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A simulation of the Turkish Straits System (TSS) using a high-resolution, three-dimensional, unstructured mesh ocean circulation model with realistic atmospheric forcing for the 2008–2013 period is presented. The depth of the pycnocline between the upper and lower layers remains stationary after 6 years of integration, indicating that despite the limitations of the modelling system, the simulation maintains its realism. The solutions capture important responses to high-frequency atmospheric events such as the reversal of the upper layer flow in the Bosphorus due to southerly severe storms, i.e. blocking events, to the extent that such storms are present in the forcing dataset. The annual average circulations show two distinct patterns in the Sea of Marmara. When the wind stress maximum is localised in the central basin, the Bosphorus jet flows to the south and turns west after reaching the Bozburun Peninsula. In contrast, when the wind stress maximum increases and expands in the north–south direction, the jet deviates to the west before reaching the southern coast and forms a cyclonic gyre in the central basin. In certain years, the mean kinetic energy in the northern Sea of Marmara is found to be comparable to that of the Bosphorus inflow.

The Regional Ocean Modeling System ocean model is used to simulate the decadal evolution of the regional waters in offshore Iberia in response to atmospheric fields given by ECMWF ERA-40 (1961–2001) and ERA-Interim (1989–2008) reanalyses. The simulated sea surface temperature (SST) fields are verified against satellite AVHRR SST, and they are analysed to characterise the variability and trends of coastal upwelling in the region. Opposing trends in upwelling frequency are found at the northern limit, where upwelling has been decreasing in recent decades, and at its southern edge, where there is some evidence of increased upwelling. These results confirm previous observational studies and, more importantly, indicate that observed SST trends are not only due to changes in radiative or atmospheric heat fluxes alone but also due to changes in upwelling dynamics, suggesting that such a process may be relevant in climate change scenarios. Keywords: climate change, upwelling, ROMS, reanalyses (Published: 22 May 2013) Citation: Tellus A 2013, 65 , 19245, http://dx.doi.org/10.3402/tellusa.v65i0.19245

For these last thirty years, earth observation and numerical models improved greatly and provide now a huge amount of accurate, yet heterogeneous, information on geophysics fluids dynamics and structures. Optimization methods from the eighties called variational data assimilation are capable of merging information from different sources. They have been used to estimate the parameters of numerical models and better forecast oceanic and atmospheric flows. Unfortunately, these powerful methods have trouble making benefit of always more complex information, suffering from the lack of available powerful calculators. The approach developed here, focuses on the use of multigrid methods, that are commonly used in the context of differential equations systems, to solve high resolution data assimilation. Multigrid methods are iterative methods improved by the use of feedback corrections evaluated on coarse resolution. First in the case of linear assimilation, we study the robustness of multigrid approach and the efficiency of the coarse grid correction step. We then apply the multigrid algorithms on a non linear 1-D Burgers equation and on a 2-D Shallow-Water model. We study two types of algorithms, the Gauss Newton Multigrid, which lays on global linearization, and the Full Approximation Scheme. Their behavior is compared to more traditional approaches as incremental and multi-incremental ones., Depuis ces trente dernières années, les systèmes d'observation de la Terre et les modèles numériques se sont perfectionnés et complexifiés pour nous fournir toujours plus de données, réelles et numériques. Ces données, de nature très diverse, forment maintenant un ensemble conséquent d'informations précises mais hétérogènes sur les structures et la dynamique des fluides géophysiques. Dans les années 1980, des méthodes d'optimisation, capables de combiner les informations entre elles, ont permis d'estimer les paramètres des modèles numériques et d'obtenir une meilleure prévision des courants marins et atmosphériques. Ces méthodes puissantes, appelées assimilation variationnelle de données, peinent à tirer profit de la toujours plus grande complexité des informations de par le manque de puissance de calcul disponible. L'approche, que nous développons, s'intéresse à l'utilisation des méthodes multigrilles, jusque là réservées à la résolution de systèmes d'équations différentielles, pour résoudre l'assimilation haute résolution de données. Les méthodes multigrilles sont des méthodes de résolution itératives, améliorées par des corrections calculées sur des grilles de plus basses résolutions. Nous commençons par étudier dans le cas d'un modèle linéaire la robustesse de l'approche multigrille et en particulier l'effet de la correction par grille grossière. Nous dérivons ensuite les algorithmes multigrilles dans le cadre non linéaire. Les deux types d'algorithmes étudiés reposent d'une part sur la méthode de Gauss Newton multigrille et d'autre part sur une méthode sans linéarisation globale : le Full Approximation Scheme (FAS). Ceux-ci sont appliqués au problème de l'assimilation variationnelle de données dans le cadre d'une équation de Burgers 1D puis d'un modèle Shallow-water 2D. Leur comportement est analysé et comparé aux méthodes plus traditionnelles de type incrémentale ou multi-incrémentale.

This paper presents a system for mission planning for an autonomous underwater vehicle in time-varying ocean currents. The mission planning system is designed for the AUV “SLOCUM Glider” to collect oceanographic data along the Newfoundland and Labrador Shelf. The data will be used in conjunction with a numerical ocean model currently under development by the Department of Fisheries and Oceans Canada. This allows for the validation and the modification of existing ocean current and climate models as well as the design of new models with the aim of improving the accuracy of forecasts. The use of the ocean current forecast data in netCDF format in an ocean current model, the algorithms which consider glider-specific behaviour, details of the program’s technical implementation in C++, and, preliminary results will be described., OCEANS 2010, 24-27 May 2010, Sydney, Australia