HOLIVAR2006 Abstracts
Coherent Sea Surface Change at ~6000 BP across the eastern North Atlantic, as revealed by Dinoflagellate Cyst and Coccolith Assemblages.
Sandrine Solignac1, Anne de Vernal1 and Jacques Giraudeau2
1GEOTOP-UQAM-McGill, CP 8888, Succ. Centre-Ville, Montréal, Québec H3C 3P8, Canada
2EPOC, CNRS – Université Bordeaux 1, Avenue des Facultés, 33405 Talence CEDEX, France
Contact: S. Solignac (solignac.sandrine@courrier.uqam.ca)
Coccolith and dinoflagellate cyst (dinocysts) population counts were conducted on three North Atlantic Drift-influenced records spanning the Holocene. Multivariate analyses performed on coccolith and dinocyst assemblages show a high coherency between the two proxies in all three cores throughout the Holocene, with the first axes of variance fluctuating in a parallel way for both microfossil records. The most marked change is observed around 6000 years BP, when distinct shifts in assemblages characterise all the records. However, based on the species driving the main variability in the different records, we cannot easily relate this change to a single temperature signal at all three sites.
Investigations are conducted on other possible mechanisms that might have been more prominent, such as wind stress curl, water column stability, or surface current velocity. Moreover, multivariate analysis on assemblages from two cores from the Labrador Sea, while depicting the same strong coherency between the dinocyst and coccolith records, do not show any change at 6000 BP but rather a major regime shift at 8000 BP. It suggests that the North Atlantic is a complex system with distinct hydrographical behaviours in eastern and western regions.
Sandine is presently doing a PhD at the Universite du Quebec a Montreal under the supervision of Anne de Vernal. Her main research interests are the paleoceanography of the North Atlantic during the Holocene, as well as the use of micropaleontological tracers (especially dinoflagellate cysts and coccoliths) as proxies (both qualitative and quantitative) of past sea surface conditions and past current dynamics.