Non-mass dependent oxygen isotope effect observed in water vapours from Alert, Canada

Twenty-six precipitation samples from Chicago, IL and northwest part of Indiana were collected from 2003 to 2005. Twenty-five water vapour samples were collected at Alert, Canada (82.5 degrees N, 62.3 degrees W) from 2002 to 2005 by Environment Canada. Seven ice core samples from Dasuopu Glacier, Chinese Himalayas (28.2 degrees N, 85.4 degrees E) were drilled by Lonnie G. Thompson and prepared by Mary E. Davis. Sample of Standard Light Antarctic Precipitation (SLAP) is available in the laboratory. Water samples were reacted with bromine pentafluoride to produce oxygen, which was then purified and measured by Delta E gas source mass spectrometer. Oxygen isotopic compositions are reported in delta notations and relative to VSMOW. A λMDF (H2O) = 0.5292 ± 0.0031 (2σ) is determined from three-isotope plot of local precipitation samples. No oxygen isotopic anomaly is found in ice core samples from Dasuopu Glacier, Chinese Himalayas. Δ17O of 0.076 ± 0.075 per mille (2σ) is observed in water vapour from Alert, Canada. The SLAP possesses a positive anomaly of 0.059 per mille. Stacked seasonal trend of Δ17O observed at Alert, Canada points toward a maximal value in late spring, which may be due to the lowering of the tropopause level, increasing tropopause folding events, and lowering the Planetary Boundary Layer (PBL) mixing height at the Arctic during spring time. Thus, the intrusion of stratospheric air is at its maximum. (author)