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Abstract. Ice core water isotope records from Greenland and Antarctica are a valuableproxy for paleoclimate reconstruction, yet the processes influencing theclimate signal stored in the isotopic composition of the snow are beingchallenged and revisited. Apart from precipitation input, post-depositionalprocesses such as wind-driven redistribution and vapor–snow exchange processes at and below the surface are hypothesized to contribute to the isotope climate signal subsequently stored in the ice. Recent field studies have shown that surface snow isotopes vary between precipitation events and co-vary with vapor isotopes, which demonstrates that vapor–snow exchange is an important driving mechanism. Here we investigate how vapor–snow exchange processes influence the isotopic composition of the snowpack. Controlled laboratory experiments under forced sublimation show an increase in snow isotopic composition of up to 8 ‰ δ18O in the uppermost layer due to sublimation, with an attenuated signal down to 3 cm snow depth over the course of 4–6 d. This enrichment is accompanied by a decrease in the second-order parameter d-excess, indicating kinetic fractionation processes. Our observations confirm that sublimation alone can lead to a strong enrichment of stable water isotopes in surface snow and subsequent enrichment in the layers below. To compare laboratory experiments with realistic polar conditions, we completed four 2–3 d field experiments at the East Greenland Ice Core Project site (northeast Greenland) in summer 2019. High-resolution temporal sampling of both natural and isolated snow was conducted under clear-sky conditions and demonstrated that the snow isotopic composition changes on hourly timescales. A change of snow isotope content associated with sublimation is currently not implemented in isotope-enabled climate models and is not taken into account when interpreting ice core isotopic records. However, our results demonstrate that post-depositional processes such as sublimation contribute to the climate signal recorded in the water isotopes in surface snow, in both laboratory and field settings. This suggests that the ice core water isotope signal may effectively integrate across multiple parameters, and the ice core climate record should be interpreted as such, particularly in regions of low accumulation.
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This content will become publicly available on March 14, 2026
Atmosphere to Surface Profiles of Water‐Vapor Isotopes and Meteorological Conditions Over the Northeast Greenland Ice Sheet
Abstract On polar ice sheets, water vapor interacts with surface snow, and through the exchange of water molecules, imprints an isotopic climate signal into the ice sheet. This exchange is not well understood due to sparse observations in the atmosphere. There are currently no published vertical profiles of water isotopes above ice sheets that span the planetary boundary layer and portions of the free troposphere. Here, we present a novel data set of water‐vapor isotopes (O, D, ) and meteorological variables taken by fixed‐wing uncrewed aircraft on the northeast Greenland Ice Sheet (GIS). During June–July (2022), we collected 104 profiles of water‐vapor isotopes and meteorological variables up to 1,500 m above ground level. Concurrently, surface snow samples were collected at 12‐hr intervals, allowing connection to surface‐snow processes. We pair observations with modeling output from a regional climate model as well as an atmospheric transport and water‐isotope distillation model. Climate model output of mean temperature and specific humidity agrees well with observations, with a mean difference of +0.095°C and −0.043 g/kg (−2.91%), respectively. We find evidence that along an air parcel pathway, the distillation model is not removing enough water prior to onsite arrival. Below the mean temperature inversion (200 m), water‐isotope observations indicate a kinetic fractionating process, likely the result of mixing sublimated vapor from the ice sheet surface along with an unknown fraction of katabatic wind vapor. Modeled does not agree well with observations, a result that requires substantial future analysis of kinetic fractionation processes along the entire moisture pathway.
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- Award ID(s):
- 2137083
- PAR ID:
- 10580998
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 130
- Issue:
- 6
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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