title: Punctuated Shutdown of Atlantic Meridional Overturning Circulation during Greenland Stadial 1.
abstract: The Greenland Stadial 1 (GS-1; ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic Meridional Overturning Circulation (AMOC), resulting in an antiphase temperature response between the hemispheres (the 'bipolar seesaw'). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon ((14)C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring (14)C records with marine (14)C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric (14)C offset was close to zero prior to GS-1, before reaching 'near-modern' values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes.
authors.affiliation: Waikato Radiocarbon Laboratory, University of Waikato, Private Bag 3105, Hamilton, New Zealand.
authors.forename: Alan
authors.initials: A
authors.lastname: Hogg
authors.affiliation: Department of Earth System Science, University of California, Irvine, CA 92697-3100, USA.
authors.forename: John
authors.initials: J
authors.lastname: Southon
authors.affiliation: Climate Change Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Australia.
authors.forename: Chris
authors.initials: C
authors.lastname: Turney
authors.affiliation: Climate Change Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Australia.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Palmer
authors.affiliation: Research Laboratory for Archaeology and the History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford OX1 3QY, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Bronk Ramsey
authors.affiliation: Gondwana Tree-Ring Laboratory, P.O. Box 14, Little River, Canterbury 7546, New Zealand.
authors.forename: Pavla
authors.initials: P
authors.lastname: Fenwick
authors.affiliation: School of Environment, University of Auckland, New Zealand.
authors.forename: Gretel
authors.initials: G
authors.lastname: Boswijk
authors.affiliation: Institute of Environmental Physics, University of Heidelberg, INF 229, D-69120 Heidelberg, Germany.|Institute of Botany, Hohenheim University, D-70593 Stuttgart, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Friedrich
authors.affiliation: GFZ German Research Centre for GeoSciences, Dendrochronology Laboratory, Telegrafenberg, 14473 Potsdam, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Helle
authors.affiliation: Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
authors.forename: Konrad
authors.initials: K
authors.lastname: Hughen
authors.affiliation: Department of Geography, Exeter University, Devon, EX4 4RJ, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Jones
authors.affiliation: Institute of Environmental Physics, University of Heidelberg, INF 229, D-69120 Heidelberg, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Kromer
authors.affiliation: Department of Earth System Science, University of California, Irvine, CA 92697-3100, USA.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Noronha
authors.affiliation: Department of Human Evolutionary Biology, Harvard University, Divinity Avenue, Cambridge, MA 02138 USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Reynard
authors.affiliation: Research Laboratory for Archaeology and the History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford OX1 3QY, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Staff
authors.affiliation: Laboratory of Ion Beam Physics, HPK, H29, Otto-Stern-Weg 5, CH-8093 Zürich, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Wacker