The paleoceanography of the Antarctic Circumpolar Current and the Weddell Gyre from sedimentary records, a patchy story

• Main Author: Kuhn, Gerhard
• Format: Conference Object
• Language: unknown
• Published: National Institute of Polar Research NIPR 2012
• Subjects: Antarc*; Antarctic; Antarctica; Drake Passage; Ice Sheet; Ice Shelves; Polar Research; Polar Science; Ross Sea; Sea ice; Southern Ocean; Weddell Sea
• Online Access: https://epic.awi.de/id/eprint/32483/; http://www.nipr.ac.jp/symposium2012/program/Multi03/E26_C_GerhardKuhn.pdf; https://hdl.handle.net/10013/epic.41094

The Antarctic Circumpolar Current (ACC) developed after the opening of the Tasman Gateway and Drake Passage between Antarctica and the adjoining continents in the upper Eocene (Huber et al., 2004; Francis et al., 2008). We have no information about prior proto Weddell Gyre (WG) conditions, such as the similarly proposed circulation in the Ross Sea (Huber et al., 2004), but models indicate a much warmer Weddell Sea compared to post conditions (Cristini et al., 2012). Studies on sediment cores from the Atlantic sector of the Southern Ocean and from the Weddell Sea provide information on the history and glacial/interglacial variability of the ACC and the WG. How does ACC flow speed interact with WG dynamics? Is the WG vitality independent from the ACC or is it rather related to seasonal and/or continuous sea ice coverage of this area? Could it be instead related to the brine formation below floating ice shelves, or to Weddell Sea Bottom Water (WSBW) and Antarctic Bottom Water (AABW) formation? Is the configuration of deep outflow passages of WSBW relevant for the WG dynamics? Very little information has been provided to these questions up to now. The initiation of circumpolar circulation in the upper Eocene changed the oceanography and the sedimentary record drastically. In addition to increasing ice- berg rafted debris (IBRD), the Smectite content of the clay mineral fraction decreased and Chlorite, together with Illite and Kaolinite, were dominating (Ehrmann et al., 1992). Decreasing atmospheric pCO2, changes in Southern Ocean deep water ventilation, and primary productivity have been recorded in several paleoenvironmental sediment proxies. After the middle Miocene Climatic Optimum, a strengthening in the Antarctic ice sheet growth is evident and clear glacial/interglacial cycles have been described from Gunnerus Ridge in the southeastern part of the WG (Hillenbrand and Ehrmann, 2003) during Pliocene time. Around the Gauss/Gilbert magnetic reversal and with the onset of Northern Hemisphere glaciation, the ...