Model estimates for the interaction of wind waves and tides in the Pechora Basin-White Sea subsystem

The “weak-interaction” approximation is used to investigate the role of wind waves in tidal dynamics. The resulting expression for the drag coefficient in the wave-affected tidal flow is incorporated into the QUODDY-4 three-dimensional finite-element hydrothermodynamic model, and the thus modified model is used to calculate the K ₁ diurnal tide in the Pechora Basin-White Sea subsystem. It is shown that, depending on a combination of local and nonlocal factors, wind waves can cause opposite variations in the amplitudes and phases of tidal oscillations of the level. Local factors control variations in the tidal regime nearly in the entire water area of the subsystem under consideration, apart from the eastern part of the Pechora Basin, the outlet from the White Sea Throat, and Dvina Bay. In the aforementioned areas, the tidal regime changes are due either to the displacement of the nearest amphidromy or to other nonlocal factors resulting from the reorganization of the fields of tidal characteristics. It is also shown that the variations in tidal characteristics induced by wind waves vary within a fairly wide range and that allowance for the interaction of wind waves and tides improves the agreement between calculated and observed values of the amplitudes and phases of tidal oscillations of the level.     

Numerical simulation of unsteady free-surface motions using a boundary integral formulation

A numerical time simulation method is described to solve fluid flow problems including unsteady free surface motion. The method is based on potential flow theory. At every time step, the problem is solved using a boundary integral formulation of the fluid domain. The linearized free surface conditions are integrated in time and the solution is marched forward. Computational results simulating the free surface motion for the cases of a linear progressive wave, wave propagating into a region of calm water and the wave maker motion are presented. Comparison with theoretical results demonstrate the feasibility of the proposed simulation scheme.     

Study of fluoride in polluted and unpolluted estuarine environments

Mindhola River estuary, which receives industrial waste containing high concentrations of fluoride, and Purna River estuary, which is free from fluoride contamination, have been investigated. While fluoride behaved conservatively in Purna River estuary, significant deviation from the theoretical dilution line (TDL) in the chlorinity range 0·5–8‰ was observed in Mindhola River estuary due to the externally added fluoride which largely remained in solution. The excess of fluroide over the theoretically calculated value was at a maximum around a chlorinity of 3‰. High natural fluoride content of the river waters resulted in F/Cl ratios exceeding 300 × 10⁻⁵ at low chlorinities. The ratio decreased rapidly with increasing chlorinity and the value near to that of seawater was observed at chlorinities above 14‰.     

Tectonics at the intersection of the East Pacific Rise with Tamayo Transform fault

During the Fall of 1979, a manned submersible program, utilizing DSRV ALVIN, was carried out at the intersection of the East Pacific Rise (EPR) with the Tamayo Transform boundary. A total of seven dives were completed in the vicinity of the EPR/Tamayo intersection depression and documented the geologic relationships that characterize the juxtaposition of these types of plate boundaries. The young volcanic terrain of the EPR axis can be traced into and across the Tamayo Transform valley but becomes buried by sedimentary talus that is being shed from sediment scarps along the unstable sediment slope that defines the north side of the intersection depression. Within 4 km of the transform boundary, the dominant trend (000°) of the fissures and faults that disrupt the rise-generated volcanics is markedly oblique to the regional direction of sea floor spreading (120°). Since no evidence was found to suggest that these structures accommodate significant amounts of strike-slip displacement, they are taken to reflect a distortion of the EPR extensional tectonic regime by a transform generated shear couple. The floor of the Tamayo Transform valley in this area is inundated by mass-wasted sediment, and the principal transform displacement zone is characterized at the surface by a narrow (<1.5 km) interval of fault scarps in sediment that trends parallel with the transform valley. Extrapolated to the west, this zone links with zones of transform deformation investigated during earlier submersible studies (CYAMEX and Pastouret, 1981). Evidence of low-level hydrothermal discharge was seen at one locality on the EPR axis and at another 8 km west of the axis at the edge of the zone of transform deformation.