ALBERT

Description: An estimate of average river particulate matter (RPM) composition was bàsed on analyses of more than 40 elements in the Amazon, Congo, Ganges, Magdalena, Mekong, Parana and Orinoco rivers, to which were added literature data for 13 other major world rivers, covering the whole spectrum of morphoclimatic features. Geographic variations of major elements in RPM are mostly linked to weathering types and to the balance between weathering rate and river transport. As a result of chemical erosion, Al, Fe and Ti are enriched in RPM with respect to the average parent rock, while Na, Ca, Mg and Sr are strongly depleted. These figures are directly related to the relative importance of dissolved and particulate transport in rivers; this has been computed for each of 40 elements. In order to study weathering on a global scale, the total observed elemental fluxes (dissolved + particulate) have been computed and compared to theoretical ones. The latter were derived from the elemental content in the average parent rock and the total quantity of weathered material, computed from the Al ratio in RPM and in parent rock. Observed and theoretical fluxes are balanced for the less mobilized elements (rare earths, Co, Cr, Cs, Fe, Mn, Rb, Si, Th, Ti, U and V) for which no enrichment relative to Al is noted in RPM, and for B, Ba, Ca, K, Mg, Na, Sr which are relatively depleted in RPM due to their high dissolved transport. Additional fluxes have been found for Br, Sb, Pb, Cu, Mo, Zn and are possible also for Ni and P. This is reflected by marked enrichments in RPM relative to Al for the poorly or moderately dissolved transports (Pb, Cu, Zn). Several hypotheses involving either the natural origin (volcanic dust, marine aerosols, geochemical fractionation) or the artificial origin (worldwide pollution) are discussed to explain these discrepancies, assuming river transport and weathering either to be in a steady state on a global scale or not. However, none of them can fully account for these additional fluxes. It is most likely that these excesses have multiple origins, anthropogenic or natural or both. The comparison between RPM and deep-sea clay compositions emphasizes the prime influence of river input on oceanic sedimentation of Si, Al, Fe, Ti, lanthanides, Sc, Rb, V, etc. A few elements such as Zn, Sb, occur in excess in RPM as compared to deep-sea clays; in order to balance this excess, a remobilization of these elements out of the sediment can be considered. Finally, the enrichment of Co, Cu, Mn and Ni in deep-sea clays compared to RPM is discussed and attributed to several sources and processes.

Description: Several types of abyssal bedforms have been discovered during surveys with a deeply towed instrument package at water depths of 1.5–6 km in the Pacific and Atlantic Oceans. Cores and current-meter records obtained at the same sites provide data for interpreting their dynamics. Wave and current ripples are best portrayed in bottom photographs, but medium-scale bedforms, including sand waves, mud waves and erosional furrows, are described by interpreting high-resolution side-looking sonar records. The largest examples affect surface-ship echograms, though their shape and structure can seldom be resolved without near-bottom observations. Wave ripples are common on the slopes of seamounts and ridges, while current ripples and sand waves occur beneath some fast thermohaline currents whose beds are shallower than the foraminiferal compensation depth. Depositional and erosional bedforms in cohesive sediment have been found beneath the deepest thermohaline currents; they may be restricted to areas where the flow is unusually steady in direction.

Description: The effects of hydrostatic pressure and dissolved oxygen concentration on oxygen consumption rates were examined in the mesopelagic, vertically migrating squid Histioteuthis heteropsis from southern California offshore waters. Elevated hydrostatic pressure (to 136 atm) had no significant effects on oxygen consumption rates at 5°C. Lox oxygen concentrations (〈0.5 ml O2 liter -1) depressed rates of oxygen consumption. These findings suggest that biosis may be necessary to supply the total nergy needs of this species at daytime depths in the oxygen minumum layer off southern California.

Description: The ratio of compressional wavevelocityV p to shear wavevelocityV s , and Poisson’s ratio in marine sediments and rocks are important in modeling the sea floor for underwater acoustics,geophysics, and foundation engineering. V p and V s versus depth information was linked at common depths in terrigenous sediments (to 1000 m) and in sands (to 20 m) to yield data on V p vs V s , and V p /V s and Poisson’s ratios versus depth. Soft, terrigenous sediments usually grade with depth into mudstones and shales; V p /V s ratios vary from about 13 or more at the sea floor to about 2.6 at 1000 m. Poisson’s ratios vary from above 0.49 at the sea floor to about 0.41 at 1000 m. In sands, V p , V s , and V p /V s have very high gradients in the first few meters; below about 5 m, V p /V s ratios decrease from about 9 to about 6 at 20 m; Poisson’s ratios vary from above 0.49 at the surface to above 0.48 at 20 m. The mean value of V p /V s in 30 laboratory samples of chalk and limestone is 1.90 (standard error: 0.03); mean Poisson’s ratio is 0.31. Literature data on basalts from the sea floor are reviewed. Equations relating V p to V s are given for terrigenous sediments, sands, and basalts.

Description: A new equation for the speed of sound in sea water has been developed with validity not only for realistic combinations of the parameters salinity, temperature, and pressure, but with extension to pure water as well. This new equation, referred to as NRL II, has a standard deviation of 0.05 m/sec. Tables are presented comparing calculations using this new model to each of eight earlier equations. Graphs are also included indicating approximate corrections that could be applied to existing sound speed profiles, but it is recommended that such profiles be recalculated and new ones obtained according to NRL II.