Changes in Arctic moisture transport over the North Pacific associated with sea ice loss

Recent work has emphasized the important role of midlatitude moisture fluxes in enhancing Arctic warming and sea ice loss. Conversely, less attention has been paid to the impact of Arctic warming and sea ice loss on midlatitude moisture fluxes. Analysis of an atmosphere-only general circulation model indicates that sea ice loss promotes changes in the large-scale midlatitude atmospheric circulation that have a substantial impact on moisture transport into and out of the Arctic. While poleward moisture transport into the Arctic does increase in a reduced sea ice climate, the increase in equatorward moisture transport out of the Arctic is larger, particularly in boreal winter over the North Pacific. A decomposition of the meridional moisture transport reveals that this increase in equatorward moisture transport is driven, at least in part, by changes in the background circulation. Specifically, sea ice loss drives a series of large-scale tropospheric circulation changes, including an increase in cyclonic Rossby wave breaking over the North Pacific that results in a preferential enhancement of equatorward moisture transport out of the Arctic in the days following the peak of the Rossby wave breaking event.