JARE61 Waves in Ice Observations
Description
The 61st Japanese Antarctic Research Expedition (JARE61) departed from Narita, Japan on November 27 2019 and set sail on the Japanese Icebreaker, the Shirase, from the port of Fremantle in Australia, their destination Syowa Station, Antarctica. One of the key research projects of JARE61 was to study the Ocean-ice Boundary Interaction and Change around Antarctica. In support of this project and in collaboration with the University of Tasmania, Australia and National Institute of Water and Atmospheric Research, New Zealand, five wave ice sensors were deployed off the Sabrina coast during the inbound leg to the Syomwa Station. The aim of this project was to observe wave propagation in the marginal ice zone (MIZ). Each sensor performed on-board spectral analysis and data quality control. The data was returned via Iridium data packets. The instrumentation development, construction and deployment was funded through the Australian Research Council Discovery Project DP170103774. The science development and analysis was funded through New Zealand's National Institute of Water and Atmospheric Research Core Funding. The wave sensors were manufactured by P.A.S. Consultants P/L, Melbourne, Australia. The sensors were deployed on the 9th and 10th of December 2019 along the longitude 120ºE. Three sensors were deployed along the ice edge, one was deployed in low sea ice concentration and another in high sea ice concentration. For all deployments, the sea ice primarily consisted of pancakes with gaps generally filled with frazil or brash ice. Wave spectra and spectral moments were captured over 11 minutes and returned via IRIDIUM Satellite. In total, 4402 wave records were captured over 6 months (from 10th December 2019 to 12th June 2020).
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Steps to reproduce
The sensors, which were manufactured by P.A.S. Consultants P/L, use the Sparton AHRS-M1, which is a micro-sized, light weight, low power Attitude Heading Reference System with a built-in adaptive calibration mode. The sensors were designed to be deployed on sea ice where they monitor acceleration in all planes. In total, 640 s (∼11 min) bursts of wave acceleration were sampled at 64 Hz and a low-pass, second-order Butterworth filter was applied with a cut-off at 0.5 Hz and subsampled to 2 Hz. A high-pass filter was then applied and the acceleration integrated twice to provide the displacement. Welch’s method, using a 10% cosine window and de-trending on four segments (each 256 s long) with 50% overlap, was applied to estimate the power spectral density. Spectral moments are also calculated and the significant wave height (Hs) is obtained from the zeroth spectral moment, defining the total variance (or energy) of the wave system. The peak period (Tp) is calculated from the power spectral density.