RECENT DEGLACIERIZATION OF THE UPPER WHEATON RIVER WATERSHED, YUKON

Over the past several decades, the rate of temperature increase in the Arctic has been twice that of the rest of the planet. Climate modeling suggests that this region will experience greater climate warming over the remainder of this century than other parts of the world. We are studying the effects of recent, rapid and significant warming on physical environments of southern Yukon Territory, which is within sub-Arctic Canada. In this paper, we document rapid glacier retreat in the Wheaton River watershed, which presently supports the only glaciers on southern Yukon Plateau. Our research involves study of the largest of the glaciers in the Wheaton watershed, hereafter referred to informally as “Wheaton Glacier”. It addresses three questions: How has Wheaton Glacier changed over the past century? What is the relationship between historic activity of the glacier and regional climate? What have been the effects of climate warming and glacier retreat on the watershed? Wheaton Glacier has shrunk in area by 41% since the first photographs of it were taken in 1948. Glacier retreat has accelerated in the past 40 years, and the glacier is now so thin and short that it may disappear within the next 20 years. The main cause of glacier thinning and retreat is an increase in mean temperature; average winter snowfall has gradually increased over the period of record. Warming and glacier recession are altering sediment delivery in the upper Wheaton River watershed. A pulse of sediment is moving downstream from the Wheaton Glacier forefield and affecting the fan at the mouth of the valley. Large, out-of-channel debris flows are spilling across the fan, aggrading and shifting the stream channel. Evidence from cores and ground-penetrating radar surveys suggest that debris flows have dominated sedimentation on the fan during the last half of the Holocene, coincident with Neoglacial advances culminating in the Little Ice Age and the period of rapid glacier retreat following the Little Ice Age. Triggers identified for some of the debris flows include the draining of a proglacial lake, a rockfall possibly caused by permafrost melt, increased sediment availability associated with glacier retreat; and rock glacier activity.