Abstract:
Strong offshore wind events (SOWEs) occur frequently near the Antarctic coast during austral winter. These wind events are typically associated with passage of synoptic- or meso-scale cyclones, which interact with the katabatic wind field and affect sea ice and oceanic processes in coastal polynyas. Based on numerical simulations from the coupled Finite Element Sea-ice Ocean Model (FESOM) driven by the CORE-II forcing, coastal polynyas along the East Antarctica coast are selected to examine the response of sea ice and oceanic properties to SOWEs. In these polynyas, the southern or western flanks of cyclones play a crucial role in increasing the offshore winds depending on the local topography. During SOWEs, the offshore component of sea ice velocity increased apparently, which is followed by dramatic decrease in sea ice concentration and increase of sea ice production by up to two to four folds. Formation of high salinity shelf water (HSSW) is detected in the coastal regions from surface to 800 m layers after several days of the SOWEs. HSSW formation averaged over winter is notably greater in years with longer duration of SOWEs.
The response of sea ice and water mass to meso- and synoptic-scale cyclones are also investigated for the Ross Ice Shelf Polynya (RISP) based on a numerical model targeted on the Ross Sea. During the passage of mesoscale cyclones, sea ice production (SIP) increased rapidly over the western side of RISP but decreased over the eastern side of RISP resulting from the different branches of cyclones. When synoptic-scale cyclones prevailed over this region, increased SIP values emerged over nearly the entire RISP. Under the two types of cyclones, HSSW formation is detected when there is a notable increase in SIP in the coastal regions. Enhancement in the HSSW formation is mainly observed over the western side of RISP, which could persistent for 12–48 hours after the passage of the cyclones.
Speaker:
Xiaoqiao Wang is a PhD candidate from the School of Oceanography, Shanghai Jiao Tong University (supervisor: Zhaoru Zhang). Now, she is visiting the Institute for Atmospheric and Earth System Research at the University of Helsinki (supervisor: Petteri Uotila). Her research is focused on the impacts of synoptic- and meso-scale atmospheric forcing on sea ice and water mass processes in Antarctic coastal polynyas.
