The diatom response to Postglacial environments in the White Sea, the European Arctic

The White Sea is a small semi-enclosed Arctic sea influenced by Atlantic waters. It was completely covered by the Scandinavian Ice Sheet in the Late Pleistocene and plays a key role in the reconstruction of the degradation of the Scandinavian Ice Sheet and Atlantic Water advection into the Arctic Ocean. We examined the inflow of Atlantic water into the White Sea Basin as the leading feature of postglacial sedimentation processes. Palaeoreconstructions were conducted through detailed studies of diatom assemblages in two sediment cores from the central area (PS-6042) and outer part (PS-6050) of Dvina Bay. Stratigraphic division of the core sediments was performed on the basis of palynostratigraphy and accelerator mass spectrometry 14C dates. The composition of diatom assemblages in postglacial sediments from Dvina Bay indicate a change in the environment from a freshwater sea bay to fully marine conditions over the past 12 cal kyr. Based on the obtained results, we established that the Atlantic water started to flow into the central Dvina Bay in the first half of the Preboreal (11.7–11.3 cal ka BP), and the greatest increase in water surface temperatures in central Dvina Bay occurred during the period from the end of the Atlantic to the first half of the Subboreal. We confirmed these conclusions through comparison with previously obtained results of aquatic palynomorphs, pollen and spores, grain size analysis, and measurements of total organic carbon and biogenic silica contents, as well as through correlation with published palaeoreconstructions of the White Sea and the Arctic Ocean.