On the excitation of resonant double Kelvin waves in the Barents Sea Opening

In the northern Barents Sea Opening (BSO) the K1 tidal energy is predominant in the diurnal tidal frequency band, suggesting the generation of a topographic wave with the K1 tidal frequency. Tidal energy of the K1 component becomes strong where bottom topography undulates in the BSO and the scale of the undulation is close to the wavelength of the K1 wave. An analytical model is developed to investigate the energy enhancement mechanism of the tidally induced topographic wave due to a resonance between tidal current, a topographic wave and periodic topography. The wave excited by the resonance is identified as a resonant double Kelvin wave (DKW) and the significant K1 energy in the BSO could be due to the excitation of the resonant DKW

Tidal motion enhancement around islands

Tidally-generated, trapped motions can significantly enhance and modify sea level and currents in the island proximity. The analytical solution for incident waves interacting with a cylindrical island with a circular sill has been constructed to investigate this phenomenon. To derive solutions for the scattering problems simple Sverdrup and Kelvin waves are used as incident waves. The amplification of the signal along the island perimeter has shown to be a function of frequency, relative dimensions of the island and the circular sill surrounding the island, relative sill depth, and the bottom friction. Although the incident diurnal tide may be amplified through the resonant response, this resonance occurs in the shallow water where the bottom friction damps the effect. The dispersion equation shows that the geometry of the problem favors amplification of semidiurnal tides. Analytical solutions obtained by superposition of the incident and scattered waves around an island are used to explain the observed peculiarities of tides in the vicinity of the Pribilof Islands, Bering Sea

Thermal expansion measurements in fresh and saline ice using fiber optic strain gauges and multipoint temperature sensors based on Bragg Gratings

This paper describes the use of Fiber Bragg Grating (FBG) sensors to investigate the thermomechanical properties of saline ice. FBG sensors allowed laboratory measurements of thermal expansion of ice samples with a range of different sizes and geometries. The high sampling frequency, accuracy, and resolution of the FBG sensors provide good quality data across a temperature range from 0°C to −20°C. Negative values of the effective coefficient of thermal expansion were observed in ice samples with salinities 6 ppt, 8 ppt, and 9.4 ppt. A model is formulated under which structural transformations in the ice, caused by temperature changes, can lead to brine transfer from closed pockets to permeable channels, and vice versa. This model is compared to experimental data. Further, in experiments with confined floating ice, heating as well as thermal expansion due to vertical migration of liquid brine, caused by under-ice water pressure, was observed

Turbulent kinetic energy dissipation from colliding ice floes

Increased knowledge about wave attenuation processes in sea ice, and hence atmosphere-wave-ice-ocean energy transfer, is necessary to improve sea ice dynamics models used for climate modeling and offshore applications. The aim of this study is to generate such much needed data by investigating colliding ice floes dynamics in a large-scale experiment and directly measuring and quantifying the turbulent kinetic energy (TKE). The field work was carried out at Van Mijen Fjord on Svalbard, where a 3x4 m ice floe was sawed out in the fast ice. Wave motion was simulated by pulling the ice floe back and forth in an oscillatory manner in a 4x6 m pool, using two electrical winches. Ice floe motion was measured with a range meter and accelerometers, and the water turbulence was measured acoustically with an acoustic Doppler current profiler and optically with a remotely operated vehicle and bubbles as tracers. TKE frequency spectra were found to contain an inertial subrange where energy was cascading at a rate proportional to the -5/3 power law. The TKE dissipation rate was found to decrease exponentially with depth. The total TKE dissipation rate was estimated by assuming that turbulence was induced over an area corresponding to the surface of the floe. The results suggest that approximately 37% and 8% of the input power from the winches was dissipated in turbulence and absorbed in the collisions, respectively, which experimentally confirms that energy dissipation by induced turbulent water motion is an important mechanism for colliding ice floe fields

Inverse Eigenvalue Problems for Perturbed Spherical Schroedinger Operators

We investigate the eigenvalues of perturbed spherical Schr\"odinger operators under the assumption that the perturbation $q(x)$ satisfies $x q(x) \in L^1(0,1)$. We show that the square roots of eigenvalues are given by the square roots of the unperturbed eigenvalues up to an decaying error depending on the behavior of $q(x)$ near $x=0$. Furthermore, we provide sets of spectral data which uniquely determine $q(x)$.Comment: 14 page