Tropical influences on the decadal-scale oscillation in cool-season Arctic precipitation

A decadal-scale oscillation in the cool season Arctic precipitation is identified in both the CPC Merged Analysis of Precipitation (CMAP) and the Global Precipitation Climatology Project (GPCP) datasets. The signal is most pronounced in the Atlantic sector of the Arctic, including the Greenland, Norwegian, and Barents Sea. This oscillation is significantly correlated with the indices of the Northern Annular Mode (NAM) and the El Niño-Southern Oscillation (ENSO). It is shown to be related to the decadal-scale fluctuations in the sea surface temperature (SST) of the tropical Pacific. A mechanism is described in which the tropical SST variability drives changes in the extratropical storm tracks and the amount of moisture transported into the Arctic, leading to the observed decadal oscillation in the Arctic precipitation. This mechanism is further tested and verified with a series of idealized GCM experiments.