Planktonic foraminifera assemblage data spanning the mid Pleistocene (ca. 400-800 ka) of IODP Site 306-U1314 from the North Atlantic Ocean. The assemblage data were generated to assess changes in the position of the Arctic front on millennial time scales across the study interval. Prior to foraminifera counting, the sediment samples were washed over a 63 micrometer sieve, dried (at 40 degC) and sieved again at 150 micrometer. Counts were made manually using a stereomicroscope (approx 250 magnification) on aliquots of the samples containing at least 234 specimens. Split size is indicated to allow calculation of the concentration and accumulation rate of planktonic foraminifera. The taxonomic concept used to identify the taxa is based on the criteria compiled by mikrotax.org. However, counts of the (sub)species Globigerinoides ruber (albus) may include individuals of G. elongatus, since these subspecies were not differentiated. All specimens present in the samples are reported and the proportion of unidentified specimens is negligible. The chronology of the time series presented here is based on tuning the benthic δ18O of Site U1314 with the LR04 global stack. The proportion of subtropical species as in https://doi.org/10.1016/j.palaeo.2011.09.004 can be calculate as the sum of the species Neogloboquadrina dutertrei, Orbulina universa, Globorotalia truncatulinoides, Globigerinoides ruber, Globorotalia crassaformis, Globorotalia hirsuta and Beella digitata. Similarly, the sum of Neogloboquadrina incompta, Globigerina bulloides and Globoconella inflata presents the proportion of subpolar-transitional species.

This dataset upgraded version of doi:10.1594/PANGAEA.820283 that only reported relative abundances of some of the species. In addition, compared to the previous version, this dataset contains more details on the methodology, sample ID and an updated taxonomy. In this update, the variants N. pachyderma sinistral and N. pachyderma dextral are now listed as separate species (N. pachyderma and N. incompta, respectively) and the taxonomy of G. ruber has been clarified. Lumping: in the publication it was defined % subtropical species =N. dutertrei+O. universa+G. truncatulinoides+G. ruber+G. crassaformis+G. hirsuta+B. digitata; and % subpolar-transitional species= N. incompta+G. bulloides+ G. inflata.