Gulf Stream – subtropical gyre properties across two Dansgaard–Oeschger cycles

Hoogakker, B. A. A. and Downy, F. and Andersson, M. A. and Chapman, M. R. and Elderfield, H. and McCave, I. N. and Lenton, T.M. and Grützner, J. (2013) Gulf Stream – subtropical gyre properties across two Dansgaard–Oeschger cycles. Quaternary Science Reviews, 81. pp. 105-113. ISSN 0277-3791 DOI 10.1016/j.quascirev.2013.09.020

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Abstract

Salinity increase in the subtropical gyre system may have pre-conditioned the North Atlantic Ocean for a rapid return to stronger overturning circulation and high-latitude warming following meltwater events during the Last Glacial period. Here we investigate the Gulf Stream – subtropical gyre system properties over Dansgaard–Oeschger (DO) cycles 14 to 12, including Heinrich ice-rafting event 5. During the Holocene and Last Glacial Maximum a positive gradient in surface dwelling planktonic foraminifera δ18O (Globigerinoides ruber) can be observed between the Gulf Stream and subtropical gyre, due to decreasing temperature, increasing salinity, and a change from summer to year-round occurrence of G. ruber. We assess whether this gradient was a common feature during stadial-interstadial climate oscillations of Marine Isotope Stage 3, by comparing existing G. ruber δ18O from ODP Site 1060 (subtropical gyre location) and new data from ODP Site 1056 (Gulf Stream location) between 54 and 46 ka. Our results suggest that this gradient was largely absent during the period studied. During the major warm DO interstadials 14 and 12 we infer a more zonal and wider Gulf Stream, influencing both ODP Sites 1056 and 1060. A Gulf Stream presence during these major interstadials is also suggested by the large vertical δ18O gradient between shallow dwelling planktonic foraminifera species, especially G. ruber, and the deep dwelling species Globorotalia inflata at site 1056, which we associate with strong summer stratification and Gulf Stream presence. A major reduction in this vertical δ18O gradient from 51 ka until the end of Heinrich event 5 at 48.5 ka suggests site 1056 was situated within the subtropical gyre in this mainly cold period, from which we infer a migration of the Gulf Stream to a position nearer to the continental shelf, indicative of a narrower Gulf Stream with possibly reduced transport.

Item Type: Article
Uncontrolled Keywords: 2013AREP; IA66;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
06 - Part-III Projects
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
06 - Part-III Projects
Journal or Publication Title: Quaternary Science Reviews
Volume: 81
Page Range: pp. 105-113
Identification Number: 10.1016/j.quascirev.2013.09.020
Depositing User: Sarah Humbert
Date Deposited: 09 Nov 2013 15:26
Last Modified: 17 Feb 2017 12:18
URI: http://eprints.esc.cam.ac.uk/id/eprint/2907

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