HR: 17:00h
AN: A42F-05    [PDF]
TI: 17O as a new tracer of the hydrological cycle
AU: * Angert, A
EM: angert@atmos.berkeley.edu
AF: The Atmospheric Science Center University of California, Berkeley, MC 4767 307 McCone Hall, Berkeley, CA 94720-4767 United States
AU: Cappa, C D
EM: cappa@uclink.berkeley.edu
AF: Department of Chemistry University of California, Berkeley, B45 Hildebrand, Berkeley, CA 94720-4767 United States
AU: DePaolo, D J
EM: depaolo@eps.berkeley.edu
AF: Department of Earth and Planetary Science University of California, Berkeley, 473 McCone Hall, Berkeley, CA 94720 United States
AB: 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 (or slope) was found to be lower for kinetic transport effects then for equilibrium effects, with very low temperature sensitivity. As a result, the 17O excess (defined similarly to deuterium excess) of precipitation is controlled primarily by kinetic effects during evaporation and ice formation and therefore, in contrast to the deuterium excess, is independent of the temperature at the site of evaporation (and condensation). This makes the 17O excess a unique tracer that complements 18O and deuterium, and may allow 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 17O of ice caps is influenced by kinetic effects in ice formation, and therefore measurement of ice 17O can be used as an additional constraint for better understanding and parameterization of these effects.
DE: 0315 Biosphere/atmosphere interactions
DE: 1655 Water cycles (1836)
DE: 3344 Paleoclimatology
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting