Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea
<p>There is an immediate need to better understand and monitor shelf sea dissolved oxygen (O<span class="inline-formula"><sub>2</sub></span>) concentrations. Here we use high-resolution glider observations of turbulence and O<span class="inline-formula...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-04-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/21/1961/2024/bg-21-1961-2024.pdf |
| _version_ | 1797202562513895424 |
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| author | C. A. J. Williams T. Hull J. Kaiser C. Mahaffey N. Greenwood M. Toberman M. R. Palmer |
| author_facet | C. A. J. Williams T. Hull J. Kaiser C. Mahaffey N. Greenwood M. Toberman M. R. Palmer |
| author_sort | C. A. J. Williams |
| collection | DOAJ |
| description | <p>There is an immediate need to better understand and monitor shelf sea dissolved oxygen (O<span class="inline-formula"><sub>2</sub></span>) concentrations. Here we use high-resolution glider observations of turbulence and O<span class="inline-formula"><sub>2</sub></span> concentrations to directly estimate the vertical O<span class="inline-formula"><sub>2</sub></span> 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 O<span class="inline-formula"><sub>2</sub></span> flux to the low-O<span class="inline-formula"><sub>2</sub></span> BML was found to be between 2.5 to 6.4 mmol m<span class="inline-formula"><sup>−2</sup></span> d<span class="inline-formula"><sup>−1</sup></span>. 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 O<span class="inline-formula"><sub>2</sub></span> 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.</p> |
| first_indexed | 2024-04-24T08:05:25Z |
| format | Article |
| id | doaj.art-bb3a9454c63543829ba5a7afb1c6150b |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-04-24T08:05:25Z |
| publishDate | 2024-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-bb3a9454c63543829ba5a7afb1c6150b2024-04-17T11:37:20ZengCopernicus PublicationsBiogeosciences1726-41701726-41892024-04-01211961197110.5194/bg-21-1961-2024Vertical mixing alleviates autumnal oxygen deficiency in the central North SeaC. A. J. Williams0T. Hull1J. Kaiser2C. Mahaffey3N. Greenwood4M. Toberman5M. R. Palmer6National Oceanography Centre, Liverpool, L3 5DA, UKCentre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT, UKCentre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UKDepartment of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, L69 3GP, UKCentre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT, UKScottish Association for Marine Science, Oban, Scotland, PA37 1QA, UKPlymouth Marine Laboratory, Plymouth, PL1 3DH, UK<p>There is an immediate need to better understand and monitor shelf sea dissolved oxygen (O<span class="inline-formula"><sub>2</sub></span>) concentrations. Here we use high-resolution glider observations of turbulence and O<span class="inline-formula"><sub>2</sub></span> concentrations to directly estimate the vertical O<span class="inline-formula"><sub>2</sub></span> 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 O<span class="inline-formula"><sub>2</sub></span> flux to the low-O<span class="inline-formula"><sub>2</sub></span> BML was found to be between 2.5 to 6.4 mmol m<span class="inline-formula"><sup>−2</sup></span> d<span class="inline-formula"><sup>−1</sup></span>. 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 O<span class="inline-formula"><sub>2</sub></span> 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.</p>https://bg.copernicus.org/articles/21/1961/2024/bg-21-1961-2024.pdf |
| spellingShingle | C. A. J. Williams T. Hull J. Kaiser C. Mahaffey N. Greenwood M. Toberman M. R. Palmer Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea Biogeosciences |
| title | Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea |
| title_full | Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea |
| title_fullStr | Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea |
| title_full_unstemmed | Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea |
| title_short | Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea |
| title_sort | vertical mixing alleviates autumnal oxygen deficiency in the central north sea |
| url | https://bg.copernicus.org/articles/21/1961/2024/bg-21-1961-2024.pdf |
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