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.

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diatoms 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.

more diatoms

If the sediment records of Char, Horseshoe, and Old Squaw lakes are deemed sufficient, we would like to extract sediment cores from each lake and use the records to reconstruct paleoenvironmental conditions in the Thule region over the past ~2,000 years. We would also like to incorporate a modern component that investigates carbon cycling in High Arctic lacustrine ecosystems as a means to understand and interpret exactly what is being deposited into the lake.