39th International Liège Colloquium on Ocean Dynamics
From decade to decade enormous progress is achieved in our understanding of oceanic turbulence. A major trigger of this progress is the technological development of both, oceanic instrumentation and numerical modeling. For the instruments, higher sampling rates, larger data storages and faster data processing facilities generally allow for better resolution but do also open perspectives for novel mechanical, acoustical and optical devices. For the numerical modeling, steadily growing computer resources allow for substantially more complex models and higher resolution than a decade ago. With applications of these innovative tools, new insights into the interaction of turbulence with waves, stratification and the marine ecosystem can be achieved.
Combining the historically broad approach of the Liege Colloquium with the specialized Warnemünde Turbulence Days, this joint venture will concentrate on five focal topics (see below): turbulence and waves, turbulence in buoyant and dense plumes, turbulence and the marine ecosystem, turbulence observations in the ocean, and turbulence modeling in the ocean. Contributions to these focal topics as well as to related problems of marine turbulence are invited to the Liege Colloquium in 2007.
Turbulence and Waves
Fabrice Ardhuin, Brest
Hans van Haren, Texel
Surface and internal gravity and inertial waves offer formidable scientific problems. Due to the presence of waves, mean flow and turbulent properties on either side of the air-sea interface are very difficult to measure and very little data is available to sort out the wide range of conceptual and numerical models that have been proposed for air-sea fluxes of gases, momentum, and the remote sensing of surface velocities and salinity. On the bottom, boundary layer processes are much better known and instrumentation has made huge progress. The sediment nature and roughness properties are still the cause of still poorly known order of magnitude changes in sediment and momentum fluxes, with large impacts on bio-geochemical properties of coastal waters and the interpretation of ocean color data. The evolution of internal and surface waves is influenced by similar processes, with breaking and induced mixing, or adiabatic interactions with the mean flow (refraction, wave mass transport, mean flow recoil … ). General theoretical contributions that are relevant to wave - mean flow - turbulence interactions are thus welcome, together with results of laboratory or field measurements that may provide decisive datasets for the validation of theoretical and numerical models. Oceanographic applications that illustrate the impact of these interactions, including wave and ocean circulation modeling and remote sensing aspects, are also warmly encouraged.
Turbulence in buoyant and dense plumes
Anna Wåhlin, Stockholm
Buoyant plumes are ubiquitous in coastal waters, mediating the transmission of freshwater signals to the open sea. Dense plumes related to outflows and overflows from marginal seas are important parts of the vertical circulation for the oceans and important for climate processes. In both dense and buoyant plumes turbulent mixing plays a crucial role with respect to their dynamics and their role and effect on the environment in which they are embedded. In both cases there is a need for realistic parameterizations of the mixing. The session organizers suspect that investigators of dense and buoyant plumes do not often talk to each other. In juxtaposing presentations on buoyant plumes at the sea surface with dense plumes, a unique opportunity is given to gain insight into both. Presentations on dynamically related topics are encouraged.
Turbulence and the marine ecosystem
Laurent Seuront, CNRS &
Luca van Duren, Middelburg
This session will focus on the effects of turbulence on biogeochemical and ecological processes in different aquatic ecosystems and at different scales, as well as the effect of biogenic structures on local turbulence. In aquatic ecosystems, physical, chemical and biological processes are strongly interlinked. The nature of these links is strongly scale-dependent and non-linear. At the smallest scales, water turbulence and viscosity may have direct and indirect effects on the physiology, behavioral processes and trophic links in aquatic organisms. At the scale of a few to tens of meters, advective and turbulent flows transport planktonic organisms and chemicals throughout the water column. Meso-scale structures such as eddies and fronts affect the dynamics of the ecosystem from the low (primary producers) to high (fish) trophic levels. Accordingly, we invite contributions covering a wide range of questions and scales. Interdisciplinary approaches are welcome, including experimental, theoretical as well as mathematical models of physical-chemical-biological interactions.
Turbulence observations in the ocean
Tom Rippeth, Bangor
Measurements of turbulence in the ocean will always be unsatisfying because of the large natural variability in geophysical turbulence. However, particular demonstrations, such as the repeatable result that turbulence dissipation @ surface buoyancy flux in convectively-driven mixed layers, provide us with some considerable quantitative confidence in what we can measure using in situ techniques in the ocean. Remote, acoustical measurement techniques are beginning to show promise as well. The present challenges are to (i) define strategies that permit clear observation of the instability mechanisms that lead to turbulence in the ocean, (ii) apply measurement techniques in creative ways that permit a quantitative assessment of the role of turbulence in not only the dynamics of flow fields but also in mixing of water masses (although these may not always be independent), and (iii) evaluate different methods for deriving turbulence parameters and assess the consistency of their results. For this session, we invite contributions of new, and especially innovative, interpretations of observations that relate feedbacks between small-scale fluid dynamical processes and ocean turbulence. These may include expanded observational data sets that allow a broader perspective of the fluid dynamics. The objective is to gain insights into both the instability problem (as we are more likely to adequately parameterize this for use in numerical models than we are to parameterize the turbulence itself) and the roles that turbulence plays in the evolution of the larger scale flow.
Turbulence modelling in the ocean
Lars Umlauf, Warnemünde
Vittorio Canuto, New York
Theoretical and numerical studies on turbulence closure models for unstratified and stratified flows will be discussed. Investigations with a relation to physical oceanography will be emphasized but contributions from neighboring disciplines like the atmospheric sciences or physical limnology will be highly welcome. Focal points will be statistical closure models (as they are typically derived from Reynolds Stress Models), investigations of turbulence with the help of fully or partially resolved approaches (LES, DNS), and investigations with a view on turbulence as a stochastic process (random-walk models, pdf-transport models, etc.). Numerical problems and methods related to turbulence modeling are invited to this session as well. Furthermore, idealized investigations of turbulent processes occurring in the ocean like stably stratified turbulence, evolution of instabilities, turbulence interaction with surface or internal waves, gravity currents, interfacial turbulence, etc. are encouraged, as well as local and regional modeling studies with an emphasis on turbulence modeling, including studies discussing the interrelation of turbulence and biogeochemical modeling.
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