Current Kinetic Energy Research Articles

The Structure of Currents in the Western Middle Caspian Sea: Present-Day Studies

Data on the dynamics of bottom currents along the western coast of the Middle Caspian are given. The contributions of the mean kinetic energy of currents and the energy of perturbation to the total energy of currents are shown at different space and time scales of variations and for different seasons of the year. The results of studies are based on experimental data collected by CTD sounding of water mass, measuring currents with the use of Potok-M instruments, ADCP Doppler acoustic current meters in the regime of sounding and towing, as well as stationary measurements at submerged buoy stations.

Reconstruction of the three-dimensional salinity and temperature fields of the Black Sea on the basis of satellite altimetry measurements

The methodology of joint processing of the satellite altimetry and occasional hydrological observations in the Black Sea for 1993–2012 is developed. The original technique for reconstruction of the 3D temperature and salinity fields in the deep-sea part is proposed and implemented. This technique makes it possible to identify the depths at which a contribution of adiabatic processes to the deformation of the temperature and salinity profiles of the sea is predominant. Daily-averaged 3D fields of the seawater temperature and salinity in a baroclinic layer on a regular grid are reconstructed. The evaluation of accuracy of the reconstructed temperature and salinity arrays is performed by comparing them with the data of hydrological exploration. Structures of the temperature and salinity fields are correlated naturally with topography of the altimetric level and clearly indicate the synoptic variability. Seasonal and interannual variabilities of the kinetic energy (averaged over horizons of the 63–400 m layer) of the geostrophic currents calculated using the dynamic method makes it possible to reveal a sharp increase in the kinetic energy of the currents in the winter season of 2002. A high correlation is found between the interannual variability of the ERA-Interim wind stress curl averaged over the surface of the deep sea part and the kinetic energy of the geostrophic currents in the 63–400 m layer.

Effect of tidal stream power generation on the region-wide circulation in a shallow sea

Abstract. This paper quantifies the backward effect on the ocean currents caused by a tidal stream farm located in the open shallow sea. Recent studies in channels with 1-D models have indicated that the power potential is not given purely by the flux of kinetic energy, as has been commonly assumed. In this study, a 3-D ocean circulation model is used to estimate (i) practically extractable energy resource at different levels of rated generation capacity of the farm, (ii) changes in the strength of currents due to energy extraction, and (iii) alterations in the pattern of residual currents and the pathways of passive tracers. As well as tidal streams, the model also takes into account the wind-driven and density-driven ocean currents. Numerical modelling has been carried out for a hypothetical tidal farm located in the Celtic Sea north of Cornwall, an area known for its high level of tidal energy. Modelling results clearly indicate that the extracted power does not grow linearly with the increase in the rated capacity of the farm. For the case study covered in this paper, a 100-fold increase in the rated generation capacity of the farm results in only 7-fold increase in extracted power. In the case of a high power farm, kinetic energy of currents is altered significantly as far as 10–20 km away from the farm. At high levels of extracted energy the currents tend to avoid flowing through the farm, an effect which is not captured with 1-D models. Residual currents are altered as far as a hundred kilometres away. The magnitude of changes in the dispersion of tracers is highly sensitive to the location. Some of the passive drifters analysed in this study experience significant variations in the end-to-start distance due to energy extraction ranging from 13% to 238% while others are practically unaffected. This study shows that both energy extraction estimates and effects on region wide circulation depend on a complex combination of factors, and the specific figures given in the paper should be generally considered as first estimates.

Ocean current and temperature time series at Brothers volcano

Time series of currents and temperatures were acquired near surface and at depth on three moorings above Brothers volcano (34° 52.25′S, 179° 04′E), ∼25 km west of the Kermadec Ridge and ∼300 km northeast of the North Island, New Zealand, from September 2004 to May 2005. Ocean current time series were previously unavailable within 300 km of this site, and few such measurements exist anywhere near magmatically or hydrothermally active volcanoes such as Brothers. Energy in near surface currents (163–527 m depth) was primarily subtidal (64%). Subtidal motions to 527 m depth are shown to be reasonably well correlated with geostrophic currents derived from satellite sea level anomalies. Although the moorings were separated laterally by only 11 km, the upper current meters also recorded significant differences in M2 tidal currents, indicating the presence of significant internal tides at this site. Below volcano summit depth (1220 m), the kinetic energy of currents was primarily tidal (54%). Longer period currents at depth evidenced the influence of volcano topography. Temperature time series showed a 3‐month period of sharply decreased temperature that extended in depth from 163 m to at least 1260 m. Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature data show colder surface water immediately above and north of Brothers over the same time period. These data together with the velocity records suggest an anomalous, deep, cold water mass arrived and lingered over Brothers for 3 months in the austral late spring and early summer of 2004–2005.

Analysis of the Large-Scale Dynamics of Surface Waters in the Southern Ocean with the Help of Lagrangian Drifters

We summarize the results of reconstruction of the monthly average surface circulation in the Southern Ocean according to the paths of autonomous drifting buoys launched in the course of the First Global Geophysical Experiment (FGGE) according to the Program of Investigation of Global Atmospheric Processes in 1978–1980. The data of numerical analysis reveal significant annual and seasonal variability in the behavior of the integral characteristics of the Antarctic Circumpolar Current, the west extension of the Agulhas Current, the zone of convergence of the Falkland and Brasil Currents, and the cyclonic gyres in the Weddell and Ross Seas. It is established that the dynamics of the large-scale surface circulation in the Southern Ocean can be described by two or three empirical orthogonal modes. In general, we observe a strong correlation between the locations of the zones with high kinetic energy of currents and the zones of bottom rise.

Statistical characteristics of currents and seawater temperature near the Florida Strait

Average and extreme values of the current velocity, seawater temperature, and their standard deviations are considered on the basis of measurements carried out at three moorings deployed in the Florida Strait. The contributions of the low-frequency (synoptic) and mesoscale variations of currents and the seawater temperature to their temporal variability are estimated. The kinetic energy values of the averaged current and the synoptic and mesoscale variations are given. Their contributions to the general (total) kinetic energy of currents are determined. It is shown that the pulsations of the north-east trade wind can be one of the reasons for the synoptic variations in the field of currents and seawater temperature.

Control of Equatorial Ocean Currents by Turbulent Dissipation

The importance of turbulence in the flow of equatorial currents has been noted by modelers but not observed. Recent measurements of turbulence show an increase in strength at the equator and confirm its role as a sink of the kinetic energy of currents at the equator.