High-resolution pollen, plant macrofossil and sedimentary analyses from early Holocene lacustrine sediments on the Faroe Islands have detected a significant vegetation perturbation suggesting a rapid change in climate between ca. 10380 cal. yr BP and the Saksunarvatn ash (10 240 ± 60 cal. yr BP). This episode may be synchronous with the decline in δ18O values in the Greenland ice-cores. It also correlates with a short, cold event detected in marine cores from the North Atlantic that has been ascribed to a weakening of thermohaline circulation associated with the sudden drainage of Lake Agassiz into the northwest Atlantic, or, alternatively, a period with distinctly decreased solar forcing. The vegetation sequence begins at ca. 10 500 cal. yr BP with a succession from tundra to shrub-tundra and increasing lake productivity. Rapid population increases of aquatic plants suggest high summer temperatures between 10 450 and 10 380 cal. yr BP. High pollen percentages, concentrations and influx of Betula, Juniperus and Salix together with macrofossil leaves indicate shrub growth around the site during the initial phases of vegetation colonisation. Unstable conditions followed ca. 10 380 cal. yr BP that changed both the upland vegetation and the aquatic plant communities. A decrease in percentage values of shrub pollen is recorded, with replacement of both aquatics and herbaceous plants by pioneer plant communities. An increase in total pollen accumulation rates not seen in the concentration data suggests increased sediment delivery. The catchment changes are consistent with less seasonal, moister conditions. Subsequent climatic amelioration reinitiated a warmth-driven succession and catchment stabilisation, but retained high precipitation levels influencing the composition of the post-event communities.
- Programområde 5: Natur og klima