| Summary: | Maintenance and Update Frequency: notPlanned Statement: Three sources of data are procured to perform the Diatom Transfer Function (DTF). The first set taken is the ranked diatom species data from core tops (i.e. Antarctic Diatom Database). The second data set is taken from the modern environmental variable to be related. In this study, the present-day reference for sea-surface temperature, the World Ocean Atlas (WOA, 1994) is used. The third dataset comprises the down-core data which contains the ranked data derived from the same diatom species used in the modern database. The main differences between the DTF 166/34/4 and the DTF 109/24/6 are related to the number of factors involved, the inclusion of the dissolution data and the differences in the species identified. In terms of the models output, the DTF 166/34/4 will provide estimates that can be in error by up to ±4oC through the 0 to 12oC range, most of the abnormalities being referable to the inclusion of the warm-water dissolution samples. The DTF 109/24/6 under-estimates in the 4-8oC range and over-estimates in the 0-4oC range, but in each case the residuals are confined to within ±2oC. The model does not take into account dissolution of the diatoms in the samples, but does increase the number of factors to account for the wider distributional patterns. It is probable that the 'real' SST signal lies between the model estimates. The model diagnostics and lower number of non-analogue events from DTF 109/24/6 over that of results produced by DTF 166/34/4 suggest that SST estimates are closer to those provided by the former model. Cooler estimates provided by the DTF have been shown in the reference 109 database to be possibly over-estimated by up to 1.5oC. The answer may simply lie in the fact that the 109 database is too small and restrictive. Parameters for Antarctic Diatom Database: Diatom species, Leanne K. Armand code, core code, core coordinates (degrees, decimal minutes), total number of specimens recorded in each core, % of old species, % of data ...
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