OXYGEN AND HYDROGEN ISOTOPES IN THE HYDROLOGIC CYCLE

TLDR

Isotopic composition of water shifts through the hydrologic cycle, with evaporation and precipitation fractionating H and O isotopes so that meteoric waters are depleted and evaporative systems enriched, while aquifer transport is largely conservative except at elevated temperatures. These isotopic variations in atmospheric, surface, soil, and groundwater, as well as in the biosphere, are applied to characterize hydrological systems and to serve as paleo‑climatic indicators in proxy archives such as ice, lake sediments, and organic materials.

Abstract

▪ Abstract Changes of the isotopic composition of water within the water cycle provide a recognizable signature, relating such water to the different phases of the cycle. The isotope fractionations that accompany the evaporation from the ocean and other surface waters and the reverse process of rain formation account for the most notable changes. As a result, meteoric waters are depleted in the heavy isotopic species of H and O relative to ocean waters, whereas waters in evaporative systems such as lakes, plants, and soilwaters are relatively enriched. During the passage through the aquifers, the isotope composition of water is essentially a conservative property at ambient temperatures, but at elevated temperatures, interaction with the rock matrix may perturb the isotope composition. These changes of the isotope composition in atmospheric waters, surface water, soil, and groundwaters, as well as in the biosphere, are applied in the characterization of hydrological system as well as indicators of paleo-climatological conditions in proxy materials in climatic archives, such as ice, lake sediments, or organic materials.