title: Millennial-scale variability in Antarctic ice-sheet discharge during the last deglaciation.
abstract: Our understanding of the deglacial evolution of the Antarctic Ice Sheet (AIS) following the Last Glacial Maximum (26,000-19,000 years ago) is based largely on a few well-dated but temporally and geographically restricted terrestrial and shallow-marine sequences. This sparseness limits our understanding of the dominant feedbacks between the AIS, Southern Hemisphere climate and global sea level. Marine records of iceberg-rafted debris (IBRD) provide a nearly continuous signal of ice-sheet dynamics and variability. IBRD records from the North Atlantic Ocean have been widely used to reconstruct variability in Northern Hemisphere ice sheets, but comparable records from the Southern Ocean of the AIS are lacking because of the low resolution and large dating uncertainties in existing sediment cores. Here we present two well-dated, high-resolution IBRD records that capture a spatially integrated signal of AIS variability during the last deglaciation. We document eight events of increased iceberg flux from various parts of the AIS between 20,000 and 9,000 years ago, in marked contrast to previous scenarios which identified the main AIS retreat as occurring after meltwater pulse 1A and continuing into the late Holocene epoch. The highest IBRD flux occurred 14,600 years ago, providing the first direct evidence for an Antarctic contribution to meltwater pulse 1A. Climate model simulations with AIS freshwater forcing identify a positive feedback between poleward transport of Circumpolar Deep Water, subsurface warming and AIS melt, suggesting that small perturbations to the ice sheet can be substantially enhanced, providing a possible mechanism for rapid sea-level rise.
authors.affiliation: Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, 50935 Cologne, Germany.
authors.forename: M E
authors.initials: ME
authors.lastname: Weber
authors.affiliation: College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: P U
authors.initials: PU
authors.lastname: Clark
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Alten Hafen 26, 27568 Bremerhaven, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Kuhn
authors.affiliation: International Pacific Research Center, School of Ocean and Earth Sciences and Technology, University of Hawaii at Manoa, 2525 Correa Road, Honolulu, Hawaii 96822, USA.
authors.forename: A
authors.initials: A
authors.lastname: Timmermann
authors.affiliation: Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, 50935 Cologne, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Sprenk
authors.affiliation: Arctic Centre, University of Lapland, PO Box 122, 96101 Rovaniemi, Finland.
authors.forename: R
authors.initials: R
authors.lastname: Gladstone
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Alten Hafen 26, 27568 Bremerhaven, Germany.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Alten Hafen 26, 27568 Bremerhaven, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Lohmann
authors.affiliation: 1] Climate Change Research Centre, Level 4, Mathews Building, University of New South Wales, Sydney, New South Wales 2052, Australia [2] ARC Centre of Excellence for Climate System Science, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Menviel
authors.affiliation: International Pacific Research Center, School of Ocean and Earth Sciences and Technology, University of Hawaii at Manoa, 2525 Correa Road, Honolulu, Hawaii 96822, USA.
authors.forename: M O
authors.initials: MO
authors.lastname: Chikamoto
authors.affiliation: International Pacific Research Center, School of Ocean and Earth Sciences and Technology, University of Hawaii at Manoa, 2525 Correa Road, Honolulu, Hawaii 96822, USA.
authors.forename: T
authors.initials: T
authors.lastname: Friedrich
authors.affiliation: Hans-Ertel Centre for Weather Research/Climate Monitoring Branch, Meteorological Institute, University of Bonn, Auf dem Hügel 20, 53121 Bonn, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ohlwein