Size distributions of small ice pieces calved from icebergs

Abstract

This study was part of a larger project currently underway to develop an operational iceberg drift and deterioration model for the Canadian Ice Service (CIS), Environment Canada. This new iceberg model, as distinct from previous drift computations, will include estimates of iceberg calving and production of smaller ice pieces in the bergy bit and growler size ranges. These smaller size pieces can cause large forces upon impact with offshore structures. It is important to have information about the probability of encountering these small ice pieces in the neighborhood of the parent iceberg. Calving can result from wave-induced erosion at the waterline of a floating iceberg. When the waterline notch caused by wave erosion reaches a critical size, the weight of the overhanging slab will be large enough to cause it to break off and fracture into many thousands of small ice pieces. The focus of the present paper is on the size-frequency distribution function for the ice pieces that are generated. The correlations presented are based primarily on the field observations of calving by Crocker [Crocker, G.B., 1993, Size distributions of bergy bits and growlers calved from deteriorating icebergs. Cold Reg. Sci. Technol., 22, 113–119.]. The initial size distribution of the calved pieces forms an essential starting point for the subsequent analyses of small ice piece deterioration and drift that are embodied in the operational model.