Physical structures, advection and mixing in the region of Goban spur

Huthnance, John M.; Coelho, Henrique Sérgio Moraes; Griffiths, Colin; Knight, P.; Rees, Andrew P.; Sinha, Bablu; Vangriesheim, Annick; White, Martin; Chatwin, Paul G.

doi:10.1016/s0967-0645(01)00030-3

Cited by 51 publications

(45 citation statements)

References 111 publications

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“…Station 4 on the slope was excluded from the calculations as the above assumptions (negligible advection, SS model) would not hold: firstly this station presents a deep mixed layer, indicating high dynamic and probably advection related to strong slope currents (e.g. Huthnance et al, 2001); secondly the large deficit of 234 Th/ 238 U, even at the base of the profile at 80 m, was ascribed to a former export event (see Section 3.4).…”

Section: Th Distribution and Fluxes In The Upper Watersmentioning

confidence: 99%

Particle export during a bloom of Emiliania huxleyi in the North-West European continental margin

Schmidt

Harlay

Borges

et al. 2013

Journal of Marine Systems

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Coccolithophores, the dominant pelagic calcifiers in the oceans, play a key role in the marine carbon cycle through calcification, primary production and carbon export, the main drivers of the biological CO 2 pump. In May 2002 a cruise was conducted on the outer shelf of the North-West European continental margin, from the north Bay of Biscay to the Celtic Sea (47.0°-50.5°N, 5.0°-11.0°W), an area where massive blooms of Emiliania huxleyi are observed annually. Biogeochemical variables including primary production, calcification, partial pressure of CO 2 (pCO 2 ), chlorophyll-a (Chl-a), particle load, particulate organic and inorganic carbon (POC, PIC) and 234 Th, were measured in surface waters to assess particle dynamic and carbon export in relation to the development of a coccolithophore bloom. We observed a marked northward decrease in Chl-a concentration and calcification rates: the bloom exhibited lower values and may be less well developed in the Goban Spur area. The export fluxes of POC and PIC from the top 80 m, determined using the ratios of POC and PIC to 234 Th of particles, ranged from 81 to 323 mg C m − 2 d − 1 and from 30 to 84 mg C m − 2 d − 1 , respectively. The highest fluxes were observed in waters presenting a well-developed coccolithophore bloom, as shown by high reflectance of surface waters. This experiment confirms that the occurrence of coccolithophores promotes efficient export of organic and inorganic carbon on the North-West European margin.

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Section: Th Distribution and Fluxes In The Upper Watersmentioning

confidence: 99%

Particle export during a bloom of Emiliania huxleyi in the North-West European continental margin

Schmidt

Harlay

Borges

et al. 2013

Journal of Marine Systems

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“…Internal tides with comparable peak currents are particularly strong at the Celtic Sea shelf edge (e.g. Pingree and New, 1989) and carry on-offshore exchange up to 1.3 m 2 /s in their wave-forms on the summer thermocline (Huthnance et al, 2001). At the shelf edge, the internal tides mix and diffuse the seasonal thermocline, and cooler water brought nearer to the surface is exposed by wind mixing as a cool surface band.…”

Section: Celtic Seamentioning

confidence: 99%

Deep ocean exchange with west-European shelf seas

2009

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Abstract. We review mechanisms and studies of exchange between the north-east Atlantic and the adjacent shelf seas. Well-developed summer upwelling and associated filaments off Portugal and north-west Spain give exchange O(3 m 2 /s per unit length of shelf). Prevailing westerly winds further north drive exchange O(1 m 2 /s). Poleward flow along most of the upper slope has associated secondary circulation O(1 m 2 /s), meanders and eddies. Eddies are shed from slope waters into the Bay of Biscay, and local exchanges occur at shelf spurs and depressions or canyons (e.g. dense-water cascading of order 1 m 2 /s). Tidal transports are larger, but their reversal every six hours makes exchange largely ineffective except where internal tides are large and non-linear, as in the Celtic Sea where solitons carry water with exchange O(1 m 2 /s). These various physical exchanges amount to an estimated 2-3 m 2 /s per unit length of shelf, between ocean and shelf. A numerical model estimate is comparable: 2.5×10 6 m 3 /s onto and off the shelf from Brittany to Norway. Mixing controls the seasonal thermocline, affecting primary production and hence fluxes and fate of organic matter. Specifically, CO 2 take-up by primary production, settling below the thermocline before respiration, and then off-shelf transport, make an effective shelf-sea "pump" (for CO 2 from the atmosphere to the deep ocean). However, knowledge of biogeochemical fluxes is generally sparse, giving scope for more measurements, model validation and estimates from models.

