Robust wavebuoys for the marginal ice zone: Experiences from a large persistent array in the Beaufort Sea

Abstract

An array of novel directional wavebuoys was designed and deployed into the Beaufort Sea ice cover in March 2014, as part of the Office of Naval Research Marginal Ice Zone experiment. The buoys were designed to drift with the ice throughout the year and monitor the expected breakup and retreat of the ice cover, forced by waves travelling into the ice from open water. Buoys were deployed from fast-and-light air-supported ice camps, based out of Sachs Harbour on Canada’s Banks Island, and drifted westwards with the sea ice over the course of spring, summer and autumn, as the ice melted, broke up and finally re-froze. The buoys transmitted heave, roll and pitch timeseries at 1 Hz sample frequency over the course of up to eight months, surviving both convergent ice dynamics and significant waves-in-ice events. Twelve of the 19 buoys survived until their batteries were finally exhausted during freeze-up in late October/November. Ice impact was found to have contaminated a significant proportion of the Kalman-filter-derived heave records, and these bad records were removed with reference to raw x/y/z accelerations. The quality of magnetometer-derived buoy headings at the very high magnetic field inclinations close to the magnetic pole was found to be generally acceptable, except in the case of four buoys which had probably suffered rough handling during transport to the ice. In general, these new buoys performed as expected, though vigilance as to the veracity of the output is required.

Observations of Surface Wave Dispersion in the Marginal Ice Zone

“…To determine a baseline noise spectrum, a quiescent period was identified. During this period there was almost no detectable wave energy; the average significant wave height over 7 h was 0.01 m, well under the minimum accuracy (Doble et al, ), thus the resulting spectrum was dominated by noise. The mean spectral shape over this 7 h period, which decays from low to high frequencies, serves as the basis of a threshold.…”

“…In the absence of these effects and in the presence of ice, deviations of k e / k ow from 1 can be interpreted as the modification of waves due to ice. A perfect response of our buoy is reasonable because it was an updated version of that used in (Doble et al, ) with reduced weight (∼20 kg) and smaller draft (∼5 cm). These changes significantly increased buoyancy and surface following ability.…”

“…The wave buoys were designed and built by author MD at Polar Scientific Ltd., and discussion of the design criteria and further technical Journal of Geophysical Research: Oceans 10.1029/2018JC013788 details can be found in Doble et al (2017). A microelectromechinal (MEM) system combined three-axis accelerometers, gyroscopes, and magentometers.…”

Integrated Observations of Global Surface Winds, Currents, and Waves: Requirements and Challenges for the Next Decade

“…Wave measurements from these cost-effective and compact counterparts to the moored wave buoys have been shown to compare well with traditional accelerometer methods (Colbert, 2010;Herbers et al, 2012). Applications of these drifting buoys include wave attenuation in ice (Doble and Bidlot, 2013;Doble et al, 2017;Sutherland and Dumont, 2018), targeted sampling under storm tracks, wave-current interactions (Zippel and Thomson, 2017;Veras Guimarães et al, 2018), and wave observations on high seas where mooring buoys are technically challenging and costly. For detailed characteristics of in situ wave measurements, we refer the reader to Ardhuin et al (2019).…”

An Autonomous Approach to Observing the Seasonal Ice Zone in the Western Arctic

“…Wave Buoys (Doble et al, 2017) installed on the ice used accelerometers and tiltmeters to measure spectral surface wave properties. These instruments quantified surface wave activity that penetrated into ice-covered waters.…”