The Increasing Efficiency of the Poleward Energy Transport Into the Arctic in a Warming Climate

Abstract

This study quantifies the contribution to Arctic winter surface warming from changes in the tropospheric energy transport (Ftrop) and the efficiency with which Ftrop heats the surface in the RCP8.5 warming scenario of the Community Earth System Model Large Ensemble. A metric for this efficiency, Etrop, measures the fraction of anomalous Ftrop that is balanced by an anomalous net surface flux (NSF). Drivers of Etrop are identified in synoptic-scale events during which Ftrop is the dominant driver of NSF. Etrop is sensitive to the vertical structure of Ftrop and pre-existing Arctic lower-tropospheric stability (LTS). In RCP8.5, winter-mean Ftrop decreases from 95.1 to 85.4 W m−2, while Etrop increases by 5.7%, likely driven by decreased Arctic LTS, indicating an increased coupling between Ftrop and the surface energy budget. The net impact of decreasing Ftrop and increasing efficiency is a positive 0.7 W m−2 contribution to winter-season surface heating.