Climate Dynamics

, Volume 21, Issue 1, pp 53–62 | Cite as

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

Article

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.

Notes

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.

References

  1. Bemis BE, Spero HJ, Bijma J, Lea DW (1998) Reevaluation of the oxygen isotopic composition of planktonic foraminifera: experimental results and revised paleotemperature equations. Paleoceanography 13: 150–160Google Scholar
  2. Boyle EA, Keigwin LD (1985/86) Comparison of Atlantic and Pacific paleochemical records for the last 215,000 years: changes in deep ocean circulation and chemical inventories. Earth Planet Sci Lett 76: 135–150Google Scholar
  3. Dansgaard W, Johnsen SJ, Reeh N, Gundestrup N, Calusen HB, Hammer CU (1975) Climatic changes, Norsemen and modern man. Nature 255: 24–28Google Scholar
  4. deMenocal P, Ortiz J, Guilderson T, Sarnthein M (2000) Coherent high- and low-latitude climate variability during the Holocene warm period. Science 288: 2198–2202CrossRefPubMedGoogle Scholar
  5. Dyke AS, England J, Reimnitz E, Jette H (1997) Changes in driftwood delivery to the Canadian Arctic Archipelago: the hypothesis of postglacial oscillations of the Transpolar Drift. Arctic 50: 1–16Google Scholar
  6. Gatien MG (1976) A study in the slope water region south of Halifax. J Fish Res Board Can 33: 2213–2217Google Scholar
  7. Herbert TD (2001) Review of alkenone calibrations (culture, water column, and sediments). Geochem Geophys Geosyst 2: 2000GC000055Google Scholar
  8. Jennings AE, Weiner NJ (1996) Environmental change in eastern Greenland during the last 1300 years: evidence from foraminifera and lithofacies in Nansen Fjord, 68°N. The Holocene 6: 179–191Google Scholar
  9. Keigwin LD (1996) The little ice age and medieval warm period in the Sargasso Sea. Science 274: 1504–1508PubMedGoogle Scholar
  10. Khatiwala SP, Fairbanks RG, Houghton RW (1999) Freshwater sources to the coastal ocean off northeastern North America: evidence from H2 18O/H2 16O. J Geophys Res 104: 18,241–18,255Google Scholar
  11. King LH, Fader GBJ (1986) Wisconsinan glaciation of the Atlantic continental shelf of southeast Canada. Geological Survey of Canada, pp 1–72Google Scholar
  12. Koerner RM (1977) Devon Island ice cap: core stratigraphy and paleoclimate. Science 196: 15–18Google Scholar
  13. Koerner RM, Fisher DA (1990) A record of Holocene summer climate from a Canadian high-Arctic ice core. Nature 343: 630–631Google Scholar
  14. Kohfeld KE, Fairbanks RG, Smith SL, Walsh ID (1996) Neogloboquadrina pachyderma (sinistral coiling) as paleoceanographic tracers in polar oceans: Evidence from Northeast Water Polynya plankton tows, sediment traps, and surface sediments. Paleoceanography 11: 679–699Google Scholar
  15. Kontopoulos N, Piper DJW (1982) Storm graded sand at 200 m water depth, Scotian Shelf, eastern Canada. Geo-Marine Lett 2: 77–81Google Scholar
  16. Lazier JRN, Wright DG (1993) Annual velocity variations in the Labrador Current. J Phys Oceanogr 23: 659–678CrossRefGoogle Scholar
  17. Lear CH, Rosenthal Y, Slowey N (2002) Benthic foraminiferal Mg/Ca-paleothermometry: a revised core-top calibration. Geochim Cosmochim Acta (in press)Google Scholar
  18. Levac E (2001) High resolution Holocene palynological record from the Scotian Shelf. Mar Micropaleo 43: 179–197CrossRefGoogle Scholar
  19. Loder JW, Petrie B, Gawarkiewicz G (1998) The coastal ocean off northeastern North America: a large-scale view. In: Robinson AR, Brink KH (eds) The sea. John Wiley, 11, pp 105–133Google Scholar
  20. Müller PJ, Kirst G, Ruhland G, von Storch I, Rosell-Mele A (1998) Calibration of the alkenone paleotemperature index Uk′ 37 based on core-tops from the eastern South Atlantic and the global ocean (60°N–60°S). Geochim Cosmochim Acta 62: 1757–1772CrossRefGoogle Scholar
  21. Overpeck J, Hughen K, Hardy D, Bradley R, Case R, Douglas M, Finney B, Gajewski K, Jacoby G, Jennings A, Lamoureux S, Lasca A, MacDonald G, Moore J, Retelle M, Smith S, Wolfe A, Zielinski G (1997) Arctic environmental changes of the last four centuries. Science 278: 1251–1256Google Scholar
  22. Petrie B, Drinkwater K (1993) Temperature and salinity variability on the Scotian Shelf and in the Gulf of Maine 1945–1990. J Geophys Res 98: 20,079–20,089PubMedGoogle Scholar
  23. Piper DJW, Fehr SD (1991) Radiocarbon chronology of late Quaternary sections on the inner and middle Scotian Shelf, south of Nova Scotia. Current Research, Part E; Geological Survey of Canada, pp 321–325Google Scholar
  24. Prahl FL, Muehlhausen L, Zahnle D (1988) Further evaluation of long-chain alkenones as indicators of paleocenaographic conditions. Geochim Cosmochim Acta 52: 2303–2310Google Scholar
  25. Proshutinsky AV, Johnson MA (1997) Two circulation regimes of the wind-driven Arctic Ocean. J Geophys Res 102: 12,493–12,514Google Scholar
  26. Rosenthal Y, Field P, Sherrell R (1999) Precise determination of element/calcium ratios in calcareous samples using sector field inductively coupled plasma mass spectrometry. Analyt Chem 71: 3248–3253CrossRefGoogle Scholar
  27. Sachs JP, Lehman SJ (1999) Subtropical North Atlantic temperatures 60,000 to 30,000 years ago. Science 286: 756–759CrossRefPubMedGoogle Scholar
  28. Scott DB, Mudie PJ, Vilks G, Younger DC (1984) Latest Pleistocene–Holocene paleoceanographic trends on the continental margin of eastern Canada: foraminiferal dinoflagellate and pollen evidence. Mar Micropaleo 9: 181–218Google Scholar
  29. Sikes EL, Volkman JK, Robertson LG, Pichon J-J (1997) Alkenones and alkenes in surface waters and sediments of the Southern Ocean: implications for paleotemperature estimation in polar regions. Geochim Cosmochim Acta 61: 1495–1505CrossRefGoogle Scholar
  30. Tremblay L-B, Mysak LA, Dyke AS (1997) Evidence from driftwood records for century-to-millennial scale variations of the high latitude atmospheric circulation during the Holocene. Geophys Res Lett 24: 2027–2030Google Scholar
  31. Vilks G, Rashid MA (1976) Post-glacial paleo-oceanography of Emerald Basin, Scotian Shelf. Can J Earth Sci 13: 1256–1267Google Scholar

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
  2. 2.Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room E34-254, Cambridge, MA 02139, USA
  3. 3.Institute of Marine and Coastal Sciences, and Department of Geology, Rutgers, The State University, 71 Dudley Road, New Brunswick, NJ 08901-8521, USA

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