Relative Contributions of Atmospheric Energy Transport and Sea-Ice Loss to the Recent Warm Arctic Winter

Abstract

The relative contributions of atmospheric energy transport (via heat and moisture advection) and sea-ice decline to recent Arctic warming were investigated using high-resolution reanalysis data up to 2017. During the Arctic winter, a variation of downward longwave radiation (DLR) is fundamental in modulating Arctic surface temperature. In the warm Arctic winter, DLR and precipitable water (PW) are increasing over the entire Arctic;however, the major drivers for such increases differ regionally. In areas such as the northern Greenland Sea, increasing DLR and PW are caused mainly by convergence of atmospheric energy transport from lower latitudes. In regions of maximum sea-ice retreat (e.g., northern Barents？Kara seas), continued sea-ice melting from previous seasons drive the DLR and PW increases, consistent with the positive ice-insulation feedback. Distinct local feedbacks between open-water and ice-retreat regions were further compared. In open-water regions, a reduced ocean？atmosphere temperature gradient caused by atmospheric warming suppresses surface turbulent heat flux (THF) release from the ocean to the atmosphere;thus, surface warming cannot accelerate. Conversely, in ice-retreat regions, sea-ice reduction allows the relatively warm ocean to interact with the colder atmosphere via surface THF release. This increases temperature and humidity in the lower troposphere consistent with the positive ice-insulation feedback. The implication of this study is that Arctic warming will slow as the open-water fraction increases. Therefore, given sustained greenhouse warming, the roles of atmospheric heat and moisture transport from lower latitudes are likely to become increasingly critical in the future Arctic climate.