Last modified: 2011-08-21
Abstract
The Modern Analogue Technique (MAT) for dinoflagellate cysts is a transfer function method used in palaeoceanography for the quantification of past sea-surface conditions. The main presupposition of the MAT is that similar dinoflagellate cyst assemblages derive from similar environments, and that the environmental variables of interest are ecologically important.
The validation exercise of the SH350 database (350 Southern Hemisphere surface samples from 10 different studies) results in a striking correlation between the observed and estimated SSS and SST values, which gives the impression that the MAT is capable to perform SSS and SST reconstruction with high accuracy. However, the background data shows a geographical clustering of the analogues in the immediate vicinity of the sites from which their SSS and SST are attempted to be estimated. 75% of the analogues were selected in the same cluster, while 63% were found within a range of 2.5° longitude/latitude. In the open ocean, the environmental variables remain rather unchanged within a 2.5° range. So any variable which varies less within clusters than between clusters will appear possible to reconstruct, irrespective of its ecological relevance. Furthermore, the MAT does not consider interaction between the ecological parameters, which considerably influences the assemblages.