Paper No. 20-11
Presentation Time: 1:30 PM-5:30 PM
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.