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On the currents over the shelf off cap blanc in the northwest African upwelling areaстатья
Информация о цитировании статьи получена из
Scopus
Дата последнего поиска статьи во внешних источниках: 28 мая 2015 г.
- Авторы: Mittelstaedt E., Koltermann K.P.
- Журнал: Deutsche Hydrographische Zeitschrift
- Том: 26
- Номер: 5
- Год издания: 1973
- Первая страница: 193
- Последняя страница: 215
- DOI: 10.1007/BF02232613
- Аннотация: An interpretation of current measurements yields, as a typical feature of the cross-component over the upper slope, two circulation cells with opposite rotation. Here coastal upwelling has been assumed to be mainly a two-dimensional phenomenon. Over the upper continental slope the core of the subsurface onshore return flow (∼+10 cm s-1) occurs at intermediate depths of 60 m to 70 m and above the bottom over the shelf. This flow causes a convergence just beneath the actual relatively shallow upwelling layer. A great part of the water masses of the return flow feeds the Ekman flux in the surface layer. Another minor part, however, sinks down the slope contributing to a weak offshore component above the bottom. It is suggested that the strength, the thickness and the depth of the onshore compensation flow increase with the intensity of upwelling. The observations, moreover, give evidence of a ’coastal jet’ at the surface and a poleward going undercurrent. The amplitude of the effective fluctuations superposing the mean flow is larger over the slope than over the shelf. In the spectra the amplitude of the semi-diurnal tide is dominating. It seems to be constant within the upper 100 m independent of depth, but is increasing at greater depths. Over the shelf no significant fluctuations with periods smaller than the semi-diurnal tide have been observed. This is probably due to relatively strong mixing, dissipating the short oscillations of lower energy over the shelf. However, in contrast to the conditions over the slope, even longer periods than the semidiurnal tide, as for example the inertial fluctuations (∼33 h), are insignificant over the shelf during the period of observations. © 1973 Deutsches Hydrographisches Institut.
- Добавил в систему: Koltermann Klaus Peter