Quantifying the Stable Water Isotopologue Exchange Between the Snow Surface and Lower Atmosphere by Direct Flux Measurements

Wahl, Sonja; Steen-Larsen, Hans Christian; Reuder, Joachim; Hörhold, Maria

doi:10.1029/2020jd034400

Cited by 38 publications

(38 citation statements)

References 85 publications

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“…However, we show that in a low accumulation site (0.0075 m yr −1 ) today, 3%–24% of snow at the surface could be lost due to sublimation, accompanied by a lowering of the surface snow d‐excess value of 7‰ (from 2‰ to −5‰), which is consistent with the results in Wahl et al. (2021). Sublimation also elevates the δD and δ 18 O values of the remaining ice.…”

Section: Discussionsupporting

confidence: 92%

“…Finally, while the land component of iCESM considers the sublimation of surface snow and ice, sublimation is assumed to be a non-fractionating process (Dütsch et al, 2019). However, we show that in a low accumulation site (0.0075 m yr −1 ) today, 3%-24% of snow at the surface could be lost due to sublimation, accompanied by a lowering of the surface snow d-excess value of 7‰ (from 2‰ to −5‰), which is consistent with the results in Wahl et al (2021). Sublimation also elevates the δD and δ 18 O values of the remaining ice.…”

Section: Implications For Paleoclimate Studies and Climate Modelssupporting

confidence: 89%

“…At the same time, the sublimed vapor has lower δD and δ 18 O values and higher d-excess values compared to the remaining snow, constituting a potentially important secondary source of vapor in Antarctica (Pang et al, 2019). Overall, our modeling results underscore the necessity of including fractionation during sublimation into surface mass-and isotope balance in Antarctica in future versions of the iCESM land model (Dütsch et al, 2019;Wahl et al, 2021). We note that certain forward models for high-elevation mountain ice cores have attempted to parameterize sublimation and take isotopic fractionation into account (Hurley et al, 2016).…”

Section: Implications For Paleoclimate Studies and Climate Modelsmentioning

confidence: 63%

“…However, these parameters, specifically factors that determine the sublimation rate, are still critically under-constrained in situ. We note that there have been attempts to measure the exchange of the stable water isotopes between the atmosphere and the snow surface (Hughes et al, 2021;Wahl et al, 2021). It would be helpful to measure the isotopic composition of vapor in the pore space and of the individual ice grains to directly evaluate the hypothesis presented in this study.…”

Section: Implications For Paleoclimate Studies and Climate Modelsmentioning

confidence: 99%

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Sublimation Origin of Negative Deuterium Excess Observed in Snow and Ice Samples From McMurdo Dry Valleys and Allan Hills Blue Ice Areas, East Antarctica

Yan

Yeung

et al. 2022

JGR Atmospheres

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The oxygen and hydrogen isotopic composition in snow and ice have long been utilized to reconstruct past temperatures of polar regions, under the assumption that post‐depositional processes such as sublimation do not fractionate snow. In low‐accumulation (<0.01 m yr−1) areas near the McMurdo Dry Valleys in Antarctica, surface snow and ice samples have exceptionally low deuterium excess values (d‐excess ≡ δD – 8*δ18O)—sometimes as negative as −5‰—an uncommon phenomenon that is not fully understood. Here we use both an isotope‐enabled general circulation model and an ice physics model and establish that such exceptionally low d‐excess values can only arise from precipitation if the majority of the moisture is sourced from the Southern Ocean (south of 55°S). However, the model results show that moisture sourced from oceans north of 55°S contributes significantly (>50%) to precipitation in Antarctica today. We thus propose that sublimation must have occurred to yield the low d‐excess values in snow observed in and near the Dry Valleys, and that solid‐phase‐diffusion in ice grains is sufficiently fast to allow Rayleigh‐like isotopic fractionation in similar environments. We calculate that under present‐day conditions at the Allan Hills outside the Dry Valleys, 3%–24% of the surface snow is lost due to sublimation. Because the magnitude of sublimation may be nonstationary (i.e., it could vary in time) during past cold periods, we suggest that sublimation‐induced fractionation can alter the relationship between the snow isotopic composition and polar temperatures.

