Sea ice, ice‐rafting, and ocean climate across Denmark Strait during rapid deglaciation (∼16–12 cal ka BP) of the Iceland and East Greenland shelves

Abstract

ABSTRACTA suite of cores from the North‐West Iceland and East Greenland shelves sampled fossiliferous or unfossiliferous basal glacial diamictons. Radiocarbon dates above the diamictons are similar on both shelves, but the value of the ocean reservoir correction, ΔR, is unknown. Deglaciation occurred either ∼16 or 14 cal ka BP depending on the choice of ΔR. The ice sheets were behind the present coastline by 12.2 cal ka BP. We examine seven cores that record the glacial/deglacial transition and present new data on the sea‐ice biomarkers IP25 and C25:2 from four of the cores plus data on ice‐rafted debris counts, grain‐size spectra, δ18O on the near‐surface planktonic foraminifera Neogloboquadrina pachyderma (s), foraminifera assemblages, and quartz percentage. IP25 concentrations are markedly higher for the East Greenland sites, while they are frequently below the limit of quantification off Iceland, observations that parallel the wt% quartz in the sediments. The δ18O N. pachyderma (s) data show a strong gradient across Denmark Strait with lighter δ18O values towards the East Greenland shelf indicative of a large freshwater flux. The presence of the chilled Atlantic Water benthic foraminifera, Cassidulina neoteretis indicates that rapid ice sheet retreat was associated with ocean forcing, combined with other factors.