Productivity reconstructions in the North Pacific based on diatom transfer functions

Abstract:

Diatoms are the most common primary producers in the oceans, and are one of the best preserved microfossil in marine sediments from the North Pacific (NPacific) . As rapidly blooming organisms, they are sensitive to oceanic and atmospheric conditions. Although general insight may come from qualitative diatom studies relationships, the development of quantitative methods allows quantitative reconstructions. For paleoceanographic applications it is important to understand what is really controlling different species presence and/or absence, and which statistical approaches provide unbiased quantitative information on past ecological/environmental conditions avoiding intercorrelations between oceanic properties, when developing mathematical/statistical environmental prediction functions. Here, statistically significant transfer functions based on diatom assemblages will be presented for productivity in the North Pacific area. The ability of quantitativally reconstruct how much primary productivity (gC/m2/y) there is at the surface, represents the delimitation of an end member of the Carbon cycle and provides information for Carbon models.These calculations results from modern calibrations comprising more than 200 core top samples and in situ and satellite derived data for the North Pacific. Several statistical methods were applied and Unimodal techniques are compared with Modern Analog Techniques and Artificial Neural Networks. From the resulting significant calibrations, derived equations will be applied in order to reconstruct past oceanic properties, including primary productivity. These past reconstructions will be presented and compared for the Last Glacial Maximum and if possible for other time slices. In addition, since the NE Pacific comprises an upwelling area, a comparison of modern calibrations and downcore results will also be presented. This comparison will allow for a better understanding regarding reconstructions of primary productivity reconstructions in upwelling versus non-upwelling regimes for the NE and NW Pacific.