In her recent PhD at Alfred Wegener Institute, Bremerhaven, Germany, Verena Haid investigated the influence of coastal polynyas in the Weddell Sea, Antarctica, on heat flux, sea ice production and water mass modification. Coastal polynyas are areas where mechanical forces (mostly wind) remove the sea ice cover and thus locally high ocean-atmosphere heat flux occurs. This leads to high sea ice formation rates and the salt rejected in the process causes the underlying water masses to densify. On continental shelves thus High Salinity Shelf Water is formed, which is an important ingredient in the formation of Antarctic Bottom Water.
The simulation was executed with the Finite Element Sea ice-Ocean Model (FESOM) which was developed at Alfred Wegener Institute. The finite element method allows for local grid refinement so that with a global model domain resolutions of 5-3 km at the Weddell Sea coastline could be realized. Starting in 1980, a 30-year simulation forced with daily NCEP/NCAR Reanalysis data was performed. In April 2007, a simulation forced with GME (Global Model Europe) data (60 km, 6-hourly) was branched off and from this simulation in March 2008 two short simulations with regional high-resolution data (15 km/5 km, 1-hourly) from the COSMO (Consortium for Small-scale Modelling) model were branched off. While basin-scale mean values of the different simulation branches are in reasonable agreement, the local differences between simulations can be substantial. Particularly in 2008, a year under the influence of a La Nina/positive Southern Oscillation Index event, large differences between the NCEP and GME forced simulations are apparent.

Lecturer
Verena Haid
CMCC, Bologna