South Atlantic intermediate water advances into the North-east Atlantic with reduced Atlantic meridional overturning circulation during the last glacial period

作者：Dubois Dauphin Quentin; Bonneau Lucile; Colin Christophe; Montero Serrano Jean Carlos; Montagna Paolo; Blamart Dominique; Hebbeln Dierk; Van Rooij David; Pons Branchu Edwige; Hemsing Freya; Wefing Anne Marie; Frank Norbert

来源：Geochemistry Geophysics Geosystems, 2016, 17(6): 2336-2353.

DOI：10.1002/2016GC006281

• neodymium isotopes
• cold-water corals
• Mediterranean outflow water
• East Antarctic intermediate water
• Mediterranean sea water
• Gulf of Cadiz

The Nd isotopic composition (epsilon Nd) of seawater and cold-water coral (CWC) samples from the Gulf of Cadiz 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 Cadiz over the past 40 ka. epsilon Nd of glacial and Holocene CWC from the Alboran Sea and the northern Gulf of Cadiz 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; epsilon Nd approximate to -9.4) and Mediterranean Sea Water (MSW; epsilon Nd approximate to -9.9). In contrast, glacial epsilon Nd values for CWC collected at thermocline depth (550-827 m) in the southern Gulf of Cadiz display a higher average value (-8.90.4) compared to the present-day value (-11.70.3). 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 epsilon Nd values (approximate to -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 epsilon Nd values remained stable during the last glacial period, it is suggested that these radiogenic epsilon Nd values most likely reflect an enhanced northward propagation of glacial EAAIW into the eastern Atlantic Basin.

• 出版日期2016-6