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| Titel |
New sedimentary 231Pa/230Th and benthic stable isotopes records suggest AMOC changes prior to MIS3 Heinrich Events. |
| VerfasserIn |
Pierre Burckel, Claire Waelbroeck, Jeanne Gherardi, Matthieu Roy Barman, François Thil, Sylvain Pichat, Helge Arz, Joerg Lippold |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250086878
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| Publikation (Nr.) |
 EGU/EGU2014-820.pdf |
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| Zusammenfassung |
| The region of the North Eastern Brazilian margin is of major interest in the study of the
variability of the oceanic circulation because of the large part of the Atlantic Meridonal
Overturning Circulation (AMOC) passing through it.
In order to better understand the changes in the AMOC during Heinrich events, we chose
to study two sediment cores at different water depths so that we may observe not only
changes in the intensity of circulation of the water masses influencing the cores, but as well
changes in the vertical extent of these water masses.
Heinrich Events are particularly well defined on the Brazilian margin. Indeed,
they are associated with southward shifts of the Inter-Tropical Convergence Zone
(ITCZ) that induce increased precipitations over our study site [1]. This causes
higher terrigenous fluxes as revealed by marked Ti/Ca peaks in our marine sediment
cores.
Due to the difference in particle reactivity of 231Pa and 230Th in the water column
sedimentary 231Pa/230Th (Pa/Th) may be used to record changes in AMOC. In the case of the
western equatorial Atlantic region, the sedimentary Pa/Th vertical profile measured on recent
sediment is consistent with a dominant role of the AMOC, rather than particle scavenging,
thereby demonstrating that Pa/Th can indeed be used to monitor changes in water mass
overturning rates in that region [2]. Benthic foraminifer carbon isotopic ratio on the
other hand has been widely used to assess changes in nutrient content of the water
masses.
We present new measurements of sedimentary Pa/Th and foraminifer stable isotopes over
Heinrich 2 and 4. These data combined with a robust 14C-based age model, enable us to
reconstruct the timing and extent of the AMOC changes related to these two Heinrich Events.
We show that the AMOC went through depth dependent changes during Heinrich Events.
Moreover, the good constraints on Heinrich Events timing brought by the Ti/Ca peaks and the
14C age model allow us to assess the timing of the circulation changes with respect to
Heinrich Events.
[1] Jaeschke (2007) Paleoceanography 22, PA4206. [2] Lippold (2011) Geophys. Res.
Lett 38, L20603. |
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