A 1,500 YEAR RECORD OF LATE HOLOCENE CLIMATE CHANGE IN NEWFOUNDLAND USING OXYGEN ISOTOPE ANALYSIS OF LAKE SEDIMENT CORES

High-resolution (decadally resolved) paleoclimate records from the Maritime Provinces of eastern Canada that span the late Holocene are quite rare. As a result, the exact nature of decadal scale climate variations across the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), two well-known climate events in the North Atlantic region, is still actively debated. Here, we present a decadal resolution carbonate oxygen isotope (δ¹⁸O) record spanning the last ~ 1,500 calendar years before present (cal yr BP) from a small, hydrologically open-basin marl lake located in west-central Newfoundland. Stable isotope data from regional lakes, rivers, and precipitation samples indicate the carbonate δ¹⁸O record primarily reflects changes in the δ¹⁸O of meteoric precipitation and atmospheric temperature. Climate sensitivity simulations conducted with a lake hydrologic and isotope mass balance model are used to quantify the sensitivity of the lake (and therefore δ¹⁸O record) to changes in the seasonality of precipitation, temperature, and shifting moisture sources from atmospheric circulation variability associated with the North Atlantic Oscillation. A general trend of decreasing δ¹⁸O values over the last ~ 1,500 cal yr BP is broadly consistent with cooling associated with declining Boreal summer insolation. Large fluctuations in δ¹⁸O values occur across the last millennium with persistent negative δ¹⁸O values during the MCA and more variable values across the LIA. We compare the δ¹⁸O record against records of external forcing, Greenland ice core δ¹⁸O data, and regional terrestrial and marine paleoclimate records to explore the underlying climate forcings or mechanisms that could explain the observed changes.