Continuous monitoring of summer surface water vapor isotopic composition above the Greenland Ice Sheet

Steen‐Larsen, Hans Christian; Johnsen, S. J.; Masson‐Delmotte, Valérie; Stenni, Barbara; Risi, Camille; Sodemann, Harald; Balslev-Clausen, David; Blunier, Thomas; Dahl-Jensen, Dorthe; Ellehoj, M. D.; Falourd, S.; Grindsted, Aslak; Gkinis, Vasileios; Jouzel, Jean; Popp, Trevor; Sheldon, Simon G.; Simonsen, Sebastian B.; Sjolte, Jesper; Steffensen, Jørgen Peder; Sperlich, Peter; Sveinbjörnsdóttir, Árný E.; Vinther, Bo M.; White, James W. C.

doi:10.5194/acp-13-4815-2013

Cited by 183 publications

(259 citation statements)

References 49 publications

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“…We therefore do not expect the snow surface to take up a significant isotopic signal from the surface hoar formed during the night. We do notice that, during clear-sky days, the diurnal cycle of sublimation/condensation is reflected in the water vapor diurnal cycles of both δ 18 O v and d-excess v as also observed by Steen-Larsen et al (2013).…”

Section: Possible Causes For Change In Snow Surface and Water Vapor Imentioning

confidence: 82%

“…We do not expect that the data gaps due to drift calibrations produce any significant effect on the analysis. When the vertical gradients of water stable isotopes were investigated in Steen-Larsen et al (2013), it was shown that they only depict diurnal gradients, and that water vapor isotopes covary at the day-to-day scale at different heights. This was also verified for our new measurements (not shown), and here we will only describe and discuss the measurements obtained at 3 m height ( Table 1).…”

Section: Crds-analyzer Measurementsmentioning

confidence: 99%

“…The flow speed of the tube being sampled was ∼ 5 L min −1 , while the flow speed through each of the tubes not being sampled was ∼ 2 L min −1 . To correct for the humidity dependence on the measured isotope signal, a humidity-isotope response curve was calibrated in the beginning of each measurement campaign according to the description in Steen-Larsen et al (2013). The isotopic measurements were converted to the VSMOW-SLAP scale by measuring standards of known isotopic composition.…”

Section: Crds-analyzer Measurementsmentioning

confidence: 99%

“…Inside this tent we installed a temperatureregulated box able to control the temperature to within 0.2 • C. A commercial laser-based spectrometer from Picarro Inc. (product number L1102-i) was installed inside this box. The detailed sampling and post-calibration procedure is given in Steen-Larsen et al (2013). The inlet tubes were placed in insulation material and heated to above 50 • C. Bottles with holes in the bottom were placed at the beginning of the inlet to prevent snow from getting inside the tubes.…”

Section: Crds-analyzer Measurementsmentioning

confidence: 99%

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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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Section: Possible Causes For Change In Snow Surface and Water Vapor Imentioning

confidence: 82%

Section: Crds-analyzer Measurementsmentioning

confidence: 99%

Section: Crds-analyzer Measurementsmentioning

confidence: 99%

Section: Crds-analyzer Measurementsmentioning

confidence: 99%

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What controls the isotopic composition of Greenland surface snow?

et al. 2014

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“…Whereas cryogenic trapping provides grab samples generally averaging a couple of hours, laser spectrometry performs continuous high frequency (up to ∼ 1 Hz) measurements of δ v (Kerstel and Gianfrani, 2008). This technology offers new insights into processes that affect the isotopic composition of atmospheric water vapour and the number of studies based on continuous ground level isotope measurements over multiweek periods is continuously increasing, either using a tunable diode laser (TDL) (Lee et al, 2006;Wen et al, 2010Wen et al, , 2012Griffis et al, 2011;Welp et al, 2012), off-axis integrated cavity output spectroscopy (OA-ICOS) (Sturm and Knohl, 2010;Sunmonu et al, 2012;Farlin et al, 2013;SteenLarsen et al, 2013) or wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) Tremoy et al, 2012;Steen-Larsen et al, 2013. Among these experiments are some low latitude studies which have focused on the tracing of tropical or subtropical convective activity in West Africa (Tremoy et al, 2012) or in South America .…”

