E. Linacre and B. Geerts
Much of northern N. America and Siberia has a tundra landscape. A tundra is a treeless region characterised by peat soils covered by mosses, lichens and low shrubs. The winters are extremely cold, and the summers short, therefore a permafrost exists, which typically is several meters thick. The amount of carbon stored in the Arctic tundra equals about a third of that in the global atmosphere. The large storage is the result of excess production over decay of plant material; both production and decay occur almost exclusively during the short summer.
Measurements in Alaska indicate that the local tundra has ceased being an important absorber of carbon (in the growth of the vegetation), and on the whole is now releasing it to the air (1). In many places the tundra’s permafrost appears have thinned and broken up during the last few decades. The deeper the top layer is that melts during the summer, the more carbon in the buried vegetation can be oxidised to form carbon dioxide gas. As a result, lakes and streams in Arctic Alaska are supersaturated with dissolved carbon dioxide, leading to release of the gas into the atmosphere, and thus more global warming, especially at high latitudes where, according to climate models, an increase in greenhouse gas concentrations leads to the largest increase in surface temperature. In other words, the tundra soil provides a positive feedback to global warming.
(1) Press release by G.W. Kling, University of Michigan, 15/12/96.