Australien C. Teichert,Stratigraphy of Western Australia

Ohne Zusammenfassung     

Junge Vulkano-Plutone in Südwestafrika

Ohne Zusammenfassung     

Do bottom-intensified diurnal tidal currents shape the alignment of carbonate mounds in the NE Atlantic?

Measurements of near-seabed currents at different carbonate mound locations have demonstrated the presence and influence of bottom-magnified diurnal-period tidal motions. These bottom-trapped waves occur at a depth where the product of local vertical density stratification and seabed slope is a maximum. The seabed currents are magnified significantly if the diurnal forcing period is resonant with the combination of stratification and seabed slope. At the Belgica mounds (eastern Porcupine Sea Bight), there is a correlation between the cross-slope alignment of individual carbonate mounds and the direction of the major axis of the largest (diurnal) tides. The pattern suggests that the enhanced tidal currents play a major role in the shape of developing mounds over a long time period. A similar relation appears to hold at the Logachev mounds (SE Rockall Bank), although less clear because tides are not amplified to the same degree. At other mound locations where enhanced diurnal currents are not present, a more irregular distribution is observed. This suggests that the diurnal currents may be important only at certain carbonate mound locations, and that at these locations a more distinctive alignment of mound structures is produced.     

An examination of the radiative and dissipative properties of deep ocean internal tides

In this study, the energy flux and energy dissipation of deep ocean internal tides are examined. Properties of the internal tide from two distinct generation regions are contrasted: the Mid-Atlantic Ridge (MAR) and the Hawaiian Ridge. Considerable differences are noted for the baroclinic energy flux, u^′p^′, radiated from each site. Radiation from the MAR is relatively rich in high modes, with an energy flux spectral peak at mode 5 and modes 10 and greater accounting for 40% of the total flux. In contrast, Hawaiian Ridge radiation is dominantly composed of modes 1 and 2, with modes 10 and greater accounting for less than 5% of the total flux. Depth integrated energy flux levels are at the MAR site, and at the Hawaiian Ridge. Despite these differences, observed turbulent dissipation rates at these sites are similar in magnitude and depth dependence. Decay scales, estimated as , range from O(100)km to . The mean decay scale based on the MAR data is 230 km, a factor of 3 smaller than at the Hawaiian Ridge site. We demonstrate that the dissipation level scales with the energy flux available in the high modes, which is comparable at both sites, rather than the total energy flux.     

Total organic carbon in seawater — comparison of measurements using persulfate oxidation and high temperature combustion

A method is described for the determination of organic carbon in liquid seawater samples by combustion at a high temperature. Although the method is not easy to perform, it has been successfully employed for a direct comparison to the standard method of persulfate oxidation. With seawater from the central western North Atlantic Ocean, the standard method measured an average of 78% as much carbon as the high temperature method. This indicates organic matter in seawater that is resistant to oxidation by persulfate; some of it appears to be of a colloidal nature. The persulfate resistant organic matter is most noticeable in a region below the surface 100 m and seems to decrease slowly with depth, indicating deep ocean biological utilization of organic matter. Due to a possible procedural error in the standard persulfate oxidation method, the differences indicated here may actually be conservative and the content of total organic carbon in the sea may be as much as twice as high as has been indicated by previous estimates.