Jeudi 7 juillet - Crossroads of the Oceanic Circulation
Jul 07, 2016
from 11:00 AM to 12:00 PM
Alberto Baudena, PhD Student, LOCEAN Paris
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Titre : Crossroads of the Oceanic Circulation
With the increasing pressure of human activities over the oceans, monitoring marine areas is assuming an even more important role. Here we examine a specific problem, namely the early detection of a harmful pollutant which is dispersed in the ocean upper layer. In particular, we ask the following question: assuming that a polluting is released into a determined area and advected by the currents, how can we optimally choose the position of monitoring sites in an attempt to retrieve the contaminants with the higher probability? In order to answer to this question, we borrow some concepts from network theory and develop a new Lagrangian diagnostic, that we call crossroadness (CR), which allows to locate the main sites (that we will call as stations) that represent "crossroads" of the surface flux and that therefore collect waters coming from larger ocean surfaces.\\
In order to verify the accuracy of the new diagnostic, we analysed the trajectories of 43 drifters released around the region of Kerguelen in November 2011. The stations computed with our method from regional and global altimetry products allow to intercept about the double of drifters caught with a regular grid. The extension of this diagnostic to scientific and societal applications will also be discussed.
Then I will discuss briefly about the importance of the features identified by this and other Lagrangian diangostic, such as the Lyapunov Exponents, as structures able to aggregate living organisms like fish. In order to do that we developed a 2D model, focusing on the Southern Ocean and in particular on the region around Kerguelen island.