A model for the consolidation of rafted sea ice

Abstract

[1] Rafting is one of the important deformation mechanisms of sea ice. This process is widespread in the north Caspian Sea, where multiple rafting produces thick sea ice features, which are a hazard to offshore operations. Here we present a one-dimensional, thermal consolidation model for rafted sea ice. We consider the consolidation between the layers of both a two-layer and a three-layer section of rafted sea ice. The rafted ice is assumed to be composed of layers of sea ice of equal thickness, separated by thin layers of ocean water. Results show that the thickness of the liquid layer reduced asymptotically with time, such that there always remained a thin saline liquid layer. We propose that when the liquid layer is equal to the surface roughness the adjacent layers can be considered consolidated. Using parameters representative of the north Caspian, the Arctic, and the Antarctic, our results show that for a choice of standard parameters it took under 15 h for two layers of rafted sea ice to consolidate. Sensitivity studies showed that the consolidation model is highly sensitive to the initial thickness of the liquid layer, the fraction of salt release during freezing, and the height of the surface asperities. We believe that further investigation of these parameters is needed before any concrete conclusions can be drawn about rate of consolidation of rafted sea ice features.

The refreezing of melt ponds on Arctic sea ice

“…where the density ratio of seawater to sea ice q ocean q ice 51:09 accounts for the expansion of sea ice on freezing, / is the solid fraction of sea ice at the ice-ocean interface, and F ocean is the heat flux at the sea ice bottom [Bitz and Lipscomb, 1999;Feltham et al, 2006;Bailey et al, 2010]. At the ice-lid-pond (z 5 h a ) and sea-icepond (z 5 h b ) interfaces, the Stefan boundary condition is …”

“…, and L 5 3.014 3 10 8 J m 23 is the volumetric latent heat of fusion of pure ice [Bitz and Lipscomb, 1999;Feltham et al, 2006;Bailey et al, 2010]. The effective thermal conductivity of sea ice is given by…”

“…where F LW and F SW are the downward fluxes of longwave and shortwave radiation, e 5 0.99 is the emissivity of sea ice, r 5 5.67 3 10 28 J (K 4 m 2 s) 21 is the Stefan-Boltzmann constant, a is the albedo of sea ice and the lid which are assumed to be identical, I 0 is the fraction of solar radiation penetrating the surface layer (considered to be of negligible thickness), and F sen T 5 T L S ocean ð Þ s and F lat are the sensible and latent heat fluxes [Ebert and Curry, 1993;Maykut and Untersteiner, 1971;Taylor and Feltham, 2004;Bailey et al, 2010].…”

“…A similar problem to the refreezing of melt pond was studied by Bailey et al [2010] who developed a one-dimensional consolidation model to investigate the freezing process between two rafted ice sheets separated by a thin liquid layer. Since the liquid layer was narrow, they assumed the temperature would remain uniform.…”

“…In this paper, we present a one-dimensional model that was developed based on similar principle to that of Bailey et al [2010] to investigate the refreezing of melt ponds in the Arctic. The model we have implemented considers the heat and salt balances in the ice lid, trapped pond, and underlying sea ice.…”