Theoretical Estimates of the Various Mechanisms Involved in Iceberg Deterioration in the Open Ocean Environment.

Abstract

Theoretical estimates are developed for a variety of mechanisms for the deterioration of icebergs in the open ocean environment. Although all the estimates are of an elementary nature, primarily algebraic correlations, the estimates seem to be in good agreement with the limited experimental data available. Formulas are given for computing the static stability of an iceberg from observations of the exposed shape. Simple theoretical estimates are made for the response of an iceberg to a sudden change in wind or water current and the speed at which a berg is driven by the wind. These dynamic estimates are supplemented by wind tunnel measurements of the drag of the submerged portion of model tabular and non-tabular bergs. Solar insolation and buoyant meltwater convection are shown to be minor contributions to deterioration, with melt rates of 2-20 cm/day at best. Forced underbody convection due to winddriven effects is more important, with melt rates estimated at 5-20 cm/day/C of water/ice temperature difference. The most important mechanism is wave erosion, with waterline melt rates estimated as high as 150 cm/day/C. Digital computer finite difference results for the fracture of an overhanging ice slab plus wave erosion theory lead to a theoretical estimate for the calving time of an iceberg subjected to a wave environment.