Fractionation Factor of 18O between Water Vapour and Ice

Majoube, M.

doi:10.1038/2261242a0

Cited by 76 publications

(118 citation statements)

References 7 publications

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“…As a reference case we switch between complete (equation (2)) and zero (equation (1)) equilibration at 0øC and then vary the altitude of the switch to gauge the magnitude of this uncertainty (see Table 1). Standard equilibrium fractionation factors are used [Majoube, 1970[Majoube, , 1971 Two temperature profiles are used in the analysis, one a mean sounding from Menado (124 ø E, 1 ø N), and the other a moist adiabat tied to the sounding at 850 hPa. The Menado sounding is a November through February mean.…”

Section: Isotopic Constraints On T-stementioning

confidence: 99%

Stratosphere‐troposphere exchange: Inferences from the isotopic composition of water vapor

Keith¹

2000

J. Geophys. Res.

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Abstract. Air may cross the tropical tropopause either by gradual ascent or in localized episodes associated with convection. While observations demonstrate that water vapor mixing ratios of air entering the tropical stratosphere are consistent with the mean tropical tropopause temperature, they do not resolve key mechanistic questions, such as the relative contribution of gradual or episodic transport, or the role of thin cirrus. As Moyer et al. [ 1996] clearly argue, observations of the isotopic content of water entering the tropical stratosphere can provide a strong constraint on models of water vapor transport across the tropopause. For example, stratospheric HDO is too abundant to be compatible with the assumption that all moisture enters the stratosphere as vapor during convection. Analysis of recent H2180 observations shows that kinetic effects cannot explain the HDO excess. Lofting and evaporation of cloud ice can explain the observed stratospheric water vapor content and its isotopic composition, but the relative importance of gradual or episodic transport remains unresolved.

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Section: Isotopic Constraints On T-stementioning

confidence: 99%

Stratosphere‐troposphere exchange: Inferences from the isotopic composition of water vapor

Keith¹

2000

J. Geophys. Res.

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“…2.7, to the observed data in Fig. 4, with the mean summer isotopic values summarized in Table 3 (Majoube, 1971), ice (Majoube, 1970;Merlivat and Nief, 1967), and ice but with new fractionation coefficients estimated by Ellehoj et al (2013).…”

Section: Comparison Between Measured Surface Snow Isotopic Compositiomentioning

confidence: 99%

“…2.2) (integrated 12 h back) to estimate the expected isotopic composition of the snow surface at equilibrium with the water vapor. The calculation is performed (i) using the fractionation coefficients for liquid water extrapolated below 0 • C (Majoube, 1971), then (ii) using the fractionation coefficients for ice (Majoube, 1970) (Merlivat and Nief, 1967) and (iii) new fractionation coefficients for ice determined by Ellehoj et al (2013). We justify the calculations assuming liquid water by the fact that the summer temperatures at NEEM are close to 0 • C (Fig.…”

Section: Calculation Of Equilibrium Between Surface Snow and Water Vamentioning

confidence: 99%

What controls the isotopic composition of Greenland surface snow?

et al. 2014

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Abstract. Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically enabled atmospheric models. However, postdepositional processes linked with snow metamorphism remain poorly documented. For this purpose, monitoring of the isotopic composition (δ 18 O, δD) of near-surface water vapor, precipitation and samples of the top (0.5 cm) snow surface has been conducted during two summers (2011)(2012) at NEEM, NW Greenland. The samples also include a subset of 17 O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between near-surface vapor δ 18 O and air temperature (0.85 ± 0.11 ‰ • C −1 (R = 0.76) for 2012). The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess) is strongly anti-correlated with δ 18 O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1-5-day periods between precipitation events, our data demonstrate parallel changes of δ 18 O and d-excess in surface snow and near-surface vapor. The changes in δ 18 O of the vapor are similar or larger than those of the snow δ 18 O. It is estimated using the CROCUS snow model that 6 to 20 % of the surface snow mass is exchanged with the atmosphere. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or deposition. Comparisons with atmospheric models show that day-to-day variations in near-surface vapor isotopic composition are driven by synoptic variations and changes in air mass trajectories and distillation histories. We suggest that, in between precipitation events, changes in the surface snow isotopic composition are driven by these changes in near-surface vapor isotopic composition. This is consistent with an estimated 60 % mass turnover of surface snow per day driven by snow recrystallization processes under NEEM summer surface snow temperature gradients. Our findings have implications for ice core data interpretation and model-data comparisons, and call for further process studies.

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“…α l is the liquid/vapor equilibrium fractionation coefficient (Majoube, 1971), α k is the kinetic fractionation coefficient, h is the relative humidity, 1−f evappond is the fraction of pond water that remains after evaporation, and R l0 is the initial liquid isotope ratio. The kinetic fraction is calculated as…”

Section: Mass Balance For Surface Water and Fluxesmentioning

confidence: 99%

Determining water sources in the boundary layer from tall tower profiles of water vapor and surface water isotope ratios after a snowstorm in Colorado

et al. 2013

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The D/H isotope ratio is used to attribute boundary layer humidity changes to the set of contributing fluxes for a case following a snowstorm in which a snow pack of about 10 cm vanished. Profiles of H2O and CO2 mixing ratio, D/H isotope ratio, and several thermodynamic properties were measured from the surface to 300 m every 15 min during four winter days near Boulder, Colorado. Coeval analysis of the D/H ratios and CO2 concentrations find these two variables to be complementary with the former being sensitive to daytime surface fluxes and the latter particularly indicative of nocturnal surface sources. Together they capture evidence for strong vertical mixing during the day, weaker mixing by turbulent bursts and low level jets within the nocturnal stable boundary layer during the night, and frost formation in the morning. The profiles are generally not well described with a gradient mixing line analysis because D/H ratios of the end members (i.e., surface fluxes and the free troposphere) evolve throughout the day which leads to large uncertainties in the estimate of the D/H ratio of surface water flux. A mass balance model is constructed for the snow pack, and constrained with observations to provide an optimal estimate of the partitioning of the surface water flux into contributions from sublimation, evaporation of melt water in the snow and evaporation from ponds. Results show that while vapor measurements are important in constraining surface fluxes, measurements of the source reservoirs (soil water, snow pack and standing liquid) offer stronger constraint on the surface water balance. Measurements of surface water are therefore essential in developing observational programs that seek to use isotopic data for flux attribution

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Fractionation Factor of 18O between Water Vapour and Ice

Cited by 76 publications

References 7 publications

Stratosphere‐troposphere exchange: Inferences from the isotopic composition of water vapor

Stratosphere‐troposphere exchange: Inferences from the isotopic composition of water vapor

What controls the isotopic composition of Greenland surface snow?

Determining water sources in the boundary layer from tall tower profiles of water vapor and surface water isotope ratios after a snowstorm in Colorado

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