16:00 〜 16:15
[MIS03-03] Upslope flow of mCDW across the continental shelf using a high-resolution model in the Cape Darnley Bottom Water formation region.
キーワード：Southern Ocean, Dense water production, Circumpolar Deep Water, Downslope vs. upslope flow, Ocean-ice modelling
In the Southern Ocean, the upslope flow of warm modified Circumpolar Deep Water (mCDW) onto the Antarctic shelf is of crucial importance because these warm waters affect ice shelf melting and play a role in the material cycle. The upslope flow of mCDW is favored by the presence of canyons across the continental slope. In a recent study, Morrison et al. (2020) demonstrated that the upslope flow of CDW in canyons is strongly correlated to the downslope flow of Dense Shelf Water (DSW) in dense water formation regions. They also proposed a mechanism explaining the upslope flow by the existence of a cross-canyon pressure gradient and a barotropic geostrophic balance within the canyons.
Here, we develop a high-resolution model (500 m horizontal and 20 m vertical grid spacing) and compare it with Morrison et al. (2020)’s, whose resolution was (O)100 km. Our model domain is the Cape Darnley region in East Antarctica, where DSW is formed and flows down the continental slope -via several canyons- to form Cape Darnley Bottom Water. There, very-high resolution bathymetric data were recently acquired by Japanese icebreaker Shirase around the Wild Canyon system. The high-resolution bathymetric data and model offer a unique opportunity to further investigate the dynamics affecting the upslope flow as well as interaction with bottom water formation by analyzing data within individual canyons of the Wild Canyon system. Combining our model results with mooring observations of temperature and current velocity, we focus on the processes affecting the upslope flow near the top and bottom of the continental slope. Our results suggest that near the top of the slope, both mesoscale eddies and the in-canyon mechanism proposed by Morrison et al. (2020) affect the upslope flow with a ~2-day dominant period. At depths > 2000 m, the variability is dominated by a ~5-day periodic phenomenon which is likely a topographic wave. We discuss the possibility that interactions between the processes affecting the bottom and top of the slope are responsible for bringing mCDW from far offshore to the near-shore.
Here, we develop a high-resolution model (500 m horizontal and 20 m vertical grid spacing) and compare it with Morrison et al. (2020)’s, whose resolution was (O)100 km. Our model domain is the Cape Darnley region in East Antarctica, where DSW is formed and flows down the continental slope -via several canyons- to form Cape Darnley Bottom Water. There, very-high resolution bathymetric data were recently acquired by Japanese icebreaker Shirase around the Wild Canyon system. The high-resolution bathymetric data and model offer a unique opportunity to further investigate the dynamics affecting the upslope flow as well as interaction with bottom water formation by analyzing data within individual canyons of the Wild Canyon system. Combining our model results with mooring observations of temperature and current velocity, we focus on the processes affecting the upslope flow near the top and bottom of the continental slope. Our results suggest that near the top of the slope, both mesoscale eddies and the in-canyon mechanism proposed by Morrison et al. (2020) affect the upslope flow with a ~2-day dominant period. At depths > 2000 m, the variability is dominated by a ~5-day periodic phenomenon which is likely a topographic wave. We discuss the possibility that interactions between the processes affecting the bottom and top of the slope are responsible for bringing mCDW from far offshore to the near-shore.