Deuterium excess in Greenland snow: Analysis with simple and complex models
International audience A simple Rayleigh-type isotope model, typical of those used to develop algorithms for extracting climatic information from stable water isotope paleodata, is evaluated against the more complex and presumably more reliable calculations of a general circulation model (GCM) fitte...
Published in: | Journal of Geophysical Research: Atmospheres |
---|---|
Main Authors: | , , , |
Other Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
1998
|
Subjects: | |
Online Access: | https://hal.archives-ouvertes.fr/hal-02923817 https://hal.archives-ouvertes.fr/hal-02923817/document https://hal.archives-ouvertes.fr/hal-02923817/file/98JD00274.pdf https://doi.org/10.1029/98JD00274 |
Summary: | International audience A simple Rayleigh-type isotope model, typical of those used to develop algorithms for extracting climatic information from stable water isotope paleodata, is evaluated against the more complex and presumably more reliable calculations of a general circulation model (GCM) fitted with isotope tracer diagnostics. The evaluation centers on an analysis of how the temperature T e of an oceanic moisture source affects the deuterium excess d of Greenland precipitation. The annual Te-d relationship derived from the GCM diagnostics is largely reproduced by the simple isotope model when the latter is properly initialized. This, coupled with the fact that the GCM itself reproduces observed isotope behavior, suggests that the simpler model's atmospheric calculations are indeed adequate for isotope studies. Furthermore, the GCM results support the idea, originally developed with the simpler models, that polar deuterium excess values contain information on meteorological conditions at distant evaporative sources. 1. Introduction The stable isotopes of water, HDO and H}sO, have been measured in ice cores and other paleowaters in varying concentrations. Through a detailed analysis of current isotope concentration fields, isotope/climate relationships have been derived which allow the extraction of paleoclimatic temperatures from paleowater measurements (see Jouzel et al. [1997] for a recent review). A related isotopic quantity, deuterium excess, is now being used to infer additional paleoclimatic information. Deuterium excess d was defined by Daansgaard [1964] as d = •D-8•sO, where • indicates a permil deviation from the corresponding isotope ratio in standard mean ocean water (SMOW). The factor 8 comes from the meteoric water line, which defines the locus of modern precipitation in a 5D/5•80 plot [Craig, 1961]. Using a simple evaporation model and a Rayleigh-type precipitation model, Merlivat and Jouzel [1979] inferred that the deuterium excess of precipitation primarily depends on the mean relative ... |
---|