Over the past few decades, climatologists have documented a gradual reduction in both the thickness and the expanse of Arctic sea ice, a result of global warming that has been documented across the planet. This summer, as was reported on PBS last evening, new and unexpected findings in the Arctic appear to offer additional evidence of Earth's ongoing climate change.
Several large sinkholes have been discovered on the Arctic tundra of northern Siberia; edged by loose soil, there was initial suspicion that they might represent small impact craters. Others suggested that the holes may have resulted from the eruption of subterranean pockets of methane. At this point, however, most of the investigators have concluded that they are true sinkholes, having developed due to melting of deeper layers within the permafrost; this process has created water channels, undermining the surface of the tundra.
While the surface of the Arctic tundra has long thawed during the summer months, the deeper permafrost has remained frozen since the last glacial period of the Pleistocene. Apparently, the global warming that began at the peak of that glaciation (some 20,000 years ago) and has accelerated since the onset of the industrial revolution, has now reached a point where the permafrost is threatened. As more sinkholes develop, climatologists also suspect that significant amounts of carbon dioxide and methane might be released from the Arctic subsoil, a potential massive source of the greenhouse gasses that fuel global warming.
