Cooling and freshening at 8.2 ka on the NW Iceland Shelf recorded in paired δ 18 O and Mg/Ca measurements of the benthic foraminifer Cibicides lobatulus

• Published in: Quaternary Research
• Main Authors: Quillmann, Ursula, Marchitto, Thomas M., Jennings, Anne E., Andrews, John T., Friestad, Birgitte F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2012
• Subjects: Arctic; Greenland; Greenland ice cores; Iceland; North Atlantic Deep Water; North Atlantic
• Online Access: http://dx.doi.org/10.1016/j.yqres.2012.08.003; http://api.elsevier.com/content/article/PII:S0033589412000944?httpAccept=text/xml; http://api.elsevier.com/content/article/PII:S0033589412000944?httpAccept=text/plain; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589400008905

Abstract A shallow marine sediment core from NW Iceland provides evidence for a brief cooling and freshening at ~ 8200 cal yr BP, consistent with the hypothesis that the catastrophic outburst flood of the proglacial lakes Oijbway and Agassiz caused the 8.2 ka event. This is the first high-resolution record reconstructing near-surface temperatures and δ 18 O sw by paired measurements of Mg/Ca and δ 18 O calcite of a benthic foraminifer. We developed a new Mg/Ca temperature calibration for Cibicides lobatulus . Our down-core Mg/Ca derived temperature reconstruction dates the 8.2 ka cooling event between ~ 8300 cal yr BP and ~ 8100 cal yr BP, which is similar to the timing and 160-yr duration recorded in the Greenland ice cores. The near-surface temperature drop of ~ 3 to 5°C during the 8.2 ka event was accompanied by lighter δ 18 O sw values. Synchronously to the changes in the geochemical proxies, the percentages of two Arctic benthic foraminifers increased and the percent calcium carbonate decreased. Our record, combined with several others from the region, suggests that the freshwater outburst spread far from the source into the high-latitude North Atlantic. This freshwater input could have directly caused substantial high-latitude cooling, with reduced North Atlantic Deep Water formation amplifying the climatic impact.