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Reconstructing North Atlantic deglacial surface hydrography and its link to the Atlantic overturning circulation

Thornalley, DJR; Elderfield, H; McCave, IN; (2011) Reconstructing North Atlantic deglacial surface hydrography and its link to the Atlantic overturning circulation. Global and Planetary Change , 79 (3-4) 163 - 175. 10.1016/j.gloplacha.2010.06.003. Green open access

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Abstract

Paired Mg/Ca–δ18O measurements on multiple species of planktic foraminifera are combined with published benthic isotope records from south of Iceland in order to assess the role North Atlantic freshwater input played in determining the evolution of hydrography and climate during the last deglaciation. We demonstrate that Globigerina bulloides and Globorotalia inflata are restricted to intervals when warm Atlantic waters reached the area south of Iceland, and therefore Mg/Ca–δ18O data from these species monitor changes in the temperature and seawater δ18O signature of the northward inflow of Atlantic water to the area. In contrast, Neogloboquadrina pachyderma (sinistral) calcifies within local subpolar/polar waters and new Mg/Ca–δ18O analyses on this species document changes in this water mass. We observe two major surface ocean events during Heinrich Stadial 1 (∼ 17–14.7 ka): an early freshening of the Atlantic Inflow (∼ 17–16 ka), and a later interval (16–14.7 ka) of local surface freshening, sea-ice formation and brine rejection that was associated with a further reduction in deep ocean ventilation. Centennial-scale cold intervals during the Bølling–Allerød (BA, 14.7–12.9 ka) were likely triggered by the rerouting of North American continental run-off during ice-sheet retreat. However, the relative effects of these freshwater events on deep ventilation and climate south of Iceland appear to have been modulated by the background climate deterioration. Two freshwater events occurred during the Younger Dryas cold interval (YD, 12.9–11.7 ka), both accompanied by a reduction in deep ventilation south of Iceland: an early YD freshening of the Atlantic Inflow and local subpolar/polar waters, and a late YD ice-rafted detritus event that was possibly related to brine formation south of Iceland. Based on our reconstructions, the strengthening of the Atlantic Meridional Overturning Circulation at the onset of BA and Holocene may have been promoted by the subsurface warming of subpolar/polar water, brine formation that drew warm saline Atlantic water northwards, and the high background salinity of the Atlantic Inflow.

Type: Article
Title: Reconstructing North Atlantic deglacial surface hydrography and its link to the Atlantic overturning circulation
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.gloplacha.2010.06.003
Publisher version: http://dx.doi.org/10.1016/j.gloplacha.2010.06.003
Language: English
Additional information: © 2010. This manuscript version is published under a Creative Commons Attribution Non-commercial Non-derivative 4.0 International licence (CC BY-NC-ND 4.0). This licence allows you to share, copy, distribute and transmit the work for personal and non-commercial use providing author and publisher attribution is clearly stated. Further details about CC BY licences are available at http://creativecommons.org/licenses/by/4.0.
Keywords: deglaciation; North Atlantic; melt water; climate; temperature; salinity
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography
URI: https://discovery.ucl.ac.uk/id/eprint/1396384
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