title: Glacial reduction and millennial-scale variations in Drake Passage throughflow.
abstract: The Drake Passage (DP) is the major geographic constriction for the Antarctic Circumpolar Current (ACC) and exerts a strong control on the exchange of physical, chemical, and biological properties between the Atlantic, Pacific, and Indian Ocean basins. Resolving changes in the flow of circumpolar water masses through this gateway is, therefore, crucial for advancing our understanding of the Southern Ocean's role in global ocean and climate variability. Here, we reconstruct changes in DP throughflow dynamics over the past 65,000 y based on grain size and geochemical properties of sediment records from the southernmost continental margin of South America. Combined with published sediment records from the Scotia Sea, we argue for a considerable total reduction of DP transport and reveal an up to ∼ 40% decrease in flow speed along the northernmost ACC pathway entering the DP during glacial times. Superimposed on this long-term decrease are high-amplitude, millennial-scale variations, which parallel Southern Ocean and Antarctic temperature patterns. The glacial intervals of strong weakening of the ACC entering the DP imply an enhanced export of northern ACC surface and intermediate waters into the South Pacific Gyre and reduced Pacific-Atlantic exchange through the DP ("cold water route"). We conclude that changes in DP throughflow play a critical role for the global meridional overturning circulation and interbasin exchange in the Southern Ocean, most likely regulated by variations in the westerly wind field and changes in Antarctic sea ice extent.
authors.affiliation: Marine Geology Section, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany; Frank.Lamy@awi.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Lamy
authors.affiliation: Department of Marine Geology, Leibniz Institute for Baltic Sea Research, 18119 Rostock-Warnemünde, Germany;
authors.forename: Helge W
authors.initials: HW
authors.lastname: Arz
authors.affiliation: Geologie, Fachbereich Raum- und Umweltwissenschaften, Universität Trier, 54286 Trier, Germany; Instituto de la Patagonia, Universidad de Magallanes, 6200000 Punta Arenas, Chile;
authors.forename: Rolf
authors.initials: R
authors.lastname: Kilian
authors.affiliation: Department of Oceanography and Center for Oceanographic Research in the Eastern South Pacific (COPAS), COPAS Sur-Austral Program, University of Concepción, 4030000 Concepción, Chile;
authors.forename: Carina B
authors.initials: CB
authors.lastname: Lange
authors.affiliation: Marine Geology Section, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany;
authors.forename: Lester
authors.identifier: http://orcid.org/0000-0002-6873-8533
authors.initials: L
authors.lastname: Lembke-Jene
authors.affiliation: Marine Geology Section, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany;
authors.forename: Marc
authors.initials: M
authors.lastname: Wengler
authors.affiliation: Department of Marine Geology, Leibniz Institute for Baltic Sea Research, 18119 Rostock-Warnemünde, Germany;
authors.forename: Jérôme
authors.initials: J
authors.lastname: Kaiser
authors.affiliation: Geologie, Fachbereich Raum- und Umweltwissenschaften, Universität Trier, 54286 Trier, Germany;
authors.forename: Oscar
authors.initials: O
authors.lastname: Baeza-Urrea
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, United Kingdom;
authors.forename: Ian R
authors.initials: IR
authors.lastname: Hall
authors.affiliation: Research and Development Center for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokosuka 237-0061, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Harada
authors.affiliation: Marine Geology Section, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany;
authors.forename: Ralf
authors.initials: R
authors.lastname: Tiedemann
keywords: Antarctic Circumpolar Current; Drake Passage; glacial–interglacial changes; paleoceanography; sedimentology