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 and heat budget confirm 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 warming at the coast in a gyre regime.  Combinations of these regimes also experience coastal warming under a constant  positive offset in the winds.