HR: 1330h
AN: PP23A-02    [Abstracts]
TI: The Oxygen and Hydrogen Isotope Composition of Atmospheric Water Vapor at Pinery Provincial Park, Southern Great Lakes Area, Canada
AU: * Jin, H
EM: hjin4@uwo.ca
AF: The University of Western Ontario, Department of Earth Sciences Biology and Geology Building, London, ON N6A 5B7 Canada
AU: Longstaffe, F J
EM: flongsta@uwo.ca
AF: The University of Western Ontario, Department of Earth Sciences Biology and Geology Building, London, ON N6A 5B7 Canada
AU: Webb, E A
EM: ewebb5@uwo.ca
AF: The University of Western Ontario, Department of Earth Sciences Biology and Geology Building, London, ON N6A 5B7 Canada
AB: More than 300 atmospheric water vapor samples were obtained between July 2004 and January 2005 at Pinery Provincial Park, southwestern Ontario, Canada. This area, which is located on the shore of Lake Huron, is variably influenced by Pacific, Tropical Atlantic and Arctic air masses, depending on the time of year. Each month, samples were collected from a sparsely vegetated dune and a nearby oak savannah site at regular intervals over a 24-hour period at 3 and 0.5m above ground level. The majority of the data describe a local water vapor line: δD=7.3δ¹⁸O+1.6. The broad positive correlation between surface temperature and the isotopic composition of the water vapor follows the expected seasonal pattern. The isotopic compositions of the water vapor showed seasonally consistent differences between the 3 and 0.5m sampling heights at both locations. During the summer months, the 3m samples were depleted of oxygen-18 and hydrogen-2 by 0.3 and 3 per mil, respectively, relative to the 0.5m samples. During the summer months, transpiration is a significant contributor to atmospheric vapor at both the 3 and 0.5m levels. However, the shallow soil water tapped by the grasses is enriched in oxygen-18 and hydrogen-2 relative to the deeper soil water utilized by the trees. This difference is likely sufficient to explain the observed pattern. By late autumn, these differences in oxygen and hydrogen isotope compositions between the high and low sampling sites were much smaller, +0.1 and -1 per mil, respectively. By the winter, the pattern was completely reversed, with the 3m samples being enriched in oxygen-18 and hydrogen-2 by 1.1 and 10 per mil, respectively. We suggest that vapor contribution from ground-level sublimation of snow is largely responsible for this behavior. The diurnal variations in isotopic composition at both sites can be substantial (e.g., δ¹⁸O = -28.3 to -19.1 per mil versus -21.4 to -20.0 per mil. The main controlling factor appears to be the meteorological conditions and air mass(es) present at the time of sampling.
DE: 0315 Biosphere/atmosphere interactions
DE: 1040 Isotopic composition/chemistry
DE: 1610 Atmosphere (0315, 0325)
DE: 1818 Evapotranspiration
DE: 1866 Soil moisture
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2005 Joint Assembly