New Arctic Feedback is Draining, Drying Lakes

Above: A lake in northwest Alaska that drained in the summer of 2018. Photo by David Swanson, National Park Service.

Whoops, I missed this one when it came out in August.
Climate change once again shown to be counter-intuitive. Arctic lakes that should be multiplying are disappearing.
Unappreciated impact of permafrost breakdown.

Nature Climate Change:

Lakes constitute 20–40% of Arctic lowlands, the largest surface water fraction of any terrestrial biome. These lakes provide crucial habitat for wildlife, supply water for remote Arctic communities and play an important role in carbon cycling and the regional energy balance. Recent evidence suggests that climate change is shifting these systems towards long-term wetting (lake formation or expansion) or drying. The net direction and cause of these shifts, however, are not well understood. Here, we present evidence for large-scale drying across lake-rich regions of the Arctic over the past two decades (2000–2021), a trend that is correlated with increases in annual air temperature and autumn rain. Given that increasing air temperatures and autumn rain promote permafrost thaw, our results indicate that permafrost thaw is leading to widespread surface water decline, challenging models that do not predict a net decrease in lake area until the mid-twenty-first or twenty-second centuries.

Naomi Oreskes in Scientific American:

Research sometimes proves, with data, what we more or less already know. Exercise is good for you, and polluted air isn’t. Still, sometimes our intuitions are incorrect, and scientific findings surprise researchers, along with the rest of us. A recent example is the phenomenon of disappearing lakes in the Arctic tundra.

You might think these lakes would be expanding, not vanishing. As climate change warms the tundra—melting surface snow and ice and thawing the permafrost—there should be more surface water. Existing lakes should grow because of the extra water, and new ones might appear. Recently, however, scientists have observed not just shrinking lakes but lakes that have completely gone away. A paper published this year in Nature Climate Change, based on satellite imagery, found widespread lake loss across the Arctic over the past 20 years. Led by University of Florida postdoctoral researcher Elizabeth Webb, the scientific team found that lakes have shrunk or disappeared completely across 82 percent of the Arctic’s lake-rich regions.

Scientists have long recognized that global warming would thaw permafrost, and like many climate effects, that one appears to be happening faster than predicted. But the surprise is really about the bodies of water in the permafrost environment.

Many scientists shared the commonsense expectation that as permafrost thawed, lakes would at first expand because of increased meltwater flowing into them. Eventually, researchers projected, progressive warming during the 21st and 22nd centuries would dry out the Arctic enough that lakes would begin to shrink. But now it looks as if Arctic lakes are disappearing a century or more sooner than predicted.

There is a big difference between a lake gradually dwindling during a hotter climate and a lake vanishing from sight in less than a year. At the end of the summer of 2018, following the warmest and wettest winter on record at that time, 192 lakes in northwestern Alaska had completely or partly drained away. Some large lakes, believed to have existed for millennia, shrank drastically in what appears to have been a matter of months. Scientists have labeled this phenomenon “catastrophic lake drainage.”

What caused this? Basically, the ground is becoming more permeable. We talk about “solid ground,” but its particles of rock, mineral and organic matter actually have spaces between them. Outside the Arctic, those spaces are filled with air or water; surface water drains into them. (You see this after it rains, when after a few hours the puddles have disappeared.) Arctic landscapes are different. In permafrost, the pore spaces are filled with solid ice, so liquid water cannot readily penetrate. But when the permafrost thaws, water can flow downward. So these far northern lakes are disappearing because surface water can drain rapidly into the subsurface as the permafrost warms up.

Why did scientists miss this? One reason, offered by Webb and her colleagues, is that most climate models assume that permafrost thaw is driven only by warming air. New evidence suggests that rainfall—particularly increasing autumn rain—is now contributing substantially to permafrost loss. The rainfall carries heat into the ground. Yet none of the models in the large Coupled Model Intercomparison Projects (CMIPs) includes such processes. This is a good example of why—no matter how sophisticated our models are or may one day be—we need direct observation of the natural world.

Lakes make up as much as 40 percent of Arctic lowlands, where they provide crucial freshwater for Indigenous communities and critical habitat for a wide range of plant and animal life. The loss of marshy areas that accompany these lakes can also lead to an increase in wildfires, which, in a troubling feedback loop, melts more permafrost. This permafrost holds a huge amount of methane, a greenhouse gas that can create 80 times as much atmospheric warming as carbon dioxide in the short term. Rapid release of this methane could accelerate global warming dramatically.

Yale Environment 360:

Arctic lakes are drying out nearly a century earlier than projected, depriving the region of a critical source of fresh water, according to new research.

Models had predicted that as warmer weather thaws the Arctic, melting ice would feed into lakes, causing them to expand. Eventually, as ice melted away, those lakes would drain and dry out, sometime later this century, according to earlier projections. But satellite imagery reveals that lakes across the Arctic are shrinking rapidly today.

Researchers tracked a distinct downward trend in Arctic lake cover from 2000 to 2021, observing declines across 82 percent of the study area, which included large swaths of Canada, Russia, Greenland, Scandinavia, and Alaska. As warmer air and more abundant autumn rainfall melt permafrost around and beneath Arctic lakes, water is draining away, scientists say. The effect of rainfall was unaccounted for in prior models, which showed the lakes draining much later. The study was published in the journal Nature Climate Change.

The sooner-than-expected loss of surface water could have a profound effect, scientists say. Lakes comprise 20 to 40 percent of Arctic lowlands, serve as a critical habitat for migratory birds and other wildlife, and supply freshwater to remote Arctic communities.

The climate implications of rapidly melting permafrost are also troubling, researchers say. “Permafrost soils store nearly two times as much carbon as the atmosphere,” Elizabeth Webb, a postdoctoral researcher at the University of Florida and lead author of the study, said in a statement. “There’s a lot of ongoing research suggesting that as permafrost thaws, this carbon is vulnerable to being released to the atmosphere in the form of methane and carbon dioxide.”

Science Daily:

“Our findings suggest that permafrost thaw is occurring even faster than we as a community had anticipated,” Webb said. “It also indicates that the region is likely on a trajectory toward more landscape-scale drainage in the future.”

In addition to rising temperatures, the study also revealed that increases in autumn rainfall cause permafrost degradation and lake drainage. “It might seem counterintuitive that increasing rainfall reduces surface water,” said Jeremy Lichstein, Webb’s advisor and a co-author of the study. “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.”