ABSTRACT: We have found that species within high-rank taxa, with the exception of Actinommidae and Eucyrtidiidae, covary across environments in the Nordic Seas. One possible explanation is converging ecological requirements within taxonomic groups. Over the last decade, relative abundance data of species-level taxa have been successfully used to reconstruct environmental conditions in the Nordic Seas via the application of a suite of statistical techniques, including Imbrie-Kipp Factor Analysis. In this study, we test whether the same statistical approach, but based on high-rank groupings of the same dataset, yields similar results to using species-level data.We applied this technique both tomodern samples and to Upper Pleistocene/Holocene cores. The results of this study are encouraging, as the statistical analyses for species and high-rank taxa give very similar results. The success of the method is due both to the ecological covariation within some high-rank taxa, and the dominance of one species in other taxa. Future paleotemperature studies in the Nordic Seas may reliably apply a high-rank approach, and thus substantially reduce noise due to misidentification and rare taxa.