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An iron budget during the natural iron fertilisation experiment KEOPS (Kerguelen Islands, Southern Ocean) 5
Chever, F.; Sarthou, G.; Bucciarelli, E.; Blain, S.; Bowie, A. R..
Total dissolvable iron (TDFe) was measured in the water column above and in the surrounding of the Kerguelen Plateau (Indian sector of the Southern Ocean) during the KErguelen Ocean Plateau compared Study (KEOPS) cruise. TDFe concentrations ranged from 0.90 to 65.6 nmol L-1 above the plateau and from 0.34 to 2.23 nmol L-1 offshore of the plateau. Station C1 located south of the plateau, near Heard Island, exhibited very high values (329-770 nmol L-1). Apparent particulate iron (Fe-app), calculated as the difference between the TDFe and the dissolved iron measured on board (DFe) represented 95 +/- 5% of the TDFe above the plateau, suggesting that particles and refractory colloids largely dominated the iron pool. This paper presents a budget of DFe and...
Tipo: Text Palavras-chave: Phytoplankton bloom; Dissolved iron; Atlantic ocean; Central california; Carbon sequestration; Coastal waters; Surface waters; Plateau region; Organic carbon; Bound iron.
Ano: 2010 URL: https://archimer.ifremer.fr/doc/00205/31605/30036.pdf
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Biological productivity regime and associated N cycling in the vicinity of Kerguelen Island area, Southern Ocean 5
Cavagna, A. J.; Fripiat, F.; Elskens, M.; Dehairs, F.; Mangion, P.; Chirurgien, L.; Closset, I.; Lasbleiz, M.; Flores–leiva, L.; Cardinal, D.; Leblanc, K.; Fernandez, C.; Lefèvre, D.; Oriol, L.; Blain, S.; Quéguiner, B..
Although the Southern Ocean is considered a High Nutrient Low Chlorophyll area (HNLC), massive and recurrent blooms are observed over and downstream the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N-uptake (NO3− and NH4+), and nitrification rates were measured at 8 stations in austral spring 2011 (October–November) during the KEOPS2 cruise in the Kerguelen area. Iron fertilization stimulates primary production, with integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m−2 d−1 and up to 0.31 d−1, respectively) compared to the HNLC reference site (12...
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Ano: 2014 URL: https://archimer.ifremer.fr/doc/00294/40558/39445.pdf
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Distributions and stoichiometry of dissolved nitrogen and phosphorus in the iron-fertilized region near Kerguelen (Southern Ocean) 5
Blain, S.; Capparos, J.; Gueneugues, A.; Obernosterer, I.; Oriol, L..
During KEOPS2 (Kerguelen Ocean and Plateau Compared Study 2), we determined dissolved inorganic and organic nitrogen and phosphorus species in the naturally fertilized region of Kerguelen Island (Southern Ocean). Above 150 m, stations were clearly separated by the polar front (PF), with concentrations of NO3-, NO2- and PO43- overall lower north of the PF than south. Though less pronounced, a similar trend was detectable for dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP). At all stations offshore and above the plateau, a subsurface maximum of NH4+ was observed between 50 and 150 m. We examined nutrient stoichiometry by calculating the linear combination N* = [NO3-]-16 [PO43-]. The majority of stations and depths revealed N* close to...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00292/40343/38883.pdf
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Export fluxes in a naturally iron-fertilized area of the Southern Ocean - Part 1: Seasonal dynamics of particulate organic carbon export from a moored sediment trap 5
Rembauville, M.; Salter, I.; Leblond, N.; Gueneugues, A.; Blain, S..
A sediment trap moored in the naturally iron-fertilized Kerguelen Plateau in the Southern Ocean provided an annual record of particulate organic carbon and nitrogen fluxes at 289 m. At the trap deployment depth, current speeds were typically low (similar to 10 cm s(-1)) and primarily tidal-driven (M2 tidal component). Although advection was weak, the sediment trap may have been subject to hydrodynamical and biological (swimmer feeding on trap funnel) biases. Particulate organic carbon (POC) flux was generally low (< 0.5 mmol m(-2) d(-1)), although two episodic export events (< 14 days) of 1.5 mmol m(-2) d(-1) were recorded. These increases in flux occurred with a 1-month time lag from peaks in surface chlorophyll and together accounted for...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00295/40578/39496.pdf
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Export fluxes in a naturally iron-fertilized area of the Southern Ocean - Part 2: Importance of diatom resting spores and faecal pellets for export 5
Rembauville, M.; Blain, S.; Armand, L.; Queguiner, B.; Salter, I..
