HOLOCENE CLIMATE INFERRED FROM A 9,000-YEAR-LONG PROGLACIAL LAKE SEDIMENT RECORD ON NORTHEASTERN BAFFIN ISLAND, ARCTIC CANADA

The Arctic has a disproportionately large response to changes in radiative forcing of climate, and glaciers respond sensitively to these changes. Understanding past climate change is important for placing current changes into a longer term context. We obtained a ¹⁴C- and ^239+240Pu-dated surface core/percussion core pair from a proglacial lake on northeast Baffin Island. Together these cores span 9000 years and the sediments are varved, as verified by the ^239+240Pu analysis, for at least the past ~1000 years. Here, we pursue the use of varve thickness, an abiotic temperature proxy, to expand our understanding of late Holocene temperature changes on northeast Baffin Island. Although the early and mid-Holocene sediments are not varved, we interpret glacier activity based on physical characteristics of the sediment. Magnetic susceptibility, a proxy for the input of glacigenic sediment to the lake, was high during the early Holocene, decreased to near-zero values during the mid-Holocene and increased during the past 2500 years to reach the highest values in the record around 1000 years ago. Organic matter content (loss-on-ignition) had an opposite trend, with the highest values in the mid-Holocene. Sedimentation rate was constant during most of the Holocene (0.03 cm yr ^-1) and increased during the past 1000 years to 0.05 cm yr ^-1. These parameters suggest active glaciation in the lake catchment during the early Holocene, but the absence of glaciation during the mid-Holocene. Glacier activity reinitiated ~2500 years ago and reached peak Holocene activity over the last 1000 years. The varve thickness record for the past 500 years shows thin (< 0.5 mm average) varves during the 17^th and 18^th centuries (possible Little Ice Age signal), followed by a thickening trend (up to ~1 mm average) into the 21^st century. The thickening trend indicates regional warming since the mid-18^th century, consistent with other paleoclimate records in the region. A longer varve thickness record, as well as the Holocene record, will be presented.