Direct observations of wave-sea ice interactions in the Antarctic Marginal Ice Zone

Abstract

Wave energy propagating into the Antarctic marginal ice zone affects 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. Sea ice is 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 in 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 to 7 · 10 m in spring, and approximately five-fold larger in winter. The attenuation coefficients show a power law frequency dependence, with power coefficient 3.3 in spring and 4 in winter. The in-situ data also shows a change in wave direction, where wave direction tends to be more perpendicular to the ice edge farther into the sea ice. A possible explanation for this might be a change in the dispersion relation caused by changing sea ice composition. These observations can help shed further light on the influence of sea ice on waves propagating into the Marginal Ice Zone, 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).…”