The biological composition of the material exported to a moored sediment trap located under the winter mixed layer of the naturally fertilized Kerguelen Plateau in the Southern Ocean was studied over an annual cycle. Despite iron availability in spring, the annual particulate organic carbon (POC) export (98.2 mmol m(-2)) at 289m was low, but annual biogenic silica export was significant (114 mmol m(-2)). This feature was related to the abundance of empty diatom cells and the ratio of full to empty cells exerted a first-order control in BSi : POC export stoichiometry of the biological pump. Chaetoceros Hyalochaete spp. and Thalassiosira antarctica resting spores were responsible for more than 60% of the annual POC flux that occurred during two very short...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00295/40579/39498.pdf
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Fe and C co-limitation of heterotrophic bacteria in the naturally fertilized region off the Kerguelen Islands 5
Obernosterer, I.; Fourquez, M.; Blain, S..
It has been univocally shown that iron (Fe) is the primary limiting nutrient for phytoplankton metabolism in high-nutrient, low-chlorophyll (HNLC) waters, yet the question of how this trace metal affects heterotrophic microbial activity is far less understood. We investigated the role of Fe for bacterial heterotrophic production and growth at three contrasting sites in the naturally Fe-fertilized region east of the Kerguelen Islands and at one site in HNLC waters during the KEOPS2 (Kerguelen Ocean and Plateau Compared Study 2) cruise in spring 2011. We performed dark incubations of natural microbial communities amended either with iron (Fe, as FeCl3) or carbon (C, as trace-metal clean glucose), or a combination of both, and followed bacterial abundance and...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00291/40255/38635.pdf
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High variability in dissolved iron concentrations in the vicinity of the Kerguelen Islands (Southern Ocean) 5
Queroue, Fabien; Sarthou, Geraldine; Planquette, Helene; Bucciarelli, Eva; Chever, Fanny; Van Der Merwe, P.; Lannuzel, Delphine; Townsend, A. T.; Cheize, Marie; Blain, S.; D'Ovidio, F.; Bowie, A. R..
Dissolved Fe (dFe) concentrations were measured in the upper 1300 m of the water column in the vicinity of the Kerguelen Islands as part of the second KErguelen Ocean Plateau compared Study (KEOPS2). Concentrations ranged from 0.06 nmol L-1 in offshore, Southern Ocean waters to 3.82 nmol L-1 within Hillsborough Bay, on the north-eastern coast of the Kerguelen Islands. Direct island runoff, glacial melting and resuspended sediments were identified as important inputs of dFe that could potentially fertilise the northern part of the plateau. A significant deep dFe enrichment was observed over the plateau with dFe concentrations increasing up to 1.30 nmol L-1 close to the seafloor, probably due to sediment resuspension and pore water release. Biological uptake...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00274/38482/36942.pdf
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Iron budgets for three distinct biogeochemical sites around the Kerguelen Archipelago (Southern Ocean) during the natural fertilisation study, KEOPS-2 5
Bowie, A. R.; Van Der Merwe, P.; Queroue, Fabien; Trull, Thomas; Fourquez, M.; Planchon, F.; Sarthou, Geraldine; Chever, Fanny; Townsend, A. T.; Obernosterer, I.; Sallee, Jean-baptiste; Blain, S..
Iron availability in the Southern Ocean controls phytoplankton growth, community composition and the uptake of atmospheric CO2 by the biological pump. The KEOPS-2 (KErguelen Ocean and Plateau compared Study 2) "process study", took place around the Kerguelen Plateau in the Indian sector of the Southern Ocean. This is a region naturally fertilised with iron on the scale of hundreds to thousands of square kilometres, producing a mosaic of spring blooms which show distinct biological and biogeochemical responses to fertilisation. This paper presents biogeochemical iron budgets (incorporating vertical and lateral supply, internal cycling, and sinks) for three contrasting sites: an upstream high-nutrient low-chlorophyll reference, over the plateau and in the...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00276/38726/37233.pdf
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Microbial food web dynamics during spring phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean) 5
Christaki, U.; Lefevre, D.; Georges, C.; Colombet, J.; Catala, P.; Courties, C.; Sime-ngando, T.; Blain, S.; Obernosterer, I..
