Radiosonde measurements and Polar WRF simulations of low-level wind jets in the Amundsen Sea Embayment, West Antarctica

We show that low-level jets (LLJs) occurred in 11 out of 22 radiosonde profiles in late austral summer over the coastal region of the Amundsen Sea Embayment, with ten of the LLJs directed offshore. The LLJs had core speeds from 9 to 32 m s-1, jet core heights from 80 to 800 m, and were associated with strong, low-level temperature inversions. Seven of the observed offshore LLJs were reasonably simulated by the polar-optimised Weather, Research and Forecasting (Polar WRF) model, with output from the model subsequently used to elucidate their generation mechanisms. This showed that one of the offshore LLJs simulated by Polar WRF was caused by katabatic winds, while the remaining six were caused by the enhancement of katabatic winds by synoptic forcing in response to a low-pressure system over the Bellingshausen Sea, i.e., the offshore wind component associated with this system plays a crucial role in the enhancement of the katabatic LLJ. Examination of the Polar WRF output further showed the LLJs extending over large areas of the Amundsen Sea Embayment, resulting in substantially enhanced near-surface wind speeds over both the Thwaites and Pine Island ice shelves, as well as the open ocean over the continental shelf. The wind-driven forcing associated with the LLJs could perhaps have important impacts on the redistribution of snow over the ice shelves, as well as affecting sea-ice and ocean circulation variability, including the transport of relatively warm water over the continental shelf to the ice shelf cavities, and by extension basal melting.