Water Isotopes: Tracing Hydro-Meteorological Processes

Stable isotopes (¹⁶O, ¹⁷O, ¹⁸O, ¹H, ²H) and radioactive (³H) isotopes in water within water molecules have become indispensable tools for investigating the atmospheric and terrestrial branches of the hydrological cycle. Measurements of isotopic compositions in precipitation, atmospheric vapor, surface water, groundwater, and snow have provided valuable insights into moisture sources, transport pathways, cloud microphysical processes, and groundwater recharge. These applications span a range of temporal and spatial scales, from synoptic weather systems and convective events to seasonal and interannual variability.

Over the last several decades, isotope hydrology has undergone substantial development through coordinated observational programs and advances in analytical techniques. The Global Network of Isotopes in Precipitation (GNIP) provides invaluable long-term records of precipitation isotopes worldwide. While monthly composite observations have enabled significant progress in understanding regional hydrological processes, many key atmospheric and terrestrial processes operate on much shorter timescales. Cloud microphysics, moisture transport, convective organization, atmospheric moisture residence time, and tropical cyclones evolve on hourly to weekly timescales. Consequently, understanding modern hydrological processes increasingly requires high-resolution observations and process-based approaches for interpretation.

At the same time, anthropogenic warming is fundamentally altering the global water cycle. Atmospheric content of water vapor is projected to increase at a rate close to 7% per degree Celsius of warming, whereas global precipitation is expected to increase at only about 2–3% per degree. This discrepancy highlights one of the major unresolved questions in climate science: how efficiently atmospheric moisture is converted into precipitation. While the thermodynamic controls on evaporation are relatively well understood, the processes governing precipitation formation, moisture recycling, cloud microphysics, and precipitation efficiency remain incompletely constrained. Water isotopes provide a unique observational framework to address these questions because they integrate the cumulative history of evaporation, condensation, transport, rainout, and recycling. Long-term measurements of precipitation and atmospheric vapor isotopes, satellite observations, and isotope-enabled climate models offer unprecedented opportunities to investigate changes in atmospheric moisture processing and the evolving hydrological cycle.

The objective of this Research Topic is therefore to advance the understanding of modern hydro-meteorological processes and to promote the application of water isotopes in contemporary hydrological studies.

In particular, the Research Topic aims to address several overarching scientific questions:
· How do moisture source, transport pathways, cloud microphysics, and precipitation efficiency control precipitation isotope variability across weather to seasonal timescales?
· How are these processes being modified by anthropogenic warming and an intensifying hydrological cycle?
· To what extent can long-term precipitation and atmospheric vapor isotope observations improve our understanding of moisture recycling, atmospheric moisture residence time, and large-scale circulation?
· Groundwater dynamics, recharge processes, and surface water–groundwater interactions constrained by water stable and radioactive isotopes.
· Emerging applications of triple oxygen isotopes and other novel isotope tracers to understand contemporary hydrological processes.

We welcome observational, modeling, theoretical, methodological, and interdisciplinary contributions that advance our understanding of the water cycle through isotopic approaches.

Article types and fees

This Research Topic accepts the following article types, unless otherwise specified in the Research Topic description:

• Brief Research Report
• Community Case Study
• Conceptual Analysis
• Data Report
• Editorial
• FAIR² Data
• General Commentary
• Hypothesis and Theory
• Methods
• ... View all formats

Articles that are accepted for publication by our external editors following rigorous peer review incur a publishing fee charged to Authors, institutions, or funders.

Article types

This Research Topic accepts the following article types, unless otherwise specified in the Research Topic description:

• Brief Research Report
• Community Case Study
• Conceptual Analysis
• Data Report
• Editorial
• FAIR² Data
• General Commentary
• Hypothesis and Theory
• Methods
• Mini Review
• Opinion
• Original Research
• Perspective
• Policy and Practice Reviews
• Policy Brief
• Review
• Systematic Review
• Technology and Code

Keywords: Stable water isotopes, Hydrogen and oxygen isotopes, Isotope hydrology, Hydrological cycle, Precipitation isotopes, Atmospheric water vapor isotopes

Important note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.