SMALL ICEBERGS AND ICEBERG FRAGMENTS OFF NEWFOUNDLAND - RELATIONSHIPSTO DETERIORATION MECHANISMS AND THE REGIONAL ICEBERG POPULATION

Several sets of previously compiled data on iceberg size distributions in areas between North America and Greenland are compared and analyze d. The obtained results indicate that populations of icebergs with len gths L greater than or equal to 20 m are well-described by lognormal a nd gamma distributions together with statistical parameters which are compatible with existing understanding of regional iceberg deteriorati on and change processes. A lesser amount of data on size distributions in Newfoundland icebergs with L < 20 m show occurrence probabilities which increase exponentially with decreasing iceberg length. Evidence is presented to show that these data are most consistent with the domi nance of fracture processes in determining iceberg occurrence versus l ength relationships. Physical arguments are presented to suggest that the key fracture events are initiated in the larger icebergs by coinci dences of wave-generated bending stress maxima and randomly distribute d structural paws. Similar considerations and use of a simple sequenti al fracture model imply that size distributions in icebergs (and icebe rg fragments) with L < 20 m are more consistent with the presence of a n alternative, spontaneous failure mechanism also acting at randomly d istributed structural defects. The implications of these results for f orecasting and monitoring populations of small icebergs are discussed.