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The timing of Cordilleran Ice Sheet deglaciation along the central coast of British Columbia, Canada, informs climate forcing and early human migration. Thirty‐two 10Be exposure ages from glacial erratics and local bedrock on the western margin of the former ice sheet represent the earliest exposure ages for the Cordilleran Ice Sheet during the last deglaciation. These data show the western ice margin was retreating by 18.1 ± 0.2 ka, consistent with the global record of ice mass loss. In contrast, parts of the southern margin reached a maximum at ca. 17.6‐16.6 ka, and our data demonstrate a diachronous response of the Cordilleran Ice Sheet during deglaciation. We also show that a low altitude site was exposed by at least 17.7 ± 0.3 ka, implying that numerous ice‐free areas existed along the coastal margin by this time, providing a viable route for the first humans entering the Americas.

[1] We reconstruct the terminus position of a mountain glacier in British Columbia, Canada from annual push moraines formed between 1959 and 2007. Our reconstruction represents the longest, annually-resolved record of length change for a North American glacier. Comparison of annual recession with climate records indicates that glacier recession is controlled by air temperatures during the ablation season and accumulation season precipitation during the previous decade. Analysis among records of glacier frontal variation and mass balance in western North America similarly reveals an immediate terminus reaction to summer and net balance and a delayed reaction to winter and net balance. Other mountain ranges may contain long series of push moraines that could be exploited as climate proxies, and to improve understanding of glacier response to climate.

[1] Disparate climate proxies from the Northern Hemisphere record a climate event at 4.2–3.8 ka. Here we show that glaciers throughout the mountain ranges of western Canada advanced at about this time. This conclusion is based on (1) new and previously reported radiocarbon ages on in situ stumps, logs, branches, and soils exposed by recent retreat in glacier forefields and (2) clastic-rich sediment intervals in cores retrieved from four montane lakes. These glacier and lacustrine data indicate a period of several decades to century length when climate conditions (cool summers, wet winters or both) favoured glacier nourishment and advance across western Canada.

[1] We use the Shuttle Radar Topography Mission (SRTM) data and digital terrain models from aerial photography to quantify the change of glacier volume in British Columbia (BC), Canada for the period 1985–1999. We note substantial elevation bias in the SRTM elevations, typically on the order of −12 m km−1. The bias-corrected thinning rate is −0.78 ± 0.19 m a−1 which yields an annual volume loss of 22.48 ± 5.53 km−3a−1. This rate of glacier volume loss is 65% of the estimate uncorrected for elevation bias (34.7 km−3a−1) and cautions against the use of uncorrected SRTM data for glacier change studies. Glacier recession in BC could account for ca. 0.67 ± 0.12 mm of sea level rise over the period 1985–1999 (0.05 ± 0.009 mm yr−1) or about 8.3% of the contribution from mountain glaciers and ice caps. The recent rate of glacier loss in the Coast Mountains (17.0 km−3a−1) is approximately double that observed for the previous two decades.