Coherent Response of Antarctic Intermediate Water and Atlantic Meridional Overturning Circulation During the Last Deglaciation: Reconciling Contrasting Neodymium Isotope Reconstructions From the Tropical Atlantic

Type Article
Date 2017-10
Language English
Author(s) Gu Sifan1, Liu Zhengyu1, 2, Zhang JiaxuORCID1, 3, 4, Rempfer Johannes5, 6, Joos FortunatORCID3, 4, Oppo Delia W.7
Affiliation(s) 1 : Univ Wisconsin Madison, Dept Atmospher & Ocean Sci, Madison, WI USA.
2 : Ohio State Univ, Dept Geog, Atmospher Sci Program, Columbus, OH 43210 USA.
3 : Los Alamos Natl Lab, Computat Phys & Methods, Los Alamos, NM USA.
4 : Los Alamos Natl Lab, Ctr Nonlinear Studies, Los Alamos, NM USA.
5 : Univ Bern, Inst Phys, Climate & Environm Phys, Bern, Switzerland.
6 : Univ Bern, Oeschger Ctr Climate Change Res, Bern, Switzerland.
7 : Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA 02543 USA.
Source Paleoceanography (0883-8305) (Amer Geophysical Union), 2017-10 , Vol. 32 , N. 10 , P. 1036-1053
DOI 10.1002/2017PA003092
WOS© Times Cited 15
Keyword(s) AAIW, AMOC, deglacial, neodymium isotope, paleocirculation tracer
Abstract

Antarctic Intermediate Water (AAIW) plays important roles in the global climate system and the global ocean nutrient and carbon cycles. However, it is unclear how AAIW responds to global climate changes. In particular, neodymium isotopic composition (epsilon(Nd)) reconstructions from different locations from the tropical Atlantic have led to a debate on the relationship between northward penetration of AAIW into the tropical Atlantic and the Atlantic meridional overturning circulation (AMOC) variability during the last deglaciation. We resolve this controversy by studying the transient oceanic evolution during the last deglaciation using a neodymium-enabled ocean model. Our results suggest a coherent response of AAIW and AMOC: when AMOC weakens, the northward penetration and transport of AAIW decrease while its depth and thickness increase. Our study highlights that as part of the return flow of the North Atlantic Deep Water, the northward penetration of AAIW in the Atlantic is determined predominately by AMOC intensity. Moreover, the inconsistency among different tropical Atlantic epsilon(Nd) reconstructions is reconciled by considering their corresponding core locations and depths, which were influenced by different water masses in the past. The very radiogenic water from the bottom of the Gulf of Mexico and the Caribbean Sea, which was previously overlooked in the interpretations of deglacial epsilon(Nd) variability, can be transported to shallow layers during active AMOC and modulates epsilon(Nd) in the tropical Atlantic. Changes in the AAIW core depth must also be considered. Thus, interpretation of epsilon(Nd) reconstructions from the tropical Atlantic is more complicated than suggested in previous studies.

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Gu Sifan, Liu Zhengyu, Zhang Jiaxu, Rempfer Johannes, Joos Fortunat, Oppo Delia W. (2017). Coherent Response of Antarctic Intermediate Water and Atlantic Meridional Overturning Circulation During the Last Deglaciation: Reconciling Contrasting Neodymium Isotope Reconstructions From the Tropical Atlantic. Paleoceanography, 32(10), 1036-1053. Publisher's official version : https://doi.org/10.1002/2017PA003092 , Open Access version : https://archimer.ifremer.fr/doc/00495/60709/