Abstract: Water masses and exchanges in the region around the northern tip of the Antarctic Peninsula were analyzed based on CTD (Conductivity-Temperature-Depth profiler) and XCTD (eXpendable CTD) data observed during the 28th Chinese National Antarctic Research Expedition in December 2011 to January 2012. The Weddell Deep Water (WDW) with significant warm core, the Weddell Sea Deep Water(WSDW) and Weddell Sea Bottom Water(WSBW, with potential temperature less than -0.7℃) with neutral density greater than 28.27 kg·m^-3 were found in the southern deep area of observing region, especially in Powell Basin. The WDW on the surrounding slope showed relative weaker core characteristics because of mixing with peripheral waters. In some locations with complex bottom topography, such as the Philip Ridge and Hesperides Trough, stronger mixing and a thermohaline intrusion occurred at the WDW layer. WDW with a deeper saline core at 1 500 db, overlaid by warm water with vertically uniform temperature and salinity, was observed to the northeast of Elephant Island, indicating that the WDW might have come from different sources and undergone different modifications. No Circumpolar Deep Water was found in the Bransfield Strait; however, some mesoscale processes, such as eddies on the shelf near King George Island, could influence exchange between the Drake Passage and Bransfied Strait.

Key words: water mass, circulation, Antarctic Peninsula, South Shetland Islands, South Orkney Plateau