Éditeur(s) : Elsevier Sci Ltd
Résumé : This study analyses the impact on the oceanic mean state of the evolution of the oceanic component (NEMO) of the climate model developed at Institut Pierre Simon Laplace (IPSL-CM), from the version IPSL-CM4, used for third phase of the Coupled Model Intercomparison Project (CMIP3), to IPSL-CM5A, used for CMIP5. Several modifications have been implemented between these two versions, in particular an interactive coupling with a biogeochemical module, a 3-band model for the penetration of the solar radiation, partial steps at the bottom of the ocean and a set of physical parameterisations to improve the representation of the impact of turbulent and tidal mixing. A set of forced and coupled experiments is used to single out the effect of each of these modifications and more generally the evolution of the oceanic component on the IPSL coupled models family. Major improvements are located in the Southern Ocean, where physical parameterisations such as partial steps and tidal mixing reinforce the barotropic transport of water mass, in particular in the Antarctic Circumpolar Current) and ensure a better representation of Antarctic bottom water masses. However, our analysis highlights that modifications, which substantially improve ocean dynamics in forced configuration, can yield or amplify biases in coupled configuration. In particular, the activation of radiative biophysical coupling between biogeochemical cycle and ocean dynamics results in a cooling of the ocean mean state. This illustrates the difficulty to improve and tune coupled climate models, given the large number of degrees of freedom and the potential compensating effects masking some biases.
Ocean Modelling (1463-5003) (Elsevier Sci Ltd), 2013-12 , Vol. 72 , P. 167-184

Droits : 2013 The Authors. Published by Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00170/28102/26612.pdf
DOI:10.1016/j.ocemod.2013.09.001
http://archimer.ifremer.fr/doc/00170/28102/

Éditeur(s) : HAL CCSD
Résumé : Integrating ecological connectivity into marine ecosystem management and planning is important, especially in a global context of severe fish stocks depletion and growing habitat degradation. Environmental tools such as Marine Protected Areas have been proposed to protect biodiversity, restore damaged ecosystems, sustain fisheries, and rebuild overexploited stocks. The effectiveness of marine protected areas depends in part on the maintenance of connectivity between marine populations, linked by ecological processes such as larval dispersal. In this thesis, we applied a biophysical model driven by ocean currents derived from satellite altimetry to evaluate connectivity between Western Indian Ocean reefs and across the current MPA system in the Mediterranean Sea. We applied different methods of analysis such as graph-theoretic and clustering. In the Western Indian Ocean, marine connectivity analyses show that the number of connections between reefs increases with fish pelagic larval duration. It also highlights a low connectivity across the region and a high interconnectivity within several regions (Mozambique Channel, Mascarene archipelago). In the Mediterranean Sea, connectance is globally low at the regional scale. This connectance is more important in Western than Eastern Mediterranean. Moreover, the marine connectivity analyses revealed high domestic connectivity rates. Depending on the study area, priority reefs or sites for MPA implementation are proposed. Finally, implications for transboundary marine policies and regional cooperation are discussed.
Intégrer les connaissances sur la connectivité écologique dans la gestion des écosystèmes marins est essentiel, surtout dans un contexte d'appauvrissement des ressources marines et de dégradation des habitats côtiers à l'échelle mondiale. Des outils environnementaux, tels que les Aires Marines Protégées ont été mises en œuvre pour protéger la biodiversité, restaurer les écosystèmes endommagés, soutenir les pêcheries et reconstituer les stocks surexploités. Leur efficacité dépend en partie du maintien de la connectivité entre les populations marines, assurée à travers divers processus écologiques dont la dispersion larvaire. Dans le cadre de ce travail de thèse, un modèle biophysique intégrant des données de courants, issues de mesures d'altimétrie par satellite, a été utilisé pour évaluer la connectivité entre les récifs de l'océan Indien d'une part, et à travers le réseau d'AMP de Méditerranée d'autre part. Différentes méthodes d'analyse ont été utilisées, telles que la théorie des graphes et le clustering. Dans l'océan Indien occidental, l'analyse des connectivités marines montre que le nombre de connexions entre les récifs augmente avec la durée de vie larvaire des poissons. Elle met également en évidence une faible connectivité à l'échelle de la région, mais une forte inter-connectivité au sein de plusieurs sous-régions (Canal du Mozambique, Mascareignes). En Méditerranée, la connectance est globalement faible à l'échelle régionale, bien que plus importante dans le bassin occidental que le bassin oriental. L'analyse des connectivités marines montre également un taux de connectivité élevé à l'échelle d'un même pays. Selon le cas d'étude, une liste de récifs ou de sites prioritaires dans la mise en œuvre des AMP a été proposée. Enfin, les implications de ces résultats en termes de politiques transfrontalières et de coopération régionale sont discutées.
https://tel.archives-ouvertes.fr/tel-01269631

