The cumulative effect of wintertime weather systems on the ocean mixed-layer stable isotope composition in the Iceland and Greenland Seas

Sodemann, Harald, Weng, Yongbiao, Touzeau, Alexandra, Jeansson, Emil, Thurnherr, Iris, Barrell, Chris ORCID: https://orcid.org/0000-0002-0494-9884, Renfrew, Ian A. ORCID: https://orcid.org/0000-0001-9379-8215, Semper, Stefanie, Våge, Kjetil and Werner, Martin (2024) The cumulative effect of wintertime weather systems on the ocean mixed-layer stable isotope composition in the Iceland and Greenland Seas. Journal of Geophysical Research: Atmospheres, 129 (19). ISSN 2169-897X

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Abstract

The Iceland and Greenland Seas are characterized by strong heat fluxes from the ocean to the atmosphere during wintertime. Here we characterize the atmospheric signal of this strong evaporation in terms of water vapor isotopes and investigate if such a signal can have a cumulative imprint on the ocean mixed-layer. Observations include continuous water vapor isotope measurements, event-based precipitation samples, and sea-water samples taken at various depths from the research vessel Alliance during the Iceland-Greenland Seas Project cruise in February and March 2018. In conjunction with a simulation from a regional, isotope-enabled atmospheric model, we find that the predominant atmospheric isotope signature during predominant marine cold-air outbreak conditions is −129.8 ± 16.6‰ for δ2H and −18.10 ± 2.87‰ for δ18O, with a d-excess of 15.1 ± 7.9‰, indicating enhanced non-equilibrium fractionation compared to the global average. During events of warm-air intrusion from mid-latitudes, near-surface vapor becomes saturated and the vapor d-excess approaches equilibrium or becomes negative. Similarly, precipitation d-excess is lower and thus closer to equilibrium conditions during warm-air intrusions. There are indications that an evaporation signal of waters exiting the Nordic Seas through Denmark Strait could be locally enhanced over seasons to years, as supported by simple model calculations. Our findings thus suggest that evaporation signals could be transferred into the ocean isotope composition in this region, potentially enabling mass-balance constraints in isotope-enabled coupled ocean-atmosphere models.

Item Type:	Article
Additional Information:	Data Availability Statement: The data presented in this paper can be obtained as follows: The documented stable isotope data set from the IGP cruise is available at the CEDA archive (url: https://dx.doi.org/10.5285/705abc2d9988444ba79e942f22219bc0, Sodemann & Weng, 2022), as well as radiosonde (url:https://catalogue.ceda.ac.uk/uuid/5acca11ececb4d8283b7e633370b6751/, Brooks, 2019) and surface-layer meteorological measurements (url: https://catalogue.ceda.ac.uk/uuid/b4ba8f11459c422d84d7293b9211ccf7/, Barrell & Renfrew, 2020). Airborne water vapor isotope data are also archived at CEDA (url: https://dx.doi.org/10.5285/7c8ce1c47da548a08146fa62158303c5, Sodemann & Touzeau, 2022). Sea-ice edge and sea surface temperature data are available from the Copernicus climate Change Service (https://doi.org/10.24381/cds.29c46d83, Aaboe et al., 2023; https://doi.org/10.24381/cds.cf608234, C3S, 2019). Historical sea water isotope data have been extracted from the database of Schmidt et al. (1999) (url: https://data.giss.nasa.gov/o18data/). Acknowledgments: This research has been supported by the Norges Forskningsråd (Grants 262710 and 245907). S.S. acknowledges support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement 101022251. E.J. acknowledges support from the Research Council of Norway through the project VENTILATE (229791). FARLAB at University of Bergen is gratefully acknowledged for providing the vapor analyzer during the cruise. The IGP meteorological measurements were made possible by NERC Grant NE/N009754/1. We are grateful to Árný Erla Sveinbjörnsdóttir, Institute of Earth Sciences, University of Iceland, Reykjavik, for providing a vaporizer and calibration standards for the duration of the NRV Alliance cruise. We thank all people onboard the NRV Alliance who enabled the acquisition of the measurement data. Ulysses Ninnemann is acknowledged for helpful comments on an earlier version of this manuscript. The computations were performed on resources provided by Sigma2—the National Infrastructure for High-Performance Computing and Data Storage in Norway. This manuscript has partly been generated using Copernicus Climate Change Service information 2024. We thank three anonymous reviewers for their thorough and thoughtful comments which substantially improved the manuscript.
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User:	LivePure Connector
Date Deposited:	30 Sep 2024 12:30
Last Modified:	16 Nov 2024 20:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/96829
DOI:	10.1029/2024JD041138

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