[M-IS05] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

[MIS05-P17] Ocean circulation in the shelf-slope region of East Antarctica as suggested by satellite radar altimetry

*Kohei Mizobata¹, Mao Mori¹ (1.Tokyo University of Marine Science and Technology)

Keywords:Dynamic Ocean Topography, Ocean Circulation, Circumpolar Deep Water, Southern Ocean

The mass loss of ice shelf/sheet due to intrusion of warm Circumpolar Deep Water (CDW) has been pointed out. CDW is basically observed in the deep basin area, so that the transport mechanisms of CDW from deep basin to shelf is needed to be elucidated for understanding the future fate of ice shelf/sheet of Antarctica. However, because of the presence of sea ice, it is difficult to describe the spatio-temporal variability of ocean circulation using only hydrographic observations. The Dynamic Ocean Topography (DOT) derived from the satellite altimeters is another method to reveal the ocean circulation even in the sea ice area. Our previous DOT data showed four clockwise eddies, which contributes to poleward CDW transport, off the Sabrina coast. Here, we introduce newly developed DOT using the retrievals of satellite radar altimeters, the CryoSat-2/SIRAL, Sentinel-3A/SRAL, Sentinel-3B/SRAL, Jason-3/Posidon-3B, and Saral/AltiKa. Our products revealed the existence of the clockwise circulation at the continental slope area. In particular, stationary clockwise circulation was observed offshore of ice sheet/shelf such as Shirase Glacier, Amery Ice Shelf, and Totten Ice Shelf, where basal melting due to CDW has been suggested in recent years. Moreover, the increased number of radar altimeter retrievals made it possible to visualize the ocean circulation in the shelf-slope region that were unknown in the previous products. A clockwise circulation was also observed in the continental shelf region, and it was frequently coupled with the aforementioned circulation. In other words, this coupled circulation between the slope and shelf regions suggests that CDW in the ocean basin is efficiently transported to the continental shelf of East Antarctica, where the ACC is relatively far from the slope than in West Antarctica. On the other hand, a counterclockwise circulation was observed in the shallow region adjacent Cape Poinsett near Totten Glacier, where sea ice is present all year round. It is implied that this circulation may be preventing the sea ice flush out.