Holocene Rapid Climate Change: Pervasive Millennial-Scale Climate Variability across the North Atlantic

Abstract

Rapid climate change (RCC) during the Holocene, particularly post-dating the demise of large Northern Hemisphere ice sheets after 8000 cal. yr BP, is a global phenomenon and is almost certainly driven by long-term changes in insolation, upon which solar variability, although a weak direct forcing mechanism, is superimposed. At least five significant intervals are identified in numerous palaeoclimate records since the major 9000-8000 cal. yr RCC, within which the intensively studied 8200 cal. yr ‘event’ is embedded; these are: 6000-5000, 4200-3800, 3500-2500, 1200-1000 and 600-150 cal. yr BP. Most of the Holocene RCCs are associated with bipolar cooling, an expansion-intensification of high latitude circulation systems and drying-aridity at low latitudes. Here, we present proxy-records from a fjord basin located on the Atlantic margins of NW Europe which contain evidence for these combined forcing mechanisms. Giant piston core (MD04-2832) from the main basin of Loch Sunart, Argyll, NW Scotland, is 22 m long and appears to contain a record of continuous sedimentation back to nearly 8000 cal. yr BP. Based upon the age-depth model for core MD04-2832, isotopic shifts recorded in the benthic foraminifera Ammonia beccarii coincide with both the rate and magnitude of the Holocene RCCs. We show that the renewal history of bottom waters in the fjord basins appear to be driven by large-scale atmospheric circulation changes that may have characterised the entire mid-latitude NE Atlantic region.