Holocene palaeoceanographic changes in Barrow Strait, Canadian Arctic: Foraminiferal evidence

摘要

Holocene changes in the benthic and planktic foraminiferal fauna (>63 μm) from a marine sediment core (ARC-3 Canadian Arctic Archipelago, 74° 16.050' N, 91° 06.380' W, water depth 347 m) show that significant environmental and palaeoceanographic variations occurred during the last 10 ka. Foraminiferal assemblages are restricted to the ca. 4.5-10 ka interval as younger samples are mostly barren of foraminifera due to intense carbonate dissolution after ca. 4.5 ka. Foraminiferal assemblages in the ca. 4.5-10 ka interval are dominated by the benthic species Islandiella helenae and Cassidulina reniforme (57% of total), with Elphidium clavatum, Cibicides lobatulus and Buccella frigida also being common in this interval. The dominance of these species indicates a seasonal sea ice regime which is consistent with the occurrence of the sea ice diatom-derived organic geochemical biomarker IP_(25) throughout the core. The abundances of C. reniforme and E. clavatum decline upcore; consistent with more frequent mixing of the Barrow Strait water column during the early Holocene. It is likely that the influence of CO_2-rich Arctic surface water masses have caused an increase in bottom water corrosivity after ca. 8.5 ka, and dissolution has been further enhanced by sea ice-related processes after ca. 6 ka, concomitant with increased IP_(25) fluxes. Dissolution is strongest when IP_(25) fluxes are highest, suggesting a link between the sea ice and benthic systems.