Wind‐Driven Barotropic Velocity Dynamics on an Antarctic Shelf

Abstract

AbstractReanalysis surface stress around the Antarctic continent is used to obtain the cross‐shelf sea surface height (SSH) gradient from the shallow water equations in the long‐wave limit, and the result is compared to the observed barotropic current sampled by current meters on the western Antarctic Peninsula shelf. Similar to the dynamics of SSH, intraseasonal velocity fluctuations (periods 3–100 days) largely consist of a circumpolar‐coherent wavenumber zero mode and of barotropic shelf waves; however, an important distinction from previous studies is the importance of second mode barotropic shelf waves in the velocity signal. Fluctuations with period 40–60 days are particularly energetic. This is partly due to strong fluctuations in the wavenumber zero mode at this period, as previously demonstrated in Drake Passage transport, but also due to excitement of the second mode barotropic shelf wave. After diagnosing the wind‐driven dynamics, some of their implications for shelf‐slope exchange are discussed. Firstly, it is shown that wintertime upwelling of warm water at a coastal canyon head is associated with a coastal SSH drop. Secondly, it is argued that the waves' subtle baroclinicity over the steep continental slope modifies isopycnal depth and affects shelf access to warm water.