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Abstract Advances in uncrewed surface vehicles enable expanded observations in the critically undersampled Southern Ocean—a region vital for global heat uptake. Using data from three Saildrone missions 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 fluxes. Enhanced heat flux variability is primarily linked to synoptic‐scale southwesterly winds, with decorrelation scales of 50 km and 10 hr, consistent across seasons. These scales are influenced by both atmospheric forcing and oceanic variability, with sharp sea surface temperature changes occasionally driving pronounced shifts in sensible heat flux. 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 data sets 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% 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 4 km in width. However, due to their larger abundance, the total change of sensible heat flux over smaller (1 km) fronts is an order of magnitude greater than larger fronts (>4 km). These results highlight the role of fine‐scale atmosphere‐ocean interactions relating to heat flux variability in the Southern Ocean, offering valuable insights for enhancing flux estimates in this critical region. 

Abstract Determining the injection of glacial meltwater into polar oceans is crucial for quantifying the climate system response to ice sheet mass loss. However, meltwater is poorly observed and its pathways poorly known, especially in winter. Here we present winter meltwater distribution near Pine Island Glacier using data collected by tagged seals, revealing a highly variable meltwater distribution with two meltwater-rich layers in the upper 250 m and at around 450 m, connected by scattered meltwater-rich columns. We show that the hydrographic signature of meltwater is clearest in winter, when its presence can be unambiguously mapped. We argue that the buoyant meltwater provides near-surface heat that helps to maintain polynyas close to ice shelves. The meltwater feedback onto polynyas and air-sea heat fluxes demonstrates that although the processes determining the distribution of meltwater are small-scale, they are important to represent in Earth system models.