[M-IS08] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

[MIS08-P08] No Holocene sediment deposition in Powell Basin due to enhanced Antarctic Bottom Water formation

*Minoru Ikehara¹, Michael E Weber² (1.Center for Advanced Marine Core Research, Kochi University, 2.University of Bonn)

Keywords:Antarctic Bottom Water, Weddell Sea Bottom Water, Holocene, Southern Ocean

Antarctic Bottom Water (AABW) is the primary source of bottom water that occupies the deepest layers of the world ocean, and stores large amounts of chemicals at cold, saline, and dense seawaters. Weddell Sea Bottom Water (WSBW), formed in the southern Weddell Sea, one of the formation areas of the AABW, is the largest bottom water of the four major formation areas around Antarctica. The Powell Basin, in the northern extension of the Weddell Sea, is the basin through which the WSBW passes as it drains into the Scotia Sea, but there is little evidence from paleoceanographic studies. During the R/V Hakuho-maru KH-19-6 cruise, we successfully collected a piston core from the Powell Basin. Variations in magnetic susceptibility (MS) of core KH-19-6-PC06 in the Powell Basin is correlated with those of GC04-G03 and MD07-3134, which were well-dated sediment cores from the Powell Basin and Scotia Sea by previous studies. These MS changes are strongly correlated with non-sea slat Ca2+ concentration (dust input) in ice core and are strongly influenced by atmospheric circulation in the Southern Ocean. Based on the dust chronology, we conclude that no Holocene sediments are present in the Powell Basin, although glacial sediments were recovered at least at two sites. This is supported by radiocarbon dates of acid-solved organic matters in core top sediments. The lack of sediment deposition in Powell Basin after the last deglaciation is likely due to enhanced Holocene WSBW throughflow.