Observations Reveal Intense Air‐Sea Exchanges Over Submesoscale Ocean Front

Abstract

Air‐sea exchanges across oceanic fronts are critical in powering cloud formation, precipitation, and atmospheric storms. Oceanic submesoscale fronts of scales 1–10 km are characterized by strong sea surface temperature (SST) gradients. However, it remains elusive how submesoscale fronts affect the overlying atmosphere due to a lack of high‐resolution observations or models. Based on rare high‐resolution in situ observations in the Kuroshio Extension region, we quantify the air‐sea exchanges across an oceanic submesoscale front. The cross‐front SST and turbulent heat flux gradients reaches 2.4°C/km and 47 W/m2/km, respectively, far stronger than that typically found in mesoscale‐resolving products. The stronger SST gradient drives substantially stronger air‐sea fluxes and vertical mixing than mesoscale fronts, enhancing cloud formations. The intense air‐sea exchanges across submesoscale fronts are confirmed in idealized model simulations, but not resolved in mesoscale‐resolving climate models. Our finding provides essential knowledge for improving simulations of cloud formation, precipitation, and storms in climate models.

Atmospheric Fronts Shaping the (Sub)Mesoscale SST‐Wind Coupling Over the Southern Ocean: Observational Case

“…The mesoscale SST-wind coupling processes have been relatively extensively investigated in previous studies (see reviews by R. D. Small et al (2008); Seo et al (2023)), but the smallscale oceanic forcing (below the deformation radius) on the MABL processes is only beginning to be investigated (Czaja et al, 2019). Recently, both observations (Acquistapace et al, 2022;de Szoeke et al, 2021;Gaube et al, 2019;Iyer et al, 2022;Shao et al, 2019;Yang et al, 2024) and simulations (Conejero et al, 2024;Strobach et al, 2022;Sullivan & McWilliams, 2022;Sullivan et al, 2020;Wenegrat & Arthur, 2018) have shown that submesoscale SST variability can have direct impacts on the MABL, including surface wind speed, air-sea heat flux, and cloud formation (Acquistapace et al, 2022). The energetic submesoscale processes in the Southern Ocean also implied the strong submesoscale air-sea coupling (Siegelman et al, 2020;Su et al, 2018;Swart et al, 2023), but it remains largely unexplored, particularly from the observation perspective.…”