On the characteristics of internal tides and coastal upwelling behaviour in Marguerite Bay, west Antarctic Peninsula

Internal waves and coastal upwelling have important roles in both physical oceanography and marine ecosystems, via processes such as mixing of water masses and transfer of heat and nutrients to biologically-active layers. In this paper we use quasi-weekly hydrographic profiles and moored records of temperature, salinity and water velocity to investigate the nature of internal tides and coastal upwelling behaviour in northern Marguerite Bay at the western Antarctic Peninsula. Within Ryder Bay, a near-coastal site in northern Marguerite Bay, atmospherically-forced oscillations of the water column with periods around 2-7 days are observed, associated with wind-induced coastal upwelling and downwelling. Sea ice cover is seen to play a role in the seasonal suppression of these oscillations. Significant internal tides are also observed at this site. A range of processes are seen to be important in controlling internal tide variability, including changes in local stratification and sea ice conditions. Both diurnal and semi-diurnal internal tidal species are observed, despite the study region being poleward of the critical latitude for diurnal internal tides. This suggests that at least the diurnal internal tides are generated close to the study location, and we investigate likely sources. Our work adds understanding to how such phenomena are generated, and what controls their variability, in a region of rapid physical change and profound ecosystem importance.

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