Internal waves and velocity fine structure in the Arctic Ocean

A series of closely spaced velocity profiles made in the ice-covered Canada Basin of the Arctic Ocean during April 1985 are used to investigate the spatial scales and dynamics of small-scale motions. The velocity fluctuations are very different from those found in mid-latitudes, containing about 40–50 times less WKB normalized energy at low wave numbers and about 10 times less WKB normalized shear variance. The vertical wave number spectrum is much flatter, with the deficit in energy occurring primarily for wavelengths greater than 30 m. The horizontal wave number magnitude spectrum of horizontal kinetic energy can be estimated only for velocity fluctuations with vertical wavelengths near 40 m. Combined with estimates of kinetic and potential energy, this determines the distribution of energy between motions with various types of dynamics in this band. Near-inertial frequency internal waves account for about two-thirds of the energy. The data suggest such waves are generated during storms. Velocity fine structure accounts for about a quarter of the kinetic energy and has an absolute energy level comparable to that found at mid-latitudes. It is dynamically distinct from internal waves and has a Rossby number near or greater than unity. High frequency internal waves account for a small fraction of the energy but carry most of the superinertial potential energy.