Wave–ice interactions in the neXtSIM sea-ice model

Abstract

Abstract. In this paper we describe a waves-in-ice model (WIM), which calculates ice breakage and the wave radiation stress (WRS). This WIM is then coupled to the new sea-ice model neXtSIM, which is based on the elasto-brittle (EB) rheology. We highlight some numerical issues involved in the coupling and investigate the impact of the WRS, and of modifying the EB rheology to lower the stiffness of the ice in the area where the ice has broken up (the marginal ice zone or MIZ). In experiments in the absence of wind, we find that wind waves can produce noticeable movement of the ice edge in loose ice (concentration around 70 %) -up to 36 km, depending on the material parameters of the ice that are used and the dynamical model used for the broken ice. The ice edge position is unaffected by the WRS if the initial concentration is higher ( 0.9). Swell waves (monochromatic waves with low frequency) do not affect the ice edge location (even for loose ice), as they are attenuated much less than the higher-frequency components of a wind wave spectrum, and so consequently produce a much lower WRS (by about an order of magnitude at least).In the presence of wind, we find that the wind stress dominates the WRS, which, while large near the ice edge, decays exponentially away from it. This is in contrast to the wind stress, which is applied over a much larger ice area. In this case (when wind is present) the dynamical model for the MIZ has more impact than the WRS, although that effect too is relatively modest. When the stiffness in the MIZ is lowered due to ice breakage, we find that on-ice winds produce more compression in the MIZ than in the pack, while off-ice winds can cause the MIZ to be separated from the pack ice.

Drift of Pancake Ice Floes in the Winter Antarctic Marginal Ice Zone During Polar Cyclones

“…By calibrating C a and C w properly, free drift with no internal stress or wave effect, as might be caused by Stokes drift (Yiew et al, 2017), slope sliding (Grotmaack & Meylan, 2006), or wave radiation stresses (Masson, 1991), produces very good model results compared with observations, especially under storm conditions. Williams et al (2017) and Boutin et al (2019) recently integrated wave radiation stresses into large-scale numerical models that include wave attenuation and wave-induced ice breakup, based on the wave-ice interaction model of Williams et al (2013aWilliams et al ( , 2013b. They found that large wave radiation stresses, proportional to the wave attenuation rate, remain concentrated at the edge (Williams et al, 2017); wind and ocean stresses dominate ice drift over longer distances.…”

“…Williams et al (2017) and Boutin et al (2019) recently integrated wave radiation stresses into large-scale numerical models that include wave attenuation and wave-induced ice breakup, based on the wave-ice interaction model of Williams et al (2013aWilliams et al ( , 2013b. They found that large wave radiation stresses, proportional to the wave attenuation rate, remain concentrated at the edge (Williams et al, 2017); wind and ocean stresses dominate ice drift over longer distances. Moreover, Williams et al (2017) found that wave radiation stresses are appreciable only for wave periods < 10 s; the measurements reported here have dominant periods > 15 s. The small floes observed during our measurements, smaller floes than tested by Williams et al (2017), would induce even weaker radiation stresses.…”

“…They found that large wave radiation stresses, proportional to the wave attenuation rate, remain concentrated at the edge (Williams et al, 2017); wind and ocean stresses dominate ice drift over longer distances. Moreover, Williams et al (2017) found that wave radiation stresses are appreciable only for wave periods < 10 s; the measurements reported here have dominant periods > 15 s. The small floes observed during our measurements, smaller floes than tested by Williams et al (2017), would induce even weaker radiation stresses. Although wave-induced drift is negligible, it is expected that the significant waves measured will have induced turbulence in the water sublayers (Alberello, Onorato, Frascoli, et al, 2019;Smith & Thomson, 2019;Zippel & Thomson, 2016), enhancing mixing and heat fluxes under sea ice (Ackley et al, 2015;Smith et al, 2018).…”

A two layer model for wave dissipation in sea ice

“…The MIZ is a complex and heterogeneous environment, which comprises of ice floes of arbitrary shape and a variety of ice types from newly formed ice to fragmented multi-year ice. While surface waves are expected to be a dominant process controlling the total extent of the MIZ as well as the size distribution of ice floes, there still exist large uncertainties about the exact mechanisms for wave attenuation in sea ice (Williams et al, 2013(Williams et al, , 2017Kohout et al, 2014;Meylan et al, 2014). In addition to affecting the floe size distribution, the attenuation of surface gravity waves is also important in controlling the extent of the MIZ via the wave radiation stress (Liu et al, 1993;Williams et al, 2017;Sutherland & Dumont, 2018).…”

Wave-induced stress and breaking of sea ice in a coupled hydrodynamic discrete-element wave–ice model

“…Parameterizations of waveice interactions for large-scale continuum models (i.e., those in which ice is treated as a continuous mass rather than as discrete particles) are crucial for further development of those models. However, although appreciable effort has been made in that direction in recent years (Dumont et al, 2011;Doble and Bidlot, 2013;Squire et al, 2013;Williams et al, 2013Williams et al, , 2017; The WAVEWATCH III®Development Group , WW3-DG; Bennetts et al, 2017), our understanding of many aspects of wave-ice interactions is still too limited to allow formulating such parameterizations, especially those suitable for a wide range of conditions. Strong fragmentation of the in the above-mentioned parameterizations by Williams et al (2013), Bennetts et al (2017), and others.…”