HR: 09:15h
AN: PP11A-06    [Abstracts]
TI: Evolution Of Late Holocene Sea-Surface Parameters In The Beaufort Sea Area (Mackenzie Slope, Canadian Arctic): Insights From CASES 2004-804-803 Cores
AU: Rochon, A
EM: andre_rochon@uqar.qc.ca
AF: GEOTOP, CP 8888, succ. Centre-Ville, Montreal, QC H3C 3P8, Canada
AU: Rochon, A
EM: andre_rochon@uqar.qc.ca
AF: ISMER-UQAR, 310, allée des Ursulines, Rimouski, QC G5L 3A1, Canada
AU: * Bringué, M
EM: mbringue@hotmail.com
AF: GEOTOP, CP 8888, succ. Centre-Ville, Montreal, QC H3C 3P8, Canada
AU: * Bringué, M
EM: mbringue@hotmail.com
AF: ISMER-UQAR, 310, allée des Ursulines, Rimouski, QC G5L 3A1, Canada
AB: This study aims at reconstructing late Holocene sea-surface parameters in the Beaufort Sea area (Western Canadian Arctic) on the basis of sedimentary cores collected over the Mackenzie Slope. Piston, trigger and box cores were sampled at station 803 in 2004 aboard the CCGS Amundsen (CASES) at 218 m water depth. Sedimentation at this particular location is influenced by both the Beaufort gyre and the Mackenzie River, whose sedimentary discharge is by far the largest among all other Arctic rivers. The chronology of the piston core is constrained by 4 AMS-¹⁴C dates, as the sedimentation rate in the box core is assessed from ²¹⁰Pb data. We obtain a continuous composite sequence covering the last 4600 years, with a sedimentation rate of ∼140 cm/kyr. Palynological data reveal that dinocyst assemblages are dominated by Operculodinium centrocarpum (mean of 43.3%), with the accompanying taxa Brigantedinium spp. (19.6%), Islandinium minutum (15.6%) and cysts of Pentapharsodinium dalei (13.7%). Four zones have been established on the basis of dinocyst relative abundances, with the following key taxa. Zone I (4600-4000 cal BP): high relative abundances of cysts of P. dalei (mean of 14.9%) and I. minutum var. cezare (up to 8.9%); zone II (4000-2600 cal BP): high abundances of Spiniferites frigidus/elongatus (up to 7.3%); zone III (2600-1600 cal BP): well- represented heterotrophic taxa Brigantedinium spp. (30.8%) and cysts of Polykrikos sp. arctic/quadratus (up to 4.2%); zone IV (1600 cal BP - present): high relative abundances of I. minutum (mean of 19.8%) and cysts of P. dalei (17.3%). Quantitative reconstructions of sea-surface parameters indicate relatively stable conditions from 4600 to 1600 cal BP. Conversely, a trend of increasing summer (August) sea-surface temperature (from ∼5° C to ∼6° C; actual value = 6° C), increasing salinity (from ∼20 to ∼26 psu; modern value = 19 psu) and decreasing sea-ice cover (from ∼9 to 8 month/yr; actual value = 10) is observed over the last 1600 yrs. These data are consistent with similar studies held in adjacent areas, describing the warming of Western Canadian Arctic, in comparison with a cooling Eastern Arctic. Prevailing hydroclimatic cycles in the Beaufort Sea area are also investigated on the basis of freshwater input indicators concentrations, using spectral and wavelet analysis. Potential links with the Arctic Oscillation and the Pacific Decadal Oscillation are discussed.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4944 Micropaleontology (0459, 3030)
DE: 4954 Sea surface temperature
DE: 9315 Arctic region (0718, 4207)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2009 Joint Assembly