Diapycnal mixing across the photic zone of the NE Atlantic
<p>Variable physical conditions such as vertical turbulent exchange, internal wave, and mesoscale eddy action affect the availability of light and nutrients for phytoplankton (unicellular algae) growth. It is hypothesized that changes in ocean temperature may affect ocean vertical density stra...
| Published in: | Ocean Science |
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| Main Authors: | , , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-02-01
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| Online Access: | https://os.copernicus.org/articles/17/301/2021/os-17-301-2021.pdf |
| Summary: | <p>Variable physical conditions such as vertical turbulent exchange, internal wave, and mesoscale eddy action affect the availability of light and
nutrients for phytoplankton (unicellular algae) growth. It is hypothesized that changes in ocean temperature may affect ocean vertical density
stratification, which may hamper vertical exchange. In order to quantify variations in physical conditions in the northeast Atlantic Ocean, we
sampled a latitudinal transect along 17 <span class="inline-formula">±</span> 5<span class="inline-formula"><sup>∘</sup></span> W between 30 and 63<span class="inline-formula"><sup>∘</sup></span> N in summer. A shipborne conductivity–temperature–depth (CTD) instrumented package was used with a custom-made modification of the pump inlet to minimize detrimental effects of ship motions on its data. Thorpe-scale analysis was used to establish turbulence values for the upper 500 <span class="inline-formula">m</span> from three to six profiles obtained in a short CTD yo-yo, 3 to 5 <span class="inline-formula">h</span> after local sunrise. From south to north, average temperature decreased together with stratification while turbulence values weakly increased or remained constant. Vertical turbulent nutrient fluxes did not vary significantly with stratification and latitude. This apparent lack of correspondence between turbulent mixing and temperature is likely due to internal waves breaking (increased stratification can support more
internal waves), acting as a potential feedback mechanism. As this feedback mechanism mediates potential physical environment changes in temperature, global surface ocean warming may not affect the vertical nutrient fluxes to a large degree. We urge modellers to test this deduction as it could imply that the future summer phytoplankton productivity in stratified oligotrophic waters would experience little alterations in nutrient input from deeper waters.</p> |
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| ISSN: | 1812-0784 1812-0792 |