An Incidence of Multi-Year Sediment Storage on Channel Snowpack in the Canadian High Arctic

Аннотация

During June 2005, we identified the presence of sediment buried within multi-year channel snowpack of a small river located near Cape Bounty, Melville Island, Nunavut (74°55' N, 109°35' W). Photographic evidence indicates that the sediment was deposited during the 2003 season by the initial meltwater flowing on the snowpack, which was dammed by snow upstream of a channel constriction. The resulting pond covered a minimum area of 180 m2 and contained an estimated minimum 27 Mg of sediment. Suspended sediment measurements during the 2003 season indicate that deposition on the snowpack at this location represented 49%–65% of the sediment transport prior to the ponding and emplacement of the sediment on the snow, and approximately 20% of the measured sediment flux for the entire season. Multi-year snow accumulations immediately downstream exhibited similar sediment deposition on snow, but no evidence of multi-year sediment storage was present. By contrast, a similar stream in an adjacent watershed channelized rapidly, with minimal sediment deposition on the snow, and delivered a large pulse of sediment to the downstream lake. These results provide quantitative evidence for the magnitude of sediment storage on snowpack and point to the unique role that snow plays in the fluvial geomorphology of High Arctic watersheds.