In this paper the important mechanisms affecting the deterioration of Arctic icebergs are modeled based on parameterizations developed for the International Ice Patrol. The model simulations of the deterioration of three icebergs in the Grand Banks/Labrador Sea area off the Canadian east coast are compared with observations. The model parameterizations provide a reasonable approximation of iceberg deterioration with best results being obtained where detailed observations of the above-water and underwater portions of the iceberg are available enabling accurate estimations of iceberg mass and other parameters needed for the model. A quantitative assessment of the deterioration of icebergs in the Grand Banks/Labrador Sea area is also carried out for each month of the year when the sea surface temperature was above zero. Wave erosion is found to be the major deterioration mechanism. Wave erosion and the resulting calving of overhanging slabs together account for more than 80 percent of the deterioration rate. A small iceberg drifting on the Grand Banks could lose up to one third of its mass in one day.
This paper describes the details of a field study on the deterioration of two icebergs grounded outside St John’s harbour in Newfoundland, Canada. Observational data was collected during the period 10-25 June 1983, and included berg-related, meteorological and océanographie data. The study indicated the need for a stable observation platform to enable accurate measurements of iceberg profiles. The observed decay of the two icebergs is compared with simulations from a model that predicts mass losses due to insolation, buoyant vertical convection, forced convection in air and water, wave erosion and calving of the resulting overhanging ice slabs. There was good agreement between observations and model simulations with the model underestimating the mass losses by about ten percent. Other salient features noted during the field study are also discussed.
A numerical model is presented for predicting iceberg drift trajectories from known or derived information regarding iceberg characteristics and the environmental forces affecting the motion of an iceberg. The validity of such a model is studied by comparing predicted and observed trajectories of icebergs near Saglek, Labrador, duri n g a storm on 21-22 August 1972. At this time, iceberg positions (determined by radar), winds, and currents were monitored as part of an oceanographic study, conducted by the Faculty of Engineering and Applied Science, Memorial University of Newfoundland. The comparison between observed and predicted iceberg drift trajectories is good when the characteristics of the iceberg are assumed to be those of a mediumsized non-tabular iceberg. In order to appreciate the effect of wind and current. forces on the drift of the iceberg, several trajectories are plotted in which various environmental forces are excluded. From this study, it is evident t.hat a good predict.ion of an iceberg drift. trajectory is only possible if rather detailed information is available on the current and wind field. LIST OF SYMBOLS
ABSTRAm P r e v i o u s s t u d i e s t o c o r r e l a t e i c e b e r g d r a f t w i t h i t s above water dimensions are reviewed. Their f i n d i n g s are t e s t e d u s i n g d a t a on measurements of over 200 icebergs. The correlation between the d r a f t and t h e l e n g t h , w i d t h , h e i g h t and mass of each of t h e s e i c e b e r g s i s presented. The anal y s i s i n d i c a t e d t h a t t h e u p p e r limit of iceberg d r a f t is i t s l e n g t h , 1.5 times i t s width, or 10.5 times i t h e i g h t . The lower limit was 0.25 i t s l e n g t h , 0.4 i t s w i d t h , o r i t s h e i g h t . A simple e m p i r i c a l e x p r e s s i o n t o r e l a t e t h e h e i g h t of an i c e b e r g t o i t s d r a f t / h e i g h t r a t i o f o r each type of iceberg was obtained, based on t h e measured d a t a . The e x p e c t e d e r r o r i n v o l v e d i n e s t i m a t i n g i c e b e r g d r a f t u s i n g t h e e m p i r i c a l e x p r e s s i o n s and t h e d e g r e e of c o n f i d e n c e i n t h e e s t i m a t e d v a l u e a r e e v a l u a t e d .
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