The timing of deglacial circulation changes in the Atlantic

Well-dated benthic foraminifer oxygen isotopic records (delta O-18) from different water depths and locations within the Atlantic Ocean exhibit distinct patterns and significant differences in timing over the last deglaciation. This has two implications: on the one hand, it confirms that benthic delta O-18 cannot be used as a global correlation tool with millennial-scale precision, but on the other hand, the combination of benthic isotopic records with independent dating provides a wealth of information on past circulation changes. Comparing new South Atlantic benthic isotopic data with published benthic isotopic records, we show that (1) circulation changes first affected benthic delta O-18 in the 1000-2200 m range, with marked decreases in benthic delta O-18 taking place at similar to 17.5 cal. kyr B.P. (ka) due to the southward propagation of brine waters generated in the Nordic Seas during Heinrich Stadial 1 (HS1) cold period; (2) the arrival of delta O-18-depleted deglacial meltwater took place later at deeper North Atlantic sites; (3) hydrographic changes recorded in North Atlantic cores below 3000 m during HS1 do not correspond to simple alternations between northern-and southern-sourced water but likely reflect instead the incursion of brine-generated deep water of northern as well as southern origin; and (4) South Atlantic waters at similar to 44 degrees S and similar to 3800 m depth remained isolated from better-ventilated northern-sourced water masses until after the resumption of North Atlantic Deep Water (NADW) formation at the onset of the Bolling-Allerod, which led to the propagation of NADW into the South Atlantic.


Atlantic Ocean, benthic oxygen isotope, last deglaciation, ocean circulation

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Waelbroeck C., Skinner L. C., Labeyrie L., Duplessy J. -C., Michel E., Vazquez Riveiros Natalia, Gherardi J. M., Dewilde F. (2011). The timing of deglacial circulation changes in the Atlantic. Paleoceanography. 26 (PA3213). 1-10.,

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