Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea

Williams, Charlotte A. J., Hull, Tom ORCID:, Kaiser, Jan ORCID:, Mahaffey, Claire, Greenwood, Naomi, Toberman, Matthew and Palmer, Matthew R. (2024) Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea. Biogeosciences, 21 (7). pp. 1961-1971. ISSN 1726-4189

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There is an immediate need to better understand and monitor shelf sea dissolved oxygen (O2) concentrations. Here we use high-resolution glider observations of turbulence and O2 concentrations to directly estimate the vertical O2 flux into the bottom mixed layer (BML) immediately before the autumn breakdown of stratification in a seasonally stratified shelf sea. We present a novel method to resolve the oxycline across sharp gradients due to slow optode response time and optode positioning in a flow “shadow zone” on Slocum gliders. The vertical O2 flux to the low-O2 BML was found to be between 2.5 to 6.4 mmol m−2 d−1. Episodic intense mixing events were responsible for the majority (up to 90 %) of this oxygen supply despite making up 40 % of the observations. Without these intense mixing events, BML O2 concentrations would approach ecologically concerning levels by the end of the stratified period. Understanding the driving forces behind episodic mixing and how these may change under future climate scenarios and renewable energy infrastructure is key for monitoring shelf sea health.

Item Type: Article
Additional Information: Data availability: All data are publicly available via Zenodo (FAIR compliant) from the BODC glider data archive under AlterEco 5 Kelvin (, Williams, 2024) and under the NERC Open Government License. Financial support: The glider work was funded by the UK National Environment Research Council (NERC; grant nos. NE/P013899/1, NE/P013902/2, NE/P013740/1, and NE/P013864/1), the UK Government Department for Environment, Food and Rural Affairs (Defra), and the World Wide Fund for Nature (WWF).
Uncontrolled Keywords: sdg 7 - affordable and clean energy ,/dk/atira/pure/sustainabledevelopmentgoals/affordable_and_clean_energy
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
Faculty of Science > Research Groups > Collaborative Centre for Sustainable Use of the Seas
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Depositing User: LivePure Connector
Date Deposited: 17 Apr 2024 16:30
Last Modified: 21 Apr 2024 23:54
DOI: 10.5194/bg-21-1961-2024


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