Variability in mid-depth ventilation of the western Atlantic Ocean during the last deglaciation

Author(s):Show less -

Voigt, I. ^[1] ; Cruz, A. P. S. ^[2] ; Mulitza, S. ^[1] ; Chiessi, C. M. ^[3] ; Mackensen, A. ^[4] ; Lippold, J. ^[5] ; Antz, B. ^[6] ; Zabel, M. ^[1] ; Zhang, Y. ^[1] ; Barbosa, C. F. ^[2] ; Tisserand, A. A. ^[7]

Affiliation

^[1] Univ Bremen, MARUM Ctr Marine Environm Sci, Bremen - Germany

^[2] Univ Fed Fluminense, Programa Posgrad Geoquim, Outeiro Sao Joao Batista S-No, Niteroi, RJ - Brazil

^[3] Univ Sao Paulo, Sch Arts Sci & Humanities, Sao Paulo - Brazil

^[4] Alfred Wegener Inst, Bremerhaven - Germany

^[5] Heidelberg Univ, Inst Earth Sci, Heidelberg - Germany

^[6] Heidelberg Univ, Inst Environm Phys, Heidelberg - Germany

^[7] Bjerknes Ctr Climate Res, Uni Res Climate, Bergen - Norway

• Document type: Journal article
• Source: PALEOCEANOGRAPHY; v. 32, n. 9, p. 948-965, SEP 2017.
• Web of Science Citations: 10

Abstract

Negative stable carbon isotopic excursions have been observed throughout most of the mid-depth (similar to 1000-3000m) Atlantic Ocean during Heinrich Stadial 1 (HS1) and the Younger Dryas (YD). Although there is an agreement that these mid-depth excursions were in some way associated with a slowdown of the Atlantic Meridional Overturning Circulation (AMOC), there is still no consensus on the precise mechanism(s). Here we present benthic stable carbon and oxygen isotopic (C-13 and O-18) records from five cores from the western equatorial Atlantic (WEA). Together with published benthic isotopic records from nearby cores, we produced a WEA depth transect (similar to 800-2500m). We compare HS1 and YD data from this transect with data from previously published North and South Atlantic cores and demonstrate that the largest negative C-13 excursions occurred in the WEA during these times. Moreover, our benthic O-18 records require the presence of two water masses flowing from the Southern Ocean, bisected by a Northern Component Water (NCW). Given that O-18 is a conservative water mass tracer, we suggest that C-13 was decoupled from water mass composition and does not correspond to simple alternations between northern and southern sourced waters. Instead, C-13 behaved non-conservatively during HS1 and the YD. Consistently with our new Pa-231/Th-230 record from the WEA transect, that allowed the reconstruction of AMOC strength, we hypothesize that the negative C-13 excursions reflect an increase in the residence time of NCW in response to a weakened AMOC, allowing for a marked accumulation of C-13-depleted respired carbon at the mid-depth WEA. (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 type: Research Program on Global Climate Change - Young Investigators