Antarctic intermediate water circulation in the South Atlantic over the past 25,000 years

Type Article
Date 2016-10
Language English
Author(s) Howe Jacob N. W.1, Piotrowski Alexander M.1, Oppo Delia W.2, Huang Kuo-Fang2, 3, Mulitza StefanORCID4, Chiessi Cristiano M.5, Blusztajn Jurek2
Affiliation(s) 1 : Univ Cambridge, Dept Earth Sci, Cambridge, England.
2 : Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA USA.
3 : Acad Sinica, Inst Earth Sci, Taipei, Taiwan.
4 : Univ Bremen, MARUM Ctr Marine Environm Sci, Bremen, Germany.
5 : Univ Sao Paulo, Sch Arts Sci & Humanities, Sao Paulo, Brazil.
Source Paleoceanography (0883-8305) (Amer Geophysical Union), 2016-10 , Vol. 31 , N. 10 , P. 1302-1314
DOI 10.1002/2016PA002975
WOS© Times Cited 27
Keyword(s) Antarctic Intermediate Water, neodymium isotopes, degalciation, South Atlantic
Abstract

Antarctic Intermediate Water is an essential limb of the Atlantic meridional overturning circulation that redistributes heat and nutrients within the Atlantic Ocean. Existing reconstructions have yielded conflicting results on the history of Antarctic Intermediate Water penetration into the Atlantic across the most recent glacial termination. In this study we present leachate, foraminiferal, and detrital neodymium isotope data from three intermediate-depth cores collected from the southern Brazil margin in the South Atlantic covering the past 25kyr. These results reveal that strong chemical leaching following decarbonation does not extract past seawater neodymium composition in this location. The new foraminiferal records reveal no changes in seawater Nd isotopes during abrupt Northern Hemisphere cold events at these sites. We therefore conclude that there is no evidence for greater incursion of Antarctic Intermediate Water into the South Atlantic during either the Younger Dryas or Heinrich Stadial 1. We do, however, observe more radiogenic Nd isotope values in the intermediate-depth South Atlantic during the mid-Holocene. This radiogenic excursion coincides with evidence for a southward shift in the Southern Hemisphere westerlies that may have resulted in a greater entrainment of radiogenic Pacific-sourced water during intermediate water production in the Atlantic sector of the Southern Ocean. Our intermediate-depth records show similar values to a deglacial foraminiferal Nd isotope record from the deep South Atlantic during the Younger Dryas but are clearly distinct during the Last Glacial Maximum and Heinrich Stadial 1, demonstrating that the South Atlantic remained chemically stratified during Heinrich Stadial 1.

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How to cite 

Howe Jacob N. W., Piotrowski Alexander M., Oppo Delia W., Huang Kuo-Fang, Mulitza Stefan, Chiessi Cristiano M., Blusztajn Jurek (2016). Antarctic intermediate water circulation in the South Atlantic over the past 25,000 years. Paleoceanography, 31(10), 1302-1314. Publisher's official version : https://doi.org/10.1002/2016PA002975 , Open Access version : https://archimer.ifremer.fr/doc/00421/53216/