The Transition from Moving to Fast Ice In Western Viscount Melville Sound

An unexpected result of the recording of underwater noise under sea-ice is the ability to detect the difference in character of the noise generated by ice in motion in relation to the noise generated under shore-fast ice. The detection of motion was easily made by ob-serving the hourly samples of underwater noise recorded by a remote instrument package (RIP). One RIP (see cover picture) was installed in the sea bottom south of Melville Island in August 1967 in the location shown in Fig. 1 and was recovered one year laterl. A sample strip-chart record of the change of underwater noise-power with time in the 150-300 Hz frequency band is shown in Fig. 2. In th is figure, the envelope is formed by the hourly noise samples where each sample is a measure of the noise power, in decibels, averaged over a 4 minute interval within each hour. The example shown covers 6 days in November 1967. The time interval, indicated by the cap-tion “moving ice”, covers a period of 32 hours in which the hourly noise samples fail to form FIG. 1. Map showing the site of RIP installation. r”