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A 1600-year history of the Labrador Current off Nova Scotia

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Abstract

A multicore from Emerald Basin, on the continental margin off Nova Scotia, has a modern 14C age at the top, and other 14C dates indicate a linear sedimentation rate of ∼30 cm/ka to 1600 calendar years BP. This rate is great enough to record century-to-millennial scale changes in the surface and deep (∼250 m) waters in the basin that are influenced by the Labrador Current. We applied five proxies for seawater temperature changes to the sediments of Emerald Basin, including the percent abundance and the oxygen isotope ratio (δ18O) of the polar planktonic foraminifer N. pachyderma (s.), the unsaturation ratio of alkenones (Uk′ 37) produced by prymnesiophyte phytoplankton, and the δ18O and Mg/Ca of benthic foraminifera. All five proxies indicate the ocean warmed suddenly sometime in the past 150 years or so. The exact timing of this event is uncertain because 14C dating is inaccurate in recent centuries, but this abrupt warming probably correlates with widespread evidence for warming in the Arctic in the nineteenth century. Because the Canadian Archipelago is one of the two main sources for the Labrador Current, warming and melting of ice caps in that region may have affected Labrador Current properties. Before this recent warming, sea surface temperature was continually lower by 1–2 °C, and bottom water was colder by about 6 °C in Emerald Basin. These results suggest that there was no Medieval Warm Period in the coastal waters off Nova Scotia. Because there is also no evidence of medieval warming in the Canadian archipelago, it seems likely that coastal waters from Baffin Bay to at least as far south as Nova Scotia were continually cold for ∼1500 of the past 1600 years.

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Acknowledgements.

We acknowledge NSF grants OCE9709686 to LDK for OCE voyage 326 and associated laboratory work, and OCE9819675 to YR. We acknowledge the MIT Wade Fund and a Doherty Professorship for providing funding for this work to JPS. We also thank Eben Franks for his coring skills at sea, and for his operation of the mass spectrometer, and Ellen Roosen for her micropaleontology skills; Ying Chang for assistance with alkenone analyses; the AMS facility at WHOI, Ken Buesseler for 210Pb dating; and Kate Moran, David Piper, and Iris Hardy for discussions about core locations on the Canadian margin and for providing samples. In particular, Kate Moran recommended the location of MC-29. We thank David Piper and Lawrence Mysak for reviews of the manuscript, and Mysak's suggestion to add Fig. 6.

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Authors and Affiliations

  1. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

    L. D. Keigwin

  2. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room E34-254, Cambridge, MA 02139, USA

    J. P. Sachs

  3. Institute of Marine and Coastal Sciences, and Department of Geology, Rutgers, The State University, 71 Dudley Road, New Brunswick, NJ 08901-8521, USA

    Y. Rosenthal

Authors
  1. L. D. Keigwin
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  2. J. P. Sachs
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  3. Y. Rosenthal
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Correspondence to L. D. Keigwin.

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Keigwin, L.D., Sachs, J.P. & Rosenthal, Y. A 1600-year history of the Labrador Current off Nova Scotia. Climate Dynamics 21, 53–62 (2003). https://doi.org/10.1007/s00382-003-0316-6

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  • DOI: https://doi.org/10.1007/s00382-003-0316-6

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