HR: 0800h
AN: PP41C-0674    [Abstracts]
TI: Quantitative reconstructions of oceanic paleoproductivity using dinocysts: the approach and application to the Last Glacial Maximum in the Northern North Atlantic
AU: * Radi, T
EM: radi.taoufik@courrier.uqam.ca
AF: GEOTOP-UQAM & McGill, Case postale 8888, Succursale Centre Ville, Montreal, Qc H3C 3P8, Canada
AU: de Vernal, A
EM: devernal.anne@uqam.ca
AF: GEOTOP-UQAM & McGill, Case postale 8888, Succursale Centre Ville, Montreal, Qc H3C 3P8, Canada
AB: In order to develop a proxy of past productivity, we explored the relationship between the assemblages of organic- walled dinoflagellate cysts (or dinocysts) in marine sediment and productivity estimated from remote sensing. Dinoflagellates represent an important part of the primary production in the ocean. Their populations, which include both phototrophic and heterotrophic taxa, depend upon the trophic structure of upper water masses. Here, we used dinocyst data from 1171 surface sediment samples collected in the North Atlantic, Arctic and North Pacific oceans. For each sample site, we compiled two sets of primary productivity data derived from satellite observations: (1) The dataset from the Coastal Zone Color Scanner (CZCS) program applied to observations from 1978 to 1989 and (2) the data set from the MODerate resolution Imaging Spectroradiometer (MODIS) program using observations from 2002 to 2005. Canonical correspondence analyses (CCA) were performed with 57 dinocyst taxa and 8 sea-surface parameters (winter and summer salinity, winter and summer temperature, sea-ice cover, summer, winter and annual primary productivity). Results show that primary productivity is significantly correlated with the first or second component of dinocyst assemblages, depending upon the ocean basin considered, with the strongest relation being observed in the North Pacific. We tested the modern analogue technique (MAT) for quantitative reconstruction of productivity using dinocysts. The error of prediction is ±15-25 % depending upon the productivity dataset, with the best performance obtained for winter productivity using the MODIS data. It is noteworthy that the error of prediction for all estimated productivity parameters is lower than the differences between productivity data derived from the MODIS and CZCS datasets. Therefore, we conclude that dinocysts can be used to reconstruct productivity with reliability as good as possible given the uncertainty inherent to primary productivity estimates from satellite observations. MAT has been applied to northern North Atlantic time series, with special attention paid to the last glacial maximum (LGM). The reconstructions using MODIS and CZCS datasets indicates generally low productivity during the glacial stage, especially during the Younger Dryas and Heinrich events, with annual productivity of less than 100 gC m-2. Past productivity estimates for the LGM are consistent with simulation of the North Atlantic Ocean productivity in the hypothesis of reduced Atlantic Meridional Overturning as proposed by Schmittner (Nature, 2005) based on coupled climate-ecosystem model simulation.
DE: 0434 Data sets
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 3252 Spatial analysis (0500)
DE: 4944 Micropaleontology (0459, 3030)
DE: 4952 Palynology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting