Holocene glacier history of Frank Mackie Glacier, northern British Columbia Coast Mountains

Abstract

Frank Mackie Glacier repeatedly advanced across the Bowser River valley in northwestern British Columbia to impound Tide Lake during the Holocene. The most recent infilling of Tide Lake was associated with a late Little Ice Age glacier advance and ended around 1930 when the lake catastrophically drained. Over the last century Frank Mackie Glacier has retreated and down wasted to reveal multiple glaciogenic sedimentary units within the proximal faces of prominent lateral moraines. The units are separated by buried in-situ tree stumps and laterally contiguous wood mats deposited on paleosols. Dendroglaciological and radiocarbon dating of these wood remains show that Frank Mackie Glacier expanded into standing forests at 3710–3300, 2700–2200, 1700–1290, 900–500, and 250–100 cal. years BP. These advances coincide closely in time with the previously established Tide Lake glacier dam chronology and with the Holocene history of other glaciers in the Bowser River watershed. The findings emphasize the likelihood that most glaciers within northwestern British Columbia underwent substantial size and mass balance changes over the last 4000 years, and often spent hundreds of years in advanced positions before retreating.

Neoglacial history of Robson Glacier, British Columbia

“…This, combined with radiocarbon error terms, suggests that it is difficult to distinguish between (or correlate) inferred glacier events that may be 200-300 years apart from small amounts of detrital materials. Studies from lateral moraine sections and historical materials in British Columbia, Alaska, and the Alps (e.g., Barclay et al 2013;Le Roy et al 2015;St-Hillaire and Smith 2017) indicate several periods with multiple late Neoglacial glacier advances that may be only a few centuries apart. It is therefore likely that the late Neoglacial history of the Rockies is more complex than the limited story presented here and that continued work in glacier forefields is needed to elucidate a more complete history.…”

“…Increasingly, studies of this wood and buried, glacially overridden, forests are being used to define earlier periods of glacier advance and link them to global-scale climatic controls (e.g., Le Roy et al 2015;Solomina et al 2016). Although increasing numbers of such forefield records are becoming available, including many from British Columbia (e.g., Koch et al 2007;Menounos et al 2009;Mood and Smith 2015;St-Hillaire and Smith 2017), few such records are available for the Canadian Rockies (Osborn et al 2001;Wood and Smith 2004;Luckman 2006). These sites are relatively rare and, individually, only provide a partial record of local glacier histories: regional history must be compiled by the assembly, analysis, and correlation of records from many sites.…”