Strong bottom currents and cyclogenesis in Drake Passage

Abstract

Observations from 38 bottom-moored Current and. Pressure Recording Inverted Echo Sounders (CPIES) deployed in Drake Passage during the 2007-2008 International Polar Year provide unprecedented coverage of near-bottom currents and pressures spanning the entire Antarctic Circumpolar Current. Year-long-mean currents exceed 10 cm s-1 north of the Polar Front, and mean directions are not, in general, aligned with the surface fronts. Topographic steering is most evident at the continental margins. Deep eddy kinetic energy (EKE) is maximum at about 200 cm2 s-2 between the Subantarctic and Polar Fronts, coinciding with the location but about one quarter of the value of a maximum in surface EKE. Multiple high-speed current events, with peak speeds of 60-70 cm s-1 and lasting 30 to 70 days, are coherent across sites separated by 45 km. The observed spinup of eddies coinciding with meanders in the surface fronts is consistent with deep cyclogenesis. Copyright 2009 by the American Geophysical Union.