Arctic sea ice concentration and volume have declined due to greenhouse gas radiative forcing and an overall positive climate feedback. At the same time, there have been noteworthy weather and climate circulation anomalies both within the Arctic and extending through the midlatitudes and even into the tropics, leading some studies to conclude that the circulation anomalies are caused by sea ice changes. However, the direct link between sea ice and the atmosphere (i.e. the energy exchange) has not been heavily studied. Our study evaluates the Arctic surface energy budget using a large 33-member ensemble of the fully-coupled Community Earth System Model 1-Community Atmosphere Model version 5 (CESM1-CAM5). From this dataset, mean ensemble trends were calculated from 2011-2040 which is the time period of most severe and consistent sea ice loss. The spatial and seasonal distribution of both the climatology and the trends in the Arctic surface energy budget vary substantially for the radiative and turbulent fluxes (shortwave, longwave, sensible heat, and latent heat), though much of this seasonal and spatial heterogeneity can be understood to coincide with spatial and seasonal changes in sea ice. Four disparate regions stand out and the seasonal dependence of both the climatology and trend are investigated in detail: the Central Arctic, the Chukchi Sea, the Barents Sea, and the Greenland-Iceland-Norwegian Seas. Areas with year-round ice coverage in 2040 (i.e. Central Arctic) have a simple energy budget in which shortwave absorption is offset by a steady amount of longwave release throughout the year which does not change much over the course of the 30-year time period of interest. The Chukchi and Barents Seas transition from persistent to marginal and seasonal ice coverage in the projections, resulting in increased summer shortwave absorption that is generally overcompensated primarily via enhanced turbulent heat flux in the late fall and early winter. Marginal sea ice in the northern Greenland-Iceland-Norwegian Seas is effectively removed in the projections, resulting in highly variable but generally strong decreases in the upward turbulent and longwave fluxes as the sea ice is removed even in winter; the strong variability depends on the sea ice distribution projected in each individual ensemble member. Averaged over the whole Arctic, the change in the energy budget is qualitatively similar to that of the Central Arctic: loss of Arctic sea ice results in increased shortwave absorption during the summer which is mostly offset through enhanced longwave release, but how these fluxes are altered is highly geographically and seasonally dependent. This study strongly suggests that fully-coupled models are essential to recreate physically realistic atmospheric, oceanic, and sea ice conditions as the Arctic continues to experience drastic changes. Drawing physically conclusive links between sea ice concentration declines and impacts on oceanic atmospheric circulations requires further understanding of the Arctic energy budget, particularly which components are modified and where when these changes take place with respect to reduced sea ice.
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