Precipitation stable isotopes can be used to trace the water cycle and to interpret paleoclimate archives. Forecasts of natural and future anthropogenic impacts on climate affecting fresh water require a better understanding of the factors controlling regionalized precipitation regimes. This is especially important in tropical areas, where the complexities of atmospheric circulation and the water cycle’s seasonal intensity limit our capacity to predict changes in precipitation patterns and water availability. This CRP focuses on present-day isotope information in modern precipitation and its use for the interpretation and validation of climate and hydrological models, and paleoclimatic archives in tropical regions. Laser spectroscopic technology will facilitate low-cost stable isotope data collection at daily or event-based resolutions, which will be compared to isotope data obtained from various paleoclimate archives in the tropics, to better inform predictive regional and global climate impact models.
To improve capability and expertise among Member States in the use of environmental isotopes to better assess impacts of climate change on water resources variability, availability and sustainability.
Improve interpretation of past climate archives such as speleothems, lake sediments, ice cores, tree rings, etc. using environmental isotopes in order to better understand regional to local climate dynamics and their possible impact on water resources at present and in the future
Improve regional climate and water balance model outputs by using present-day precipitation/vapour isotope data
Initiate/consolidate daily and/or event-based monitoring programmes of precipitation stable isotopes; strengthen laser-based isotope analyses in Member States
Review/assess the level of understanding of the links between stable isotopes of precipitation and the various factors (effects) that control them in tropical regions at different spatial and temporal scales
The CRP successfully addressed and filled a major gaps related to the proper characterization of isotopic composition of precipitation in the tropics required for the use of stable isotopes in various scientific disciplines and many other practical and scientific applications. The fourteen participating teams established or reactivated an unprecedented number of rain monitoring sites (75) across the tropical regions, involving regular sampling at various temporal scales (daily, weekly and monthly). The unique isotope database generated in the framework of this CRP is required to better understand the atmospheric circulation and meteorological processes responsible of the observed isotope variability in precipitation and for the implementation of isotope hydrology project in several TC projects. This CRP provided a major contribution to the IAEA/WMO GNIP programme.
The generation of baseline isotope data of precipitation in the tropics has improved the isotope coverage of the GNIP database and provided a large data set to reassess the factors controlling isotope variability in areas where the temperature variations through the year are minimal. Many environmental applications besides isotope hydrology, such as atmospheric sciences, atmospheric circulation modeling, paleoclimatic reconstructions, ecology or food authentication will eventually benefit from the new isotope data generated.