The autonomous measurement of waves propagating across the Arctic Ocean

For decades sea-ice researchers have used different methods to measure the propagation of waves, originating from ocean swell, through sea ice. Most of these instruments were delicate to transport, maintain and labour intensive to install. Furthermore they required constant attention to ensure that the sensors were always in range, and due to the relatively high recording frequency, data was recorded internally. This in turn demanded that the instrument be revisited for data recovery. Advancement in both satellite technology and sensor development have overcome these limitations and enabled an autonomous tiltmeter buoy to be developed to record the propagation of waves through the sea ice. Two key features are the use of the Iridium satellite communications system as a way of ensuring continuous remote data recovery, and a novel auto-zeroing technique to ensure the sensors are always in range. Each system was configured to transmit around 70 minutes of tilt data, sampled at 2 Hz, every 12 hours at 00:00 and 12:00 GMT. Moreover, GPS positions were determined every hour and packaged with the rest of the transmitted data. At present there is intense interest in the propagation of waves through sea ice, stimulated in part by a recent theory that suggests that we can use the changes in the wave spectra as it propagates through the ice to gather information on the area- averaged thickness of the sea ice. Consequently the synoptic measurement of ice thickness could be obtained through the deployment of a number of buoys at different location within the Arctic Ocean. In April 2007 five tiltmeter buoys where deployed at different locations in the Arctic Ocean. This paper describes the operation of these buoys, their deployment and summaries initial results.