Kinetic 17O effects in the hydrologic cycle: Indirect evidence and implications

Alon Angert*, Christopher D. Cappa, Donald J. DePaolo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

109 Scopus citations

Abstract

The abundances of 18O and deuterium in the present and past hydrologic cycle have proven to be an important tool in Earth systems science. In contrast, the abundance of 17O in precipitation has thus far been assumed to carry no additional information to that of 18O. Here, we demonstrate, using known constraints on oxygen isotope abundances from the O2 cycle and existing data about the natural abundance of 17O in water, that the relationship between the discrimination against 17O and 18O in water may vary. This relationship, presented here as θ = ln (17α)/ln (18α), is found to be 0.511 ± 0.005 for kinetic transport effects and 0.526 ± 0.001 for equilibrium effects, with very low temperature sensitivity. As a result, the 17Δ of precipitation is controlled primarily by kinetic effects during evaporation of the initial vapor and, in contrast to the deuterium excess, is independent of the temperature at the evaporation (and condensation) site. This makes 17Δ a unique tracer that complements 18O and deuterium, and may allow for a decoupling of changes in the temperature of the ocean, that serves as the vapor source, from changes in the relative humidity above it. In addition, the 17Δ of ice caps is influenced by the kinetic effects in ice formation, and therefore measurement of ice 17Δ can be used as an additional constraint for better understanding and parameterization of these effects.

Original languageAmerican English
Pages (from-to)3487-3495
Number of pages9
JournalGeochimica et Cosmochimica Acta
Volume68
Issue number17
DOIs
StatePublished - 1 Sep 2004
Externally publishedYes

Bibliographical note

Funding Information:
We would like to thank Boaz Luz, Thomas Blunier, Kristie Boering, Ron Cohen, Michele Bender and Inez Fung for valuable discussion. Comments of Martin Miller James Farquhar and an anonymous reviewer significantly helped to improve the manuscript. AA is supported by NSF grant ATM-9987457, NASA Carbon Program grant NAG5-11200, and NASA EOS-IDS grant NAG5-9514. DJD is supported by the Director, Office of Energy Research, Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences Division of the U.S. Department of Energy under Contract No. De-AC03-76SF00098 to the Lawrence Berkeley National Laboratory. CDC is supported by a National Defense Science and Engineering Graduate Fellowship.

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