Oxygen Isotope Anomaly found in water vapor from Alert,

Canada

Y. Lin, R. N. Clayton, L. Huang, N. Nakamura, J. R. Lyons

2012 Apr.25, Vienna, EGU

Mass-dependent fractionation (MDF)

(1 + 17O/1000) = (1 + 18O/1000)

17O = 18O, ≈ 0.52 (e.g. Clayton, 1993)

17O = 17O – 18O

Non-mass-dependent (NMD) fractionation

17O = 103ln(1+17O) – 103ln(1+18O), approximated by

Terrestrial fractionation line (TFL) (Thiemens, 1999)

1000ln(δ18O/1000 +1) (‰)

1000

ln(δ

17O

/100

0 +1)

(‰

)

NMD effect in ozone and other gases(e.g. Mauersberger et al., 1993; Thiemens et al., 1995)

1000ln(δ18O/1000 +1) (‰)

1000

ln(δ

17O

/100

0 +1)

(‰

)

NMD effect in ozone formation and dissociation in the lab（ e.g. Heidenreich and Thiemens, 1983)

Modeled Δ17O in stratospheric water （ Zahn et al., 2006)

- 1

- 0. 5

0

0. 5

1

1. 5

2

0 5 10 15 20 25

Water vapor mixing ratio (ppmv)

D17O

Δ17

O (

‰)

Δ17O in the lowermost stratospheric water (Franz and Röckmann, 2005)

Brewer-Dobson Circulation (e.g. Hintsa et al., 1998)

“Age”of stratospheric air (Rosenlof et al., 1995)

Water Samples

2002−2005 ： 25 Alert water vapor (provide by Environment Canada)

1930−1996 ： 7 Ice core samples from Dasuopu Glacier, Chinese Himalayas (Provided by Lonnie Thompson)

2003−2005 ： 27 Chicago local precipitation (CLP)

Collection of water vapor at Alert station

2BrF5 + 2H2O 2BrF3 + 4HF + O2

Fluorination of water

Delta E IRMS

Equilibrium fractionation line of CLP

Results

Stacked seasonal variation of Δ17O in water vapor samples from Alert, Canada

Schematic of 17O transport and mixing in the Earth’s atmosphere in the northern hemisphere

Stratospheric water has averageΔ17O=40‰, only an order of magnitude estimation due to the simplicity of the model

Alert snow Δ17O=43±5ppm（ 2σ error ） , rel. VSMOW

Conclusions

Chicago local precipitation defined λMDF(H2O)=0.5292±0.0030 (2σ observed scatter).

Δ17O value of 76±16 ppm (2σ standard error) was observed in the water vapor samples from Alert, Canada. Stacked seasonal trend shows a maximum in late spring and a minimum in the fall.

The positive anomaly presumably originating from stratospheric ozone, was then transported downward into the troposphere and was significantly diluted by lateral mixing with low-latitude air with negligible Δ17O.

6 Alert snow samples analyzed at LSCE, France has Δ17O=43±5 ppm relative to VSMOW. We think the difference between Alert snow and Alert water vapor is due to inter-laboratory difference in analytical techniques.

Average Δ17O for stratospheric water of ~40‰ was calculated using a steady-state box model, however this is only an order of magnitude estimation. The value is somewhat higher than the chemical model predictions of 0−30 ‰ for stratospheric water vapor [Lyons, 2003; Zahn et al., 2006], and is much greater than the observation of <2‰ for the lower stratosphere [Franz and Röckmann, 2005]. We suspect that the sampled air in the latter study had possibly exchanged with tropospheric air.

Future work is to measure Δ17O in Alert water vapor and snow samples collected on shorter and more regular period, and to measure Δ17O of stratospheric water .

Acknowledgments

The authors sincerely thank personnel from Environment Canada for water vapor sample collection, for providing us the temperature, pressure, relative humidity, and precipitation data.

Contribution of ice core samples by Lonnie G. Thompson (The Ohio State University) and preparation by Mary E. Davis

Robert N. Clayton, Frank M. Richter, Andrew M. Davis, Lawrence Grossman from the University of Chicago

Measurement of Alert snow samples by Amaelle Landais This project was funded by the U.S. National Science Foundation

(EAR 0439925).