Sea Surface Temperature and Sea Ice Variability at the Onset of the Holocene – Diatom Inferred Reconstructions from Baffin Bay from 15-10.9 cal. ka BP

Abstract:

Baffin Bay is an important location for studying past paleoceanographic and –climatic changes because it is an area where relatively warm high-salinity West Greenland Current waters meet cold Polar waters from the Arctic Ocean. Baffin Bay is a sensitive area due to close link between ocean circulation and ice sheet dynamics. In this study, we present high-resolution reconstructions of August sea surface temperatures (aSST) and sea ice cover based on fossil marine diatoms for the time interval 15-10.9 cal. ka BP. A 600 cm-long marine sediment core GeoTü SL-170, recovered from 1 078 m water depth from central Baffin Bay was studied for diatom assemblages on 5 cm intervals. The age-depth model was created by using 8 radiocarbon dates, with an average chronological resolution of 11.3 yr cm^-1. The raw diatom data was converted into aSSTs by using the weighted averaging partial least squares (WA-PLS) transfer function method and a calibration dataset consisting of 184 surface samples from the North Atlantic and Baffin Bay with 52 diatom species. The sea ice reconstruction was based both on a qualitative method based on the statistically defined occurrence of diatom assemblages (Fragilariopsis spp.) according to their relation to modern surface hydrography, and a quantitative method for May sea ice cover based on the Maximum Likelihood transfer function method. The results show cooling of aSSTs at the onset of Younger Dryas (YD) around 12.6 ka BP. The YD stage ended with gradual warming around 11.7 ka BP when relative abundances of diatom species Thalassiosira Antarctica var. borealis spore and Actinocyclus curvatulus decreased. The final stage of the YD is characterized by a decline of sea ice related species (Fragilariopsis spp.) and a distinctive peak of increased proportion of relatively warmer water species Thalassiosira gravida around 11.4 cal. ka BP.