Biogeosciences Discuss., 9, 7257-7289, 2012
www.biogeosciences-discuss.net/9/7257/2012/
doi:10.5194/bgd-9-7257-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
Quantitative reconstruction of sea-surface conditions over the last ~150 yr in the Beaufort Sea based on dinoflagellate cyst assemblages: the role of large-scale atmospheric circulation patterns
L. Durantou1, A. Rochon1, D. Ledu2, and G. Massé2
1Institut des sciences de la mer (ISMER), Université du Québec à Rimouski, 310 allée des Ursulines, Rimouski, G5L 3A1, Canada
2UMR 7159 LOCEAN Institut Pierre-Simon Laplace, 4 Place Jussieu, BP100, 75252 Paris Cedex 05, France

Abstract. Dinoflagellate cyst (dinocyst) assemblages have been widely used over the Arctic Ocean to reconstruct sea-surface parameters on a quantitative basis. Such reconstructions provide insights into the role of anthropogenic vs natural forcings in the actual climatic trend. Here, we present the palynological analysis of a 36 cm-long core collected from the Mackenzie Through in the Canadian Beaufort Sea. Dinocyst assemblages were used to quantitatively reconstruct the evolution of sea surface conditions (temperature, salinity, sea ice) and freshwater palynomorphs influxes were used as local paleo-river discharge indicators over the last ~150 yr. Dinocyst assemblages are dominated by autotrophic taxa (68 to 96 %). Pentapharsodinium dalei is the dominant specie throughout most of the core, except at the top where the assemblages are dominated by Operculodinium centrocarpum. Quantitative reconstructions of sea surface parameters display a serie of relatively warm, lower sea ice and saline episodes in surface waters, alternately with relatively cool and low salinity episodes. The warm episodes are characterized with high dinocyst productivity. Variations of dinocyst influxes and reconstructed sea surface conditions are closely linked to large scale atmospheric circulation patterns such as the Pacific Decadal Oscillation (PDO) and to a lesser degree, the Arctic Oscillation (AO). Positive phases of the PDO correspond to increases of dinocyst influxes, warmer and saltier surface waters, which we associate with upwelling events of warm and relatively saline water from Pacific origin. Freshwater palynomorph influxes increased in three phases from AD 1857 until reaching maximum values in AD 1991, suggesting that the Mackenzie River discharge followed the same trend when its discharge peaked between AD 1989 and AD 1992. The PDO mode seems to dominate the climatic variations at multi-annual to decadal timescales in the Western Canadian Arctic and Beaufort Sea areas.

Citation: Durantou, L., Rochon, A., Ledu, D., and Massé, G.: Quantitative reconstruction of sea-surface conditions over the last ~150 yr in the Beaufort Sea based on dinoflagellate cyst assemblages: the role of large-scale atmospheric circulation patterns, Biogeosciences Discuss., 9, 7257-7289, doi:10.5194/bgd-9-7257-2012, 2012.
 
Search BGD
Discussion Paper
    XML
    Citation
    Final Revised Paper
    Share