Recent environmental changes in the Arctic and links with the atmospheric circulation (Invited Presentation)

The Arctic has seen significant environmental changes over the past several decades. The most obvious are pronounced winter and spring warming over Arctic and sub-Arctic land areas, reductions in sea ice extent, and warming and increased areal extent of the Arctic Ocean's Atlantic layer. Other studies point to increased river discharge, warming of soils and permafrost, and increased shrubbiness. There is overwhelming evidence of strong links with increasing dominance of the positive phases of the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO). The AO/NAO are natural modes of atmospheric variability and there is debate as to whether they are in fact separate phenomena. While the recent AO/NAO trend has been related to slowly varying sea surface temperatures, there is growing evidence of associations with increasing greenhouse gas concentrations and stratospheric ozone loss.

The AO/NAO does not explain everything. For example, the summer Arctic frontal zone, associated with differential heating between the cold Arctic Ocean and snow-free land, has significant impacts on the atmospheric circulation and hydrology. AO/NAO links with precipitation and net precipitation over the Arctic draining Eurasian watersheds are rather weak. While there is a demonstrated relationship between the winter AO and subsequent summer sea ice conditions, variability in the summer circulation is also important. A good example is provided by the record low sea ice conditions observed in 2002.