Submerged turbulence detection with optical satellites

During fall periods in 2002, 2003 and 2004 three major oceanographic expeditions were carried out in Mamala Bay, Hawaii. These were part of the RASP Remote Anthropogenic Sensing Program. Ikonos and Quickbird optical satellite images of sea surface glint revealed ~100 m spectral anomalies in km^2 averaging patches in regions leading from the Honolulu Sand Island Municipal Outfall diffuser to distances up to 20 km. To determine the mechanisms behind this phenomenon, the RASP expeditions monitored the waters adjacent to the outfall with an array of hydrographic, optical and turbulence microstructure sensors in anomaly and ambient background regions. Drogue tracks and mean turbulence parameters for 2x10^4 microstructure patches were analyzed to understand complex turbulence, fossil turbulence and zombie turbulence near-vertical internal wave transport processes. The dominant mechanism appears to be generic to stratified natural fluids including planet and star atmospheres and is termed beamed zombie turbulence maser action (BZTMA). Most of the bottom turbulent kinetic energy is converted to ~100 m fossil turbulence waves. These activate secondary (zombie) turbulence in outfall fossil turbulence patches that transmit heat, mass, chemical species, momentum and information vertically to the sea surface for detection in an efficient maser action. The transport is beamed in intermittent mixing chimneys.Comment: 8 pages, 7 figures, SPIE Optics+Photonics 2007 Coastal Ocean Remote Sensing Aug. 27, San Diego, CA, see http://sdcc3.ucsd.edu/~ir11

BASEWECS - Influence of the Baltic Sea and its annual ice coverage on the water and energy budget of the Baltic Sea

BASEWECS is a contribution to the German Climate Research Program DEKLIM. The project started in May 2001 and lasted until December 2004. BASEWECS aimed at the investigation of the influence of the Baltic Sea and its annual ice coverage on the water and energy budget of the BALTEX are

Turbulence and Fossil Turbulence in Oceans and Lakes

Turbulence is defined as an eddy-like state of fluid motion where the inertial-vortex forces of the eddies are larger than any of the other forces that tend to damp the eddies out. Energy cascades of irrotational flows from large scales to small are non-turbulent, even if they supply energy to turbulence. Turbulent flows are rotational and cascade from small scales to large, with feedback. Viscous forces limit the smallest turbulent eddy size to the Kolmogorov scale. In stratified fluids, buoyancy forces limit large vertical overturns to the Ozmidov scale and convert the largest turbulent eddies into a unique class of saturated, non-propagating, internal waves, termed fossil-vorticity-turbulence. These waves have the same energy but different properties and spectral forms than the original turbulence patch. The Gibson (1980, 1986) theory of fossil turbulence applies universal similarity theories of turbulence and turbulent mixing to the vertical evolution of an isolated patch of turbulence in a stratified fluid as its growth is constrained and fossilized by buoyancy forces. These theories apply to the dynamics of atmospheric, astrophysical and cosmological turbulence.Comment: 31 pages, 11 figures, 2 tables, see http://www-acs.ucsd.edu/~ir118 Accepted for publication by the Chinese Journal of Oceanology and Limnolog

Importance of salt fingering for new nitrogen supply in the oligotrophic ocean.

The input of new nitrogen into the euphotic zone constrains the export of organic carbon to the deep ocean and thereby the biologically mediated long-term CO2 exchange between the ocean and atmosphere. In low-latitude open-ocean regions, turbulence-driven nitrate diffusion from the ocean’s interior and biological fixation of atmospheric N2 are the main sources of new nitrogen for phytoplankton productivity. With measurements across the tropical and subtropical Atlantic, Pacific and Indian oceans, we show that nitrate diffusion (171±190 mmolm 2 d 1) dominates over N2 fixation (9.0±9.4 mmolm 2 d 1) at the time of sampling. Nitrate diffusion mediated by salt fingers is responsible for ca. 20% of the new nitrogen supply in several provinces of the Atlantic and Indian Oceans. Our results indicate that salt finger diffusion should be considered in present and future ocean nitrogen budgets, as it could supply globally 0.23–1.00 TmolNyr 1 to the euphotic zone.MALASPINA (CSD2008-00077)Versión del editor10,015

Continuous VM-ADCP (vessel-mounted acoustic Doppler current profiler) profiles of horizontal velocities and raw acoustic gain control data during Polarstern cruise ANT-XVIII/2

