Sensitivity of the δ18-O-temperature relationship to the distribution of continents

Abstract

Paleoclimate studies commonly interpret the stable water isotope ratio in precipitation as a proxy for temperature based on observed present day spatial and temporal correlations. The temperature-isotope relationship results both from the greater efficiency of isotopic fractionation at low temperatures and from the preferential condensation of the heavy isotopic species during moisture transport, which tend to coincide for the present day climate. The Melbourne University General Circulation Model is used to simulate an alternative scenario where these two effects are opposed, with idealized continents located in such a way that moisture transport occurs from cooler to warmer latitudes. It is found that the positive correlation between isotopic ratio and temperature breaks down for cases with oceans limited to mid- and high latitudes, indicating that the observed present day correlation between isotopic ratio and temperature is not invariant, but depends on the specific distributions of continents and resulting moisture transport. Copyright 2004 by the American Geophysical Union.