Wave Attenuation in Drifting Sea Ice: A Mechanistic Model for Observed Decay Profiles

TL;DR

The paper addresses how waves attenuate in drifting sea ice, challenging the common exponential decay assumption by incorporating ice-drift drag into a moving-frame energy-transport model. It derives a nonlinear amplitude equation and an asymptotic solution that yields a drifting extinction location and non-exponential decay, aligning with Antarctic MIZ observations. The authors fit the model to ICESat-2 transects and perform Monte Carlo experiments to reproduce inter-transect variability, showing drift can dominate attenuation and determine the extent of wave-affected ice. Overall, the framework provides a physical basis for interpreting wave attenuation in the MIZ and can be extended to include additional attenuation mechanisms in coupled models.

Abstract

Wave-sea ice interactions shape the transition zone between open ocean and pack ice in the polar regions. Most theoretical paradigms, implemented in coupled wave-sea ice models, predict exponential decay of the wave energy but recent observations deviate from this behaviour. Expanding on a framework based on wave energy dissipation due to ice-water drag, we account for drifting sea ice to derive an improved model for wave energy attenuation. Analytical solutions replicate the observed non-exponential wave energy decay and the spatial evolution of the effective attenuation rate in Antarctic sea ice.

Figures (3)

• Figure 1: Sample amplitude (a) and corresponding attenuation (b) profiles according to our model and formulations by kohout2011wave and herman2019wave. Dashed lines denote $x^*$. Amplitude is normalised by the initial amplitude and distance by $x_\text{end}$ for $\alpha=0$. Attenuation rate is normalised by $\alpha$.
• Figure 2: Amplitude (left) and corresponding attenuation profiles (right) for Transect A (top) and B (bottom). Measurements (red dots) are shown against model predictions. Distance is normalised with respect to the wave-affected sea ice extent $x_{\text{MIZ}}$ and amplitude/attenuation with respect to the measurement closest to the sea ice edge as reported in voermans2025finely.
• Figure 3: Averaged attenuation rates (in black; for negative velocity in green) and interquartile range (shaded in grey). On the right axis, number of measurements (in red) and distribution of the extinction location (shaded in blue; not to scale). Insets show the drift velocity distribution.