Submesoscale circulation and top marine predator behaviors : Contribution of multiscales and multisensors analyses
The ocean is governed by complex movements at all spatio-temporal scales. Within an mean and global circulation exists a secondary circulation inhabited by fronts, meanders, narrow jets, eddies, named mesoscale circulation. Observation with satellites allows a description and a synoptic evaluation of this dynamics at mesoscale by using altimetric and scatterometric data. This evaluation was the first objective of the thesis and allowed to develop a product distributed to the international scientific community : the GEKCO product. However, the description of submesoscale processes at finer resolution requires the use of super-resolution data (like ocean color or sea surface temperature) which have the ability to represent all the complexity of an ocean in fully developed turbulence. A method between physical oceanography and "science of the complexity" using the microcanonical formulation of the multiplicative cascade, the GEKCO product and sea surface temperature images was the topic of the second part of this manuscript. The ocean dynamics being the keystone of all marine ecosystems, the last part of this thesis was dedicated to the meso and submesoscale impact of the ocean dynamics to the trophic chain by focusing on its two extremities. Study of the flow at submesoscale allowed to show that it plays a preponderant role on the marine biomass ; role of activator in open ocean and role of inhibitor in the east boundary upwelling systems. Various studies on top marine predator paths demonstrated the necessity of taking into account the ocean dynamics to interpret their navigational behavior.