ABSTRACT: The Bridge Advance: Pre-Little Ice Age dendroglaciology at Bridge Glacier, British Columbia Coast Mountains.

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Abstract

Dendroglaciological investigations at Bridge Glacier in the British Columbia Coast Mountains have substantiated previous indications of a glacial advance prior to the Medieval Warm Period in Pacific North America. Located on the eastern side of the Pacific Ranges west of Lillooet, Bridge Glacier is a prominent eastward flowing valley glacier whose source area is the Lilloett Icefields. Field investigations in 2002 and 2003 led to the identification 7 distinct Little Ice Age (LIA) moraine-building events that lichenometic and radiocarbon dating indicate occurred between 1468 and 1909 A.D. The discovery of ice-proximal buried in situ stumps and boles exposed by recent glacier retreat and stream erosion, provides evidence that Bridge Glacier was advancing down valley into an established >300 year old forest composed of whitebark pine (Pinus albicaulis (Engelm.)) and subalpine fir (Abies lasiocarpa (Hook)) trees between the 5th and 6th centuries. Identified as the Bridge Advance, this glacial episode predates early-LIA glacial activity in the 12th and 13th centuries by 600-700 years. The climatic sensitivity of these buried trees, other detrital wood samples and living trees sampled in the surrounding area, is providing an opportunity to develop tree ring chronologies that potentially span the last 1500 years. These overlapping records of environmental change will be used to reconstruct a long-term mass balance history for Bridge Glacier that will be examined to describe the climate forcing mechanisms that led to the pre-LIA Bridge Advance.

Bibliography of Canadian Geomorphology