NNT : 2015LARE0003
tel-01269631
https://tel.archives-ouvertes.fr/tel-01269631
https://tel.archives-ouvertes.fr/tel-01269631/document
https://tel.archives-ouvertes.fr/tel-01269631/file/2015lare0003_ECrochelet.pdf

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Climate may act on the dispersal and connectivity of marine populations through changes in the oceanic circulation and temperature, and by modifying species' prey and predator distributions. As dispersal and connectivity remain difficult to assess in situ, a first step in studying the effects of climate change can be achieved using biophysical models. To date, only a few biophysical models have been used for this purpose. Here we review these studies and also include results from other recent modelling efforts. We show that increased sea temperature, a major change expected under climate warming, may impact dispersal and connectivity patterns via changes in reproductive phenology (e.g., shift in the spawning season), transport (e.g., reduced pelagic larval duration under faster development rates), mortality (e.g., changes in the exposure to lethal temperatures), and behaviour (e.g.. increased larval swimming speed). Projected changes in circulation are also shown to have large effects on the simulated dispersal and connectivity patterns. Although these biophysical modelling studies are useful preliminary approaches to project the potential effects of climate change, we highlight their current limitations and discuss the way forward, in particular the need for adequate coupled hydrodynamic-biogeochemical simulations using atmospheric forcing from realistic climate change scenarios. (C) 2010 Elsevier Ltd. All rights reserved.
Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2010-10 , Vol. 87 , N. 1-4 , P. 106-113

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00031/14176/11522.pdf
DOI:10.1016/j.pocean.2010.09.005
http://archimer.ifremer.fr/doc/00031/14176/

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : In the present work, a biophysical dispersal model is used to understand the role of the physical environment in determining reef fish larval dispersal patterns in the South-West Lagoon of New Caledonia. We focus on a reef fish species, the humbug damselfish Dascyllus aruanus, to investigate seasonal variability of simulated larval retention at the scale of a reef patch and at the scale of the lagoon, and to explore links between larval retention and wind variability. The model shows that retention exhibits considerable temporal variability and periodically reaches values much larger than anticipated. Non-zero larval settlement occurs over a large part of the lagoon. Nevertheless, settlement values decrease quickly away from the natal reef and mean dispersal distances are of order 25-35 km. Cross-correlation analyses indicate that weather conditions characterized by strong south east trade winds lead to low retention rates at both local (reef) and regional (lagoon) scales. By contrast, subtropical weather conditions characterized by weak winds result in high retention rates. These results suggest that large-scale weather regimes can be used as proxies for larval retention of the humbug damselfish in the South-West Lagoon of New Caledonia. Nevertheless, relatively small mean dispersal distances suggest that meta-population dynamics occur on relatively small spatial scales.
Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2014-03 , Vol. 122 , P. 105-115

Droits : 2013 Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00170/28115/26326.pdf
DOI:10.1016/j.pocean.2013.12.006
http://archimer.ifremer.fr/doc/00170/28115/

Éditeur(s) : HAL CCSD Springer International Publishing
Résumé : Industrial agriculture has clearly reached its limits. Industrial agriculture is not able anymore to satisfy the basic needs of the growing worldwide population while ensuring the conditions of reproduction of natural assets. New production models have to be designed to protect and reclame polluted and degraded agricultural areas. Agroecology is considered as a promising way to achieve ecologically-intensive agrosystems, since the seminal contribution of Altieri in 1995. Nevertheless agroecology has not fully emerged as a scientific discipline yet. Agroecology is more that a traditional scientific discipline because agroecology breaks the frontiers between biophysical sciences and social sciences. This chapter reviews the roots and evolution of agroecology in the first section. Here we propose a mathematical theory of viability to handle uncertainty and complexity within agrosystems. This theory allows to define a kern of viability in which the agrosystem stay viable in the long term (section “Scientific stakes: New frontiers”). However, agroecological innovations create new uncertainties and controversies that must be solved. Some solutions can be found individually while other solutions must by co-constructed using innovative collective actions and hydrid forums (Callon et al. 2001, section “Scientific controversy and uncertainty”). Such collective knowledge makes agroecology as the starting point of a representative democracy by setting up adaptive governance on territories (section “How to manage agrosystems in the context of global changes?”).
Sustainable Agriculture Reviews 14

ISBN : 978-3-319-06015-6
hal-01195372
https://hal.archives-ouvertes.fr/hal-01195372
DOI : 10.1007/978-3-319-06016-3_1
PRODINRA : 270790