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Section: Discussionsupporting

confidence: 92%

Section: Implications For Paleoclimate Studies and Climate Modelssupporting

confidence: 89%

Section: Implications For Paleoclimate Studies and Climate Modelsmentioning

confidence: 63%

Section: Implications For Paleoclimate Studies and Climate Modelsmentioning

confidence: 99%

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Sublimation Origin of Negative Deuterium Excess Observed in Snow and Ice Samples From McMurdo Dry Valleys and Allan Hills Blue Ice Areas, East Antarctica

Yan

Yeung

et al. 2022

JGR Atmospheres

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“…Our data clearly show that we have isotopic fractionation in this period which is otherwise characterized by sublimation , in opposition to the classically assumed process of uniform sublimation of ice layers on perfectly spherical snow grains in line with (Madsen et al, 2019) and (Wahl et al, 2021). This is likely a result of the porosity of the snow grains, for which it was shown that sublimation would occur with isotopic fractionation (Ebner et al, 2017;Hughes et al, 2021;Touzeau et al, 2018).…”

Section: Phase 1: Sublimationsupporting

confidence: 79%

Water Isotopic Signature of Surface Snow Metamorphism in Antarctica

Casado

Zuhr

Landais

et al. 2022

Preprint

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Water isotope ratios of ice cores are a key source of information on past temperatures. Through fractionation within the hydrological cycle, temperature is imprinted in the water isotopic composition of snowfalls. However, this signal of climatic interest is modified after deposition when snow remains at the surface exposed to the atmosphere. Comparing time series of surface snow isotopic composition at Dome C with satellite observations of surface snow metamorphism, we found that long summer periods without precipitation favor surface snow metamorphism altering the surface snow isotopic&#160; composition. Using excess parameters (combining dD, d17O, and d18O fractions) allow the identification of this alteration caused by sublimation and condensation of surface hoar. The combined measurement of all three isotopic compositions could help identifying ice core sections influenced by snow metamorphism in sites with very low snow accumulation.

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Quantifying the glacial meltwater contribution to mountainous streams using stable water isotopes: What are the opportunities and limitations?

Wanner,

Zischg,

Wanner

2023

Hydrological Processes

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This study aims to determine the opportunities and limitations of using stable water isotopes to quantify the glacial meltwater contribution to mountainous streams. For this purpose, three partially glaciated catchments in the Swiss Alps were selected as the study area. In the three catchments, stable isotope analysis (δ18O and δ2H) was conducted of the streams and the end‐members that contribute to the stream discharge (glacial meltwater, rain, snow). The investigations revealed that the contribution of glacial meltwater to mountainous streams can be quantified using stable water isotopes if three criteria are met: (A) The snow meltwater contribution to mountainous streams must be negligible due to its highly variable stable isotope signature; (B) the groundwater input needs to be either insignificant during this snow‐free period or the groundwater residence time must be short such that groundwater contribution does not delay the end‐member signal arriving in the streams; and (C) the isotope signal of the glacial melt end‐member needs to be distinct from the other end‐members. One of the three investigated catchments fulfilled these criteria in August and September, and the glacial meltwater contribution to the mountainous streams could be estimated based on stable water isotopes. During this time period, the glacial meltwater contribution to the stream discharge corresponded to up to 85% ± 2% and to 28.7% ± 10% of the total annual discharge, respectively. This high glacial meltwater contribution demonstrates that the mountainous stream discharges in August and September will probably strongly decrease in the future due to global warming‐induced deglaciation. Overall, this study demonstrates that many hydrogeological conditions need to be met so that stable water isotopes can be used to quantify the glacial meltwater contribution to mountainous streams. This highlights the challenges when using stable water isotopes for hydrograph separation and serves as a guide for future stable water isotope studies in mountainous regions.

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Quantifying the Stable Water Isotopologue Exchange Between the Snow Surface and Lower Atmosphere by Direct Flux Measurements

Cited by 38 publications

References 85 publications

Sublimation Origin of Negative Deuterium Excess Observed in Snow and Ice Samples From McMurdo Dry Valleys and Allan Hills Blue Ice Areas, East Antarctica

Sublimation Origin of Negative Deuterium Excess Observed in Snow and Ice Samples From McMurdo Dry Valleys and Allan Hills Blue Ice Areas, East Antarctica

Water Isotopic Signature of Surface Snow Metamorphism in Antarctica

Quantifying the glacial meltwater contribution to mountainous streams using stable water isotopes: What are the opportunities and limitations?

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