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

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