The Impact of CO2-Driven Climate Change on the Arctic Atmospheric Energy Budget in CMIP6 Climate Model Simulations

Abstract

The Arctic amplification is driven by several intertwined causes that are embedded in an overall changing energy balance of the atmosphere and ocean. We investigate the impact of quadrupled CO2 concentrations on the Arctic atmospheric energy budget in CMIP6 models. The decomposition of the energy budget accounts for the atmospheric radiation budgets, the sensible and latent heat flux at the surface, and the convergence of atmospheric energy transport. The CO2 response of these components is found to strongly depend on the Arctic season and underlying surface type. While the widespread Arctic radiative-advective equilibrium remains intact during boreal summer, profound changes are restricted to the winter season: Strongly increasing surface heat fluxes over areas of retreating sea ice are largely counteracted by dropping positive heat fluxes over open Arctic ocean. For retreating sea ice, the increase in the surface fluxes is stronger for a subset of climate models with weaker Arctic amplification. For these regions, we propose an intermediate transformation of the local radiative-advective equilibrium to a radiative-convective equilibrium. The wintertime changes in the components of the atmospheric energy budget strongly relate to alterations at the surface, concerning the modification of sea ice extent, surface temperature and stability. We find robust linear correlations for the mediating effect during winter. The energy transport convergence is derived as residual in our energetic framework as main mechanism to ensure the local energy budget. On a large scale, we find an overall decreasing transport convergence to balance the surplus energy from the surface which outruns the intensification of the Arctic radiation deficit in a warmer climate.

Keywords

• arctic atmospheric energy budget
• cmip6 models
• radiative-advective equilibrium
• arctic amplification
• climate change