Similar mid-depth Atlantic water mass provenance during the Last Glacial Maximum and Heinrich Stadial 1

Howe, Jacob N.W. and Huang, Kuo-Fang and Oppo, Delia W. and Chiessi, Cristiano M. and Mulitza, Stefan and Blusztajn, Jurek and Piotrowski, Alexander M. (2018) Similar mid-depth Atlantic water mass provenance during the Last Glacial Maximum and Heinrich Stadial 1. Earth and Planetary Science Letters, 490. pp. 51-61. ISSN 0012-821X DOI

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The delivery of freshwater to the North Atlantic during Heinrich Stadial 1 (HS1) is thought to have fundamentally altered the operation of Atlantic meridional overturning circulation (AMOC). Although benthic foraminiferal carbon isotope records from the mid-depth Atlantic show a pronounced excursion to lower values during HS1, whether these shifts correspond to changes in water mass proportions, advection, or shifts in the carbon cycle remains unclear. Here we present new deglacial records of authigenic neodymium isotopes – a water mass tracer that is independent of the carbon cycle – from two cores in the mid-depth South Atlantic. We find no change in neodymium isotopic composition, and thus water mass proportions, between the Last Glacial Maximum (LGM) and HS1, despite large decreases in carbon isotope values at the onset of HS1 in the same cores. We suggest that the excursions of carbon isotopes to lower values were likely caused by the accumulation of respired organic matter due to slow overturning circulation, rather than to increased southern-sourced water, as typically assumed. The finding that there was little change in water mass provenance in the mid-depth South Atlantic between the LGM and HS1, despite decreased overturning, suggests that the rate of production of mid-depth southern-sourced water mass decreased in concert with decreased production of northern-sourced intermediate water at the onset of HS1. Consequently, we propose that even drastic changes in the strength of AMOC need not cause a significant change in South Atlantic mid-depth water mass proportions.

Item Type: Article
Uncontrolled Keywords: 2018AREP; IA72
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 490
Page Range: pp. 51-61
Identification Number:
Depositing User: Sarah Humbert
Date Deposited: 30 Jul 2018 10:16
Last Modified: 30 Jul 2018 10:16

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