Multiproxy evidence of the Neoglacial expansion of Atlantic Water to eastern Svalbard: Does ancient environmental DNA complement sedimentary and microfossil records?

• Main Authors: Pawłowska, Joanna, Łącka, Magdalena, Kucharska, Małgorzata, Pawlowski, Jan, Zajączkowski, Marek
• Format: Text
• Language: English
• Published: 2019
• Subjects: Svalbard; Sea ice; Storfjorden
• Online Access: https://doi.org/10.5194/cp-2019-21; https://www.clim-past-discuss.net/cp-2019-21/

The main goal of this study was to reconstruct the paleoceanographic development of Storfjorden during the Neoglacial (~ 4 cal ka BP). A multiproxy approach was applied to provide evidence for interactions between the inflow of Atlantic Water (AW) and sea-ice coverage, which are the major drivers of environmental changes in Storfjorden. The sedimentary and microfossil records indicate that a major reorganization of oceanographic conditions in Storfjorden occurred at ~ 2.7 cal ka BP. A general cooling and the less pronounced presence of AW in Storfjorden during the early phase of the Neoglacial are prerequisite conditions for the formation of an extensive sea-ice cover. The period after ~ 2.7 cal ka BP was characterized by alternating short-term cooling and warming intervals. Warming was associated with pulsed inflows of AW and sea-ice melting that stimulated phytoplankton blooms and organic matter supply to the bottom. The cold phases were characterized by heavy and densely packed sea ice resulting in a decrease in productivity. The ancient environmental DNA (aDNA) records of foraminifera and diatoms reveal the timing of the major pulses of AW (~ 2.3 and ~ 1.7 cal ka BP) and the variation in sea-ice cover. The AW inflow was marked by an increase in the percentage of DNA sequences of monothalamous foraminifera associated with the presence of fresh phytodetritus, while cold and less productive intervals were marked by an increased proportion of monothalamous taxa known only from environmental sequencing. The diatom aDNA record indicates that primary production was continuous during the Neoglacial regardless of sea-ice conditions. However, the colder periods were characterized by the presence of diatom taxa associated with sea ice, whereas the present-day diatom assemblage is dominated by open-water taxa.