High-precision isotope measurements of H<sub>2</sub><sup>16</sup>O, H<sub>2</sub><sup>17</sup>O, H<sub>2</sub><sup>18</sup>O, and the Δ <sup>17</sup>O-anomaly of water vapor in the southern lowermost stratosphere

Abstract

Abstract. We report the first high-precision measurements of δ 18O and Δ 17O at high southern latitudes that can resolve changes in the isotopic composition of water vapor in the lowermost stratosphere and upper troposphere. A strong increase of δ 18O with decreasing mixing ratio above the tropopause is evident in the data. Since also the water vapor mixing ratio decreases above the tropopause, the effect seen in the isotope data can be explained by mixing of moist air from the tropopause with dry stratospheric air. However, the source of this dry stratospheric air is not known; both fast transport from the extratropical tropopause or mixing with air from the dehydrated polar vortex are likely. The magnitude of the Δ 17O-anomaly (departure from mass-dependent fractionation (MDF)) was below 2 per mil for each datapoint, and a zero anomaly in lower level stratospheric water vapor is possible. Various transport histories for the stratospheric data are discussed based on the mixing ratio and isotope data.

Deglaciation records of <sup>17</sup>O-excess in East Antarctica: reliable reconstruction of oceanic normalized relative humidity from coastal sites

“…Furthermore, Vostok may be affected by local 17 Oexcess inputs such as clear sky precipitation (diamond dust) or stratospheric water vapour inputs Miller, 2008;Zahn et al, 1998). From the available results of Franz and Röckmann (2005) reporting a 17 O-anomaly of 0 ± 1800 ppm in lowermost stratospheric water vapour over Antarctica, stratospheric influence on tropospheric precipitation has been considered negligible (Landais et al, 2008b). Still, due to the large uncertainty of this result, the 17 Oanomaly of water vapour from the stratosphere may be greater than zero and therefore may influence 17 Oexcess of precipitation at Vostok significantly.…”

Global distributions of water vapour isotopologues retrieved from IMG/ADEOS data

“…The study of atmospheric water vapour has further gained interest since the discovery of the increasing humidity over the last half century (Rosenlof et al, 2001;2003), the causes of which are not yet fully understood (Kuang et al, 2003;McCarthy et al, 2004;Franz and Rockmann, 2005;Schmidt et al, 2005;Coffey et al, 2006). In the stratosphere, the amount of water vapour has a direct impact on the concentration of the OH radical, which is involved in catalytic cycles of ozone destruction, chlorine activation, denitrification and methane decomposition (Forster and Shine, 2002;Kirk-Davidoff et al, 1999;Tabazadeh et al, 2000;Shindell, 2001;McCarthy et al, 2004).…”

A water isotope (2H, 17O, and 18O) spectrometer based on optical feedback cavity-enhanced absorption for in situ airborne applications

“…It measures all three water isotope ratios of interest, 2 [24,25]. In comparison to the Alias spectrometer built by Webster and colleagues [23], our design differs in several respects: Iris uses a near-infrared laser, avoiding the need for cryogens, and it uses a variation of the cavity ring-down spectroscopy (CRDS) technique to achieve a substantially longer effective optical absorption path length (∼ 6 km versus 80 m).…”

“…Analytical errors are reported as ∼ 50 ‰ for all isotopes, and larger at low water concentration (< 10 ppmv). Franz and Röckmann [24] used a small-volume whole-air sampler in combination with a modified small-sample isotope ratio mass spectrometry (IRMS) analysis procedure [25] to obtain a precision of ∼ 2 ‰ for the oxygen isotope ratio measurements. However, due to a strong correlation between the individual measurements, the 17 O anomaly, defined as 18 O, could be determined with a precision of 0.3 to 2 ‰, depending on the sample size.…”