Stable oxygen and hydrogen isotopes in precipitation

Abstract

The fact that water on earth moves in a cycle, from oceans to clouds to rivers to oceans, has been known since ancient civilizations existed on different parts of the globe. However, the quantification of fluxes between various parts of the cycle, particularly the atmospheric and surface parts, has been difficult to achieve even today. Understanding of climatic processes controlling these fluxes and, therefore, the ability to predict variability and changes in the hydrologic cycle, also depends upon the quantification of moisture fluxes between atmospheric and surface reservoirs. Soon after the discovery of the heavy isotopes of oxygen and hydrogen in the 1920s and early 1930s, significant differences were observed in the isotopic contents of seawater, freshwater, and snow (Gilfillan, 1934; and review by Rankama, 1954). By the early 1950s, as a result of the availability of better measurement techniques, the dependence of isotope content of rain on a variety of climatic factors such as surface air temperature, amount of rain, and the altitude and latitude of precipitation, were also observed (Friedman, 1953; Dansgaard, 1953; Epstein, 1956). Together with the known temperature dependence of isotope ratios (Urey, 1947), the observed relationship between isotopes and climate also provided a means to study past climates by using isotope distributions in continental and marine archives (Emiliani, 1955). The foundations for the use of isotopes to help quantify fluxes in the hydrologic cycle were firmly established by the 1950s, albeit with a limited scope and limited records of measurements (Craig, 1961; Dansgaard, 1964). Atmospheric nuclear testing of the 1950s and consequent requirements to monitor the tritium fallout resulted in an exponential increase in the number and geographic distribution of stable isotope measurements in the hydrologic cycle (Dansgaard, 1964; Ericsson, 1965; Froehlich et al., this volume). In this summary review, we discuss the developments in stable oxygen and hydrogen isotope measurement techniques, the nomenclature of isotope measurements, the structure of the IAEA/WMO global network of isotopes in precipitation (GNIP), and an analysis of GNIP data from 1961 to 2000. © 2005 IEA.