Late Pleistocene and Holocene Fire History of the Swiftcurrent Lake basin, eastern Glacier National Park, Montana

High altitude alpine landscapes of the northern U.S. Rocky Mountains are geomorphically dynamic and sensitive to climate change. Understanding the timing and magnitude of past changes in temperature, aridity, and other factors such as seasonality and storminess are key in constraining natural climate variability in these sensitive environments. Fire frequency can provide strong insight into past climate regimes, with increased periodicity and/or intensity of fires reflecting episodes of warming and/or aridity. Lacustrine climate records in the Rockies are most abundant either further south of northern Montana at lower elevations, or in the Canadian Rockies further north. Here we examine a ∼12,900 year long lake sediment record from the northeastern basin of Swiftcurrent Lake in eastern Glacier National Park, MT to document fire frequency as a proxy for aridity in the region. Swiftcurrent Lake is fed mainly by melt from Grinnell Glacier, and thus reflects glacial, geomorphic, and climatic processes throughout the Holocene. Existing data, such as mineralogy, percent organic carbon, C/N, and grain size will be paired with the fire frequency record over the Holocene and latest Pleistocene to develop a comprehensive environmental history of the Swiftcurrent Lake Basin and greater Grinnell Glacier Valley. A clear understanding of fire history in the basin is important for future fire management decisions in Glacier National Park. Charcoal particles were tallied at contiguous 0.5 cm intervals over the first half meter of the core, and at 1 cm intervals over the remaining ~6.0 m, then converted to charcoal abundance and accumulation rates. Based age controls from radiocarbon analyses and ash fingerprinting the sampling interval represents between 5 and 20 years. A core collected in July 2010 will be analyzed for lead-210, providing additional age control for the past few centuries. Preliminary results show low charcoal counts overall with some clear peaks. High charcoal abundance and accumulation rates appear to be tied to increased fire activity in basin. We anticipate correlation with climatic anomalies such as the Medieval Warm Period. Charcoal morphotypes, also identified and tallied in conducted charcoal counts, will be used to indicate the nature of the basin vegetation. These data will be compared to pollen data to consider changing vegetation regimes. The focus on the last few centuries will provide insight into the extent of anthropogenic effects on burn periodicity. This study will also be paired with other similar fire frequency records in the greater northern Rockies region. Finally, comparisons with total organic carbon in the core, which is tied to solar forcing over the last 7500 years, will further illuminate the environmental history of the basin over the Holocene.