| one publication added to basket [58364] | Current spectra under varying stratification conditions in the central North Sea
In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101; e-ISSN 1873-1414, more
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| Keywords |
Atmospheric forcing
Energy > Kinetic energy
Properties > Physical properties > Mechanical properties > Strength > Shear strength
Seasons > Summer
Seasons > Winter
Spectra
Stratification
Temporal variations > Periodic variations > Seasonal variations
Water waves > Internal waves
ANE, North Sea [Marine Regions]
Marine/Coastal |
| Author keywords |
spectra; seasonal stratification; central North Sea |
| Abstract |
Given strongly different vertical stratification and not significantly different kinetic energy, `internal wave' band spectral properties were studied using two 8-day representative sets of observations from the central North Sea in winter and summer. The observed similar spectral shape of the internal wave band was due to a combination of deterministic narrow band and intermittent signals. In addition to dominant tidal harmonics, 25% of total kinetic energy was found at inertial and non-linear inertial-tidal interaction frequencies in summer and about the same amount was found in broad-band response to atmospheric forcing in winter. The energy at the (seasonal) non-linear interaction frequencies was proportional to stratification, specifically, to near-inertial shear magnitude. In summer, motions at frequencies (σ) between f<σ< 2.5 cpd (cycles per day) appeared in low vertical mode, whilst the power P(σ) of motions at σ> 4 ±1 cpd obeyed canonical internal wave scaling P(σ) ~ C-2, provided the shear magnitude [S] was used instead of the buoyancy frequency N for the factor C. Motions at 2.5 <σ< 4 ± 1 cpd appeared as transition between the two regimes. In winter no inertial motions were observed. |
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