2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 298-8
Presentation Time: 9:00 AM-6:30 PM


FINKENBINDER, Matthew S., Geology and Planetary Science, University of Pittsburgh, 4107 O'Hara St, SRCC, Room 200, Pittsburgh, PA 15260, ABBOTT, Mark B., Geology and Planetary Science, University of Pittsburgh, 4107 O'Hara St, SRCC, Room 301, Pittsburgh, PA 15260 and STEINMAN, Byron A., Large Lakes Observatory and Department of Earth and Environmental Sciences, University of Minnesota Duluth, 2205 E. 5th Street RLB 205, Duluth, MN 55812, msf34@pitt.edu

Holocene reconstructions of the oxygen isotopic composition of precipitation (δ18Oppt) from the circum North Atlantic region exhibit large fluctuations during rapid ice sheet deglaciation followed by more stable conditions as interglacial boundary conditions were established. However, questions remain regarding the magnitude of century to millennial-scale δ18Oppt variations from Atlantic Canada largely due to the scarcity of paleoclimate records. Here we present a multi-decadal resolution carbonate oxygen isotope (δ18Ocal) record spanning the period 10,200 and 1,200 cal yr BP from Cheeseman Lake (49.35° N, 57.60° W, 180 m), a small, alkaline, hydrologically open lake basin located in west-central Newfoundland, Canada. Stable isotope data from regional surface waters and monthly precipitation indicate that Cheeseman Lake waters fall along the local meteoric water line. Climate sensitivity simulations conducted with a lake hydrologic and isotope mass balance model suggest that Cheeseman Lake is sensitive to temperature changes and to a lesser extent cold-season (October-March) precipitation seasonality changes, at least for the period of relative climate stability after Laurentide Ice Sheet (LIS) disintegration. A general trend of increasing δ18Ocal values between 10,200 and 7,950 cal yr BP is interpreted to reflect a combination of atmospheric circulation shifts associated with LIS retreat, moisture source changes, and warming temperatures. Abrupt δ18Ocal shifts to more negative values occur at 9,700 and 8,500 cal yr BP that coincide with cooling events in the circum North Atlantic region. After 7,950 cal yr BP, δ18Ocal values decrease until 4,300 cal yr BP, which we interpret as a cooling trend related to declining Boreal summer insolation. δ18Ocal values become slightly more positive after 4,300 to 2,500 cal yr BP and thereafter decline to the most negative values of the Holocene by 1,200 cal yr BP. Comparison with records of external forcing, Greenland ice core δ18O data, marine records from the adjacent North Atlantic Ocean, and several terrestrial hydroclimate records provides an assessment and new synthesis of climate change in Newfoundland during the Holocene.