An Improved Understanding of Water Isotope Fractionation in Atmospheric Vapor and Its Source

San Diego State University Foundation, San Diego CA

Investigators

Abstract

This research project aims to establish a premium water isotope research station with high quality, frequent and uninterrupted atmospheric vapor isotope (2H and 18O) measurements to investigate vapor isotope fractionation and its applications on ecosystem-atmosphere water and CO2 exchange. The research builds upon current understanding of water vapor isotopic fractionation under the influence of vegetation-atmosphere interaction. This project will evaluate a number of critical assumptions in hydrospheric isotope models, identify key fractionation processes, and develop mechanistic algorithms to address caveats that mask the potential of hydrogen and oxygen isotope tracers in hydrological and carbon cycle research. Objectives of the research are to: quantify the extent of below-cloud evaporation during the descent of raindrops and its effects on the vapor isotope variation in forest air; determine how this recycling of water affects atmospheric moisture and precipitation; evaluate plant-based proxy as an integrator of atmospheric vapor in surface air; provide mechanistic algorithms of isotope fractionation that accompanies surface evapotranspiration in hydrospheric isotope models. Products of the research complement synthesis activities for a number of networks, including Biosphere-Atmosphere Stable Isotope Network (BASIN), Moisture Isotopes in the Biosphere and Atmosphere (MIBA), AmeriFlux, and North American Carbon Program (NACP) site interim synthesis. New courses will be added to the curriculum to promote the use of stable isotope ratio measurements in biogeoscience research, in order to ensure a breadth of technological skills in students, encourage undergraduate student participation in laboratory research, and increase public awareness of the eco-hydrological consequences of climate change.