55 Warm Times/Cold Times: Holocene Climate Variability in the North Atlantic Region (Posters)

HOLOCENE CLIMATE VARIABILITY IN NW ICELAND DERIVED FROM FJORD AND LACUSTRINE SEDIMENT CORES

Program: SYMPOSIA
Time: 1:30 PM – 4:30 PM

Authors

Abstract

Evidence from fjord and lake cores in NW Iceland is used to delineate environmental change during the Holocene. The study area is affected by the southward flowing East Greenland Current of Polar Water origin, and the warmer northward flowing Atlantic Water of the Irminger Current. The fluctuating position of the boundary between these two opposing currents greatly affects the ocean physical and chemical characteristics in the region, including sea surface temperature, salinity and sea ice extent. Changes in the extent and duration of sea ice NW of Iceland has direct impact on land temperatures, as demonstrated by instrumental records and historical accounts. We therefore believe that both marine and terrestrial archives should record changes in the flux of Polar versus Atlantic water.

Marker tephra layers and AMS 14C dates on macrofossils and bulk sediment allow for correlation between marine and lacustrine stratigraphies. Marine sediment cores document rapid ice retreat from the maximum glacier extent on the shelf, starting around 15 ka. Stepwise readvances or halts in the ice recession are recorded in the fjords ~14 ka, ~12 ka and ~11 ka. Less minerogenic sediment and higher total carbon (TC%) in the lake cores reveal the disappearance of ice from the lake basins just before 10.5 ka. Apparent consistency in magnetic susceptibility (MS) and carbonate/TC% occurs between fjord and lake cores over the last ~10 kyr. Both archives record relatively stable conditions from 9.5 ka to 5.5 ka, although a minimum in carbonate/TC% with a correlative maximum in MS is seen in both records around 8.2 ka. Our proxy records register increased instability around 5.5 ka, probably indicating the onset of Neoglaciation, with a distinct low in fjord and lake productivity after ~ 3.5 ka. A fresh input of ice rafted debris in one of the fjord cores that receives sediment from the extant ice cap Drangajokull documents the expansion of the glacier during the Little Ice Age.