Earth and Planetary Sciences ETDs

Publication Date

Summer 7-28-2026

Abstract

Understanding the processes that control water vapor isotopic composition in mountain environ- ments is essential for interpreting isotope records and predicting water resource responses to cli- mate change. This thesis applies information theory to continuous, high-resolution water vapor stable isotope measurements from the Surface Atmosphere Integrated Field Laboratory (SAIL) campaign in the East River watershed of Colorado’s Upper Gunnison Basin, spanning the winter- to-spring transition of 2022–2023. The analysis employs Shannon entropy, mutual information, transfer entropy, and joint transfer en- tropy (JTE) to quantify how environmental variables, including surface meteorology, radiation, tur- bulent fluxes, and ERA5 reanalysis products, transfer information to deuterium excess (d-excess) and δ D. A rolling-window composite JTE framework evaluates variable sub-combinations at each time point and tracks how information transfer evolves. Recovering the known Clausius-Clapeyron and Stefan-Boltzmann relationships validates the methodology. Information transfer to d-excess shifts systematically with meteorological regime. The normalized 17-input composite explains 15–55% of target entropy persistently, dominated by geopotential height and longwave radiation. A focused 3-input combination (wind speed, wind direction, net radiation) explains 5–18% intermittently, delineating three regimes: wind-driven blowing snow sublimation in late December and January (8–12%), a mid-winter period where these surface vari- ables explain less than 5%, and a spring regime where wind direction and net radiation combine synergistically (10–18%). The shift of wind direction from irrelevant in winter to the dominant syn- ergistic contributor in spring is the clearest evidence that the framework detects genuine changes in process dominance. Composite JTE time series analysis provides a model-free diagnostic for isotope hydrology, quan- tifying how the dominant controls on isotopic composition shift through time across any high- resolution environmental record.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Joseph Galewsky

Second Committee Member

Zachary Scharp

Third Committee Member

Peter Fawcett

Language

English

Keywords

Stable Isotope, Information Theory, Complex Systems, Colorado, High Elevation, Hydrology

Document Type

Thesis

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