Recent Research Results and Future Project in the Antarctic Ocean by Umitaka-Maru Research Group for Physical Oceanography

Abstract

Training research vessel Umitaka-Maru belonging to the Tokyo University of Marine Science and Technology has implemented the research cruises in the Southern Ocean, counting the 19th times in the 2015 cruise. Particularly in recent years, Umitaka-Maru has greatly contributed to various findings in oceanography in the Antarctic Ocean, such as clarification of the bottom water formation and monitoring in Lutzow Holm Bay, cooperating with the Japanese Antarctic Research Expedition. This article reviews such scientific progresses implemented by Umitaka-Maru, and further describes the recent trend of Antarctic Bottom Water from the newly obtained data. Most important findings by Umitaka-Maru are the discovery of the Antarctic bottom water (AABW) formation off the Cape Darnley with a high sea ice production polynya and the subsequent discovery of AABW formation off the Vincennes Bay with a medium sized polynya. The base oceanographic observation for physical and chemical properties has been carried out continuously along 110°E line in Australian Antarctic Basin, providing the monitoring of water mass transformation. Freshening of AABW in Australia–Antarctica Basin has been caught in a series of the observation in recent years, it is suggested that the AABW originating from the Vincennes Bay Polynya gives significant effects on the AABW in the basin. To grasp an effect of freshening of AABW on the global ocean circulation, intense hydrographic observations and deployment of a huge mooring system are now in consideration.