Microbial food web dynamics were determined during the onset of several spring phytoplankton blooms induced by natural iron fertilization off Kerguelen Island in the Southern Ocean (KEOPS2). The abundances of heterotrophic bacteria and heterotrophic nanoflagellates, bacterial heterotrophic production, bacterial respiration, and bacterial growth efficiency, were consistently higher in surface waters of the iron-fertilized sites than at the reference site in HNLC (high nutrient low chlorophyll) waters. The abundance of virus-like particles remained unchanged, but viral production increased by a factor of 6 in iron-fertilized waters. Bacterial heterotrophic production was significantly related to heterotrophic nanoflagellate abundance and viral production...
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Ano: 2014 URL: https://archimer.ifremer.fr/doc/00291/40208/38996.pdf
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Microbial iron uptake in the naturally fertilized waters in the vicinity of the Kerguelen Islands: phytoplankton-bacteria interactions 5
Fourquez, M.; Obernosterer, I.; Davies, D. M.; Trull, T. W.; Blain, S..
Iron (Fe) uptake by the microbial community and the contribution of three different size fractions was determined during spring phytoplankton blooms in the naturally Fe-fertilized area off the Kerguelen Islands (KEOPS2). Total Fe uptake in surface waters was on average 34 +/- 6 pmol Fe L-1 d(-1), and microplankton (>25 mu m size fraction; 40-69%) and pico-nanoplankton (0.8-25 mu m size fraction; 29-59 %) were the main contributors. The contribution of heterotrophic bacteria (0.2-0.8 mu m size fraction) to total Fe uptake was low at all stations (1-2 %). Iron uptake rates normalized to carbon biomass were highest for pico-nanoplankton above the Kerguelen Plateau and for microplankton in the downstream plume. We also investigated the potential competition...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00295/40598/39535.pdf
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Particulate matter stoichiometry driven by microplankton community structure in summer in the Indian sector of the Southern Ocean 5
Rembauville, M.; Blain, S.; Caparros, J.; Salter, I..
Microplankton community structure and particulate matter stoichiometry were investigated in a late summer survey across the Subantarctic and Polar Front in the Indian sector of the Southern Ocean. Microplankton community structure exerted a first order control on PON:POP stoichiometry with diatom-dominated samples exhibiting much lower ratios (4–6) than dinoflagellate and ciliate-dominated samples (10–21). A significant fraction of the total chlorophyll a (30–70%) was located beneath the euphotic zone and mixed layer and sub-surface chlorophyll features were associated to transition layers. Although microplankton community structure and biomass was similar between mixed and transition layers, the latter was characterized by elevated Chl:POC ratios...
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Ano: 2016 URL: https://archimer.ifremer.fr/doc/00324/43484/42942.pdf
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Pigments, elemental composition (C, N, P, and Si), and stoichiometry of particulate matter in the naturally iron fertilized region of Kerguelen in the Southern Ocean 5
Lasbleiz, M.; Leblanc, K.; Blain, S.; Ras, J.; Cornet-barthaux, V.; Nunige, S. Helias; Queguiner, B..
The particulate matter distribution and phytoplankton community structure of the iron-fertilized Kerguelen region were investigated in early austral spring (October-November 2011) during the KEOPS2 cruise. The iron-fertilized region was characterized by a complex mesoscale circulation resulting in a patchy distribution of particulate matter. Integrated concentrations over 200 m ranged from 72.2 to 317.7 mg m(-2) for chlorophyll a 314 to 744 mmol m(-2) for biogenic silica (BSi), 1106 to 2268 mmol m(-2) for particulate organic carbon, 215 to 436 mmol m(-2) for particulate organic nitrogen, and 29.3 to 39.0 mmol m(-2) for particulate organic phosphorus. Three distinct high biomass areas were identified: the coastal waters of Kerguelen Islands, the easternmost...
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Ano: 2014 URL: https://archimer.ifremer.fr/doc/00291/40222/39345.pdf
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Planktic foraminifer and coccolith contribution to carbonate export fluxes over the central Kerguelen Plateau 5
Rembauville, M.; Meilland, J.; Ziveri, P.; Schiebel, R.; Blain, S.; Salter, I..
