Remote pathways of ocean heat transport toward the Antarctic Ice Sheet

Transport of warm Circumpolar Deep Water (CDW) into ice shelf cavities is known to be a primary source of heat driving Antarctic Ice Sheet mass loss. This CDW originates in the open ocean, and thus, basal melt rate variability is often linked to wind-driven fluctuations in cross-shelf CDW transport. While cross-shelf heat fluxes are certainly an important part of the story, less focus has been placed on the offshore processes that bring CDW from the open ocean to the shelf break. Here, we use in situ data from profiling floats in combination with Lagrangian particle release experiments in an ocean model to investigate the pathways by which CDW moves toward the continental slope, which is a necessary precursor to the cross-shelf exchange that has been studied in more depth. Observations and models suggest that CDW transport exhibits considerable spatial heterogeneity in the form of concentrated pathways linked to bathymetric features, both on- and off- shore of the continental slope. This suggests that pathways to the shelf break are characterized by distinct timescales and varying degrees of water mass transformation across different sectors. In addition, temporal variability on mesoscale, seasonal, and interannual timescales is present. This is potentially important context through which to understand regional and long-term variations in continental shelf heat content and ice shelf basal melt, which in turn, has implications for future sea level rise.