Observations Reveal Intense Air-Sea Exchanges Over Submesoscale Ocean Front

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(degrees)C/km and 47 W/m(2)/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.