Intermediate and deep water paleoceanography of the northern North Atlantic over the past 21,000 years

Thornalley, David. J. R. and Elderfield, Harry and McCave, I. Nick (2010) Intermediate and deep water paleoceanography of the northern North Atlantic over the past 21,000 years. Paleoceanography, 25. PA1211. DOI 10.1029/2009PA001833.

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Abstract

Benthic foraminiferal stable isotope records from four high-resolution sediment cores, forming a depth transect between 1237 m and 2303 m on the South Iceland Rise, have been used to reconstruct intermediate and deep water paleoceanographic changes in the northern North Atlantic during the last 21 ka (spanning Termination I and the Holocene). Typically, a sampling resolution of ~100 years is attained. Deglacial core chronologies are accurately tied to North Greenland Ice Core Project (NGRIP) ice core records through the correlation of tephra layers and changes in the percent abundance of Neogloboquadrina pachyderma (sinistral) with transitions in NGRIP. The evolution from the glacial mode of circulation to the present regime is punctuated by two periods with low benthic δ13C and δ18O values, which do not lie on glacial or Holocene water mass mixing lines. These periods correlate with the late Younger Dryas/Early Holocene (11.5–12.2 ka) and Heinrich Stadial 1 (14.7–16.8 ka) during which time freshwater input and sea-ice formation led to brine rejection both locally and as an overflow exported from the Nordic seas into the northern North Atlantic, as earlier reported by Meland et al. (2008). The export of brine with low δ13C values from the Nordic seas complicates traditional interpretations of low δ13C values during the deglaciation as incursions of southern sourced water, although the spatial extent of this brine is uncertain. The records also reveal that the onset of the Younger Dryas was accompanied by an abrupt and transient (~200–300 year duration) decrease in the ventilation of the northern North Atlantic. During the Holocene, Iceland-Scotland Overflow Water only reached its modern flow strength and/or depth over the South Iceland Rise by 7–8 ka, in parallel with surface ocean reorganizations and a cessation in deglacial meltwater input to the North Atlantic.

Item Type: Article
Uncontrolled Keywords: 2010AREP; IA60;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Paleoceanography
Volume: 25
Page Range: PA1211
Identification Number: 10.1029/2009PA001833.
Depositing User: Sarah Humbert
Date Deposited: 25 Mar 2010 17:11
Last Modified: 23 Jul 2013 09:57
URI: http://eprints.esc.cam.ac.uk/id/eprint/1359

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