Influence of topography and winds on the distribution of water masses on the Antarctic Continental Shelf
Abstract
Central to improving our understanding  of ocean temperature change on Antarctica’s continental shelf is a better  understanding of how the ocean circulation drives the onshore flux of warm deep  waters across the shelf break. This study uses a primitive equation ocean model  to explore how the circulation regime and changes in surface stress influence  the temperature structure on Antarctica’s shelf seas. As the shelf temperature  changes are largely driven by ocean circulation changes, understanding these  becomes our focus. A simple barotropic model is used to describe the linear  theory of the difference between throughflow and gyres regimes, and their  expected response to changes in forcing. This theory informs our understanding  of the barotropic circulation response of the primitive equation model where a  momentum budget confirms that over the simulated equilibrated timescales with  surface forcing changes, the response is first-order linear. Consistent with  previous findings, we find that climate change projection-like wind shifts  (stronger westerlies that shift south) have a direct influence on Ekman  processes across the shelf break and upwell warmer waters onto the shelf. We  also find that the circulation regime (throughflow or gyre -- determined by basin  geometry), influences the mean shelf temperature and how susceptible the  existing shelf temperatures are to changes in surface stress. While the  throughflow regime can experience a complete transition in on-shelf  temperatures when the transition between westerly and easterly winds shifts  southward, we find relatively modest bottom intensified warming at the Ice  Front in a gyre regime.