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| Titel |
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 |
| VerfasserIn |
L. Durantou, A. Rochon, D. Ledu, G. Massé, S. Schmidt, M. Babin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 12 ; Nr. 9, no. 12 (2012-12-21), S.5391-5406 |
| Datensatznummer |
250007477
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| Publikation (Nr.) |
 copernicus.org/bg-9-5391-2012.pdf |
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| Zusammenfassung |
| 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 dated 36 cm-long core collected from the
Mackenzie Trough 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 fluxes were used
as local paleo-river discharge indicators over the last ~ 150 yr.
Dinocyst assemblages are dominated by autotrophic taxa (68 to 96%). Cyst
of Pentapharsodinium dalei is the dominant species 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 series of relatively warm, lower sea ice and
saline episodes in surface waters, alternately with relatively cool and low
salinity episodes. Variations of dinocyst fluxes and reconstructed
sea-surface conditions may be 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 fluxes, warmer and saltier surface
waters, which we associate with upwelling events of warm and relatively
saline water from Pacific origin. Freshwater palynomorph fluxes 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. |
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