Recent Abrupt Intensification of the Northern Polar Vortex since 1988

[摘要] Walsh (1994) reported that the surface vorticity in the Central Arctic has changed its sign from negative to positive since 1988. This study is devoted to confirm the recent abrupt change in the Arctic documented by Walsh. The analysis is extended not only to the surface but also to the upper air circulation to find the vertical structure in the vorticity change.As a result, the decreasing trend in geopotential height since 1988 is confirmed for the polar vortex throughout the troposphere. The vorticity change is thus regarded as barotropic in its structure. The surface Beaufort high has weakened associated with the strengthened upper air vortex. It is anticipated from the result that the wind-driven Beaufort gyre might undergo significant deformation, which would lead to a drastic impact on the export of sea ice to the North Atlantic Ocean through Fram Strait.

[学科分类] 大气科学