 |
| Titel |
Observations of tidal energy and tidal fluxes through the Turkish Straits System |
| VerfasserIn |
Jeffrey W. Book, Ewa Jarosz, Sukru Besiktepe, M. Kemal Cambazoğlu |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036538
|
|
|
|
|
|
| Zusammenfassung |
| From September 2008 through February 2009, The U.S. Naval Research Laboratory in
collaboration with NATO Undersea Research Centre and the Turkish Navy Office of
Navigation, Hydrography and Oceanography, used 8 Acoustic Doppler Current Profilers
(ADCPs) in 4 pairs to measure currents and pressure at the entrances and exits to the
Dardanelles and Bosphorus Straits inside the Turkish Strait System. The variability of
currents in the system are dominantly at synoptic and lower frequencies and the mean two
layer exchange of Aegean and Black Sea origin water has been the focus of much prior
research. However, current fluctuations at tidal frequencies also play a role in the Straits,
reaching 20% of the total variance in the mid-water column of the Southern Dardanelles.
Measurement of tidal currents and pressures simultaneously allows the calculation of the
energy fluxes of the barotropic tides. Preliminary estimates from select stations suggests that
net tidal energy passes from the Aegean to the Dardanelles (1.2 MW K1, 0.6 MW M2),
from the Dardanelles to the Sea of Marmara (0.3 MW K1, 0.2 MW M2), from the
Sea of Marmara to the Bosphorus (0.005 MW K1, 0.054 MW M2), and from the
Black Sea to the Bosphorus (0.006 MW K1, 0.086 MW M2). These results imply
that the Turkish Strait System acts to dissipate and/or generate baroclinic tides
from the supplied barotropic tidal energy and that this action in the Dardanelles
is frequency selective, creating an effective barrier to barotropic diurnal energy
transmission.
Although little barotropic tidal energy was found to pass from the Dardanelles to the Sea of
Marmara, total tidal energy levels inside the strait itself were similar between the southern
and northern sections. However, the distribution of tidal energy was very different between
these two sections. For M2 tides in the Dardanelles, modest levels of potential energy at the
Aegean entrance appear to be almost entirely transformed into kinetic energy at the Sea of
Marmara entrance. Thus, while tidal sea-surface-height fluctuations significantly
decrease in the Dardanelles from north to south, tidal currents increase due to both this
effect and to a narrowing of the passage. In all measured sections of the Turkish
Strait System, estimates of tidal kinetic energy greatly exceeded tidal potential
energy. For K1 tides in the Dardanelles, 97% of the kinetic energy was in the form of
vertically-uniform currents at the Aegean (southern) entrance but only 64% was in this form
at the Sea of Marmara (northern) entrance. Much less (93% to 87%) of the M2
kinetic energy was transformed in this way, suggesting the existence of a frequency
selective action of baroclinic tide generation in the Dardanelles. As expected from the
energy flux estimates, tidal energy was generally much lower in the Bosphorus
than in the Dardanelles, and primarily at semidiurnal frequencies. Also, less of the
tidal kinetic energy was carried by vertically-uniform currents in the Bosphorus for
both K1 (60% and 73%) and M2 (74% and 64%) tides. Our analysis finds that the
Turkish Strait System acts both as a barrier and a transformer of tidal fluctuations. |
|
|
|
|
|
|