Isotope effects in the evaporation of water: a status report of the Craig–Gordon model

Abstract

The Craig-Gordon model (C-G model) [H. Craig, L.I. Gordon. Deuterium and oxygen 18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperatures, E. Tongiorgi (Ed.), pp. 9-130, Laboratorio di Geologia Nucleare, Pisa (1965).] has been synonymous with the isotope effects associated with the evaporation of water from surface waters, soils, and vegetations, which in turn constitutes a critical component of the global water cycle. On the occasion of the four decades of its successful applications to isotope geochemistry and hydrology, an attempt is made to: (a) examine its physical background within the framework of modern evaporation models, (b) evaluate our current knowledge of the environmental parameters of the C-G model, and (c) comment on a general strategy for the use of these parameters in field applications. Despite its simplistic representation of evaporation processes at the water-air interface, the C-G model appears to be adequate to provide the isotopic composition of the evaporation flux. This is largely due to its nature for representing isotopic compositions (a ratio of two fluxes of different isotopic water molecules) under the same environmental conditions. Among many environmental parameters that are included in the C-G model, accurate description and calculations are still problematic of the kinetic isotope effects that occur in a diffusion-dominated thin layer of air next to the water-air interface. In field applications, it is of importance to accurately evaluate several environmental parameters, particularly the relative humidity and isotopic compositions of the 'free-atmosphere', for a system under investigation over a given time-scale of interest (e.g., hourly to daily to seasonally). With a growing interest in the studies of water cycles of different spatial and temporal scales, including paleoclimate and water resource studies, the importance and utility of the C-G model is also likely to grow in the future.

Experimental observation of transient <i>δ</i><sup>18</sup>O interaction between snow and advective airflow under various temperature gradient conditions

“…The results also support the statement that an interplay occurs between theoretically expected layer-by-layer sublimation and deposition at the icematrix surface and the isotopic content evolution of snow cover due to mass exchange between the snow cover and the atmosphere (Sokratov and Golubev, 2009). The specific surface area of snow exposed to mass exchange (Horita et al, 2008) and by the depth of the snow layer exposed to the mass exchange with the atmosphere (He and Smith, 1999) plays an important role. Our results support the interpretation that changes in surface snow isotopic composition are expected to be significant if large day-to-day surface changes in water vapour occur in between precipitation events, wind pumping is efficient and snow metamorphism is enhanced by temperature gradients in the upper first centimetres of the snow (Steen-Larsen et al, 2014a).…”

Understanding the Role of Groundwater in a Remote Transboundary Lake (Hulun Lake, China)

“…The calculation of evaporative loss based on stable isotopes in residual water was initially founded on the Craig-Gordon model [29], which described the change in stable isotope composition of residual water and vapour during the evaporation process. The Craig-Gordon model has been reformulated to express these changes as a ratio of evaporation (E) to inflow (I) [30][31][32][33]. In this reformulated case, the ratio of evaporation to inflow in a lake is:…”

Vapor hydrogen and oxygen isotopes reflect water of combustion in the urban atmosphere

“…30 km from sampling location) may be a more significant source given that lake water temperatures are warmer than those of the atmosphere throughout the winter, and this vapor is also expected to have a distinctive isotopic composition due to the high degree of evapoconcentration characterizing the lake water. We use observed GSL water isotope ratios (33) and a model for isotope fractionation during evaporation (32), modified to account for the high lake water salinity (24,34), to estimate the range of δ 2 H and δ 18 O values expected for lakederived vapor (see SI Materials and Methods). Although the estimates include d values < 10‰, the distribution of δ 2 H and δ 18 O values for this source cannot account for the observed boundary layer vapor values through mixing with background atmospheric vapor (Fig.…”