Statistical Properties of Iceberg Motion at the Western Entrance of Lancaster Sound

The Lagrangian autocorrelation coefficient, of velocities with the local mean current extracted, has e-folding time scales of 15 and 22 hours for the x and y components of motion respectively. Periodicities that might be attributed to either semidiurnal tides or inertial oscillations are evident, as are diurnal periodicities. Local vorticity is typically 5 times greater than local divergence and, apart from the coastal boundary layer, has a magnitude less than 1/5 the Coriolis parameter. This is consistent with quasigeostrophic motion. The variance and covariance of residual velocities vary from one grid to the next. Thus both the mean and residual velocity fields are inhomogeneous. An advection-diffusion model developed by 0kubo et al, (1983) can be used to calculate the uncertainty of iceberg trajectories from velocity gradients and eddy-diffusivities. This gives a good estimate of the uncertainty for periods much greater than the integral time scale.