Diatom analyses have been performed on a 425 cm long Holocene marine sediment sequence from the North Atlantic south of Iceland and a 920 cm sediment core spanning the last c. 7500 years from Skalafjord, Faeroe Islands. Additional core data include stable isotopes and results from magnetic susceptibility measurements, while chronostratigraphic control has been provided by AMS 14C measurements. The diatom records reveal distinct changes in North Atlantic surface circulation and climate that have been correlated with published terrestrial and marine records. Initial Holocene warming is dated at 9900 14C years BP, and after a Preboreal cold spell enhanced North Atlantic Current activity and warming prevailed from 9600 to 8800 14C years BP. From 8800 to 8000 14C years BP the advection of warm Atlantic water masses weakened, presumably under atmospheric circulation conditions characterized by a dominating negative NAO. Prior to the Holocene Climatic Optimum (6000-5000 14C years BP) distinct hydrographic gradients existed in the northern North Atlantic that were probably most pronounced during the reported '8200 cal. years BP cold event'. After 5000 14C years BP both core records indicate increased climate instability and periods of cooling ('Neoglaciation'), with enhanced cyclone activity affecting the northern North Atlantic particularly at around 4700, 4200, 3200, 2000, 1500 and 1000 14C years BP.
- Programområde 5: Natur og klima