Correcting for artificial heat in coupled sea ice perturbation experiments

Abstract

A common approach to assessing how polar amplification affects lower latitude climate is to perform coupled ocean-atmosphere experiments in which sea ice is perturbed to a future state. Recent work with a simple 1-dimensional energy balance model (EBM) shows that sea ice perturbation experiments impose an artificial heat flux on the climate system. We explore this effect in a broader range of models and suggest a technique to correct for the artificial heat post-hoc. Our technique successfully corrects for artificial heat in the EBM, and a possible generalization of this approach is developed to correct for artificial heat in an albedo modification experiment in a comprehensive earth system model. Generalizing this technique to sea ice perturbation methodologies that employ a ‘ghost flux’ seen only by the sea ice model would require a better understanding of the effect of ghost fluxes on the surface energy budget. Applying the correction to the comprehensive albedo modification experiment, we find stronger artificial warming than in the EBM. Failing to account for the artificial heat also leads to overestimation of the climate response to sea ice loss (SIL), and can suggest false or artificially strong ‘tugs-of-war’ between low latitude warming and SIL over some fields, for example Arctic surface temperature and zonal wind.