| Summary: | Hydrological records from High Arctic watersheds are invariably short. Records of runoff and sediment flux, and associated meteorological conditions are rarely longer than a few seasons, and commonly do not cover entire melt seasons. A longer-term perspective is needed. Lake sediments can help in assessing hydrological change on multi-decadal to centennial scales, though there are many uncertainties. Process-based studies are needed to link discharge and sediment flux to meteorological conditions, and to sediment deposition with a lake basin. Such studies provide the insight necessary to interpret changes that have occurred in the past, as observed in lake sediments. Large deep lakes in the Canadian High Arctic form end-members in the spectrum of lacustrine systems in the northern hemisphere. Lake ice cover is thick (1.5-3m) and persistent, often only melting around the margins each year. Consequently, limnological conditions are characterized by limited mixing, often leading to anoxic conditions at depth, at least seasonally. This results in minimal disturbance at the sediment-water interface, and the accumulation of annually laminated (varved) sediment. Such sediments provide an excellent chronological record. Studies of different facies in sediment cores enable the relationship
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