Limited Influence of Localized Tropical Sea-Surface Temperatures on Moisture Transport into the Arctic

Abstract

Arctic moisture transport is dominated by planetary-scale waves in reanalysis. Planetary waves are influenced by localized Sea-Surface Temperature (SST) features such as the tropical warm pool. Here, an aquaplanet model is used to clarify the link between tropical SST anomalies and Arctic moisture transport. In a zonally uniform setup with no climatological east-west gradients, Arctic moisture transport is dominated by transient planetary waves, as in reanalysis. Warming tropical SSTs by heating the ocean strengthens Arctic moisture transport, mediated mostly by changes in water vapor rather than eddies. This strengthening occurs whether the tropical warming is zonally uniform or localized. Cooling tropical SSTs weakens Arctic moisture transport; however, unlike warming, the pattern matters, with localized cooling producing stronger transport changes owing to nonlinear feedbacks in the surface energy budget. Thus, the simulations show that localized tropical SST anomalies influence Arctic moisture transport differently than uniform anomalies, but only in cooling scenarios.