The supply of nutrients due to vertical turbulent mixing: A study at the Porcupine Abyssal Plain study site in the northeast Atlantic
As part of a multidisciplinary cruise to the Porcupine Abyssal Plain (PAP) study site (49°00?N 16°30?W), in June and July 2006, observations were made of the vertical nitrate flux due to turbulent mixing. Daily profiles of nitrate and turbulent mixing, at the central PAP site, give a mean nitrate fl...
| Published in: | Deep Sea Research Part II: Topical Studies in Oceanography |
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| Main Authors: | , , , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2010
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| Subjects: | |
| Online Access: | https://eprints.soton.ac.uk/158509/ https://eprints.soton.ac.uk/158509/1/DSRIIdiffusion_postprint.pdf |
| Summary: | As part of a multidisciplinary cruise to the Porcupine Abyssal Plain (PAP) study site (49°00?N 16°30?W), in June and July 2006, observations were made of the vertical nitrate flux due to turbulent mixing. Daily profiles of nitrate and turbulent mixing, at the central PAP site, give a mean nitrate flux into the euphotic zone of 0.09 (95% confidence intervals: 0.05–0.16) mmol N m?2 d?1. This is a factor of 50 lower than the mean observed rate of nitrate uptake within the euphotic zone (5.1±1.3 mmol N m?2 d?1). By using our direct observations to ‘validate’ a previously published parameterisation for turbulent mixing, we further quantify the variability in the vertical turbulent flux across a roughly 100×100 km region centred on the PAP site, using hydrographic data. The flux is uniformly low (0.08±0.26 mmol N m?2 d?1, the large standard deviation being due to a strongly non-Gaussian distribution) and is consistent with direct measurements at the central site. It is demonstrated that on an annual basis convective mixing supplies at least 40-fold more nitrate to the euphotic zone than turbulent mixing at this location. Other processes, such as those related with mesoscale phenomena, may also contribute significantly. |
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