An entropy-based analysis method of precipitation isotopes revealing main moisture transport corridors globally

Abstract

Abstract The hydrogen (δD) and oxygen (δ18O) isotopic compositions in the water molecule have been widely used as tracers for studying the global water cycle. In 1961, the Global Network of Isotopes in Precipitation (GNIP) was established to measure D and 18O isotopes contents in precipitation around the world. However, on the spatial scale, the long-term arithmetic and/or long-term precipitation weighted mean δD and δ18O have been most commonly used to interpret the GNIP isotope data for over sixty years. The spatial distributions of mean δD and δ18O depict well the regional moisture transport, but they vary predominantly with latitude on the global scale, especially over continental areas, obscuring the continental and circulation effects. We developed a new method of using the entropy concept to reanalyze precipitation isotopic compositions data from GNIP. Calculated entropies of isotopic compositions in precipitation at GNIP stations around the world strongly correlate in a linear fashion with a slope coefficient close to unity. The spatial distributions of both isotopic compositions entropies generally reveal oceanic sources of water vapor and main moisture transport pathways from oceans to continents globally, with different patterns between summer and winter seasons. Although these results have mostly been reported in previous studies, they provide the verification of this new analysis method. The entropy method proposed here is expected to provide a new tool for data interpretation of water isotopic compositions, with implications for tracing global hydrological processes.