Advances in Uncrewed Surface Vehicles (USVs) enable expanded observations in the critically undersampled Southern Ocean - a region vital for global heat uptake. Using data from three USVs that sampled the Pacific sector of the Southern Ocean in both summer and winter, we evaluate processes and spatiotemporal scales of decorrelation that drive sensible heat flux variability. High heat flux variability is linked to synoptic-scale southwesterly winds, with decorrelation scales of ~50 km and ~10 hours, consistent across seasons and variables. Our results extend the observed relationship between wind direction and heat loss across the entire Pacific sector of the Southern Ocean, previously limited to three locations. Our datasets reveal over 8,000 temperature fronts ranging from <1 km to >20 km in width. These fine-scale ocean processes contribute to the heat flux variability 35\% percent of the time. While wind-related variability dominates sensible heat flux changes across the smallest fronts, the ocean’s role becomes increasingly significant with wider ocean fronts, particularly those over $\sim$4 km in width. However, due to their larger abundance, the total change of sensible heat flux over smaller ($\sim$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.