|
|
|
|
|
| Waelbroeck, Claire; Pichat, Sylvain; Bohm, Evelyn; Lougheed, Bryan C.; Faranda, Davide; Vrac, Mathieu; Missiaen, Lise; Vazquez Riveiros, Natalia; Burckel, Pierre; Lippold, Joerg; Arz, Helge W.; Dokken, Trond; Thil, Francois; Dapoigny, Arnaud. |
| Thanks to its optimal location on the northern Brazilian margin, core MD09-3257 records both ocean circulation and atmospheric changes. The latter occur locally in the form of increased rainfall on the adjacent continent during the cold intervals recorded in Greenland ice and northern North Atlantic sediment cores (i.e., Greenland stadials). These rainfall events are recorded in MD09-3257 as peaks in ln(Ti / Ca). New sedimentary Pa / Th data indicate that mid-depth western equatorial water mass transport decreased during all of the Greenland stadials of the last 40 kyr. Using cross-wavelet transforms and spectrogram analysis, we assess the relative phase between the MD09-3257 sedimentary Pa / Th and ln(Ti/Ca) signals. We show that decreased water mass... |
| Tipo: Text |
|
| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00460/57126/59040.pdf |
| |
|
|
| Gottschalk, Julia; Skinner, Luke C.; Lippold, Joerg; Vogel, Hendrik; Frank, Norbert; Jaccard, Samuel L.; Waelbroeck, Claire. |
| Millennial-scale climate changes during the last glacial period and deglaciation were accompanied by rapid changes in atmospheric CO2 that remain unexplained. While the role of the Southern Ocean as a 'control valve' on ocean–atmosphere CO2 exchange has been emphasized, the exact nature of this role, in particular the relative contributions of physical (for example, ocean dynamics and air–sea gas exchange) versus biological processes (for example, export productivity), remains poorly constrained. Here we combine reconstructions of bottom-water [O2], export production and 14C ventilation ages in the sub-Antarctic Atlantic, and show that atmospheric CO2 pulses during the last glacial- and deglacial periods were consistently accompanied by decreases in the... |
| Tipo: Text |
|
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00334/44544/44256.pdf |
| |
|
|
| Gutjahr, Marcus; Lippold, Joerg. |
| The Atlantic Meridional Overturning Circulation (AMOC) plays an important role in the Northern Hemisphere climate system. Significant interest went into the question of how excessive freshwater input through melting of continental ice can affect its overturning vigor and, hence, heat supply, to higher northern latitudes. Such forcing can be tested by investigating its behavior during extreme iceberg discharge events into the open North Atlantic during the last glacial period, the so-called Heinrich events (HE). Here we present neodymium (Nd) isotope compositions of past seawater, a sensitive chemical water mass tag, extracted from sediments of Ocean Drilling Program Site 1063 in the western North Atlantic (Bermuda Rise), covering the period surrounding HE... |
| Tipo: Text |
|
| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00227/33837/32443.pdf |
| |
|
|
| Burckel, Pierre; Waelbroeck, Claire; Gherardi, Jeanne Marie; Pichat, Sylvain; Arz, Helge; Lippold, Joerg; Dokken, Trond; Thil, Francois. |
| During the last glacial period, Greenland's climate shifted between cold (stadial) and warm (interstadial) phases that were accompanied by ocean circulation changes characterized by reduced Atlantic Meridional Overturning Circulation (AMOC) during stadials. Here we present new data from the western tropical Atlantic demonstrating that AMOC slowdowns preceded some of the large South American rainfall events that took place during stadials. Based on 231Pa/230Th and Ti/Ca measurements in the same sediment core, we determine that the AMOC started to slowdown 1420 ± 250 and 690 ± 180 (1σ) years before the onset of two large precipitation events associated with Heinrich stadials. Our results bring unprecedented evidence that AMOC changes could be at the origin... |
| Tipo: Text |
Palavras-chave: Heinrich stadials; Dansgaard-Oeschger stadials; AMOC; ITCZ; Pa; Th. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00296/40711/39709.pdf |
| |
|
|
|
