An Experimental Investigation of Kinetic Fractionation of Open‐Water Evaporation Over a Large Lake. Issue 21 (11th November 2017)

• Record Type: Journal Article
• Authors: Xiao, Wei; Lee, Xuhui; Hu, Yongbo; Liu, Shoudong; Wang, Wei; Wen, Xuefa; Werner, Martin; Xie, Chengyu
• Is Part Of: Journal of geophysical research. Volume 122:Issue 21(2017)
• Page Start: 11, 651
• Page End: 11, 663
• Publication Date: 2017-11-11
• Subjects: water vapor isotope -- kinetic effect -- lake evaporation -- Craig‐Gordon model; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2017JD026774
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: The oxygen isotopes of water (H2 18 O and H2 16 O) are tracers widely used for the investigation of Earth science problems. The tracer applications are based on the premise that the 18 O/ 16 O ratio of open‐water evaporation ( δ 18 OE ) can be calculated from environmental conditions. A long‐standing issue concerns the role of kinetic fractionation, or diffusion transport, in the evaporation process. Here we deployed an optical instrument at a large lake (area 2, 400 km 2 ) to make in situ measurement of δ 18 O and δ D of atmospheric vapor, then determined δ 18 O and δ D of open‐water evaporation using the gradient‐diffusion method. Our results show a much weaker kinetic effect than suggested by the kinetic factor ε k adopted in some previous studies of lake hydrology (14.2‰). By incorporating into the H2 18 O isotopic mass balance of the lake a lower ε k value (about 6.2‰) used for ocean evaporation in global climate models, we obtain an annual lake evaporation rate that agrees with an independent eddy‐covariance observation, but the rate is 72% higher than if the commonly used lake ε k value of 14.2‰ is applied. The applicability of this results to small lakes is uncertain and in need of field‐based assessment. Key Points: δ 18 OE of open‐water evaporation was determined with the gradient‐diffusion method at hourly intervals Results indicate a weak kinetic fractionation against 18 O in open‐water evaporation The often‐used kinetic parameter for lakes causes underestimation of the lake annual evaporation from the isotope mass balance method