Relative Contributions of Atmospheric, Oceanic, and Coupled Processes to North Pacific and North Atlantic Variability

Patterns of sea surface temperature (SST) variability over the northern oceans arise from a combination of atmospheric, oceanic, and coupled processes. Here we use a novel methodology and a suite of observations to quantify the processes contributing to the dominant patterns of interannual SST variability over these regions. We decompose the upper ocean heat content tendency associated with such dominant patterns into contributions from different heat fluxes: (a) atmospherically driven, (b) surface feedbacks, and (c) oceanic. We find that in the subtropics, cloud radiative flux, turbulent heat flux, and residual oceanic processes each contributes substantially to North Pacific SST variability, whereas turbulent heat flux primarily induces North Atlantic SST variability. Cloud radiative fluxes therefore provide a major source of interannual SST variability in the North Pacific but not in the North Atlantic. In midlatitudes, SST fluctuations over the northern oceans are driven by the combination of turbulent and oceanic heat fluxes. Plain Language Summary The surface temperature of the North Atlantic and North Pacific oceans naturally varies from 1 year to the next in a spatially coherent manner. This variability originates from processes in the atmosphere and ocean, as well as from atmosphere‐ocean interactions. In this investigation, we use observational data to quantify these processes, which enables us to discern their relative contributions in generating year‐to‐year sea surface temperature fluctuations. Our results show that variations in clouds, through their influence on the sunlight absorbed by the ocean, are as important as other mechanisms for sea surface temperature fluctuations in the subtropical North Pacific. By contrast, clouds' impact in the subtropical North Atlantic is small. We find that in the midlatitudes of both ocean basins, sea surface temperature changes are primarily induced by variations in surface winds that modify the exchange of heat between the ocean and atmosphere and that alter ocean circulation patterns. Key Points Anomalous energy budget of ocean mixed layer associated with North Pacific and North Atlantic variability is quantified. Mechanisms for interannual sea surface temperature variability over northern oceans exhibit pronounced geographic dependence. Anomalous cloud radiative flux is an order one process for subtropical northeast Pacific variability.