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Title: Nutrient fluxes into the seasonal thermocline of the Celtic Sea
Author: Tweddle, J. F.
ISNI:       0000 0004 2726 3492
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2007
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Estimates of vertical fluxes of nitrate (JN) into the subsurface chlorophyll maximum from the bottom mixed layer were made in a variety of hydrological regimes over the Celtic Sea in 2003 and 2005. Over a topographically flat shelf JN varied with the spring-neap tidal cycle (1.1 (neap) – 2.8 (spring) mmol m-2 day-1), driven by changes in barotropic shear generated vertical diffusivities (Kz) at the base of the thermocline. Further increases in nitrate fluxes were possible through small shear perturbations. JN is further enhanced over topographic features, such as banks on the shelf or the shelf break, by the generation and dissipation of lee waves. The strength of mixing driven by the lee waves also varies with the spring-neap cycle, with higher Kz at the base of the thermocline occurring around spring tide, compared to neap tide, associated with the greater occurrence of short period internal waves. Over banks vertical nitrate fluxes varied between 2.9 (neap) – 15.7 (spring) mmol N m-2 day-1 and over the shelf break estimated vertical nitrate fluxes were 4 (neap) –15 (spring) mmol m-2 day-1. These fluxes are capable of supporting new production of 207 mg C m-2 day-1 over the Celtic Sea shelf, which over the summer stratified period is potentially greater than the new production taking place in the spring bloom. Enhanced production of 1200 mg C m-2 day-1 is supportable over regions of the shelf affected by the generation of lee waves over banks. This equated to a 4% increase in new production within the SCM over the Celtic Sea shelf. 31% of new production in the Celtic Sea was associated with the shelf break, where 660 mg C m-2 day-1 could be supported in the shelf break region.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry ; GC Oceanography