Modelling the Arctic wave-affected marginal ice zone: a comparison with ICESat-2 observations.

We evaluate marginal ice zone (MIZ) extent in a wave-ice 25 km-resolution coupled model, compared with pan-Arctic wave-affected sea-ice regions derived from ICESat-2 altimetry over the period December 2018-May 2020. By using a definition of the MIZ based on the monthly maximum of the wave height, we suggest metrics to evaluate the model taking into account the sparse coverage of ICESat-2. The model produces MIZ extents comparable to observations, especially in winter. A sensitivity study highlights the need for strong wave attenuation in thick, compact ice but weaker attenuation as sea ice forms, as the model underestimates the MIZ extent in autumn. This underestimation may be due to limited wave growth in partially covered ice, overestimated sea-ice concentration or the absence of other processes affecting floe size. We discuss our results in the context of other definitions of the MIZ based on floe size and sea-ice concentration, as well as the potential impact of wave-induced fragmentation on ice dynamics, found to be minor at the climate scales investigated here. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'.