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“…We consider blooms of coccolithophores to be a sequence of events when their biomass constitutes a significant portion of the total phytoplankton community, enabling them to influence local biogeochemistry and trophodynamics (Smayda, 1997). These blooms further exhaust nutrients as the water column stratifies and the water mass is advected over the continental shelf, following the general residual circulation in the area (Pingree and Lecann, 1989;Huthnance et al, 2001;Suykens et al, 2010), while dinoflagellates, chrysophytes, prasinophytes and cryptophytes can become increasingly more important. This succession leads to the appearance of high reflectance (HR) patches which are associated with the dissipative stage of coccolithophorid blooms (of Emiliania huxleyi in particular), when coccoliths are shed into the water column, affecting the albedo of the surface water (Westbroek et al, 1993;Harlay et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Phytoplankton community dynamics during late spring coccolithophore blooms at the continental margin of the Celtic Sea (North East Atlantic, 2006–2008)

Oostende

Harlay

Vanelslander

et al. 2012

Progress in Oceanography

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a b s t r a c tWe determined the spatial and temporal dynamics of major phytoplankton groups in relation to biogeochemical and physical variables during the late spring coccolithophore blooms (May-June) along and across the continental margin in the Celtic Sea (2006Sea ( -2008. Photosynthetic biomass (chl a) of the dominant plankton groups was determined by CHEMTAX analysis of chromatographic (HPLC) pigment signatures.Phytoplankton standing stock biomass varied substantially between and during the campaigns (areal chl a [mg chl a m À2 ] in June 2006: 63.8 ± 26.5, May 2007: 27.9 ± 8.4, and May 2008: 41.3 ± 21.8), reflecting the different prevailing conditions of weather, irradiance, and sea surface temperature between the campaigns. Coccolithophores, represented mainly by Emiliania huxleyi, and diatoms were the dominant phytoplankton groups, with a maximal contribution of, respectively, 72% and 89% of the total chl a. Prasinophytes, dinoflagellates, and chrysophytes often co-occurred during coccolithophorid blooms, while diatoms dominated the phytoplankton biomass independently of the biomass of other groups. The location of the stations on the shelf or on the slope side of the continental margin did not influence the biomass and the composition of the phytoplankton community despite significantly stronger water column stratification and lower nutrient concentrations on the shelf. The alternation between diatom and coccolithophorid blooms of similar biomass, following the mostly diatom-dominated main spring bloom, was partly driven by changes in nutrient stoichiometry (N:P and dSi:N). High concentrations of transparent exopolymer particles (TEP) were associated with stratified, coccolithophore-rich water masses, which probably originated from the slope of the continental margin and warmed during advection onto the shelf. Although we did not determine the proportion of export production attributed to phytoplankton groups, the abundance of coccolithophores, together with TEP and coccoliths may affect the carbon export efficiency through increased sinking rates of particles formed by aggregation of TEP and coccoliths.

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Physical structures, advection and mixing in the region of Goban spur

Cited by 51 publications

References 111 publications

Particle export during a bloom of Emiliania huxleyi in the North-West European continental margin

Particle export during a bloom of Emiliania huxleyi in the North-West European continental margin

Deep ocean exchange with west-European shelf seas

Phytoplankton community dynamics during late spring coccolithophore blooms at the continental margin of the Celtic Sea (North East Atlantic, 2006–2008)

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