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| Titel |
Unpredictability of internal M2 |
| VerfasserIn |
H. Haren |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 3, no. 2 ; Nr. 3, no. 2 (2007-06-15), S.337-344 |
| Datensatznummer |
250000932
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| Publikation (Nr.) |
 copernicus.org/os-3-337-2007.pdf |
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| Zusammenfassung |
| Current observations from a shelf sea, continental slopes and the
abyssal North-East Atlantic Ocean are all dominated by the semidiurnal lunar
(M2) tide. It is shown that motions at M2 vary
at usually large barotropic and coherent baroclinic scales, >50 km
horizontally and >0.5 H vertically. H represents the waterdepth. Such
M2-scales are observed even close to topography, the potential
source of baroclinic, "internal" tidal waves. In contrast, incoherent
small-scale, ~10 km horizontally and ~0.1 H vertically,
baroclinic motions are dominated around f, the local inertial frequency,
and/or near 2Ω≈S2, the semidiurnal solar
tidal frequency. Ω represents the Earth's rotational vector. This
confirms earlier suggestions that small-scale baroclinic
M2-motions generally do not exist in the ocean in any
predictable manner, except in beams very near, <10 km horizontally, to
their source. As a result, M2-motions are not directly
important for generating shear and internal wave induced mixing. Indirectly
however, they may contribute to ocean mixing if transfer
to small-scale motions at f and/or S2 and at high internal wave frequencies can be proven. Also far
from topography, small-scale motions are found at either one or both of the
latter frequencies. Different suggestions for the scales at these particular
frequencies are discussed, ranging from the variability of "background"
density gradients and associated divergence and focusing of internal wave
rays to the removal of the internal tidal energy by non-linear interactions.
Near f and S2 particular short-wave inertio-gravity
wave bounds are found in the limits of strong and very weak stratification, which are
often observed in small-scale layers. |
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