A HIGH RESOLUTION RECORD OF POST-HYPSITHERMAL CLIMATE CHANGE FROM SOUTHWESTERN NOVA SCOTIA, CANADA

A high resolution, well-dated record of Post-Hypsithermal climate change from Canoran Lake, Nova Scotia has been constructed using δ15N, δ13C, hydrogen index, % carbon, magnetic susceptibility, and pollen. The Late Hypsithermal to Post-Hypsithermal transition (~3500 cal. yr BP) was accompanied by a subtle increase in precipitation and regional cooling as indicated by pollen records. Low δ13C values are due to a reduction in the rate of dissolved inorganic carbon uptake likely associated with lower water temperatures. A decrease in hydrogen index values and C/N ratio variability implies that the oxidative degradation of organic matter increased and the lake became well-oxygenated. The proxy response during the Medieval Warm Period (~AD 1200) indicated regional cooling in southwest Nova Scotia. Low δ15N values are associated with lower lake water levels and a decrease in littoral habitat for wetland communities. A local % carbon maximum indicates that lake levels were low and the distance between the shoreline and the core location decreased; regional aridity may be a factor. The transition from the Medieval Warm Period to the Little Ice (~AD 1550) was largely related to an increase in effective moisture. A positive excursion of δ15N and % carbon values at this time may be due to a rise in lake water levels and an increase in wetland habitat. Proxies in Canoran Lake do not appear to respond to warming during the past 150-50 years that has been documented by other workers. This lack of proxy response is possibly related to the suppression of within-lake primary productivity by anthropogenic-induced acidification.