Characterization of the Sea-Ice Floes Issuing From Their Fractal Properties

The satellite images demonstrate the fractal geometry of the fragmented ice fields in the region of the North Pole. The monitoring of the fractal patterns during a 6-week period revealed the variation of the floe fractal dimension interpreted as due to changes in the lead propagation mode. The analysis of the fractal patterns is potentially useful for predicting trends in the ice-cracking process. INTRODUCTION The fractal properties of some geophysical sites, such as fault systems (Okubo and Aki, 1987) or sea-ice floes (Rothrock and Thorndike, 1984) are well known, but the attempts to explain the mechanism of generation of the fractality are few (Erlingsson, 1988; Matsushita, 1985; Aksenov, 1994). Any applied investigations of fractal properties of ice-cover geometry are unknown to us. This preliminary communication is to demonstrate that the fractal parameters contain a piece of information concerning the properties and evolution of the crack-and-leads ensemble in seaice floes which could lead to a novel contribution to the treatment of the present and hardly diminishing problem of the assessment and prediction of sea-ice fragmentation. In this study, we analyzed a series of AVHRR images from the NOAA satellite received in the Arctic and Antarctic Research Institute in the period from 03.31.99 to 05.14.99. All the images represent the same region in the Central Arctic. A typical photograph from this series is shown in Fig. 1. FRACTAL PATTERN The analysis was carried out using a conventional technique developed for revealing and studying the fractal geometry of a crack surface in solids. The method is based on the measurement of the area-to-perimeter ratio for ice-floe fragments restricted by leads and cracks. The computer processing was performed with the scale ruler being kept constant when measuring the lengths. The criterion of fractality was taken in the form (Mecholsky, Passoja and Feinberg-Ringer, 1989):