Cross-bay winds controlling primary production in Antarctic glacial bay

Abstract Antarctic glacial bays, because of their high productivity, are vital regions of the Southern Ocean. Certain glacial bays, including our research area, Admiralty Bay, are less favorable for phytoplankton blooms due to their wind-enhanced high energy levels, but they still host biological hotspots. Westerly winds are predominant in Admiralty Bay; the strongest storms are from the east. These winds act perpendicular to the main axis of the bay. The influence of these cross-bay winds on hydrodynamics and their effects on the primary production is examined. A hydrodynamic model was run in seven wind scenarios and coupled to a Lagrangian model tracking iron-rich glacial and bottom waters. The results show that westerly winds impede outflow from the bay and promote the creation of eddies at inner inlet openings. These eddies trap iron-rich particles for periods exceeding a month, forming accumulation areas that stimulate phytoplankton growth. They are located at the same location as the observed feeding hotspots, which occur despite wind-induced weak water column stratification. Easterly winds enhance outflowing currents, flushing out bay waters, negatively impacting local productivity. The study demonstrates how the direction rather than the magnitude of cross-bay winds can either stimulate or limit productivity in glacial bays.