The North American Summer Arctic Front during 1948 to 2007

Boundaries between air masses, frontal zones, are associated with vegetation boundaries. Using gridded climate reanalysis data, we analyze the air masses and frontal zones of North America in relation to the atmospheric circulation and vegetation productivity. The position of the July Arctic front varies significantly through the period 1948-2007, with a mean position similar to that found by Bryson (1966). The variability of the frontal position can be associated with changes in the general circulation; when the AO and SOI are positive (negative), the position of the July Arctic front is further north (south). There is also more spatial variability in the July Arctic frontal position in Eastern versus Western North America. The location of the frontal zone affects the vegetation through impacts on vegetative production; when the July Arctic front is north (south) of the mean position, the boreal forest and tundra vegetation is more (less) productive. There is some evidence that climate warming is starting to shift the July Arctic front to the north.