Under global warming, the Antarctic Ice Sheet is losing mass at an accelerating rate, with over half of this loss driven by ocean-induced basal melting of ice shelves fueled by intrusions of warm Circumpolar Deep Water (CDW). However, the seasonal variability, regional patterns, and governing mechanisms of ocean heat content (OHC) on the circum-Antarctic continental shelf remain poorly constrained due to limited in-situ observations and coarse model resolutions. Here we use a high-resolution circum-Antarctic ocean-sea ice-ice shelf coupled model to systematically investigate the seasonal OHC variations and their physical controls over the Antarctic shelf and beneath ice shelves. We quantitatively diagnose OHC changes across standard shelf sectors and reveal distinct thermal regulation mechanisms through water mass classification, depth stratification, and heat budget analysis. Our results show that Antarctic shelves can be divided into warm shelves (e.g., West Antarctic Peninsula) and cold shelves (e.g., Weddell Sea). Warm shelf OHC seasonal cycles are modulated by CDW intrusion intensity, dominated by warm water mass variability, and driven primarily by horizontal heat advection, with warm waters acting as a "heat conduit". In contrast, cold shelf OHC cycles are controlled by sea ice formation/melt and polynya dynamics, dominated by cold water mass variability, and driven by surface heat fluxes, with the mixed layer serving as a "cooling conduit". Ice shelf cavity heat budget analysis further demonstrates that basal melt rates depend on both cavity OHC and heat transport efficiency, with cavity circulation and stratification playing critical roles. Warm-type cavities exhibit high heat consumption rates driving intense basal melting, while cold-type cavities have low heat consumption rates and relatively stable ice shelves. This study provides the first circum-Antarctic systematic characterization of seasonal shelf OHC variability, establishes a shelf classification system based on water mass heat content ratios, and quantifies the contributions of key physical processes, laying a foundation for improving projections of Antarctic ice shelf sensitivity to future climate change.

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