Hydrodynamic response of an Antarctic glacial bay to cross-bay winds and its potential impact on primary production.

Antarctic glacial bays are important, productive regions of the Southern Ocean. Certain glacial bays, including our research area, Admiralty Bay, are less favorable for phytoplankton growth due to wind-enhanced high energy levels, but they still host localized biological blooms. 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. This study investigates the impact of cross-bay winds on the bay’s hydrodynamics and its potential effects on primary production. A hydrodynamic model, coupled with a Lagrangian model tracking potential iron sources, was run under seven wind scenarios. Results indicate that all winds reduce water column stratification, but energy increase rates and circulation pattern shifts vary with wind direction. Westerly winds restrict outflow and promote the formation of submesoscale eddies near inner inlet openings, concentrating water masses that are expected to be iron-rich, potentially stimulating phytoplankton growth. Conversely, easterly winds enhance outflow, flushing bay waters and likely negatively impacting productivity. Limited observational and satellite-derived biological data provide supportive evidence for the model-based hypothesis that the direction of cross-bay winds, rather than just their magnitude, significantly influences local productivity.