GLACIER FLUCTUATION AND TREE-RING RECORDS FOR THE LAST MILLENNIUM IN THE CANADIAN ROCKIES

Tree-ring series and records of alpine glacier fluctuations provide complementary evidence to reconstruct decade-to-century climate fluctuations over the last millennium in the Canadian Rockies. Tree-line ring-width chronologies in this area are temperature sensitive and long (ca. 900 years) series from sites adjacent to Bennington and Athabasca Glaciers show synchronous declines in ring-width during the periods ca. 1170-1180, 1280-1290, 1330-1350, 1430-1450, 1530-1540, 1690-1705 and 1810-1825 A.D. The latter two events are replicated in many shorter tree-ring chronologies and immediately precede the two major periods of moraine development (ca. 1700-1725 and 1825-1875 A.D.) during the Little Ice Age. Dendrochronological dating of glacially-overridden trees 0.5-1.0 km upvalley of 18th century maximum positions indicate that Robson and Peyto Glaciers were advancing between 1150 and 1350 A.D. during the earliest phase of the Little Ice Age in the Canadian Rockies. Available tree-ring data suggest that the level and pattern of climate variability during the 18th and 19th centuries extends back over the last millennium. It is also hypothesised that glaciers attained their maximum Holocene extent during the Little Ice Age because of the interaction between these decade-to-century scale fluctuations and the progressive long-term decline of incoming summer solar radiation in the northern hemisphere over the last 10,000 years.