The mixing regime of the upper 180 m of a mesoscale eddy in the vicinity of the Antarctic Polar Front at 47° S and 21° E was investigated during the R.V. Polarstern cruise ANT-XVIII/2 within the scope of the iron fertilization experiment EisenEx. On the basis of hydrographic CTD and ADCP profiles we deduced the vertical diffusivity Kz from two different parameterizations. Since these parameterizations bear the character of empirical functions, based on theoretical and idealized assumptions, they were inter alia compared with Cox-number and Thorpe-scale related diffusivities deduced from microstructure measurements, which supplied the first direct insights into turbulence of this ocean region. Values of Kz in the range of 10**-4 - 10**-3 m**2/s appear as a rather robust estimate of vertical diffusivity within the seasonal pycnocline. Values in the mixed layer above are more variable in time and reach 10**-1 m**2/s during periods of strong winds. The results confirm a close agreement between the microstructure-based eddy diffusivities and eddy diffusivities calculated after the parameterization of Pacanowski and Philander [1981, Journal of Physical Oceanography 11, 1443-1451, doi:10.1175/1520-0485(1981)0112.0.CO;2]

Der MST Profiler - ein Messsystem zur Mikrostruktur- und Turbulenzuntersuchung im Meer Abschlussbericht

By the MST profiler developed in the frame of the EUREKA-EUROMAR project MISCOS (micro-structure ocean sonde, EU 1246) for microstructure and turbulence investigations even in small local scales (mm range), the turbulent mixing and transport processes of energy and substances (plancton, suspended matter, whirled up sediments) in marine and limnic waters can be studied. Simultaneous microstructure and precision measurements of physical parameters are obtained form vertical profils up to a depth of 100 m. The MST profiler is connected over a ME probe interface and the data aquisition and system control computer to the data evaluation and processing system. It can be operated in uprising and downrising mode. The profiler comprises a stainless steel housing (700 mm length, 155 mm diameter), microstructure and precision sensors with protection guard, removable weights, a ring of brushes to improve the dynamic stability, a recovery ring, a pull-relief and the output cable. Values measured by the sensors include temperature, shearing, vibration and electric conductivity. In addition to a compilation of technical data and to the results of calibration and test measurements, research results are presented obtained with the MST profiler in the Baltic Sea, in a Norwegian fjord and in seas of the Alps. (WEN)SIGLEAvailable from TIB Hannover: F97B614+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Comparison of dissipation of turbulent kinetic energy determined from shear and temperature microstructure

A total of 826 temperature and shear microstructure profiles, measured during 12 days in March 1996 in Lake Neuchatel (Switzerland), are used to compare estimates of turbulent kinetic energy dissipation, determined by the Batchelor (mu T; temperature) and the dissipation (mu S; shear) methods. Positioned horizontally 35 m apart, the two different profilers were raised through the nearly-homogeneous surface boundary layer. The collected time series covered different atmospheric forcings, including calm (approximate to 1 m s(-1)) and windy (> 10 m s(-1)) periods, as well as periods of thermally-induced convection (nights) and stratification (sunny days). Consequently, dissipation varied over 6 orders of magnitudes from 10(-11) to 10(-5) W kg(-1). The comparison of the 72'674 pairs of dissipation estimates, determined from 25 cm long vertical profile segments, reveals excellent agreement for the bulk of the estimates, with deviations smaller than a factor of 2. In a relatively small subset, collected under strong heating, deviations of up to a factor of 6 occur in 1-4 m depth. These deviations are, however, just about within the 95% confidence limits of the bootstrap distribution. Under low turbulence the mu T method tends to provide slightly larger dissipation, whereas for high wind-induced turbulence the mu S method gives larger dissipation

Measurement and simulation of viscous dissipation in the wave affected surface layer

In this study we compare turbulence parameters from field observations and model simulations specifically under the influence of weak to moderate wind forcing and breaking short waves. The experiment was performed during 12 days under very weak stratification at a fetch-limited lake in Switzerland. The near surface observations were obtained by using a quasi-free rising profiler which measured small scale shear and temperature fluctuations. We used a two-equation k-epsilon. turbulence model with an algebraic second-moment Closure scheme. The one-dimensional numerical model was extended to consider breaking waves by a shear-dependent parameterisation. The agreement of observed and simulated turbulence quantities is very promising. Especially well simulated is the enhanced turbulence level in the wave-affected-surface-layer (WASL) of a few din thickness. The logarithmic slope of the turbulent dissipation rate in this WASL was found to vary between -2.1 and -1.7. Below the WASL the classic law-of-the-wall was well reproduced by the data and the model