TREE-RING DATING OF LITTLE ICE AGE GLACIER ADVANCES AND ASSOCIATED ICE-DAMMED LAKES IN KLUANE NATIONAL PARK AND RESERVE, YUKON TERRITORY, CANADA

Although mountains, glaciers, and ice fields cover over 80% of Kluane National Park and Reserve (KNPR), in southwest Yukon Territory, relatively little is known about the timing and amplitude of late-Holocene glacier fluctuations in the region. The lack of well-dated chronologies of glacier activity in the northern St. Elias Mountains frustrates comparison to adjacent regions, for example, coastal Alaska and the Coast Mountains of British Columbia, where recent work has yielded a complex story of glacier activity during the Little Ice Age. Here we present initial results of several investigations that are broadly targeted at elucidating the response of glaciers in KNPR to climate variability during the Little Ice Age. Dendrochronological techniques were used to refine the history of Neoglacial Lake Alsek, which formed at least three times since the early 17th century when Lowell Glacier blocked drainage of the south-flowing Alsek River. Crossdated driftwood associated with different phases of Lake Alsek constrains the timing of advanced positions of Lowell Glacier. Similar methods are being used to develop the first high-resolution chronology of ice-dammed Lake Donjek, which potentially threatens the Alaska Highway transportation corridor north of Kluane Lake. At Kaskawulsh Glacier, white spruce stems were sheared and tilted when terminal moraines were deposited during the culmination of its most extensive Little Ice Age advance. The ages of seven such stems, which we dated by comparing their ring-width patterns to a ~900 year tree-ring chronology from nearby south Kluane Lake, suggest that Kaskawulsh Glacier was at its most extensive Holocene position in the early-mid 18th century. In addition to highlighting the potential for long tree-ring records to provide decadal-scale dating of geomorphic events in the northern St. Elias Mountains, our results have important implications for park management at KNPR, particularly with respect to natural hazards and long-term ecological change.