Water properties on the west Antarctic Peninsula continental shelf: a model study of effects of surface fluxes and sea ice

A vertical- and time-dependent numerical mixed-layer and sea-ice model is used to analyze processes responsible for sea-ice and surface mixed-layer water properties on the continental shelf on the west side of the Antarctic Peninsula. Atmospheric observations from Faraday and Palmer stations along with satellite sea-ice observations and shipboard water observations (four hydrographic cruises between January 1993 to February 1994) are used for forcing and verification. The focus of this study is the year 1993 during which the best observations exist. However, a 16-year simulation is completed to analyze interannual variations of ice thickness and mixed-layer depth. This model study shows that surface waters of the west Antarctic Peninsula are heated in the summer by solar radiation and cooled in the winter by sensible heat losses. Diffusive-convection is important for upward heat flux across the pycnocline. Ice melt in the spring is due to solar warming of open water, which then melts ice; the direct melting for ice by solar heating is negligible. The near closure of surface heat and salt budgets over 1 year supports the minor importance, or at least the compensation, of near-surface lateral exchanges. Intrusion of Upper Circumpolar Deep water from the Antarctic Circumpolar Current onto the subpycnocline shelf is a critical element of both salt and heat budgets. A 16-year simulation (1978–1993) reproduces most high and low ice years as observed by satellite microwave measurements, thus supporting the major contribution of thermodynamic (local) processes in creating sea-ice and mixed-layer properties.