Stable isotope compositions of precipitation from Gunnison, Colorado 2007-2016: implications for the climatology of a high-elevation valley

David W Marchetti; Suzanne B Marchetti

doi:10.1016/j.heliyon.2019.e02120

Stable isotope compositions of precipitation from Gunnison, Colorado 2007-2016: implications for the climatology of a high-elevation valley

Heliyon. 2019 Jul 22;5(7):e02120. doi: 10.1016/j.heliyon.2019.e02120. eCollection 2019 Jul.

Authors

David W Marchetti¹, Suzanne B Marchetti²

Affiliations

¹ Geology Program, Western Colorado University, 1 Western Way, Gunnison, CO, 81231, USA.
² Forest Health Management, Rocky Mountain Region, USDA Forest Service, 216 N. Colorado St., Gunnison, CO, 81230, USA.

Abstract

Stable isotope ratios of precipitation are useful tracers of climatic and hydrological processes. To better understand the isotope hydro-climatology of a high-elevation Rocky Mountain valley we collected meteoric water samples from Gunnison, Colorado, USA and determined stable isotope values for 239 individual precipitation events over a nine year period. Annual precipitation in Gunnison is moderately bi-modal with significant winter snowfall and convective summer thunderstorms associated with the North American Monsoon. Stable isotope values of precipitation span a large range, with summer rains as high as δ²H = +19‰ and δ¹⁸O = +4.8‰ (relative to V-SMOW) and winter snowfall as low as δ²H = -286‰ and δ¹⁸O = -36.7‰. These data define a local meteoric water line for Gunnison of δ²H = 7.2 δ¹⁸O - 4.2. Monthly meteoric water lines have slopes similar to the Global Meteoric Water Line (∼8) for winter months and more evaporated slopes (∼6) during the summer. Monthly mean temperature most strongly controls the monthly isotopic composition of precipitation (m = 0.61-0.64 ‰/°C); the slope of the isotope/temperature relationship is steeper in summer than winter.

Keywords: Atmospheric science; Climatology; Earth-surface processes; Environmental chemistry; Geochemistry; Hydrology; North American Monsoon; Precipitation; Rocky Mountains; Stable isotopes.