Constraints on the Circulation of the Interior South Atlantic During the Last Glacial Maximum Inferred from a Highly-Resolved Sedimentary Depth Transect

Many models show that the relative intensity of stratification is a primary variable governing the sequestration and release of carbon from the ocean over ice ages. The wide-scale observations necessary to test these model-derived hypotheses are not yet sufficient, but sedimentary depth transects represent a promising approach for making progress. Here we present new glacial and late Holocene stable isotopic and trace metal data from benthic foraminifera collected from a detailed depth transect from the deep SE Atlantic. Following the approach developed in Lund et al. (2011) [1] for δ¹⁸O, we use conservative tracers (e.g. δ¹⁸O and Mg/Ca) to constrain the relative strength of meridional transport as compared to vertical diffusivity at the Last Glacial Maximum (LGM) and during the late Holocene. We compare our new results from the SE Atlantic to a similar analysis of published depth profiles from other regions. These measurements, when combined with radiocarbon data for the same cores, provide insights into the relationship between alterations in deep/mid-depth stratification and changes in the ventilation of carbon in the deep ocean.

[1] Lund, D. C., J. F. Adkins, and R. Ferrari (2011), Abyssal Atlantic circulation during the Last Glacial Maximum: Constraining the ratio between transport and vertical mixing, Paleoceanography, 26, PA1213, doi:10.1029/2010PA001938.