Salinity history of the northern Atlantic during the last deglaciation

Salinity history of the northern Atlantic during the last deglaciation The claim has been made (see Broecker et al., 1988) that production of North Atlantic Deep Water terminated during Younger Dryas time and that the onset of this termination occurred about 11,000 years ago when the flow of meltwater from a large segment of the southern margin of the Laurentide ice sheet was diverted from the Mississippi to the St. Lawrence drainage. Fairbanks (1989) points out a serious weakness in this argument. Based on a sea level curve derived from radiocarbon dates on coral obtained from borings made off the Barbados coast, he suggests that a lull in the melting of the ice caps during Younger Dryas time may have more than compensated for the impact of the diversion. The purpose of this paper is to reassess the situation regarding the origin of the Younger Dryas in light of this new evidence. Currently the salinity of surface waters in the northern Atlantic is influenced by three fluxes. Water vapor transport from the Atlantic drainage basin to the Pacific‐Indian basin tends to raise the salinity of the entire Atlantic. The excess over evaporation of precipitation and runoff poleward of 40°N tends to reduce the salinity of waters in this region relative to the Atlantic average. The conveyor circulation of the Atlantic trades more salty waters of the Atlantic with less salty waters outside the Atlantic tending to drive down the Atlantic's salinity. The conveyor circulation also flushes the northern Atlantic, pushing its salinity toward the mean for the Atlantic. During the period of deglaciation meltwater emanating from the Laurentide and Scandinavian ice sheets was also important. This flux tended to lower not only the salinity of the entire Atlantic but also the salinity of surface waters in the northern Atlantic relative to the Atlantic's mean. As deepwater formation in the northern Atlantic depends critically on the salinity of surface waters, the interactions among these fluxes can change the strength of the conveyor. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Paleoceanography Wiley

Salinity history of the northern Atlantic during the last deglaciation

Paleoceanography, Volume 5 (4) – Aug 1, 1990

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Publisher
Wiley
Copyright
Copyright © 1990 by the American Geophysical Union.
ISSN
0883-8305
eISSN
1944-9186
D.O.I.
10.1029/PA005i004p00459
Publisher site
See Article on Publisher Site

Abstract

The claim has been made (see Broecker et al., 1988) that production of North Atlantic Deep Water terminated during Younger Dryas time and that the onset of this termination occurred about 11,000 years ago when the flow of meltwater from a large segment of the southern margin of the Laurentide ice sheet was diverted from the Mississippi to the St. Lawrence drainage. Fairbanks (1989) points out a serious weakness in this argument. Based on a sea level curve derived from radiocarbon dates on coral obtained from borings made off the Barbados coast, he suggests that a lull in the melting of the ice caps during Younger Dryas time may have more than compensated for the impact of the diversion. The purpose of this paper is to reassess the situation regarding the origin of the Younger Dryas in light of this new evidence. Currently the salinity of surface waters in the northern Atlantic is influenced by three fluxes. Water vapor transport from the Atlantic drainage basin to the Pacific‐Indian basin tends to raise the salinity of the entire Atlantic. The excess over evaporation of precipitation and runoff poleward of 40°N tends to reduce the salinity of waters in this region relative to the Atlantic average. The conveyor circulation of the Atlantic trades more salty waters of the Atlantic with less salty waters outside the Atlantic tending to drive down the Atlantic's salinity. The conveyor circulation also flushes the northern Atlantic, pushing its salinity toward the mean for the Atlantic. During the period of deglaciation meltwater emanating from the Laurentide and Scandinavian ice sheets was also important. This flux tended to lower not only the salinity of the entire Atlantic but also the salinity of surface waters in the northern Atlantic relative to the Atlantic's mean. As deepwater formation in the northern Atlantic depends critically on the salinity of surface waters, the interactions among these fluxes can change the strength of the conveyor.

Journal

PaleoceanographyWiley

Published: Aug 1, 1990

References

  • Cadmium: Chemical tracer of deepwater paleoceanography
    Boyle, Boyle
  • The chronology of the last deglaciation: Implications to the cause of the Younger Dryas event
    Broecker, Broecker; Andree, Andree; Wolfli, Wolfli; Oeschger, Oeschger; Bonani, Bonani; Kennett, Kennett; Peteet, Peteet
  • Planktonic foraminiferal and oxygen isotopic stratigraphy and paleoclimatology of Norwegian Sea deep‐sea cores
    Kellogg, Kellogg; Duplessy, Duplessy; Shackleton, Shackleton

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