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An Estimate of Thorium 234 Partition Coefficients Through Global Inverse Modeling ArchiMer
Le Gland, Guillaume; Aumont, Olivier; Memery, Laurent.
Thorium-234 (Th-234), an insoluble radioisotope scavenged by marine particles, can be used as a proxy of the biological carbon pump. Thorium-234 observations can constrain biogeochemical models, but a necessary first step is to estimate the poorly known partition coefficients between particulate and dissolved phases. In this study, the Th-234 partition coefficients for five particle types, differing in size and chemical composition, are estimated by fitting a global 3-D Th-234 model based on the coupled ocean general circulation-biogeochemistry model NEMO-PISCES (at a resolution of 2 degrees) to a global Th-234 data set (including GEOTRACES data). Surface partition coefficients are estimated between 0.79 and 16.7x10(6). Biogenic silica has the smallest...
Tipo: Text Palavras-chave: Thorium 234; Inverse modeling; Partition coefficient; Biological carbon pump.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00605/71666/70108.pdf
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Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? ArchiMer
Le Gland, Guillaume; Memery, Laurent; Aumont, Olivier; Resplandy, Laure.
Radium-228 (Ra-228), an almost conservative trace isotope in the ocean, supplied from the continental shelves and removed by a known radioactive decay (T-1/2 - 5.75 years), can be used as a proxy to constrain shelf fluxes of other trace elements, such as nutrients, iron, or rare earth elements. In this study, we perform inverse modeling of a global Ra-228 dataset (including GEOSECS, TTO and GEOTRACES programs, and, for the first time, data from the Arctic and around the Kerguelen Islands) to compute the total Ra-228 fluxes toward the ocean, using the ocean circulation obtained from the NEMO 3.6 model with a 2 degrees resolution. We optimized the inverse calculation (source regions, cost function) and find a global estimate of the Ra-228 fluxes of 8.01-8.49...
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Ano: 2017 URL: https://archimer.ifremer.fr/doc/00616/72811/72571.pdf
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Modélisation 0D des efflorescences d'Alexandrium en rade de Brest en compétition inter-spécifique ArchiMer
Le Gland, Guillaume.
Since 2010, planktonic algae Alexandrium minutum, cause of the PSP (Paralytic Shellfish Poisoning) syndrome, has been proliferating in early summer in the bay of Daoulas, within the roadstead of Brest. During this internship, a model has been designed in order to derive these blooms from physical parameters (temperature, irradiance, nutrient supply, dilution rate …). In the model, A.minutum competes with 50 other plankton species with randomly attributed optimal temperature and nutrient uptake abilities. It turns out to reproduce well the bloom of 2012, with a correct date of maximum concentration and a relevant order of magnitude. It reproduces the order of magnitude of 2013 concentrations, but the bloom then is too spread in time around the maximum....
Tipo: Text Palavras-chave: Alexandrium minutum; Phytoplancton; Efflorescence (bloom); Nutriments; Lumière; Température; Dilution; Absorption (uptake); Quota cellulaire; Croissance; Compétition; Modèle; Rade de Brest.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00209/32004/30442.pdf
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Resource Competition Affects Plankton Community Structure; Evidence from Trait-Based Modeling ArchiMer
Sourisseau, Marc; Le Guennec, Valerie; Le Gland, Guillaume; Plus, Martin; Chapelle, Annie.
Understanding the phenology of phytoplankton species is still a challenge and despite a lot of theoretical work on competition for ressources this process is under-represented in deterministic models. To study the main driver of the species selection, we thus used a trait-based model that keeps phenotypic variability through physiological trait parameterization. We next validate the results by using a key species, the toxic dinoflagellate Alexandrium minutum. Due to their monitoring, we show that harmful algae are ideal models for studying ecological niches and for contributing to this more global challenge. As a first step, a dimensionless model of an estuary (France) was built with water temperature and water exchanges deduced from a hydro-dynamic model....
Tipo: Text Palavras-chave: Droop; Competition; Inter-specific; Estuary; Bay of Brest; Alexandrium minutum; Phenology; Niches.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00373/48414/48624.pdf
Registros recuperados: 4
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