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Abstract

Atmospheric circulation transports moist static energy from the mid-latitudes to the Arctic as compensation for radiative imbalances between Arctic and lower latitudes. Variations in sea ice cover, ocean temperature and atmospheric conditions can potentially modulate these moist static energy transports. We compare the transports of atmospheric energy in total as well as its components between an early and a late period of Arctic amplification. In particular, we analyze the dependence of the transport changes on region, height and season in reanalysis data. A barotropic wind field correction is applied before the calculations of the atmospheric energy transport accounting for inconsistencies in mass-fluxes due to the assimilation process. An increased meridional energy transport during summer is mostly compensated by a decrease in late winter. The changes in the dry static and latent components of the energy transport differ between individual months. In the vertical, changes in dry static energy transport extend into the stratosphere. Our hypothesis on the influence of changing background conditions on the atmospheric energy transport and Arctic amplification is tested with model experiments. An ensemble of idealized model simulations with the global icosahedral non-hydrostatic atmosphere model ICON was carried out. The model experiments distinguish between effects of sea ice retreat, ocean warming, and increased concentrations of greenhouse gases. Parts of the observed changes are reproduced in the simulations. To elucidate potential mechanisms of Arctic-midlatitude linkages, we analyze the changing frequency of tropospheric and stratospheric circulation regimes and the coupling between troposphere and stratosphere.