Section: Introductionmentioning

confidence: 99%

Deuterium excess in the atmospheric water vapour of a Mediterranean coastal wetland: regional vs. local signatures

2015

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Abstract. Stable isotopes of water vapour represent a powerful tool for tracing atmospheric vapour origin and mixing processes. Laser spectrometry recently allowed high timeresolution measurements, but despite an increasing number of experimental studies, there is still a need for a better understanding of the isotopic signal variability at different time scales. We present results of in situ measurements of δ 18 O and δD during 36 consecutive days in summer 2011 in atmospheric vapour of a Mediterranean coastal wetland exposed to high evaporation (Camargue, Rhône River delta, France). The mean composition of atmospheric vapour (δ v ) is δ 18 O = −14.66 ‰ and δD = −95.4 ‰, with data plotting clearly above the local meteoric water line on a δ 18 O-δD plot, and an average deuterium excess (d) of 21.9 ‰. Important diurnal d variations are observed, and an hourly time scale analysis is necessary to interpret the main processes involved in its variability. After having classified the data according to air mass back trajectories, we analyse the average daily cycles relating to the two main meteorological situations, i.e. air masses originating from North Atlantic Ocean and Mediterranean Sea. In both situations, we show that diurnal fluctuations are driven by (1) the influence of local evaporation, culminating during daytime, and leading to an increase in absolute water vapour concentration associated to a δ v enrichment and d increase; (2) vertical air mass redistribution when the Planetary Boundary Layer collapses in the evening, leading to a d decrease, and (3) dew formation during the night, producing a δ v depletion with d remaining stable. Using a twocomponent mixing model, we calculate the average composition of the locally evaporated vapour (δ E ). We find higher d (E) under North Atlantic air mass conditions, which is consistent with lower humidity conditions. We also suggest that δ v measured when the PBL collapses is the most representative of a regional signal. Strong, cold and dry winds coming from the north bring an isotopically depleted vapour, while light, warm and wet winds coming from the south bring an isotopically enriched vapour. Under northern conditions, a strong advection rate dilutes the contribution of the locally evaporated vapour (δ E ) to the ambient moisture (δ v ). The higher d values measured under northern conditions, compared to the Mediterranean situation, thus results from the combination of a higher d in both local and regional vapour. This depiction of typical daily cycles of water vapour isotopic composition can be used as a framework for further quantitative analyses of vapour sources during specific days.

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Deuterium excess in marine water vapor: Dependency on relative humidity and surface wind speed during evaporation

et al. 2014

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We provide the first continuous measurements of isotopic composition (δD and δ 18 O) of water vapor over the subtropical Eastern North Atlantic Ocean from mid-August to mid-September 2012. The ship was located mostly around 26°N, 35°W where evaporation exceeded by far precipitation and water vapor at 20 m largely originated from surface evaporation. The only large deviations from that occurred during a 2 day period in the vicinity of a weak low-pressure system. The continuous measurements were used to investigate deuterium excess (d-excess) relation to evaporation. During 25 days d-excess was negatively correlated with relative humidity (r 2 = 0.89). Moreover, d-excess estimated in an evaporative model with a closure assumption reproduced most of the observed variability. From these observations, the d-excess parameter seems to be a good indicator of evaporative conditions. We also conclude that in this region, d-excess into the marine boundary layer is less affected by mixing with the free troposphere than the isotopic composition. From our data, the transition from smooth to rough regime at the ocean surface is associated with a d-excess decrease of 5‰, which suggests the importance of the ocean surface roughness in controlling d-excess in this region.

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Continuous monitoring of summer surface water vapor isotopic composition above the Greenland Ice Sheet

Cited by 183 publications

References 49 publications

What controls the isotopic composition of Greenland surface snow?

What controls the isotopic composition of Greenland surface snow?

Deuterium excess in the atmospheric water vapour of a Mediterranean coastal wetland: regional vs. local signatures

Deuterium excess in marine water vapor: Dependency on relative humidity and surface wind speed during evaporation

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