Given uncertainty in the processes involved in polar amplification, elucidating the role of poleward heat and moisture transport is crucial.
The Polar Amplification Model Intercomparison Project (PAMIP) permits robust separation of the effects of sea ice loss from sea surface warming under climate change. A moist isentropic circulation framework accounts for moisture transport, condensation, and eddy transport, while connecting the midlatitudes and the Arctic. It is found that sea ice loss reduces poleward heat transport (PHT) by warming the returning branch of the moist isentropic circulation at high latitudes, while warming of the ocean surface strengthens the overturning circulation, increasing the total PHT. Inter-model spread of PHT into the Arctic reflects the tug-of-war between sea-ice and surface-warming effects.