfall reduces surface water,” said study senior author Jeremy Lichstein, an associate professor of Ecology at the same university. “But it turns out the physical explanation was already in the scientific literature: rainwater carries heat into the soil and accelerates permafrost thaw, which can open up underground channels that drain the surface.”
Since the permafrost is currently storing nearly two times as much carbon as the atmosphere, its thawing may release massive amounts of carbon dioxide and methane in the atmosphere, further exacerbating climate change. However, the drainage of Arctic lakes may have a silver lining: the permafrost near these lakes is not thawing so fast. “It’s not immediately clear exactly what the trade-offs are, but we do know that lake expansion causes carbon losses orders of magnitude higher than occurs in surrounding regions,” Dr. Webb explained.
Nevertheless, lake drainage remains a hazard for a vast number of ecosystems. According to the scientists, curbing greenhouse gas emissions could help curtail these lakes’ demise and thus protect wildlife and Indigenous communities. “The snowball is already rolling. It’s not going to work to keep on doing what we’re doing,” Dr. Webb concluded.
The study is published in the journal Nature Climate Change.