Northeastern Section - 42nd Annual Meeting (12–14 March 2007)

Paper No. 10
Presentation Time: 4:20 PM

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


SPOONER, Ian1, LENNOX, Brent1 and GINN, Brian2, (1)Geology Department, Acadia Univ, 12 University Avenue, Wolfville, NS B4P 2R6, Canada, (2)Paleoecological Environmental Assessment and Research Lab (PEARL) Department of Biology Queen's University, Kingston, K7L 3N6, Canada, ian.spooner@acadiau.ca

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.