Little change in ice age water mass structure from Cape Basin benthic neodymium and carbon isotopes

Hines, Sophia K.V., Bolge, Louise, Goldstein, Steven L., Charles, Christopher D., Hall, Ian R. ORCID: https://orcid.org/0000-0001-6960-1419 and Hemming, Sidney R. 2021. Little change in ice age water mass structure from Cape Basin benthic neodymium and carbon isotopes. Paleoceanography and Paleoclimatology 36 (11) , e2021PA004281. 10.1029/2021PA004281

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Abstract

A common conception of the deep ocean during ice age episodes is that the upper circulation cell in the Atlantic was shoaled at the Last Glacial Maximum (LGM) compared to today, and that this configuration facilitated enhanced carbon storage in the deep ocean, contributing to glacial CO2 draw-down. Here we test this notion in the far South Atlantic, investigating changes in glacial circulation structure using paired neodymium and benthic carbon isotope measurements from International Ocean Discovery Program (IODP) Site U1479, at 2615 m water depth in the Cape Basin. We infer changes in circulation structure across the last glacial cycle by aligning our site with other existing carbon and neodymium isotope records from the Cape Basin, examining vertical isotope gradients, while determining the relative timing of inferred circulation changes at different depths. We find that Site U1479 had the most negative neodymium isotopic composition across the last glacial cycle among the analyzed sites, indicating that this depth was most strongly influenced by North Atlantic Deep Water (NADW) in both interglacial and glacial intervals. This observation precludes a hypothesized dramatic shoaling of NADW above ∼2000 m. Our evidence, however, indicates greater stratification between mid-depth and abyssal sites throughout the last glacial cycle, conditions that developed in Marine Isotope Stage 5. These conditions still may have contributed to glacial carbon storage in the deep ocean, despite little change in the mid-depth ocean structure.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
ISSN:	2572-4517
Date of First Compliant Deposit:	26 October 2021
Date of Acceptance:	11 October 2021
Last Modified:	10 Nov 2022 09:56
URI:	https://orca.cardiff.ac.uk/id/eprint/145064

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