Transport Pathways and Residence Times of Biological Hot Spots Along the Shelf North of the South Shetland Islands and Bransfield Strait

Observations from several multidisciplinary research programs over the last four decades identified a number of localized regions around the northern Antarctic Peninsula (AP) and Bransfield Strait (BS) characterized by high biological production that is in excess of average conditions (e.g. biological hot spots). These regions typically are persistent over several years and appear to be a common feature of the Antarctic shelf environment, in particular in parts of the Southern Ocean where the Antarctic Circumpolar Current (ACC) impinges the shelf break bringing nutrient rich Circumpolar Deep Water (CDW) onto the continental shelf. Ocean circulation and the dynamical processes controlling the CDW intrusions exert a strong influence in the formation of the hot spots regions. The objective of this study is to determine dominant pathways of intrusions of CDW onto the shelf and determine residence times of eight hot spot regions along the north of the South Shetland Islands (SSI) and BS. To accomplish this goal Lagrangian tracking experiments were done using a coupled sea ice/ice shelf/ocean circulation model for the Antarctic Peninsula using the Regional Ocean Modeling System (ROMS). The results showed preferred transport pathways along the shelf break in regions characterized by bathymetric depressions. Estimated residence times varied between the hot spots located north of the SSI and inside BS. The longest residence times were observed for the hot spots along the innershelf north of SSI (50-60 days). These time scales were consistent with development times of the local mesozooplankton and may contribute to the local biological processes. The hot spots along the outer shelf were less retentive (5-10 days) and presented similar time scales as the hot spots in the eastern Bransfield Strait. Our results suggests that circulation is important in developing localized areas of high biological production, their formation and maintenance has broad implications for the different components of the food web.