Science Service System

Summary of Proposal OCE3154

TitleSurveying long-lived mode-2 internal wave systems in the world’s oceans
Investigator Magalhaes, Jorge M. - University of Porto, Interdisciplinary Centre of Marine and Environmental Resea, Department of Geosciences, Environment and Spatial Planning
Team Member
Professor da Silva, Jose - University of Porto, Interdisciplinary Centre of Marine and Environmental Resea, Department of Geosciences, Environment and Spatial Planning
Professor Buijsman, Maarten - University of Southern Mississippi, Department of Marine Science
Professor Carballido , Beatriz - Universidade de Vigo, Departamento de Ecoloxía e Bioloxía Animal
MsC Rodríguez, Marina - Universidade de Vigo, Departamento de Ecoloxía e Bioloxía Animal
SummaryMode-2 internal wave observations have only recently been documented in the literature. Their seldom occurrence in in situ measurements was believed to be associated with their isolated nature, within the much more common mode-1 internal oscillations. SAR evidence, however, has recently been proving otherwise with new observations being documented in several regions of the world’s oceans. Internal waves are a classical subject within physical oceanography, which nonetheless assume state of the art relevance owing to their importance in global ocean energetics. In particular, they are now acknowledged to provide a significant fraction of the 2 TW maintaining abyssal stratification and the Meridional Overturning Circulation (see e.g. Nikurashin and Ferrari, 2013), although open questions still remain concerning their energy dissipation, which are importantin ocean mixing and climate studies (see e.g. Zhao et al., 2012; Alford et al.,2015). At the same time, while large internal wave systems are generally assumed to come from oscillating tidal flows over rough topography, their energy partitioning between the fundamental mode and higher modes is now beginning to be tackled in more detail. In fact, mode-1 internal structures are commonly seen propagating for several hundred kilometres in the open ocean, while higher modes are assumed to be trapped near their generation sites – thus dissipating a large amount of energy there. However, SAR observations have recently revealed a much more intricate picture. For instance, internal solitary waves associated with a mode-2 vertical structure are now know to propagate for several hundred kilometres as well in at least two of the most energetic internal waves sites in the world’s oceans – the South China Sea (e.g. Guo et al., 2012) and the Mascarene Ridge of the Indian Ocean (e.g. da Silva et al.,2015). These mode-2 SAR observations had been previously overlooked, as their sea surface signatures are only inferred via their small-scale mode-1 companion waves, which may easily go unnoticed in the broader and more energetic internal wave field. This proposal, therefore, aims at taking advantage of the TerraSAR-X imaging capabilities, which simultaneously allows for wide fields of view (usually imaging multiple wavelengths) at unparalleled spatial resolutions. A proper image survey targeting key regions of the world’s oceans will undoubtedly provide unprecedented insights into these waves two-dimensional horizontal structures and hence into their generation,propagation and dissipation mechanisms. A large satellite image collection may then join an already assembled in situ and climatological database, which in turn may yield a realistic basis against which high resolution modelling simulations can be tuned and compared – ultimately rendering their much needed 3D structures. Data requirements therefore include access to the TerraSAR-X image archive, including all acquisition modes in a selection of regions of interest. Finally, significant contributions are therefore expected with immediate applications in the oil industry, future oceanographic campaigns (thus knowing typical ISW fields in advance), model parameterizations, and possible biological implications. The main outcomes will be presented at key international meetings and at least one research article will be published in a high impact factor journal – all to be made available online via a dedicated webpage at http://jmagalhae0.wix.com/internal-waves-). Additional funding for this project is available via the Brazilian National Council for Scientific and Technological Development of the Ministry of Science, Technology and Innovation (CNPq/MCTI), in the framework of a Special Visiting Researcher Fellowship, which includes funding for travelling and accommodation up to 2016 (global grant amount is 100,447.44€). Additional funding is also provided from postdoc and PhD grants provided by Portuguese and Spanish funds.

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