The Antarctic Circumpolar Current: its origin, evolution, and influence on climate and biota

Last year, Peter Barker and Ellen Thomas submitted a preliminary ACC drilling proposal with this title to IODP. It was very positively reviewed, and a full proposal will be submitted for IODP's October 2004 deadline. The proposal is for drilling in the Scotia Sea region, ideally early in 2006 (and thus for preparatory site survey in 2005). Presently, however, IODP is in its starting phase with its vessels not yet fully operative, and IODP panel decisions on proposals and ship time scheduling cannot be predicted. The preliminary proposal and a recent paper are accessible on the web site http://ethomas.web.wesleyan.edu/ACC.

Although this initial plan does not fit the timing of IPY, it is fully complementary. Two factors make this so. First, it is unusual for a drilling experiment to solve completely the problem it set out originally to address: on past experience it is more likely to move the uncertainties forward, redefining the problem or showing more precisely where additional effort should be concentrated. Second, if the proposed Scotia Sea region drilling takes place in 2006, the Preliminary Report on drilling will probably be published at the beginning of 2007, in time to inform IPY field activity. A more intimate involvement in the drilling would provide even earlier and more secure information: IODP rules provide a 12-month priority to the shipboard party. More-detailed work on samples recovered by drilling would follow, taking place during and possibly even after IPY.

The proposal involves drilling the sedimentary section for evidence of ACC development, at four or five sites in and around the Scotia Sea. Two sites are located on old ocean floor north and east of the Scotia Sea, and three on the oldest parts of the Scotia Sea itself, so that the full range of ACC onset model ages can be tested (see the web site). Sites are selected on existing seismic lines, but additional, detailed site survey is needed. Those interested in marine survey during IPY may benefit from an earlier involvement in site survey, and are asked to contact Peter (pfbarker@tiscali.co.uk) or Ellen (ethomas@wesleyan.edu) to discuss possibilities if they are interested.