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| Titel |
The evolution of an internal bore at the Malin shelf break |
| VerfasserIn |
J. Small, T. C. Sawyer, J. C. Scott |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 17, no. 4 ; Nr. 17, no. 4, S.547-565 |
| Datensatznummer |
250013716
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| Publikation (Nr.) |
 copernicus.org/angeo-17-547-1999.pdf |
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| Zusammenfassung |
Observations of internal waves were made at
the Malin shelf edge during SESAME (Shelf Edge Studies Acoustic Measurement
Experiment), a part of the NERC LOIS-SES experiment, in August-September 1996.
These measurements provide a high resolution dataset demonstrating internal wave
generation and propagation. This note presents observations of the evolution of
an internal bore. The process is shown clearly in a sequence of thermistor chain
tows across the shelf break covering a complete tidal cycle, as the double-sided
bore transforms into a group of undulations and eventually into more distinct
solitary waveforms. Current structures associated with the bore and waves were
also observed by ship-mounted ADCP. Analysis of the waveforms in terms of the
linear modes and empirical orthogonal functions (EOFs) indicate the dominance of
the first mode, which is typical of a shallow water seasonal thermocline
environment. Determination of the phase speed of the waves from the consecutive
ship surveys enabled the Doppler shift in the towed data to be removed, allowing
analysis of the real length scales of the waves. The bore evolution has been
modelled using a first order non-linear KdV model for the first mode,
initialised with the waveform in the first survey. Comparison of the model and
the observations show close agreement in the amplitudes, length scales, phase
speeds and separations of the leading internal waves as they evolve. Finally,
analysis of the observed internal wave shapes indicates that, within the
uncertainties of measurement, the wave-lengths lie between those predicted by
first and second order soliton theory.
Key words. Oceanography: general (continental shelf
processes; ocean prediction). Oceanography: physical (internal and inertial
waves) |
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