MODELING THE DYNAMICS AND THERMODYNAMICS OF ICEBERGS

Icebergs are a significant hazard for polar shipping, and, geophysical ly, are significant components of the mass balance of continental ice sheets while providing major freshwater inputs to the polar oceans. So me modelling of iceberg trajectories has been undertaken in the past, principally in the Labrador Sea, but here we present a hemispheric-wid e attempt to model iceberg motion in the Arctic and North Atlantic Oce ans. We show that the basic force balance in iceberg motion is between water drag and water advection, but with the pure geostrophic balance being only a minor component of the latter. Iceberg density maps esse ntially demonstrate the effect of the major boundary currents but we s how that the time and size of calving from individual tidewater glacie rs are important variables in determining the ultimate fate of bergs. The biggest bergs never leave the Arctic Ocean. All modelled icebergs have melted after about 5 years from their release date, although most melt over the first year. During their lifetime most, but not all ber gs, overturn several times. Our model shows good agreement with the li mited observational data. We therefore suggest that icebergs, both mod elled and observed, may be exploited as previously little-used geophys ical tracers. (C) 1997 Elsevier Science B.V.