ANTARCTIC CLIMATE CHANGE INDICATORS RECORD ICE SHEET INSTABILITY IN WEDDELL SEA SEDIMENTS

The Weddell Sea is the site of Antarctic Bottom Water (AABW) formation, the densest ocean water mass and an important driver of ocean circulation. By any sediment measure, piston cores, ocean drilling cores or surface samples, the geologic and climatic history of the Weddell Sea has received far less attention than most of the circum-Antarctic. Why so little is known about it’s history makes sense from a complexity and logistic perspective. The Weddell Sea receives sediment from many sources, including South Orkney Islands, Antarctic Peninsula, Transantarctic Mountains, Rhone-Filchner Ice Shelf, and East Antarctica. Yet the climatic history of the Weddell Sea remains unexplored. This is particularly surprising because Dronning Maud Land (DML), the Weddell Sea’s southeastern has been modeled as an especially stable area of Antarctica by Deconto and Pollard (2003). The Weddell Sea is also difficult to reach by sea and there is a short ice window for ships.

We are trying to decipher the Weddell Sea’s Miocene and Pliocene history using sediment from three Ocean Drilling Program sites that form a transect from Dronning Maud Land (East Antarctica) to the South Orkney Microcontinent (SOM) (Antarctic Peninsula). Although hampered by poor age control, we are constructing a sequential history of coarse sediment transport and composition on the Antarctic continental margin (Site 693), Weddell Sea Abyssal Plain (Site 694), and the SOM Microcontinent (Site 695/6). Our work shows a Miocene dominated by turbidites with intervals of turbidites and ice-rafted detritus (IRD) in the late Miocene and Pliocene. These results will be compared with those from the Andrill Sites in the Ross Sea and IODP Expedition to the Wilkes Land Margin, where excellent chronostratigraphy is available. All of these investigations show considerably more East and West Antarctic ice sheet instability than documented in most published research investigations prior to 2010.