High Arctic Biocomplexity Research - Thule, Greenland
Lacustrine paleoecology and paleoclimatology
In contrast to ice cores that primarily reflect hemispheric scale temperature-related climatic processes, lake records tend to reflect regional scale climate variability. High latitude and high altitude lakes have been shown to be particularly sensitive to changes in climate, and sediment records from these lakes have great potential to document changes in climatic conditions over time. Sediment proxies that provide information about paleoclimatic and paleoecological conditions include fossil pollen, sediment magnetic susceptibility and grain size, organic and inorganic carbon content, carbon to nitrogen ratios, and the isotopic composition of elements such as carbon, nitrogen, and oxygen.
Lakes near Thule
Several small lakes near Thule are of interest for paleoclimatological and paleoecological studies, including Char Lake on North Mountain , Horseshoe Lake in Dundas Valley , and Old Squaw Lake in the valley below BMEWS. It remains uncertain whether these lakes contain continuous, undisturbed sediment records, but we are in the process of assessing their utility.
Current work and future goals
In summer, 2004 we measured water depth, pH, conductivity, and temperature of all three lakes, and collected surface water samples. We also extracted several short cores from Old Squaw Lake with a gravity corer.
In fall, 2004 we will measure the isotopic composition of oxygen in silica
from diatoms in the sediment of Old Squaw Lake . Diatoms are
photosynthetic algae that secrete internal shells of biogenic silica
(BSiO2). The composition of oxygen isotopes in the silica
depends on the ambient water temperature and the isotopic composition of
the lake water when the shell was excreted. Changes in the isotopic
composition of oxygen can be used to reconstruct past variations in
climate and hydrology.
