Glacier change in western North America: influences on hydrology, geomorphic hazards and water quality



The glaciers of western Canada and the conterminous United States have dominantly retreated since the end of the Little Ice Age (LIA) in the nineteenth century, although average rates of retreat varied from strong in the first-half of the twentieth century, with glaciers stabilizing or even advancing until 1980, and then resuming consistent recession. This retreat has been accompanied by statistically detectable declines in late-summer streamflow from glacier-fed catchments over much of the study area, although there is some geographical variation: over recent decades, glaciers in northwest BC and southwest Yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat, and glacier-fed streams in that region have experienced increasing flows. In many valleys, glacier retreat has produced geomorphic hazards, including outburst floods from moraine-dammed lakes, mass failures from oversteepened valley walls and debris flows generated on moraines. In addition to these hydrologic and geomorphic changes, evidence is presented that glacier retreat will result in higher stream temperatures, possibly transient increases in suspended sediment fluxes and concentrations, and changes in water chemistry. With climate projected to continue warming over the twenty-first century, current trends in hydrology, geomorphology and water quality should continue, with a range of implications for water resources availability and management and hydroecology, particularly for cool and cold-water species such as salmonids. Copyright © 2008 John Wiley & Sons, Ltd.