Global High-Resolution Modeling: A New Lens on the Southern Ocean

Modern West Antarctic ice loss is generally driven by warm circumpolar deep water (CDW) reaching ice shelf grounding zones. Understanding what controls CDW delivery remains a challenge, in part because of the multiple scales involved. Most global models are too coarse to capture critical regional processes, while simulations with high-resolution regional models depend on imposed boundary conditions, precluding the possibility of capturing coupled processes across scales.  Here, we analyze a novel multi-member ensemble of global high-resolution (0.1° ocean, 0.25° atmosphere) Community Earth System Model (CESM) simulations over the historical period (1850-2005).   We compare the high-resolution runs to equivalent simulations at ~1 to 2° resolution, as well as to observational products (e.g. ECCO, WOA).  We show that biases in key ocean properties in the Southern Ocean are significantly improved in the high-resolution simulations.  This includes better representation of CDW in the high-resolution runs. We use these comparisons to explore new insights on the atmosphere and ice conditions that promote CDW delivery toward the ice shelves.