THE IMPACTS OF THE CORDILLERAN ICE SHEET AND ALPINE GLACIATIONS ON THE HYPSOMETRY OF THE CANADIAN CORDILLERA

In this study, the hypsometry of the Canadian Cordillera was examined in relation to the development of the Cordilleran Ice Sheet (CIS) from the alpine advances 25,000 ¹⁴C yr B.P. to its maximum ice sheet extent during the Last Glacial Maximum (LGM). Elevation histograms and hypsometric integrals were calculated for each 7.5 min quad across the Canadian Cordillera, and the shape and distribution of elevation peaks were compared to the glacial history of each region. Regions with a hypsometry that demonstrated a single sharp peak predominantly concentrated at low elevations include the coastline, the Chilcotin Plateau Basalts, and areas outside the LGM extent of the CIS. The smaller mountain ranges (i.e. Cassiar, Skeena, Selwyn) that were within the LGM ice sheet extent, but outside of the alpine glaciation phase and do not contain modern glaciers demonstrated a more normal elevation distribution, with a single wide peak in modal elevation. The regions that reflect a glacial buzzsaw effect, with most surface material concentrated below the modal elevation are limited to the Rockies, Coast Mountains, and St. Elias ranges, where glaciation has been ongoing throughout the last 25,000 years. Areas with high hypsometric integrals (0.44 – 0.58) are mainly found within the interior plateaus and the landward edges of the LGM extent; areas with low hypsometric integrals (0.03 – 0.28) are found mainly along the coast and the Coast Mountains. Cirque-floor elevations, a proxy for the ELA during the late alpine glacial phase of the CIS, are lowest near the coast and follow a strong, rising linear trend from west to east across the Coast Mountains, and from south to north in the Rocky Mountains. We find that the regions which experienced alpine glaciation are clearly reflected in the hypsometry of the Cordillera; in contrast, those regions that were only ice covered during the maximum ice sheet phase exhibit little or no difference in hypsometric indicators from non-glaciated regions to the south and north.