Atmosphere‐Snow Exchange Explains Surface Snow Isotope Variability

• Published in: Geophysical research letters 2022-10, Vol.49 (20), p.e2022GL099529-n/a
• Main Authors: Wahl, S., Steen‐Larsen, H. C., Hughes, A. G., Dietrich, L. J., Zuhr, A., Behrens, M., Faber, A.‐K., Hörhold, M.
• Format: Article
• Language: English
• Subjects: Abrupt/Rapid Climate Change; Air/Sea Constituent Fluxes; Air/Sea Interactions; Atmosphere; Atmospheric; Atmospheric Composition and Structure; Atmospheric Effects; Atmospheric Processes; Avalanches; Benefit‐cost Analysis; Biogeosciences; Chemical composition; Climate; Climate and Interannual Variability; Climate Change and Variability; Climate Dynamics; Climate Impact; Climate Impacts; Climate Variability; Climatology; Composition; Computational Geophysics; Cores; Cryosphere; Cryospheric Change; Decadal Ocean Variability; Disaster Risk Analysis and Assessment; Earth System Modeling; Earthquake Ground Motions and Engineering Seismology; Effusive Volcanism; EGRIP; Exchanging; Explosive Volcanism; General Circulation; Geochemistry; Geodesy and Gravity; Geological; Glaciation; Glaciology; Global Change; Global Change from Geodesy; Gravity and Isostasy; Greenland Ice Sheet; Humidity; Hydrological Cycles and Budgets; Hydrology; Ice; Ice cores; Ice Sheets; Impacts of Global Change; Informatics; Isotope composition; Isotopes; Isotopic Composition and Chemistry; Land/Atmosphere Interactions; Marine Geology and Geophysics; Mass Balance; Modeling; Mud Volcanism; Natural Hazards; Numerical Modeling; Numerical Solutions; Ocean influence of Earth rotation; Ocean Monitoring with Geodetic Techniques; Ocean/Atmosphere Interactions; Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions; Oceanic; Oceanography: Biological and Chemical; Oceanography: General; Oceanography: Physical; Oceans; Paleoceanography; Paleoclimate; paleoclimate reconstruction; Paleoclimatology; Paleoclimatology and Paleoceanography; Physical Modeling; Policy Sciences; Precipitation; Radio Oceanography; Radio Science; Records; Regional Climate Change; Regional Modeling; Research Letter; Risk; Sea Level Change; Sea Level: Variations and Mean; Seismology; Signal processing; Snow; Snow and Ice; snow‐atmosphere exchange; Solid Earth; Stable Isotope Geochemistry; Stable Isotopes; stable water isotopes; Summer; Surface Waves and Tides; Theoretical Modeling; Tsunamis and Storm Surges; Vapors; Variability; Volcanic Effects; Volcanic Hazards and Risks; Volcano Monitoring; Volcano Seismology; Volcano/Climate Interactions; Volcanology; Water Cycles
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL099529

The climate signal imprinted in the snow isotopic composition allows to infer past climate variability from ice core stable water isotope records. The concurrent evolution of vapor and surface snow isotopic composition between precipitation events indicates that post‐depositional atmosphere‐snow humidity exchange influences the snow and hence the ice core isotope signal. To date, however, this is not accounted for in paeleoclimate reconstructions from isotope records. Here we show that vapor‐snow exchange explains 36% of the summertime day‐to‐day δ18O variability of the surface snow between precipitation events, and 53% of the δD variability. Through observations from the Greenland Ice Sheet and accompanying modeling we demonstrate that vapor‐snow exchange introduces a warm bias on the summertime snow isotope value relevant for ice core records. In case of long‐term variability in atmosphere‐snow exchange the relevance for the ice core signal is also variable and thus paleoclimate reconstructions from isotope records should be revisited. Plain Language Summary Ice core water isotope records are valuable climate proxies containing information about past climate. Climate reconstructions from ice cores have been based on the interpretation of the water isotope records as precipitation signal. Here we show that the humidity exchange between atmosphere and snow influences the surface snow isotopic composition in‐between precipitation events in summer. Thus, it is not the precipitation signal alone that defines the summer snow isotope signal but a combination of precipitation and post‐depositional atmospheric vapor‐snow exchange. This suggests, that climate reconstructions from ice core isotope records should account for post‐depositional processes in the interpretation of the water isotope signal, specifically when interpreting summer isotope signals. Key Points Atmosphere‐snow exchange of water vapor is a key process for the signal formation of the snow isotopic composition Taking into account isotopic fractionation during sublimation we explain a significant share of the observed day‐to‐day isotope variability Atmosphere‐snow exchange introduces a warm‐bias in the net summer snow isotope signal that is not accounted for in ice core interpretations