Distinct roles of the Southern Ocean and North Atlantic in the deglacial atmospheric radiocarbon decline

Hain, Mathis P., Sigman, Daniel M. and Haug, Gerald H. (2014) Distinct roles of the Southern Ocean and North Atlantic in the deglacial atmospheric radiocarbon decline. Earth and Planetary Science Letters, 394, 198-208. (doi:10.1016/j.epsl.2014.03.020).

Abstract

In the context of the atmospheric CO214C/C (?Catm14) changes since the last ice age, two episodes of sharp ?Catm14 decline have been related to either the venting of deeply sequestered low-14C CO2 through the Southern Ocean surface or the abrupt onset of North Atlantic Deep Water (NADW) formation. In model simulations using an improved reconstruction of 14C production, Atlantic circulation change and Southern Ocean CO2 release both contribute to the overall deglacial ?Catm14 decline, but only the onset of NADW can reproduce the sharp ?Catm14 declines. To fully simulate ?Catm14 data requires an additional process that immediately precedes the onsets of NADW. We hypothesize that these “early” ?Catm14 declines record the thickening of the ocean's thermocline in response to reconstructed transient shutdown of NADW and/or changes in the southern hemisphere westerly winds. Such thermocline thickening may have played a role in triggering the NADW onsets.

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