Potential of the Scotia Sea region for determining the onset and development of the Antarctic circumpolar current

The strength of interaction between tectonics, ocean circulation and climate is a major concern of palaeoclimate research. To evaluate the strength, we must assess the time of onset and development of the Antarctic Circumpolar Current (ACC) and its likely effects on climate, particularly Antarctic glaciation. Developments in numerical climate modelling, marine geology, tectonics and physical oceanography have cast doubt on widely held assumptions of a causal relationship between the ACC and glacial onset, in the Eocene-Oligocene boundary interval. Here we argue that our best chance to determine ACC onset and development is in the Scotia Sea region ("Drake Passage"), south of South America. There lies the greatest tectonic uncertainty; concerning when a complete deep-water circumpolar pathway was created, and (thus) when the ACC developed as we know it today. There also, the ACC is topographically constrained, and key factors (water mass and sediment distributions, sea-floor spreading history) are sufficiently well known. Determination of the time of onset would enable solution of other questions, such as the nature of Southern Ocean circulation and primary productivity in any period (possibly Oligocene and early Miocene) when Antarctica was glaciated but before a complete circumpolar deep-water pathway existed, and the extent to which ocean circulation changes affected palaeoclimate, particularly Antarctic glaciation. We assess the parameters that might be capable of determining ACC onset, and show that suitable sedimentary records are available in the Scotia Sea region.