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The supply of nutrients due to vertical turbulent mixing: A study at the Porcupine Abyssal Plain study site in the northeast Atlantic

Martin, Adrian P.; Lucas, Michael I.; Painter, Stuart C.; Pidcock, Rosalind; Prandke, Hartmut; Prandke, Holger; Stinchcombe, Mark C.. 2010 The supply of nutrients due to vertical turbulent mixing: A study at the Porcupine Abyssal Plain study site in the northeast Atlantic [in special issue: Water Column and Seabed Studies at the PAP Sustained Observatory in the Northeast Atlantic] Deep Sea Research Part II: Topical Studies in Oceanography, 57 (15). 1293-1302. https://doi.org/10.1016/j.dsr2.2010.01.006

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Abstract/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.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1016/j.dsr2.2010.01.006
ISSN: 0967-0645
Date made live: 21 Jun 2010 13:42 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/258509

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