Modelling Ross Ice Shelf melting effect on the Southern Ocean in quasi-equilibrium
Abstract. To study the influence of basal melting of Ross Ice Shelf (BMR) on the Southern Ocean (ocean southward of 35° S) in quasi-equilibrium, numerical experiments with and without BMR effect have been performed with a global ocean-sea ice-ice shelf coupled model. In both experiments, the model started from a state of quasi-equilibrium ocean and was integrated for 500 years forced by CORE (Coordinated Ocean-ice Reference Experiment) normal year atmospheric fields. The simulation results of the last 100 years have been analysed. It’s shown that, the melt rate averaged over the entire Ross Ice Shelf is 0.253 m/a, which is associated with a freshwater flux of 3.15 mSv (1 mSv = 103 m3/s). The extra freshwater flux decreases the salinity in the Southern Ocean substantially whereas the effect of concurrent heat flux is not so significant except in the middle layer of water body (roughly from 1500 m to 3000 m). The decreased density due to BMR effect creates local circulation anomalies in the Ross Sea and nearby water with the help of ocean bathymetry. Through advection by the Antarctic Circumpolar Current, the flux anomaly from BMR gives rise to the increase of sea ice thickness and sea ice concentration in the Ross Sea adjacent to the coast and the ocean water westward. The warm advection and downwelling associated with the local circulation anomalies decrease the sea ice concentration in the rim of sea ice cover adjacent to open water in the Ross Sea in September. The decreased density weakens the sub-polar cell as well as the lower cell in the global residual meridional overturning circulation. And, northward meridional heat transport anomaly in most latitudes of the global ocean is accompanied accordingly.