Nine decades of glacier change in the Canadian Rocky Mountains.

Glaciers adjust their physical properties to changes in climate, but long records of glacier change needed to examine this relation are spatially and temporally limited. I determined changes in glacier area in the central and southern Canadian Rocky Mountains and changes in length, area, elevation, and volume of the Columbia Icefield over the past nine decades. I used Interprovincial Boundary Commission Survey (IBCS) maps of the Alberta-British Columbia (BC) border (1903-1924), aerial photographs (1948-1993), BC Terrain Resource Information Management (TRIM) data (1982-1987), and satellite imagery (1999-2009) in my analysis. From 1919-2006, total glacierized area in the Canadian Rocky Mountains decreased by 590 ± 100 km² (40 ± 7%); glaciers smaller than 1.0 km² experienced the greatest percentage loss. Slope and minimum elevation are negatively correlated with absolute area loss, and mean and median elevations are negatively correlated with relative area loss. From 1919-2009, glaciers of the Columbia Icefield retreated 1149.9 ± 34.1 m, decreased 59.60 ± 1.19 km² (22.5 ± 5.0%), thinned 49.4 ± 25.2 m w.e., and lost 14.30 ± 2.02 km³ w.e. Debris-covered ice thinned 30-60% less than bare ice. Changes in temperature and precipitation explain some of the observed changes. I detected a lag of two to ten years between climate and glacier response.