Description: Two high-resolution hydrographic sections occupied during February, March 1989 in the western and eastern basins of the North Atlantic at 14.5N are combined to study the water mass structure and meridional mass and heat transports. Absolute velocities were determined using these data and an earlier section at 8N in a linear inverse analysis. Mass balance for several layers representing the main water masses in the region and a zero net divergence for the sum of geostrophic and Ekman transport between the two sections are assumed. Using the annual mean of Ekman transports (13.6 Sv, 14.5N), (15.2 Sv, 8N) based on the climatology by Isemer and Hasse (1985) the annual average fluxes for the sections at 8N and 14.5N have been calculated. For the annual mean the strength of the meridional overturning cell at 14.5N amounts to 15.9 Sv with an associated heat transport of 1.22 PW. A similar value can be obtained at 8N where the annual mean heat transport reaches 1.18 PW and the overturning cell measures 15 Sv. The total northward heat transport is strongly dominated by the wind-driven Ekman heat transport. 'In-situ' values of heat transport using the actual wind-driven transports for the respective months yield even higher estimates. Heat transport at 14.5N rises to 1.37 +/- 0.42 PW (February) and the maximum is now at the 8N section, 1.69 +/- 0.52 PW (May). Comparisons of our results with another tropical section at 11N occupied concurrently demonstrate the large variability in heat transport related to changes in the wind field. Due to extremely weak winds in the eastern Atlantic and a resulting low Ekman transport, the 'in-situ' value of heat transport through this section ranged between 0.30 +/- 0.18 PW and 0.59 +/- 0.18 PW depending on the value chosen for the Ekman transport. The lower of the two heat transport estimates results from calculations with the actual observed winds and the other using a monthly climatological mean. That even the computations with the climatological monthly mean give such a low heat transport points to additional changes in the baroclinic structures between 11N and 14.5N.

Description: The spatial distribution of the subtropical salinity maximum is identified using historical and recent data from the eastern North Atlantic. In the regions with high frequency of occurrence of the salinity maximum, the relative contributions of advection, eddy diffusion and double diffusion to the salt balance below the maximum salinity layer are determined. McDougall's (1984, Journal of Physical Oceanography, 14, 1577–1589) salt balance equation for neutral surfaces is used in this analysis. The data base consists of two meridional CTD sections along 33° and 27°W between 10° and 35°N, mean temperature-salinity profiles in 5° × 5° squares presented by Emery and Dewar (1982), and mean velocity profiles in 3° × 3° squares evaluated by Stramma (1984, Journal of Marine Research, 42, 537–558). The tropical salinity maximum tongue is found to be quite persistent in its salinity value and its geographic distribution, but less clearly in its vertical or isopycnal position. Double diffusion due to salt-fingering appears to be an important process for the salt balance below the salinity maximum layer. An approximate estimate of the double-diffusive salt flux is obtained. Near the subtropical source region, the double-diffusive salt flux is balanced primarily by isopycnal advection; further to the south it is also balanced by isopycnal eddy diffusion. Maximum double-diffusive fluxes correspond in magnitude to the mean salt flux caused by the excess in evaporation at the surface in the central subtropics. The resulting isopycnal and diapycnal eddy-mixing coefficients derived by a linear inversion technique have the reasonable values of Ki = (11 ± 5) × 102 m2 s−1 and Kd = (4 ± 2) × 10−5 m2 s−1. Considering the intermittency of the double-diffusive process, limiting values for the mean eddy-mixing coefficients are determined by neglecting the contribution of the double-diffusive salt fluxes. This leads to Ki = (5 ± 2) × 102 m2 s−1 and Kd = (5 ± 1) × 10−5 m2 s−1 for the isopycnal and diapycnal mixing coefficients, respectively.

Description: Current data obtained from 7 moorings in the Northeast Atlantic in the course of many years are analysed with respect to semi-diurnal barotropic and baroclinic tides and diurnal barotropic tides. For semi-diurnal tides M2 and S2 the energy distribution is usually dominated by the barotropic mode; only in a few cases does the first-order baroclinic mode contain higher energy. Barotropic tidal ellipse orientations are found to be consistent with results from earlier tide gauge observations in this area. Significant deviations occur, however, in amplitudes. Results for the diurnal component K1 are also presented. With few exceptions, tides are found to be progressive waves in this area. The current ellipse pattern is similar to results obtained indirectly by Cartwright, Edden, Spencer et al. [1980] from tide gauge observations.

Description: Horizontal velocity and temperature measurements observed from a two-dimensional array of moored instruments, mooring Fl, are analysed to describe the near-surface internal wave field in the GATE (GARP Atlantic Tropical Experiment) C-scale area. Spectral properties indicate strong deviations from the Garrett and Munk (1972, 1975) deep ocean internal wave models. The frequency spectrum in the upper pycnocline is dominated by three energetic bands centered at 0.0127 (inertial frequency), 0.08 (M2-tidal frequency) and 3 cph. The latter frequency band does not correspond to the local Brunt Väisälä frequency (〈 10 cph) and contains about one half of the total internal wave energy of fluctuations with periods less than 10 hours. Cross-spectral analysis of the high frequency internal waves yields corresponding wavelengths of order 1 km consistent with westward propagating first mode wave groups, if the effect of Doppler shift due to a strong mean current is taken into account

Description: The data from six zonal sections in the World Ocean Circulation Experiment (WOCE) in the tropical and southem Atlantic are used to describe the distribution of water masses. Due to the high spatial resolution, the structure oftemperature, salinity, oxygen, silicate and nitrate displays details related to transport and mixing in this region. Temperature-salinity diagrams are also presented which indicate the effects ofbranching and recirculation loops in the water mass flow.

Description: Anhand hundertjähriger Meßreihen wurden langfristige Salzgehaltsänderungen in der Unterweser und ihre möglichen Ursachen untersucht. Dabei wurde angestrebt, die natürlichen und die anthropogenen Einflüsse auf den Salzgehalt zu trennen. Trotz des unvollständigen Datensatzes konnten der Einfluß des Einzugsgebietes und Salzgehaltsschwankungen des angrenzenden Meeresgebietes nahezu eliminiert werden. Wegen der langzeitigen Änderungen der Gezeiten in der Nordsee waren genaue Aussagen über die Auswirkung der in den letzten hundert Jahren in der Unterweser durchgeführten Baumaßnahmen auf den Salzgehalt nicht möglich. Unsere Ergebnisse geben Hinweise für moderne Meßnetze zur Bestimmung der Wasserqualität.