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 |
| Published: |
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 |
| Summary: | <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> |
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| ISSN: | 1726-4170 1726-4189 |