ARCUS | Arctic Research Consortium of the United States

7th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Richard Cullather
Authors   Richard Cullather and A. H. Lynch
Category   Physical Science
Title   The Annual Cycle and Interannual Variabliity of Atmospheric Pressure in the Vicinity of the North Pole
Affiliation   Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO, USA

Abstract

A comparison of NCEP/NCAR Reanalysis 6-hourly sea level pressure data with former Soviet drifting station observations over the central Arctic Basin reveals high monthly correlations throughout the period 1950-91, but also a preferred winter season negative bias of about 1.4 hPa. Using the reanalysis, supplemented by Arctic Ocean Buoy Program fields and in situ observations, a generalized depiction of the annual cycle of pressure fields over the Arctic may be constructed. Above the Canada Basin/Laptev Sea side of the Arctic, the annual cycle of surface pressure is dominated by the first harmonic, which has an amplitude of about 5 hPa and maximum pressure occurring in March. Along the periphery of northern Greenland and extending to the North Pole, a weak semiannual cycle is found in surface pressure with maxima in May and November. The presence of the semiannual variation over time is highly variable. Dynamically, this progression of the annual cycle may be attributed to the transfer of atmospheric mass from Eurasia and into the Canadian Archipelago in spring, and the reverse condition in autumn. Over the central Arctic Basin, springtime pressure increases result from an enhanced poleward mass transport from Eurasia. An increase of equatorward transport over the Canadian Archipelago in May and June results in central Arctic pressure decreases into summer. A less distinct temporal separation between the poleward Canadian transport and the equatorward Eurasian transport results in the weaker second pressure maximum in autumn. On interannual timescales, atmospheric mass over the central Arctic is exchanged with the storm track centers of action in the North Atlantic and North Pacific. In particular, the large decrease in central Arctic Basin sea level pressure during the late 1980s is due to a large transfer of atmospheric mass into the North Pacific.