Drivers of Atmospheric and Oceanic Surface Temperature Variance

Abstract:

Ocean-atmosphere coupling is a fundamental component of the Earth’s climate variability, yet the origin of this variability remains unclear. In this work, mid-latitude air-sea interaction is investigated by studying the mechanisms underlying surface temperature variance in both the ocean and atmosphere. This surface temperature variance technique is carried out in the frequency domain, and is shown to be a powerful tool for determining the relative contributions from various dynamic processes to surface temperature variability across a range of timescales. Analysis is carried out on an eddy-resolving, medium complexity, idealized, ocean-atmosphere model. The model is run in three different configurations: fully coupled, atmosphere-only, and partially coupled (where the effect of ocean geostrophy is removed from the sea surface velocity field). Results indicate that horizontal advection is the major driver of variability in both the ocean and atmosphere at subannual timescales. A coupling between the ocean and atmosphere is identified at interannual through multidecadal timescales that is dominated by Ekman processes. Ocean eddies play a major role in ocean temperature variability across all timescales resolved in this study, and are imprinted in the atmosphere surface temperature field in the western boundary current region at monthly and longer timescales. This study highlights the potential of idealized and computationally cheap models to enrich our understanding of the underlying dynamics in air-sea coupling, and can serve as important assets toward the goal of better predicting climate variability.