19.5: Digging Deeper-The Fate of Permafrost in a Warming World
The fate of permafrost in the future is dire. You may not think much about if you live outside the Arctic regions where permafrost is common. Scientists predict that 40 percent of the world's permafrost could thaw if temperatures rise 2 o C (3.6 o F) due to global warming. Thawing of the permfrost could allow carbon that has been stored for thousands of years to be released into the atmosphere fueling additional warming. In addition, thawing results in land subsidence and mass movement. Buildings and infrastruce-like roads, landing strips, and pipeleines, upon which residents depend have been constructed to account for the expansion and contraction that takes place in the active layer of permafrost. Rising temperature due to climate change threatens structures built under a different permafrost freeze-thaw regime.
The Arctic has experienced a signicant rise in air temperature over the last few decades and the permafrost that undelies much of the surface is undergoing substantial changes. Continuous permafrost on Alaska's North Slope has warmed 2.2 o -3.9 o C (4 o - 7 o F) over the last century making it more susceptible to erosion and mass movement. Some places in Alaska have subsided by 4.6 meters (15ft) due to thawing of the permanently frozen subsurface. Accompanied by rising sea level, Alaskan coastal communities near the Arctic Ocean and Bering Sea are being threatened. Figure 19.30 Peeking into Permafrost documents the affects of permafrost thawing on the physical environment of Alaska's Arctic coast.
Video : Peeking Into Permafrost (Courtesy USGS)