Drivers of sensible heat flux in the Southern Ocean and their relationship to submesoscale fronts

Advances in uncrewed surface vehicles (USVs) enable expanded observations in the Southern Ocean, a region vital for global heat uptake yet critically undersampled. Using data from three USVs that sampled the Pacific sector of the Southern Ocean in both summer and winter, we evaluate processes and decorrelation scales driving sensible heat flux variability. High flux variability is linked to synoptic-scale southwesterly winds, with sensible heat flux decorrelation scales of 40–60 km and 6–10 hours, consistent across seasons and variables. Fine-scale (<1–10 km) oceanic processes, including fronts, filaments, and boundaries, further influence flux variability: Our datasets reveal over 8,000 temperature fronts ranging from <1 km to >20 km in width. While wind-related variability dominates sensible heat flux changes across the smallest fronts, the ocean’s role becomes increasingly significant with front width, reaching parity at ~4 km. However, due to their abundance, the total change of sensible heat flux over smaller (~1 km) fronts is an order of magnitude greater than that of larger (>4 km) fronts. These results highlight the role of fine-scale atmosphere-ocean interactions in driving heat flux variability in the Southern Ocean, offering valuable insights for enhancing flux estimates in this critical region.