Western Canadian glaciers advance in concert with climate change circa 4.2 ka

[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.