Linking submesoscale fronts and air-sea heat fluxes in the Southern Ocean: Results from the first Saildrone circumnavigation of Antarctica
<p>The role of the Southern Ocean in the global heat and carbon cycle is fundamental towards our climate, but observational data to quantify air-sea fluxes, such as surface&#160; heat&#160; fluxes, are&#160; still&#160; scarce. In&#160; order&#160; to&#160; investigate&#160; the&#160; effects&#160; of&#160; fine- scale oceanic fronts (0.1 km&#8211;10 km) on air-sea fluxes in the Southern Ocean, high-resolution&#160; hydrographic&#160; and&#160; meteorological&#160; data&#160; collected&#160; by&#160; three&#160; un-crewed surface vehicles (Saildrones) during their first Circumnavigation of Antarctica in 2019 was assessed. Comparisons of key variables from the in situ Saildrones datasets with those from ERA5 and a stationary mooring show good&#160; agreement.&#160; Temperature-driven density fronts were detected in the Saildrone data and their impact on the turbulent heat flux was quantified during steady atmospheric conditions.&#160; Over 2000 surface ocean temperature dominated density fronts were detected at length-scales (i.e.&#160; front width) ranging from sub-kilometer to mesoscale (order of 0.1 km&#8211;100 km).&#160;<br>Temperature-driven density fronts with a length scale (as seen from the Saildrones perspective ) smaller than 1 km contributed 75% and 51% of the sensible and latent heat flux changes, respectively. The direct link between the fronts and the impact on the heat fluxes decreases sharply&#160; when the front length increases. This suggests that smaller (submesoscale) fronts have a larger impact on heat flux variability than larger (balanced) fronts . The parametrization of&#160; these&#160; fine-scale ocean-atmospheric processes&#160; in&#160; global climate&#160; models&#160; could&#160; lead to more accurate&#160; representations&#160; of&#160; the&#160; heat&#160; flux&#160; variability both at local and global scale.</p>