Holocene sea-ice and productivity changes on the Scotian Shelf, NW Atlantic

The Scotian Shelf is affected by the confluence of cold polar and warm Gulf Stream-influenced waters, making it particularly sensitive to record past ocean and climate variability. Despite this paleoenvironmental significance, major gaps in our understanding of Holocene ocean and climate dynamics persist, particularly in terms of sea ice and marine productivity. Here, we use a combination of biomarkers, specifically the sea-ice proxy IP 25 , together with biomarkers for productivity (i.e., brassicasterol, dinosterol, total organic carbon) and terrigenous input (campesterol) in a sediment core from the northeastern Scotian Shelf to resolve Holocene changes in sea ice and marine productivity. During the Early Holocene, our results show increased spring sea-ice algae and reduced marine productivity, which we posit to be linked to a strongly reduced regional sea level together with increased inflow of meltwater favoring the formation of an expanded seasonal sea-ice cover on the Scotian Shelf. After 6 cal ka BP, the Scotian Shelf became predominantly free of sea ice due to a decreased influence of meltwater and a rise in local sea level. After 2.5 cal ka BP and coinciding with the Late Holocene Neoglacial cooling, the Scotian Shelf might have been affected by episodic sea-ice readvances, consistent with other regional on- and offshore paleoclimate studies. In summary, our records suggest a strong link between sea-ice extent, marine productivity, and Holocene variations in regional sea level, and ocean and atmosphere conditions, i.e., the strength of Gulf of St. Lawrence outflow and Labrador Current, and prevailing North Atlantic Oscillation anomalies.