Open AccessSouth Atlantic intermediate water advances into the North‐east Atlantic with reduced Atlantic meridional overturning circulation during the last glacial period
Author(s) -
DuboisDauphin Quentin,
Bonneau Lucile,
Colin Christophe,
MonteroSerrano JeanCarlos,
Montagna Paolo,
Blamart Dominique,
Hebbeln Dierk,
Van Rooij David,
PonsBranchu Edwige,
Hemsing Freya,
Wefing AnneMarie,
Frank Norbert
Publication year - 2016
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2016gc006281
Subject(s) - oceanography , glacial period , radiogenic nuclide , geology , water mass , thermohaline circulation , north atlantic deep water , holocene , seawater , mediterranean climate , mediterranean sea , geochemistry , geomorphology , geography , mantle (geology) , archaeology
Abstract The Nd isotopic composition (εNd) of seawater and cold‐water coral (CWC) samples from the Gulf of Cádiz and the Alboran Sea, at a depth of 280–827 m were investigated in order to constrain middepth water mass dynamics within the Gulf of Cádiz over the past 40 ka. εNd of glacial and Holocene CWC from the Alboran Sea and the northern Gulf of Cádiz reveals relatively constant values (−8.6 to −9.0 and −9.5 to −10.4, respectively). Such values are similar to those of the surrounding present‐day middepth waters from the Mediterranean Outflow Water (MOW; εNd ∼ −9.4) and Mediterranean Sea Water (MSW; εNd ∼ −9.9). In contrast, glacial εNd values for CWC collected at thermocline depth (550–827 m) in the southern Gulf of Cádiz display a higher average value (−8.9 ± 0.4) compared to the present‐day value (−11.7 ± 0.3). This implies a higher relative contribution of water masses of Mediterranean (MSW) or South Atlantic origin (East Antarctic Intermediate Water, EAAIW). Our study has produced the first evidence of significant radiogenic εNd values (∼ −8) at 19, 23–24, and 27 ka, which are coeval with increasing iceberg discharges and a weakening of Atlantic Meridional Overturning Circulation (AMOC). Since MOW εNd values remained stable during the last glacial period, it is suggested that these radiogenic εNd values most likely reflect an enhanced northward propagation of glacial EAAIW into the eastern Atlantic Basin.