Thawing Arctic permafrost

"Across the Arctic, strange things are happening to the landscape. Massive lakes, several square miles in size, have disappeared in the span of a few days. Hillsides slump. Ice-rich ground collapses, leaving the landscape wavy where it once was flat, and in some locations creating vast fields of large, sunken polygons. It’s evidence that permafrost, the long-frozen soil below the surface, is thawing. That’s bad news for the communities built above it – and for the global climate . . . Permafrost is perennially frozen soil that covers about a quarter of the land in the Northern Hemisphere, particularly in Canada, Russia and Alaska. Much of it is rich with the organic matter of long-dead plants and animals frozen in time. These frozen soils maintain the structural integrity of many northern landscapes, providing stability to vegetated and unvegetated surfaces, similar to load-bearing support beams in buildings. As temperatures rise and patterns of precipitation change, permafrost and other forms of ground ice become vulnerable to thaw and collapse. As these frozen soils warm, the ground destabilizes, unraveling the interwoven fabric that has delicately shaped these dynamic ecosystems over millennia. Wildfires, which have been increasing across the Arctic, have been increasing the risk. Under the surface, something else is active – and it is amplifying global warming. When the ground thaws, microbes begin feasting on organic matter in soils that have been frozen for millennia. These microbes release carbon dioxide and methane, potent greenhouse gases. As those gases escape into the atmosphere, they further warm the climate, creating a feedback loop: Warmer temperatures thaw more soil, releasing more organic material for microbes to feast on and produce more greenhouse gases."