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- Author or Editor: Jürgen Kielmann x
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Abstract
A 50-day time series was obtained from a current meter mooring in the Florida Current off Miami. The results agree with earlier observations regarding the significance of several-day oscillations in the Gulf Stream. The energy spectrum of the V component shows a pronounced peak at periods of 5–6 days with an amplitude of about 20 cm sec−1. Quantitatively the results are reminiscent of barotropic shelf waves, although definite conclusions about the occurrence of such waves require additional observations.
Analysis of tidal fluctuations shows that 25% of the variance in the V component and 6% of the variance in the U component can be accounted for by the four major constituents, M2, S2, K1 and O1. The largest constituent in the V component is the O1 tide, whereas the K1 tide dominates in the U component. The results are in good agreement with earlier observations from the sea surface, indicating that the vertical structure of the tides is predominantly barotropic.
Abstract
A 50-day time series was obtained from a current meter mooring in the Florida Current off Miami. The results agree with earlier observations regarding the significance of several-day oscillations in the Gulf Stream. The energy spectrum of the V component shows a pronounced peak at periods of 5–6 days with an amplitude of about 20 cm sec−1. Quantitatively the results are reminiscent of barotropic shelf waves, although definite conclusions about the occurrence of such waves require additional observations.
Analysis of tidal fluctuations shows that 25% of the variance in the V component and 6% of the variance in the U component can be accounted for by the four major constituents, M2, S2, K1 and O1. The largest constituent in the V component is the O1 tide, whereas the K1 tide dominates in the U component. The results are in good agreement with earlier observations from the sea surface, indicating that the vertical structure of the tides is predominantly barotropic.
Abstract
Numerical experiments with an 11-level primitive equation, finite-difference model in a periodic channel are performed to analyze the properties of unstable finite-amplitude disturbances in an idealized Azores Current. Release of available potential energy due to baroclinic instability occurs preferentially on scales of about 100 km with a theoretical growth time of 8 days. At larger times, the combined effect of friction and nonlinear transfer between internal and external (depth integrated) mode and the distribution of energy among different wavenumbers of the initial disturbance determine the scale of the meandering jet. Cold water tongues with a meridional scale of several hundred km found in satellite images and hydrographic surveys east of the Azores are prescribed as initial disturbances. They develop into pairs of troughs and ridges dominated by cyclonic vortices on the poleward flank of the jet. Phase propagation is downstream at 2–4 km day−1. Extremely strong frontogenetic enhancement of temperature occurs on the downstream side of the ridges, which gives rise to vertical velocities of order 10 m day−1. Phase relations for baroclinically unstable waves indicate a mean poleward heat flux similar to observations in the Azores Current region.
Abstract
Numerical experiments with an 11-level primitive equation, finite-difference model in a periodic channel are performed to analyze the properties of unstable finite-amplitude disturbances in an idealized Azores Current. Release of available potential energy due to baroclinic instability occurs preferentially on scales of about 100 km with a theoretical growth time of 8 days. At larger times, the combined effect of friction and nonlinear transfer between internal and external (depth integrated) mode and the distribution of energy among different wavenumbers of the initial disturbance determine the scale of the meandering jet. Cold water tongues with a meridional scale of several hundred km found in satellite images and hydrographic surveys east of the Azores are prescribed as initial disturbances. They develop into pairs of troughs and ridges dominated by cyclonic vortices on the poleward flank of the jet. Phase propagation is downstream at 2–4 km day−1. Extremely strong frontogenetic enhancement of temperature occurs on the downstream side of the ridges, which gives rise to vertical velocities of order 10 m day−1. Phase relations for baroclinically unstable waves indicate a mean poleward heat flux similar to observations in the Azores Current region.
