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Casas-Prat M.,Center Internacional dInvestigacio Dels Recursos Costaners | Sierra J.P.,University of Barcelona
Natural Hazards and Earth System Science | Year: 2010

In the context of wave climate variability, long-term alterations in the wave storminess pattern of the Catalan coast (northwestern Mediterranean Sea) are analysed in terms of wave energy content and wave direction, on the basis of wave hindcast data (from 44-year time series). In general, no significant temporal trends are found for annual mean and maximum energy. However, the same analysis carried out separately for different wave directions reveals a remarkable increase in the storm energy of events from the south, which is partly due to a rise in the annual percentage of such storms. A case study of Tarragona Port (on the southern Catalan coast) highlights the importance of including changes in wave direction in the study of potential impacts of climate change. In particular, an increase in the frequency of storms from the south leads to greater agitation inside the Port. © 2010 Author(s). Source

Grifoll M.,Polytechnic University of Catalonia | Grifoll M.,Center Internacional dInvestigacio Dels Recursos Costaners | Aretxabaleta A.L.,U.S. Geological Survey | Espino M.,Polytechnic University of Catalonia | And 2 more authors.
Journal of Geophysical Research: Oceans | Year: 2012

We examine the circulation over the inner-shelf of the Catalan Sea using observations of currents obtained from three Acoustic Doppler Current Profilers (two at 24 m and one at 50 m) during March-April 2011. The along-shelf current fluctuations during that period are mainly controlled by local wind stress on short time scales and by remote pressure gradients on synoptic time scales. Different forcing mechanisms are involved in the along-shelf momentum balance. During storm conditions, wind stress, sea level gradients and the nonlinear terms dominate the balance. During weak wind conditions, the momentum balance is controlled by the pressure gradient, while during periods of moderate wind in the presence of considerable stratification, the balance is established between the Coriolis and wind stress terms. Vertical variations of velocity are affected by the strong observed density gradient. The increased vertical shear is accompanied by the development of stratified conditions due to local heating when the wind is not able to counteract (and break) stratification. The occasional influence of the Besòs River plume is observed in time scales of hours to days in a limited area in near the city of Barcelona. The area affected by the plume depends on the vertical extent of the fresher layer, the fast river discharge peak, and the relaxation of cross-shore velocities after northeast storm events. This contribution provides a first interpretation of the inner-shelf dynamics in the Catalan Sea. © 2012. American Geophysical Union. All Rights Reserved. Source

Sierra J.P.,Polytechnic University of Catalonia | Sierra J.P.,Center Internacional dInvestigacio Dels Recursos Costaners | Casas-Prat M.,Polytechnic University of Catalonia | Casas-Prat M.,Center Internacional dInvestigacio Dels Recursos Costaners
Climatic Change | Year: 2014

This study examines the main physical processes related to coastal and port engineering that could be altered by future changes in wave parameters as a consequence of climate change. To estimate the order of magnitude of the potential changes in these processes, several assumptions and simplifications are made and, in most cases, they are assessed by using simple, empirical state-of-the-art expressions. The studied processes are grouped in three categories according to whether they affect beaches, harbors or coastal structures in general. The changes in these processes are estimated as a function of the deepwater variations of the main wave parameters: wave height (H 0), wave period (T) and wave direction (θ 0). A moderate range of variation is assumed for these parameters at deep water (±10 or ±20 % in H 0 and its square root in T, and ±10o in θ 0), taking into account recent studies of future wave projections. The results indicate that potential changes in wave height will strongly affect overtopping discharge, stability and scouring of rubble-mound structures and, to a lesser extent, siltation, wave transmission and longshore sediment transport. Changes in wave direction will affect longshore sediment transport in particular and, at a lower magnitude, processes related to port operability (agitation and siltation). Siltation is the only process affected significantly by changes in T alone. © 2014 The Author(s). Source

Grifoll M.,Polytechnic University of Catalonia | Grifoll M.,Center Internacional dInvestigacio Dels Recursos Costaners | Aretxabaleta A.L.,Integrated Statistics | Espino M.,Polytechnic University of Catalonia | Espino M.,Center Internacional dInvestigacio Dels Recursos Costaners
Journal of Geophysical Research C: Oceans | Year: 2015

Cross and along-shelf winds drive cross-shelf transport that promotes the exchange of tracers and nutrients to the open sea. The shelf response to cross-shelf winds is studied in the north shelf of the Ebro Delta (Mediterranean Sea), where those winds are prevalent and intense. Offshore winds in the region exhibit strong intensities (wind stress larger than 0.8 Pa) during winter and fall. The monthly average flow observed in a 1 year current meter record at 43.5 m was polarized following the isobaths with the along-shelf variability being larger than the cross-shelf. Prevalent southwestward along-shelf flow was induced by the three-dimensional regional response to cross-shelf winds and the coastal constraint. Seaward near-surface velocities occurred predominantly during offshore wind events. During intense wind periods, the surface cross-shelf water transport exceeded the net along-shelf transport. During typically stratified seasons, the intense cross-shelf winds resulted in a well-defined two-layer flow and were more effective at driving offshore transport than during unstratified conditions. While transfer coefficients between wind and currents were generally around 1%, higher cross-shelf transfer coefficients were observed in the near-inertial band. The regional extent of the resulting surface cold water during energetic cross-shelf winds events was concentrated around the region of the wind jet. Cross-shelf transport due to along-shelf winds was only effective during northeast wind events. During along-shelf wind conditions, the transport was estimated to be between 10 and 50% of the theoretical Ekman transport. © 2015. American Geophysical Union. All Rights Reserved. Source

Grifoll M.,Polytechnic University of Catalonia | Grifoll M.,Center Internacional dInvestigacio Dels Recursos Costaners | Del Campo A.,Tecnalia | Espino M.,Polytechnic University of Catalonia | And 4 more authors.
Journal of Marine Systems | Year: 2013

The inclusion of water renewal behaviour in the risk assessment of water pollution for Bilbao harbour (located within the Nervión estuary, southeastern Bay of Biscay) is analysed. Several parameterisations of water renewal (integral and local perspectives), obtained from the numerical evolution analysis of a Eulerian tracer, were used. The local characterisation of water renewal confirmed a strong horizontal spatial variability. In addition, vertical variability on water renewal patterns, due to the 3-dimensional structure of the flow was also appreciated. For the period analysed (August 2008) the water renewal was less effective at the surface, than in deeper waters, because marine breezes counteracted water renewal at the surface, during the observed period. The incidence of this vertical variability, on harbour environmental management, was analysed in implementing a recently developed methodology to evaluate the risk of water pollution. Since this methodology takes into account water renewal, the values of risk of water pollution in Bilbao harbour differed considerably, as a function of the renewal pattern at the surface or within deeper waters. In conclusion, it was found that the water renewal should be parameterised properly, in order to improve environmental management strategies in semi-enclosed water bodies in coastal areas. The findings permitted knowledge to be gained on water renewal behaviour within Bilbao harbour, advancing the framework for the environmental management of harbour waters. © 2011 Elsevier B.V. Source

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