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Stable water isotopes in HadCM3: isotopic signature of El Nino-Southern Oscillation and the tropical amount effect

By J. C. Tindall, P.J. Valdes and Louise C. Sime

Abstract

Stable water isotopes have been added to the full hydrological cycle of the Hadley Centre Climate model (HadCM3) coupled atmosphere-ocean GCM. Simulations of delta O-18 in precipitation and at the ocean surface compare well with observations for the present-day climate. The model has been used to investigate the isotopic anomalies associated with ENSO; it is found that the anomalous delta O-18 in precipitation is correlated with the anomalous precipitation amount in accordance with the "amount effect.'' The El Nino delta O-18 anomaly at the ocean surface is largest in coastal regions because of the mixing of ocean water and the more depleted runoff from the land surface. Coral delta O-18 anomalies were estimated, using an established empirical relationship, and generally reflect ocean surface delta O-18 anomalies in coastal regions and sea surface temperatures away from the coast. The spatial relationship between tropical precipitation and delta O-18 was investigated for the El Nino anomaly simulated by HadCM3. Weighting the El Nino precipitation anomaly by the precipitation amount at each grid box gave a large increase in the spatial correlation between tropical precipitation and delta O-18. This improvement was most apparent over land points and between 10 and 20 degrees of latitude

Topics: Marine Sciences, Meteorology and Climatology, Glaciology, Hydrology, Atmospheric Sciences
Publisher: American Geophysical Union
Year: 2009
DOI identifier: 10.1029/2008JD010825
OAI identifier: oai:nora.nerc.ac.uk:11323

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