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Abstract:
Over 35% of Antarctic coastline consists of tidewater glacial termini, found mostly in West Antarctica fjords. The hydrodynamics of these bays and its variability caused by changing volume and distribution of glacial meltwater is still poorly understood. Therefore, an in-depth analysis of all-year round water level changes, circulation pattern and water properties distribution has been done in Admiralty Bay (AB), King George Island, an Antarctic bay impacted by adjacent twenty retreating glaciers. Hydrodynamic modelling has been performed in varied scenarios of volume and location of glacial meltwater input, using Delft3D Flow software. Model results revealed a pattern of circulation dominated by two cyclonic circulation cells, controlling water exchange between AB and the ocean. Horizontal and vertical limits of glacial impact have been defined. Results were confronted with measurement dataset consisting of CTD probing of water column properties performed on 142 days, in 31 sites over three-year period. This allowed an assessment of seasonally variable Glacially Modified Water (GMW) distribution and volume. A melt season has been identified for AB region. Following, another round of modelling has been carried out, with more accurately defined glacial input volumes, assessed with in situ measurement data. Due to smaller temperature variability Antarctic glacial bay circulation pattern was found to be less transformed by seasonal shifts than its northern-hemisphere counterparts. Nevertheless, a consistent seasonal variability is shown in extent of areas in which glacial inflow is locally a controlling factor of water circulation and property distribution.
