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

Author(s)

Howe, Jacob N. W. ^{[1, 2]} ; Huang, Kuo-Fang ^{[2, 3]} ; Oppo, Delia W. ^[2] ; Chiessi, Cristiano M. ^[4] ; Mulitza, Stefan ^[5] ; Blusztajn, Jurek ^[2] ; Piotrowski, Alexander M. ^[1]

Affiliation

^[1] Univ Cambridge, Dept Earth Sci, Cambridge CB2 3EQ - England

^[2] Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA 02543 - USA

^[3] Acad Sinica, Inst Earth Sci, 128, Sec 2, Acad Rd, Taipei 11529 - Taiwan

^[4] Univ Sao Paulo, Sch Arts Sci & Humanities, Av Arlindo Bettio 1000, BR-03828000 Sao Paulo, SP - Brazil

^[5] Univ Bremen, MARUM Ctr Marine Environm Sci, Leobener Str, D-28359 Bremen - Germany

• Document type: Journal article
• Source: Earth and Planetary Science Letters; v. 490, p. 51-61, MAY 15 2018.
• Web of Science Citations: 3

Abstract

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. (C) 2018 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 12/17517-3 - Response of the Western Atlantic Ocean to changes in the Atlantic meridional overturning circulation: from millennial to seasonal variability
• Grantee: Cristiano Mazur Chiessi
• Support Opportunities: Research Program on Global Climate Change - Young Investigators