Wave Attenuation by Sea Ice in the Arctic Marginal Ice Zone Observed by Spaceborne SAR.

Attenuation of ocean waves by ice is a crucial process of the interaction between waves and sea ice in marginal ice zone (MIZ), while such interaction can contribute to the retreating of sea ice in the Arctic. Based on the retrieved two‐dimensional ocean wave spectra by spaceborne Synthetic Aperture Radar, we investigated the attenuation of ocean waves in the MIZ in Svalbard and Greenland. The results show that the energy attenuation rate ranges from 0.126 × 10−4/m to 0.618 × 10−4/m. Quantitative analysis suggests that the attenuation rate is significantly related to wave height and peak wave period of coming waves. It is further found that the waves decay faster in the area with ice thickness exceeding 0.5 m. We compared the derived wave attenuation rates in the present study with those in previous studies based on in situ measurements, which reveals that waves are becoming less attenuated by sea ice in the Arctic. Plain Language Summary: The interaction between sea ice and ocean waves is one of the key processes that accelerates the retreat of sea ice in the Arctic. The attenuation of ocean waves by sea ice is crucial to understanding the wave‐ice interaction mechanism and predicting ice changes. Spaceborne Synthetic Aperture Radar (SAR), capable of imaging ocean waves and sea ice in two‐dimension with high spatial resolution, has shown tremendous potential in studies on wave‐ice interaction. In this study, SAR images acquired in ice‐covered areas near Svalbard and east of Greenland were collected, and then ocean wave spectra were retrieved from these SAR images. Ocean wave spectra depict sea states elaborately by showing the wave energy distribution in different frequencies and directions. Subsequently, we derived the wave attenuation rate in sea ice from these wave spectra. By comparing the derived attenuation rates with previous field observations, the study reveals a lower attenuation rate, which suggests the waves were less attenuated by ice in past decades under ongoing retreating and thinning of sea ice in the Arctic. This indicates that waves can penetrate sea ice easier and deeper, which may further induce the retreating of sea ice. Key Points: Wave attenuation rate in sea ice was derived based on non‐linear inversion of two‐dimensional ocean wave spectra by Synthetic Aperture Radar in the Arctic marginal ice zone (MIZ)The attenuation rate generally follows the exponential law, varying with sea state (wave height and period) and sea ice conditionsCombining previous studies and this one, we may infer that the wave attenuation in the Artic MIZ is weakening due to sea ice retreat [ABSTRACT FROM AUTHOR]