Assessment of the changing role of lower tropospheric temperature advection under arctic amplification using a large ensemble climate simulation dataset

Abstract

The role of temperature advection in the Arctic lower troposphere under changing level of global warming is investigated using a large-ensemble climate simulation dataset. Taking the 30-year climatology of the non-warming simulation (HPB-NAT) as a reference, we examined the difference in temperature advection under changing basic states of the historical experiment (HPB) and 2 K and 4 K warming experiments (HFB-2K and HFB-4K) and decomposed them into terms related to dynamical changes, thermodynamical changes and the eddy term which is a covariance term related to the effect of sub-monthly transient eddies. Under the HPB experiment, it was found that the total change in advection hangs in a balance between the positive signal located along the sea-ice boundary in the North Atlantic and along the Eurasian continent driven by a stronger dynamical term and a negative signal in the thermodynamical term and eddy term. It is found that with the progression of global warming the dynamical term of advection increases due to changes in the large-scale atmospheric circulation, but the thermodynamical term and eddy term decrease due to weaker temperature gradient and increased sensible heat flux from the newly opened ice-free ocean, respectively. Atmospheric temperature advection terms related to large-scale atmospheric circulation partially cancels one another, and the relative importance of the eddy term diverging locally induced sensible heat from the newly opened ice-free ocean dominates as global warming progresses.