WHAT DO HIGH ARCTIC FLUVIAL AND LACUSTRINE CLASTIC SEDIMENTS TELL US ABOUT CLIMATE?

Reconstructing Arctic summer temperatures from varve thickness records is a seductively simple concept. The rationale is that the annual load of sediment transferred, from a watershed to a lake or estuary, is a direct response to the magnitude and duration of runoff derived from melting snow or ice, which in turn is governed by summer warmth.

We investigated the climatic significance of sediment transfer and deposition in four High Arctic lake-watershed systems, using two complementary approaches. We conducted detailed meteorological and hydrological field measurements to assess the 'expected' climate signal contained within the downstream lacustrine records. We then examined patterns of correlation between annual varve thickness records from each lake and different annual climate parameters from the closest weather station.

Our four study sites illustrate the diversity of summer climate and sediment delivery systems in the region. We observed significant differences in the quantitative linkage of climate and sediment transfer from lake to lake, largely as a result of intrinsic watershed characteristics. Thus, it follows that the precise nature and robustness of the 'expected climate signal', contained within lake sediment records, will vary between different lakes. However, even one year of meteorological and hydrological measurements was enormously helpful in understanding the systems which deliver sediment to the lakes. Our results demonstrate promise for the use of lake sediment thickness in some basins, particularly where field investigations corroborate statistical linkages between lake sediment thickness and the instrumental record. Chronological uncertainty presents the greatest challenge to the lake sediment records developed at these sites, as accurate absolute dating of high arctic lake sediments remains problematical.