线性化重力波中脂冰的有效粘性

SAR image wave spectra to retrieve the thickness of grease-pancake sea ice using viscous wave models

Young sea ice composed of grease and pancake ice (GPI), as well as thin floes, considered to be the most common form of sea ice fringing Antarctica, is now becoming the 'new normal' also in the Arctic. Investigations to determine how an increase in GPI is affecting the climate in the far north and globally, require specific tools to monitor the GPI's thickness distribution. Directional wave spectra from satellite SAR imagery are used to determine the change in wave dispersion as a wave train enters GPI fields. The ice cover thickness is then estimated by fitting the dispersion data with two mo…

On the ocean wave attenuation rate in grease-pancake ice, a comparison of viscous layer propagation models with field data

The ability of viscous layer models to describe the attenuation of waves propagating in grease-pancake ice covered ocean is investigated. In particular, the Keller's model Keller [1998], the two-layer viscous model [De Carolis and Desiderio 2002] and the close-packing model [De Santi and Olla 2017] are extensively validated by using wave attenuation data collected during two different field campaigns (Weddell Sea, Antarctica, April 2000; western Arctic Ocean, autumn 2015). We use these data to validate the three models by minimizing the differences between the measured and model wave attenuati…

Mechanical diffusion in grease ice stirred by gravity waves

The possibility of hydrodynamic diffusion in a model of grease ice stirred by the velocity field of a gravity wave is explored. It is argued that mechanical interactions among ice crystals can induce disturbances in the fluid velocity - in the form of interstitial flows - analogous to those leading to diffusion in fixed beds. A two-fluid description of the system is introduced, in which the ice matrix is treated as a deformable porous medium. Depending on the range of parameters, the effective diffusivity of the medium can exceed the value which would be obtained by only keeping into account p…

A computational fluid dynamics model for the small-scale dynamics of wave, ice floe and interstitial grease ice interaction

The marginal ice zone is a highly dynamical region where sea ice and ocean waves interact. Large-scale sea ice models only compute domain-averaged responses. As the majority of the marginal ice zone consists of mobile ice floes surrounded by grease ice, finer-scale modelling is needed to resolve variations of its mechanical properties, wave-induced pressure gradients and drag forces acting on the ice floes. A novel computational fluid dynamics approach is presented, that considers the heterogeneous sea ice material composition and accounts for the wave-ice interaction dynamics. Results show, a…

Experiments on wave propagation in grease ice: combined wave gauges and PIV measurements

Water wave attenuation by grease ice is a key mechanism for the polar regions, as waves in ice influence many phenomena such as ice drift, ice breaking, and ice formation. However, the models presented so far in the literature are limited in a number of regards, and more insights are required from either laboratory experiments or fieldwork for these models to be validated and improved. Unfortunately, performing detailed measurements of wave propagation in grease ice, either on the field or in the laboratory, is challenging. As a consequence, laboratory data are relatively scarce, and often con…

浅壳模型对冰卫星地形松弛的启示

Implications of shallow-shell models for topographic relaxation on icy satellites

本研究从 Stokes 方程出发分析冰卫星地形松弛，发现恒定粘度壳体在波长大于冰厚时松弛时间尺度恒定，而粘度随深度递减时外壳近似刚性且松弛依赖波长，该结果对解释陨石坑剖面和推断冰壳厚度具有重要意义。