Light-induced bird strikes on vessels in Southwest Greenland

Light-induced bird strikes are known to occur when vessels navigate during darkness in icy waters using powerful searchlight. In Southwest Greenland, which is important internationally for wintering seabirds, we collected reports of incidents of bird strikes over 2-3 winters (2006-2009) from navy vessels, cargo vessels and trawlers (total n = 19). Forty-one incidents were reported: mainly close to land (<4 km, 78%), but one as far offshore as 205 km. Up to 88 birds were reported killed in a single incident. All occurred between 5 p.m. and 6 a.m. and significantly more birds were involved when visibility was poor (snow) rather than moderate or good. Among five seabird species reported, the common eider (Somateria mollissima) accounted for 95% of the bird casualties. Based on spatial analyses of data on vessel traffic intensity and common eider density we are able to predict areas with high risk of bird strikes in Southwest Greenland.     

Velocity variations in carbonate rocks due to dual porosity and wave-induced fluid flow

Stiffness variations in carbonates may be described as resulting from different concentrations of flat compliant pores or cracks, which can have a significant effect on the effective stiffness and acoustic properties (e.g., velocities and attenuations) of dry as well as saturated carbonates, although they carry extremely little porosity. As shown in this paper, the effects of dual porosity and wave-induced fluid flow or pore pressure communication may also play a significant role. On the basis of a previously published T-matrix approach to model the effective viscoelastic properties of cracked porous media, we illustrate the (frequency-dependent) effects of wave-induced fluid flow (mainly squirt flow) or pore pressure communication for a model structure consisting of a mixture of fluid-saturated porous grains and fluid-saturated cavities (vugs, etc.) that are embedded in a solid matrix associated with carbonates. We assume that the pores within the porous grains are decoupled from the pores in the solid matrix (and possibly saturated with different fluids) but that each pore system at the micro and/or mesoscale may or may not be connected. For each of four different connectivity models, we present numerical results for four different cases of microstructure (that emphasize the importance of cracks and flat compliant pores). Our numerical results indicate that the velocity and attenuation spectra of carbonates vary significantly, even when the crack density and all other volume concentrations are constant.     

An inflationary cosmological model in Dunn's scalar-tensor theory of gravitation

The gravitational field equations in Dunn's scalar-tensor theory of gravitation are generalized by including a cosmological constant. The resulting equations are solved for a Robertson-Walker line-element with flat three-space. The solution represents a cosmological model that develops into an inflationary era.     

The influence of glaciation on the basin temperature regime

The effect of glaciation on the temperature regime in a sedimentary basin has been estimated. Four modeling cases, representing glaciation with cold (permafrost) glaciers and temperate glaciers as well as non-glaciation, were undertaken. The thermal consequences of taking the glaciation into account can be significant. Subsurface temperatures during a cold (permafrost) glaciation were as much as 25°C lower than the subsurface temperatures in a non-glaciated case. Increased conductivities due to frozen pore water contributed significantly to the cooling of the subsurface. Given two cases of cold glaciation, the first with increased thermal conductivities due to freezing of pore water and the second with no effect of freezing, the first case results in up to 10°C lower subsurface temperatures than the second one. A temperate glacier with a temperature of 0°C at the ice/sediment boundary is, as expected, less significant compared to a cold glacier. In this case subsurface temperatures were up to 7°C lower than the subsurface temperatures in the non-glaciated case. Thus it is crucial to know which type of glacier is present at which time as well as the effect of frozen pore water on thermal conductivity in order to have a good estimation of subsurface temperatures in glaciated areas.     

The acoustic signature of fluid flow in complex porous media

Effective medium approximations for the frequency-dependent and complex-valued effective stiffness tensors of cracked/porous rocks with multiple solid constituents are developed on the basis of the T-matrix approach (based on integral equation methods for quasi-static composites), the elastic–viscoelastic correspondence principle, and a unified treatment of the local and global flow mechanisms, which is consistent with the principle of fluid mass conservation. The main advantage of using the T-matrix approach, rather than the first-order approach of Eshelby or the second-order approach of Hudson, is that it produces physically plausible results even when the volume concentrations of inclusions or cavities are no longer small. The new formulae, which operates with an arbitrary homogeneous (anisotropic) reference medium and contains terms of all order in the volume concentrations of solid particles and communicating cavities, take explicitly account of inclusion shape and spatial distribution independently. We show analytically that an expansion of the T-matrix formulae to first order in the volume concentration of cavities (in agreement with the dilute estimate of Eshelby) has the correct dependence on the properties of the saturating fluid, in the sense that it is consistent with the Brown–Korringa relation, when the frequency is sufficiently low. We present numerical results for the (anisotropic) effective viscoelastic properties of a cracked permeable medium with finite storage porosity, indicating that the complete T-matrix formulae (including the higher-order terms) are generally consistent with the Brown–Korringa relation, at least if we assume the spatial distribution of cavities to be the same for all cavity pairs. We have found an efficient way to treat statistical correlations in the shapes and orientations of the communicating cavities, and also obtained a reasonable match between theoretical predictions (based on a dual porosity model for quartz–clay mixtures, involving relatively flat clay-related pores and more rounded quartz-related pores) and laboratory results for the ultrasonic velocity and attenuation spectra of a suite of typical reservoir rocks.     

Deep seismic reflection profiles across the western Barents Sea

Summary. The continental crust beneath the western Barents Sea has been acoustically imaged down to Moho depths in a large scale deep seismic reflection experiment. A first-order pattern of crustal reflectivity has been established and the thickness of the crust determined. A number of features with important implications for the tectonics of the area have been discovered. The results are presented in the form of two transects.     

Viscous inflationary universe models

The research on viscous cosmological models is reviewed and carried further. Inflationary cosmological models of Bianchi type-I with shear, bulk, and nonlinear viscosity are studied. The inflation field energy is represented by a two-components cosmic fluid consisting of a vacuum fluid and a Zel'dovich fluid. It is shown that there exist models in which the viscous Zel'dovich fluid removes the initial singularity of the corresponding viscosity free models. The mean expansion of a Zel'dovich dominated unvierse is found to be independent of shear viscosity and anisotropy. Bulk viscosity and shear viscosity cause exponential decay of anisotropy, while nonlinear viscosity causes power-law decay of anisotropy.