Seasonal and inter-annual variability in nutrient supply in relation to mixing in the Bay of Biscay

Hartman, Susan E. ORCID:; Hartman, Mark C; Hydes, David J.; Jiang, Zong-Pei; Smythe-Wright, Denise; González-Pola, Cesar. 2014 Seasonal and inter-annual variability in nutrient supply in relation to mixing in the Bay of Biscay. Deep Sea Research Part II: Topical Studies in Oceanography, 106. 68-75.

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© 2014 Elsevier B.V. This is the author’s version of a work that was accepted for publication in Deep Sea Research Part II: Topical Studies in Oceanography. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was/will be published in Deep Sea Research Part II: Topical Studies in Oceanography (doi:10.1016/j.dsr2.2013.09.032)
Hartman_revised manuscript_2.pdf - Accepted Version

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A key challenge in oceanography is to capture and quantify processes that happen on short time scales, seasonal changes and inter-annual variations. To address this problem the P&O European Ferries Ltd. Ship MV Pride of Bilbao was fitted with a FerryBox from 2002 to 2010 and data returned to NOC in real time providing near continuous measurements between UK (Portsmouth) and Spain (Bilbao) of temperature, salinity, chlorophyll-fluorescence and oxygen. Additional monthly samples were collected on manned crossings. Over 6000 samples were analysed for nitrate (nitrate and nitrite) concentrations. The timing of nitrate concentration increases (with winter mixing) and decreases (with the spring bloom) are different on and off shelf and in autumn nitrate concentrations remain high on the shelf. Off shelf in the Bay of Biscay, the mixed layer depth assessed using Argo floats, was found to vary from 212 m in relatively mild winters (such as 2007/2008) to 476 m in cold winters (2009/2010). Years with deeper mixing were associated with an increase in nitrate concentrations in the surface waters (~3 μmol l−1) and the increased vertical nutrient supply resulted in higher productivity the following spring. Bloom progression could be seen through the increase in oxygen anomaly and decrease in nitrate concentrations off shelf prior to changes further north on the shelf and phytoplankton growth was initiated as shoaling begins. The full dataset demonstrates that ships of opportunity, particularly ferries with consistently repeated routes, can deliver high quality in situ measurements over large time and space scales that currently cannot be delivered in any other way.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 09670645
Additional Keywords: Nitrates; Time-series; Ship of opportunity; North East Atlantic; Bay of Biscay
Date made live: 27 Feb 2014 14:06 +0 (UTC)

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