[1] The marginal ice zone (MIZ) is the boundary between the open ocean and ice-covered seas, where sea ice is significantly affected by the onslaught of ocean waves. Waves are responsible for the breakup of ice floes and determine the extent of the MIZ and floe size distribution. When the ice cover is highly fragmented, its behavior is qualitatively different from that of pack ice with large floes. Therefore, it is important to incorporate wave-ice interactions into sea ice-ocean models. In order to achieve this goal, two effects are considered: the role of sea ice as a dampener of wave energy and the wave-induced breakup of ice floes. These two processes act in concert to modify the incident wave spectrum and determine the main properties of the MIZ. A simple but novel parameterization for floe breaking is derived by considering alternatively ice as a flexible and rigid material and by using current estimates of ice critical flexural strain and strength. This parameterization is combined with a wave scattering model in a one-dimensional numerical framework to evaluate the floe size distribution and the extent of the MIZ. The model predicts a sharp transition between fragmented sea ice and the central pack, thus providing a natural definition for the MIZ. Reasonable values are found for the extent of the MIZ given realistic initial and boundary conditions. The numerical setting is commensurate with typical iceocean models, with the future implementation into two-dimensional sea ice models in mind.
Wind waves may play an important role in the evolution of sea ice. That role is largely determined by how fast the ice layer dissipates the wave energy. The transition from a continuous layer of ice to a series of broken floes is expected to have a strong impact on the several attenuation processes. Here we explore the possible effects of basal friction, scattering, and dissipation within the ice layer. The ice is treated as a single layer that can be fractured in many floes. Dissipation associated with ice flexure is evaluated using an anelastic linear dissipation and a cubic inelastic viscous dissipation. Tests aiming to reproduce a Marginal Ice Zone are used to discuss the effects of each process separately. Attenuation is exponential for friction and scattering. Scattering produces an increase in the wave height near the ice edge and broadens the wave directional spectrum, especially for short-period waves. The nonlinear inelastic dissipation is larger for larger wave heights as long as the ice is not broken. These effects are combined in a realistic simulation of an ice break-up event observed south of Svalbard in 2010. The recorded rapid shift from a strong attenuation to little attenuation when the ice is broken is only reproduced when using a nonlinear dissipation that vanishes when the ice is broken. A preliminary pan-Arctic test of these different parameterizations suggests that inelastic dissipation alone is not enough and requires its combination with basal friction. Key Points:• A spectral wave model with effects of sea ice floe size is presented • Ice breakup is combined with three attenuations processes • Model wave heights for a break-up event reproduce observations in Svalbard apply to wide fields of pancakes that are found in the freezing season and but should rather be representative of waves interacting with solid ice pack. In these conditions, our goal is to explore plausible regimes of wave attenuation in the MIZ, given certain assumptions about wave-ice interaction processes.The different mechanisms that have been proposed to explain wave attenuation in the ice can be represented by source terms in the wave action equation describing the evolution of the wave field (Masson & LeBlond, 1989). The relative importance of the different mechanisms is still unknown in conditions encountered in the natural environment (Squire, 2007). Robin (1963) measured wave attenuation in the Weddel Sea but did not conclude on its possible source, mentioning anelastic dissipation (hysteresis) and basal friction as possible explanations. Wadhams (1973) hypothesized that wave could be dissipated by secondary creep, namely, the inelastic dissipation of waves due to the ice flexure, with a strain rate proportional to the cube of the stress, following the flow law used by Glen (1955) for very slow glacier motions. The work done during and after MIZEX emphasized scattering, that is, multiple reflections of waves by floes, as the dominant source of wave attenuation (Kohout & Meylan, 2008;Kohout et al., 2014;Montiel et...
Current large-scale sea ice models represent very crudely or are unable to simulate the formation, maintenance and decay of coastal landfast ice. We present a simple landfast ice parameterization representing the effect of grounded ice keels. This parameterization is based on bathymetry data and the mean ice thickness in a grid cell. It is easy to implement and can be used for two-thickness and multithickness category models. Two free parameters are used to determine the critical thickness required for large ice keels to reach the bottom and to calculate the basal stress associated with the weight of the ridge above hydrostatic balance. A sensitivity study was conducted and demonstrates that the parameter associated with the critical thickness has the largest influence on the simulated landfast ice area. A 6 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) simulation with a 20 km resolution sea ice model was performed. The simulated landfast ice areas for regions off the coast of Siberia and for the Beaufort Sea were calculated and compared with data from the National Ice Center. With optimal parameters, the basal stress parameterization leads to a slightly shorter landfast ice season but overall provides a realistic seasonal cycle of the landfast ice area in the East Siberian, Laptev and Beaufort Seas. However, in the Kara Sea, where ice arches between islands are key to the stability of the landfast ice, the parameterization consistently leads to an underestimation of the landfast area.
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