 |
| Titel |
Millennial-scale influence of southern intermediate component water into the North-east Atlantic during the last 40 kyr |
| VerfasserIn |
Christophe Colin, Norbert Frank, Quentin Dubois-Dauphin, Lucile Bonneau, Jean-Carlos Montero-Serrano, Dominique Blamart, David Van Rooij |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092839
|
| Publikation (Nr.) |
 EGU/EGU2014-7203.pdf |
|
|
|
|
|
| Zusammenfassung |
| Throughout the last glacial-interglacial cycle major reorganisations of water masses in the North Atlantic occurred. Mediterranean Outflow Water (MOW) being an important source of saline and warm intermediate water has been modulated regarding its strength and mean depth. The Gulf of Cadiz near the Strait of Gibraltar is located in a region influenced by the 3 major temperate Atlantic mid-depth water masses: MOW, mid-depth subtropical gyre water and Antarctic Intermediate Water (AAIW). Those water masses are today characterized by contrasted Nd isotopic composition (εNd): NACW εNd = -11.9; MOW εNd= -9.4; AAIW εNd= -6 to -7. Here, we have investigated εNd of seawater and cold-water corals (L. pertusa, M. oculata and D. dianthus) located to the Alboran Sea and to the SE of the Gulf of Cadiz (between 550 and 850 m) to constrain the present day seawater εNd and to reconstruct the past water mass mixing, i.e. MOW variability during the last 37 kyr. Seawater εNd values of ~-11.6 indicate that the NACW is today the predominant water mass at the position of the coral bearing sediment core MD08-3231. Cold-water coral fragments have been 230Th/U dated yielding ages of 4.5 to 37 kyr. The coral εNd values range from -8 to -10.4 during the last 37 kyr, most likely indicating changes of the dominant water mass provenance. Glacial cold-water corals (from 19 to 37 kyr) are characterized by more radiogenic εNd values (> -9.5) compared to the ones from the Holocene demonstrating a decreasing contribution of MOW and/or AAIW in the SE Gulf of Cadiz during climate warming. Strikingly, Heinrich events H2 and H3 reveal even more radiogenic εNd values (~-8). In addition, deep-sea corals from the Alboran Sea indicate that εNd of the MOW do not change significantly trough time. These results imply a higher contribution of AAIW at 500 m depth in the eastern temperate Atlantic. This first coral based paleo-seawater εNd record for the Gulf of Cadiz thus points to significant advance of southern component water at shallow depth into the NE Atlantic potentially even into the Mediterranean sea that needs to be further investigated. |
|
|
|
|
|
|