The Arctic tundra in Yakutia in the north.
Arctic lakes could drain an enormous reservoir of old carbon, buried deep under the permanently frozen soil, or permafrost, thereby accelerating climate change.
These lakes, which arise when the ice melts on the surface and the ground below it, can thaw the underground permafrost much faster than scientists thought possible, according to a new study. [Images of Melt: Earth’s Vanishing Ice]
Previously, scientists thought that most of this deep defrosting of Arctic permafrost would probably take place only after 2100.
Rapid changes in the Arctic
Climate change occurs more rapidly in the Arctic than on the rest of the planet, and one of the greatest risks associated with warming temperatures in the region is permafrost melt.
The deep layers of permanently frozen soil that underlie a large part of the Arctic, conceal enormous reservoirs of organic carbon, in the form of thousands of years of trapped plant material and even animal carcasses. As the soil gradually melts, these buried organisms will decay and the greenhouse gases release carbon dioxide and methane into the atmosphere, which in turn can lead to even more warming.
But most scientists believed that it would take dozens of years of warming to melt permafrost buried under the active layer of soil that freezes and defrosts with the seasons.
"The conclusions reached by Permafrost carbon modelers were that until you really deeply thaw, we will not get this big, old carbon signal and that the really deep thawing of carbon on the land will not take place until after 2100," study leader Katey Walter said. Anthony, an ecologist and biogeochemist at the University of Alaska Fairbanks, at Live Science. "What our research shows is that in a lake that deeply thaws very quickly on a scale of decades." Lakes land faster in that old carbon layer and they will release that permafrost carbon much earlier than on land. "
Walter Anthony and her colleagues have studied so-called thermal pylons, which are created when the ice-rich soil thaws, causing the earth to collapse beneath it and forming a well where the molten water collects. Thermoplasts often look like biscuits that have been bitten around their edges, explained Walter Anthony, because the liquid water does pick up bites from the surrounding frozen edges, causing it to expand more.
The lakes can also be up to 30 meters deep and if the water does not freeze all the way to the bottom in the winter, the heat in the liquid water causes the permafrost to submerge under that lake, Walter Anthony said.
"While defrosting permafrost, we get what we call a dooilamp, and that dooiknol can laterally deepen and expand," said Walter Anthony. When that happens, "what previously frozen soil with organic carbon was thawed into it, and that thawed earth releases this organic matter to microbes that decompose and produce carbon dioxide and methane."
The researchers wanted to quantify how much methane – the largest part of the gas that bubbles from the lakes – emits thermo-pollutants today and what their expected emissions are for the future. The team used a combination of computer models and measurements from fieldwork in Alaska, Canada and Siberia to chart the growth and emissions of thermal lakes.
According to their results, published on August 15 in the journal Nature Communications, the lakes would double previous estimations of permafrost caused greenhouse warming.
"It is still much smaller than fossil fuel emissions, but it is roughly equivalent to land-use change," which is the second largest source of man-made climate change, Walter Anthony told Live Science.
Original article about Live Science