Madrid, 5 (European press)
That’s the warning from research published in Nature Climate Change, led by Elizabeth Webb, a postdoctoral researcher in the University of Florida’s Department of Biology. The findings provide clues as to why the massive dehydration occurred and how the loss could be curbed.
Disappearing lakes form the cornerstone of the Arctic ecosystem. They provide a critical source of fresh water for local indigenous communities and industries. Threatened and endangered species, including migratory birds and aquatic creatures, depend on the lake’s habitat for survival.
The slope of these lakes was a surprise. Scientists expected climate change to initially cause lakes to expand across the tundra, due to changes in the Earth’s surface caused by melting ice, with a final drought in the mid-21st or 22nd century. Instead, it appears that thawing permafrost, the frozen ground that covers the Arctic, may drain the lakes and offset this pervasive effect, Webb says. The team hypothesized that thawing permafrost might reduce lake area by creating drainage channels and increasing soil erosion in lakes.
“Our results indicate that thawing permafrost is occurring faster than we would expect as a society,” Webb said in a statement. It also indicates that the area is likely to be on a path toward landscape-scale drainage in the future.
In addition to rising temperatures, the study also revealed that increased rainfall in the fall leads to deteriorating permafrost and lake drainage. “It may seem counterintuitive that increased rainfall reduces surface water,” said Jeremy Lichstein, a Webb consultant and one of the study’s authors. “But it turns out that a physical explanation was already in place in the scientific literature: rainwater carries heat to the ground and accelerates the melting of permafrost, which can open underground channels to drain the surface.”
If the accelerating thawing of permafrost is to blame, then this is bad news. Arctic permafrost is a natural storehouse of organic matter and gases that warm the planet.
“Permafrost stores nearly twice as much carbon as the atmosphere,” Webb said. “There’s a lot of research going on that suggests that as permafrost thaws, that carbon is liable to be released into the atmosphere as methane and carbon dioxide.”
There is a silver lining to the researcher’s findings. Previous models of lake dynamics predicted lake expansion, which would melt the surrounding permafrost. But because the lakes are drying up, the permafrost near the lakes likely won’t thaw as quickly.
“It’s not immediately clear what the exact trade-offs are, but we do know that lake expansion causes greater carbon losses than those occurring in the surrounding areas,” Webb said.
To achieve their results, the Webb team used satellite data to identify broad trends in surface water change across the Arctic. Webb, better known as remote sensing, says the satellite images help answer questions at scale.
“One of the things I really love about using remote sensing is that you can answer seemingly impossible big questions — now we have the ability to answer them,” Webb said. “Only in the last five or 10 years have we had the computing power and resources to pull this off.”
The research team used a machine learning approach to examine the mechanisms of climate change responsible for the change in the lake area. By making use of large sets of satellite imagery to assess patterns of surface water loss, they were able to analyze decades of data across the Arctic. Their work relied on powerful software, including the Google Earth Engine and the Python platform on the University of Florida’s HiPerGator supercomputer, to query large data sets and run models.
Webb initially set out to explore a completely different topic: the arctic albedo, or surface reflection. Webb’s previous work in Environmental Research Letters has shown that surface waters are the main driver of albedo change, but he has struggled to identify studies detailing why surface waters change in the first place. “I wrote the paper I wanted to cite in my blank sheet,” he said.
To reduce the disappearance of lakes, recent research in Frontiers in Environmental Science has shown that perhaps the best way to save permafrost is to reduce fossil fuel emissions. Reducing carbon emissions can put the planet back on track by limiting global warming.
“The snowball is already rolling,” Webb said. “We have to act now to stop these changes. It’s not going to work to continue doing what we’re doing.”