On the wave-ice attenuation and WSC variation in Fram Strait using clusters of miniature wave drifting buoy in 2021 & 2022

The rate of reduction of Arctic Ocean sea ice cover and its change is an important key issue in the study of global climate change. Wave climate variability and the wave effects in the Arctic Ocean plays important roles in influencing the rate of sea ice melting. Aiming to improve the parameterization of wave numerical model that considers the presence of sea ice in polar region and to develop the associated satellite remote sensing technologies, in situ wave observations at the sea-ice edge and Marginal Ice Zones are essential. Currently the data and observations are scarce.

This study developed a low-cost miniature wave drifting buoy, its shape is 50 cm diameter dish, built-in IMU, Iridium satellite modem and temperature and salinity sensor, etc., to monitor the wave height, period, direction and wave spectral shape, sea surface Mean Square Slope (MSS), surface ocean temperature (SST) and GPS positioning.

The signal sampling frequency is 10Hz, the spectral analysis is carried out on-board using ARM single chip computer in the buoy. The data is then encoded to Iridium satellite in real-time. In this study, in August 2021 and 2022, 8 and 10 sets of miniature buoys were deployed in Fram Strait off the western Svalbard Islands, respectively. The buoys were deployed in cluster and placed 15 km apart from each other, forming a rectangular spatial array, and drifting with West Spitzbergen Current, transported northward into the ice edge area of Svalbard northwest sea.

The observation took place every two hours for about three months. This report presents the time series of the observation data. First, we analyzed the drift trajectories of the buoy cluster, estimated the sea surface dispersion coefficient, Lyapunov index from the spatial array shape change rate of the buoy cluster. Secondly, sea surface temperature variation along the meridional trajectories was investigated. The results showed that the surface water mass was converged around Molloy Abyss, and the surrounding water body was accompanied by rapid temperature drop. On the other hand, in the wave analysis of the MIZ, the SAR images were used to identify the sea ice edge and ice concentration and to investigate the attenuation of wave spectral shape between the sea ice zone and the open ice-free waters in the vicinity.