Enhancement of the Nighttime Ocean Cool Skin Effect by Natural Surfactants

Abstract The ocean interface brightness temperature is sensitive to the biologic activity reflected by the chlorophyll‐ a concentration (Chl a ) in the upper layers of the oceans. This is shown using sea surface skin temperatures T skin retrieved from spectra recorded by the Infrared Atmospheric Sounder Interferometer and collocated measurements of bulk temperatures T bulk by drifters and of Chl a from a daily Copernicus multi‐satellite product. The results demonstrate that , with , increases with Chl a , particularly when the surface wind is weak. This finding is attributed to the hydrodynamic damping of ocean near surface turbulence by biogenic surfactants that leads to an increase of the cool‐skin thickness. Parametric formulations of the cool skin temperature difference and thickness depending on both the wind speed and Chl a are proposed. This enables to assess the global potential impact of biogenic surfactants on interfacial temperatures that is mostly a coastal and polar phenomenon.