The influence of glacier change on sediment yield, Peyto Basin, Alberta, Canada.

The relation between sediment yield and glacier fluctuations at timescales less than a century remains uncertain. The primary goal of this study was to assess the influence of glacier activity on sediment yield within the Peyto Lake watershed. The research focused on a small alpine watershed in the Rocky Mountains of Alberta containing Peyto Glacier and the proglacial Peyto Lake. Using photogrammetric methods I determined changes in length, area, and volume of Peyto Glacier from a topographic survey map (1917) and 18 sets of aerial photographs (1947-2005). I also collected 18 sediment cores from Peyto Lake that consists of laminated, silt-clay couplets which can be shown through ¹³⁷Cs activity to be clastic varves. Varve thickness and sediment properties were combined to produce an annual record (1917-2010) of specific sediment yield (SSY) for the watershed. I then compared the SSY record to dimensional changes of Peyto Glacier as well as available mass balance records, hydrometric records, and climate records over the study period (1917-2010). Over the period 1917-2005, Peyto Glacier retreated 2198 ± 18 m, shrank 4.0 ± 0.9 km², thinned 44 ± 31 m, and lost 581 ± 404 x 10⁶ m³ water equivalent (w.e.). I measured an additional 85 ± 4 x 10⁶ m³ w.e. of ice loss from thinning ice-cored moraines adjacent to the glacier. Over the period 1917-2005 SSY averaged 446 ± 176 Mg km²yr⁻¹, which is among the highest measured yields in the Canadian Cordillera; however, this value is relatively low for glaciated basins worldwide. The SSY record has a poor relation to short-term dimensional changes of Peyto Glacier, likely due to the complexity of sediment transfers in proglacial environments. Long-term trends in SSY are hypothesized to arise from increasing (1870-1940) and decreasing (1970-2010) glacier contribution to streamflow over the past century.