The Weddell Gyre history from marine sedimentary records

• Main Authors: Kuhn, Gerhard, Hillenbrand, Claus-Dieter
• Format: Conference Object
• Language: unknown
• Published: Mario Hoppema & Walter Geibert 2012
• Subjects: Antarc*; Antarctic; Antarctica; Drake Passage; Ice Shelves; Sea ice; Southern Ocean; Weddell Sea
• Online Access: https://epic.awi.de/id/eprint/32484/; https://hdl.handle.net/10013/epic.41095

The Weddell Gyre (WG) history is closely related to the formation of the Antarctic Circumpolar Current (ACC), which may have 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 only very limited information from a couple of deep-sea drill sites about proto Weddell Gyre conditions, but the available data and models indicate that its establishment was associated with oceanic cooling (Mackensen & Ehrmann, 1992; 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 since the early Oligocene. How does ACC flow speed interact with WG dynamics? Is the WG circulation independent from the ACC or is it related to seasonal and/or continuous sea ice coverage? Is its circulation related to brine formation in polynyas and subsequent supercooling of these brines below floating ice shelves, i.e., to the formation of Weddell Sea Bottom Water (WSBW) and Antarctic Bottom Water (AABW)? Was there a brine formation without floating ice shelves during glacials? Is the configuration of deep outflow of WSBW relevant for 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 an increase in the supply of ice-berg rafted debris (IBRD) to the Southern Ocean, the supply of the clay minerals chlorite and illite, which are mainly formed by physical weathering, increased on the expense of smectite, which is produced under humid and warm climatic conditions (Ehrmann & Mackensen, 1992). Decreasing atmospheric pCO2, changes in Southern Ocean deep water ventilation, and primary productivity have been recorded in several marine sediment proxies. After the middle Miocene Climatic ...