Direct Observations of Wave‐Sea Ice Interactions in the Antarctic Marginal Ice Zone

Abstract

Wave energy propagating into the Antarctic marginal ice zone effects the quality and extent of the sea ice, and wave propagation is therefore an important factor for understanding and predicting changes in sea ice cover. Wave‐sea ice interactions are notoriously hard to model and in‐situ observations of wave activity in the Antarctic marginal ice zone are scarce, due to the extreme conditions of the region. Here, we provide new in‐situ data from two drifting Surface Wave Instrument Float with Tracking (SWIFT) buoys deployed in the Weddell Sea in the austral winter and spring of 2019. The buoy location ranges from open water to more than 200 km into the sea ice. We estimate the attenuation of swell with wave periods 8‐18 s, and find an attenuation coefficient α = 4 ⋅ 10−6 to 7 ⋅ 10−5 m−1 in spring, and approximately five‐fold larger in winter. The attenuation coefficients show a power law frequency dependence, with power coefficient close to literature. The in‐situ data also shows a change in wave direction, where wave direction tends to be more perpendicular to the ice edge in sea ice compared to open water. A possible explanation for this might be a change in the dispersion relation caused by sea ice. These observations can help shed further light on the influence of sea ice on waves propagating into marginal ice zones, aiding development of coupled wave‐sea ice models.

Observations of Ocean Surface Wave Attenuation in Sea Ice Using Seafloor Cables

“…During this period, wave energy is concentrated along the dispersion curve at lower frequencies and attenuated at high frequencies (Figure 2b). Additionally, waves are shifted slightly off the classic dispersion relation, indicating a shift to a shorter wavenumber which could result from directional filtering or refraction (Wahlgren et al., 2023).…”

From apparent attenuation towards physics-based source terms – a perspective on spectral wave modeling in ice-covered seas

“…Waves in sea ice are measured using several different techniques, including, but not limited to, in situ observations by means of buoys or accelerometers placed on the ice (e.g., Squire and Moore, 1980;Cheng et al, 2017;Voermans et al, 2019;Kohout et al, 2020;Wahlgren et al, 2023), analysis of ship motion (e.g., Collins et al, 2015), remote observations from ships by stereo imaging (e.g., Smith and Thomson, 2019;Alberello et al, 2022) and from aircrafts by laser scanning (Sutherland and Gascard, 2016;Sutherland et al, 2018), satellite-based methods (e.g., Stopa et al, 2018a, b;Horvat et al, 2020;Brouwer et al, 2022;Huang and Li, 2023), or, recently, distributed acoustic sensing of seafloor cables (Smith et al, 2023). Taken together, the result of this observational effort is a large, very valuable body of data encompassing thousands of measured wave energy spectra.…”