We report the contribution of planktic foraminifers and coccoliths to the particulate inorganic carbon (PIC) export fluxes collected over an annual cycle (October 2011/September 2012) on the central Kerguelen Plateau in the Antarctic Zone (AAZ) south of the Polar Front (PF). The seasonality of PIC flux was decoupled from surface chlorophyll a concentration and particulate organic carbon (POC) fluxes and was characterized by a late summer (February) maximum. This peak was concomitant with the highest satellite-derived sea surface PIC and corresponded to a Emiliania huxleyi coccoliths export event that accounted for 85% of the annual PIC export. The foraminifer contribution to the annual PIC flux was much lower (15%) and dominated by Turborotalita...
Tipo: Text Palavras-chave: Foraminifer; Coccoliths; Export; Carbonate counter-pump; Kerguelen Plateau; Southern Ocean.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00421/53249/54722.pdf
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Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean 5
Cavagna, A. J.; Fripiat, F.; Elskens, M.; Mangion, P.; Chirurgien, L.; Closset, I.; Lasbleiz, M.; Florez-leiva, L.; Cardinal, D.; Leblanc, K.; Fernandez, C.; Lefevre, D.; Oriol, L.; Blain, S.; Queguiner, B.; Dehairs, F..
Although the Southern Ocean is considered a high-nutrient, low-chlorophyll (HNLC) area, massive and recurrent blooms are observed over and downstream of the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N uptake (NO3− and NH4+), and nitrification rates were measured at eight stations in austral spring 2011 (October–November) during the KEOPS 2 cruise in the Kerguelen Plateau area. Natural iron fertilization stimulated primary production, with mixed layer integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m−2 d−1 and up to 0.31 d−1 respectively)...
Tipo: Text
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00294/40561/39448.pdf
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Rapid formation of large aggregates during the spring bloom of Kerguelen Island: observations and model comparisons 5
Jouandet, M. -p.; Jackson, G. A.; Carlotti, F.; Picheral, M.; Stemmann, L.; Blain, S..
While production of aggregates and their subsequent sinking is known to be one pathway for the downward movement of organic matter from the euphotic zone, the rapid transition from non-aggregated to aggregated particles has not been reported previously. We made one vertical profile of particle size distributions (PSD; sizes ranging from 0.052 to several millimeters in equivalent spherical diameter) at pre-bloom stage and seven vertical profiles 3 weeks later over a 48 h period at early bloom stage using the Underwater Vision Profiler during the Kerguelen Ocean and Plateau Compared Study cruise 2 (KEOPS2, October-November 2011). In these naturally iron-fertilized waters southeast of Kerguelen Island (Southern Ocean), the total particle numerical abundance...
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Ano: 2014 URL: https://archimer.ifremer.fr/doc/00291/40223/39424.pdf
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Significant mixed layer nitrification in a natural iron-fertilized bloom of the Southern Ocean 5
Fripiat, F.; Elskens, M.; Trull, T. W.; Blain, S.; Cavagna, A. -j.; Fernandez, C.; Fonseca-batista, D.; Planchon, F.; Raimbault, P.; Roukaerts, A.; Dehairs, F..
Nitrification, the microbially mediated oxidation of ammonium into nitrate, is generally expected to be low in the Southern Ocean mixed layer. This paradigm assumes that nitrate is mainly provided through vertical mixing and assimilated during the vegetative season, supporting the concept that nitrate uptake is equivalent to the new primary production (i.e., primary production which is potentially available for export). Here we show that nitrification is significant (~40–80% of the seasonal nitrate uptake) in the naturally iron-fertilized bloom over the southeast Kerguelen Plateau. Hence, a large fraction of the nitrate-based primary production is regenerated, instead of being exported. It appears that nitrate assimilation (light dependent) and...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00296/40704/39700.pdf
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Sourcing the iron in the naturally fertilised bloom around the Kerguelen Plateau: particulate trace metal dynamics 5
Van Der Merwe, P.; Bowie, A. R.; Queroue, F.; Armand, L.; Blain, S.; Chever, Fanny; Davies, D.; Dehairs, F.; Planchon, F.; Sarthou, G.; Townsend, A. T.; Trull, T. W..
