Climate and ocean changes in the western Hudson Strait over the last 6000 years

Abstract

A record of marine and terrestrial palynomorphs from a sediment core collected from the western Hudson Strait provided evidence of past climatic and hydrographic variability over the last 6000 years with a decadal to multidecadal temporal resolution. The sequence is characterized by high and uniform sediment accumulation rates of about 0.1 cm/year. Throughout the sequence, dinoflagellate cysts (dinocysts) and organic linings of benthic foraminifers are very abundant, ranging up to ∼16,000 cysts/cm³ and ∼2500 organic linings/cm³ respectively, indicating high primary production and organic carbon fluxes. The dinocyst assemblages are dominated by the cyst of Pentapharsodinium dalei and Brigantedinium spp., and Islandinium minutum subsp. minutum, mainly accompanied by Operculodinium centrocarpum, Spiniferites ramosus, S. elongatus, Islandinium? cezare and Echinidinium karaense. Such an assemblage is typical for highly productive seasonally ice-free environments. The reconstruction of sea-surface parameters based on dinocyst assemblages indicates warmer conditions from the base of the core until ⁓2750 cal yr BP. Subsequently, a cooling trend was marked by more extensive seasonal sea-ice cover spanning up to 9 months/yr, and fluctuating conditions of salinity. In the pollen assemblages, Alnus and Betula abundance decreased upcore while Ericaceae increased, which we associate with harsher climatic conditions. Hence, both pollen and dinocyst data point to a cooling trend, with a main transition occurring between 2700 and 2000 cal yr BP.