RESTRICTED GROWTH OF THE NORTHERN CORDILLERAN ICE SHEET IN MIS 2: EXAMPLES FROM THE KLUANE RANGE, YUKON, CANADA

Regional surficial geology mapping in the Kluane Range of southwest Yukon revises ice thicknesses to more restricted extents than previously mapped. The revised limits leave broad expanses of upland plateau ice-free through the last glaciation, and are supported by the distribution of endemic plants believed to be limited to unglaciated terrain (i.e. Oxytropis arctica var. murrayii, Artemisia woodii, Draba kluanei). This revision to the northern fringe of the Cordilleran Ice Sheet has implications for predicting the timing of ice-free conditions and the availability of productive landscape for migration of plants and animals between Beringia and the rest of North America.

The Kluane Range is located in the rain shadow of the St. Elias-Wrangell Mountains and is characterized by a patchwork of unglaciated uplands divided by deep, glaciated valleys and plateaus. Formed through an expansion of ice fields in the St. Elias-Wrangell Mountains of Yukon and Alaska, the St. Elias lobe of the Cordilleran Ice Sheet (CIS) repeatedly inundated valleys and basins in interior Yukon during the Quaternary, but always remained a network of independent valley glaciers and piedmont lobes. The St. Elias lobe is one of four semi-autonomous lobes of the northern CIS with distinct sources areas and responses to global climate drivers. Increasing aridity in southwest Yukon during the Quaternary likely contributed to restricted ice growth during MIS 2 and may also have maintained endemic “Beringian” plant communities that exist in the region today.