The KEOPS2 project aims to elucidate the role of natural Fe fertilisation on biogeochemical cycles and ecosystem functioning, including quantifying the sources and processes by which iron is delivered in the vicinity of the Kerguelen Archipelago, Southern Ocean. The KEOPS2 process study used an upstream high-nutrient, low-chlorophyll (HNLC), deep water (2500 m), reference station to compare with a shallow (500 m), strongly fertilised plateau station and continued the observations to a downstream, bathymetrically trapped recirculation of the Polar Front where eddies commonly form and persist for hundreds of kilometres into the Southern Ocean. Over the Kerguelen Plateau, mean particulate (1-53 mu m) Fe and Al concentrations (pFe = 13.4 nM, pAl = 25.2 nM)...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00256/36676/35276.pdf
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Surface currents and upwelling in Kerguelen Plateau regions 5
Zhou, M.; Zhu, Y.; D'Ovidio, F.; Park, Y.-h.; Durand, I.; Kestenare, E.; Sanial, V.; Van-beek, P.; Queguiner, B.; Carlotti, F.; Blain, S..
Mean currents, horizontal diffusivity and upwelling on the Kerguelen Plateau and the deep basin east of the Kerguelen Islands were studied using 48 World Ocean Circulation Experiment (WOCE) Standard Surface Velocity Program (SVP) drifters deployed during the 2011 austral spring KEOPS II (KErguelen Ocean Plateau compared Study II) cruise. These drifter data were analyzed based on autocovariances for temporal scales, least-squares fitted streamfunctions for estimating mesoscale mean currents, wind stress fields and Ekman pumping, and Taylor's single particle diffusivity for estimating horizontal dispersion of surface waters. The results have revealed the shelfbreak current on the southern and eastern shelf slopes of the Kerguelen Islands, transport of...
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Ano: 2014 URL: https://archimer.ifremer.fr/doc/00295/40621/39568.pdf
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The annual and seasonal variability of the carbonate system in the Bay of Brest (Northwest Atlantic Shelf, 2008–2014) 5
Salt, Lesley A.; Beaumont, L.; Blain, S.; Bucciarelli, E.; Grossteffan, E.; Guillot, A.; L'Helguen, S.; Merlivat, L.; Repecaud, Michel; Quemener, Loic; Rimmelin-maury, P.; Treguer, P.; Bozec, Y..
From 2008 to 2014, the MAREL-Iroise buoy, located in the Bay of Brest, collected high-frequency measurements of partial pressure of CO2 (pCO2) and ancillary hydrographic parameters, in conjunction with a comprehensive sampling regime of two additional carbonate system variables total alkalinity (AT), and dissolved inorganic carbon (DIC). Biological processes drive variations in AT and DIC throughout the year, except in winter, when primary production is negligible and large freshwater inputs occur. Annually, the Bay of Brest generally behaves as a source of CO2 to the atmosphere (0.14 ± 0.20 mol C m− 2 yr− 1), showing inter-annual variability significantly linked to annual net community production (NCP). The presence of a large community of benthic filter...
Tipo: Text Palavras-chave: Bay of Brest; Carbonate system; Dissolved inorganic carbon; Total alkalinity.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00350/46157/45855.pdf
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The biogeochemical structuring role of horizontal stirring: Lagrangian perspectives on iron delivery downstream of the Kerguelen Plateau 5
D'Ovidio, F.; Della Penna, A.; Trull, T. W.; Nencioli, F.; Pujol, M. -i.; Rio, M.-h; Park, Y. -h.; Cotte, C.; Zhou, M.; Blain, S..
Field campaigns are instrumental in providing ground truth for understanding and modeling global ocean biogeochemical budgets. A survey however can only inspect a fraction of the global oceans, typically a region hundreds of kilometers wide for a temporal window of the order of (at most) several weeks. This spatiotemporal domain is also the one in which the mesoscale activity induces through horizontal stirring a strong variability in the biogeochemical tracers, with ephemeral, local contrasts which can easily mask the regional and seasonal gradients. Therefore, whenever local in situ measures are used to infer larger-scale budgets, one faces the challenge of identifying the mesoscale structuring effect, if not simply to filter it out. In the case of the...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00296/40722/39723.pdf
Registros recuperados: 22
Primeira ... 12 ... Última
 

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