Bridging mesoscale ocean dynamics and large-scale climate in 1° models

Climate models are commonly run at resolutions too coarse to resolve mesoscale ocean dynamics, and therefore lack oceanic eddies and fronts that strongly influence air-sea exchange. This leads to an underestimation of the ocean’s role in driving atmosphere–ocean interactions in western boundary current regions, with implications for simulated climate variability and change. We explore whether the effects of mesoscale sea surface temperature (SST) features on large-scale circulation can be represented in a standard resolution climate model using a partially coupled “pacemaker” configuration of the Norwegian Earth System Model version 2 (NorESM2). The setup introduces mesoscale SST features from a high-resolution (0.125°) ocean into the standard-resolution coupled model grid (1° ocean and atmosphere). Focusing on the Kuroshio Current, we find that mesoscale SST features amplify ocean-to-atmosphere turbulent heat fluxes, as expected, and also produce notable free tropospheric responses (a robust local strengthening of the North Pacific storm track at low levels and a poleward shift aloft). The results offer a proof of concept that 1° climate models can capture the broader climate impacts of small-scale oceanic variability without explicitly resolving it, opening promising pathways to improve predictions and projections.