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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/cp-2019-100
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2019-100
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 29 Aug 2019

Submitted as: research article | 29 Aug 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).

Surface and subsurface Labrador Shelf water mass conditions during the last 6,000 years

Annalena A. Lochte1,2, Ralph Schneider1, Janne Repschläger3, Markus Kienast4, Thomas Blanz1, Dieter Garbe-Schönberg1, and Nils Andersen5 Annalena A. Lochte et al.
  • 1Institute of Geoscience, University of Kiel, Ludewig-Meyn Str. 10, 24118 Kiel, Germany
  • 2GEOMAR Helmholtz-Centre for Ocean Research Kiel, Wischofstraße 1-3, 24148 Kiel, Germany
  • 3Max-Planck Institute for Chemistry, Hahn Meitner Weg 1, 55128 Mainz, Germany
  • 4Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax, Canada
  • 5Leibniz Laboratory for Radiometric Dating and Stable Isotope Research, University of Kiel, Max-Eyth-Str. 11–13, 24118 Kiel, Germany

Abstract. The Labrador Sea is important for the modern global thermohaline circulation system through the formation of intermediate Labrador Sea Water (LSW) that has been hypothesized to stabilize the modern mode of North Atlantic deep-water circulation. The rate of LSW formation is controlled by the amount of winter heat loss to the atmosphere, the expanse of freshwater in the convection region and the inflow of saline waters from the Atlantic. The Labrador Sea, today, receives freshwater through the East and West Greenland Currents (EGC, WGC) and the Labrador Current (LC). Several studies have suggested the WGC to be the main supplier of freshwater to the Labrador Sea, but the role of the southward flowing LC in Labrador Sea convection is still debated. At the same time, many paleoceanographic reconstructions from the Labrador Shelf focussed on late Deglacial to early Holocene meltwater run-off from the Laurentide Ice Sheet (LIS), whereas little information exists about LC variability since the final melting of the LIS about 7,000 years ago. In order to enable better assessment of the role of the LC in deep-water formation and its importance for Holocene climate variability in Atlantic Canada, this study presents high-resolution middle to late Holocene records of sea surface and bottom water temperatures, freshening and sea ice cover on the Labrador Shelf during the last 6,000 years. Our records reveal that the LC underwent three major oceanographic phases from the Mid- to Late Holocene. From 6.2 to 5.6 ka BP, the LC experienced a cold episode that was followed by warmer conditions between 5.6 and 2.1 ka BP, possibly associated with the late Holocene Thermal Maximum. Although surface waters on the Labrador Shelf cooled gradually after 3 ka BP in response to the Neoglaciation, Labrador Shelf subsurface/bottom waters show a shift to warmer temperatures after 2.1 ka BP. Although such an inverse stratification by cooling of surface and warming of subsurface waters on the Labrador Shelf would suggest a diminished convection during the last two millennia compared to the mid-Holocene, it remains difficult to assess whether hydrographic conditions in the LC have had a significant impact on Labrador Sea deep-water formation.

Annalena A. Lochte et al.
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Annalena A. Lochte et al.
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MSM45-31-1 A. A. Lochte, R. R. Schneider, J. Repschläger, M. Kienast, T. Blanz, C.-D. Garbe-Schönberg, and N. Andersen https://doi.pangaea.de/10.1594/PANGAEA.904693

Annalena A. Lochte et al.
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Short summary
The Labrador Sea is important for the modern global thermohaline circulation system through the formation of Labrador Sea Water. However, the role of the southward flowing Labrador Current in Labrador Sea convection is still debated. In order to better assess its role in deep-water formation and climate variability, we present high-resolution mid- to late Holocene records of sea surface and bottom water temperatures, freshening and sea ice cover on the Labrador Shelf during the last 6,000 years.
The Labrador Sea is important for the modern global thermohaline circulation system through the...
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