Sea ice growth processes
Understanding its growth processes is important for climate modellers and remote sensing specialists, since the composition and microstructural properties of the ice affect how it reflects or absorbs sunlight.
At its earliest stages, sea ice consists of elongated, randomly oriented crystals.
If wave and wind conditions are calm these crystals will consolidate at the surface, and by selective pressure begin to grow preferentially in the downward direction, forming nilas.
In more turbulent conditions, the frazil will consolidate by mechanical action to form pancake ice, which has a more random structure.
[3][4][5] One of the more interesting processes to occur within consolidated ice packs is changes in the saline content.
As the ice freezes, most of the salt content gets rejected and forms highly saline brine inclusions between the crystals.
[2][7] Sea-ice density is relatively stable during winter with values close to 910 kg/m3,[8] but may decrease up to 720 kg/m3 during warming mainly due to increase in air volume.
[10] The main physical processes of sea-ice desalination are gravity drainage and flushing of surface meltwater and melt ponds.
The equation can be solved using a numerical root-finding algorithm such as bisection: the functional dependencies on surface temperature are given, with e being the equilibrium vapor pressure.
While Cox and Weeks assume thermal equilibrium,[14] Tonboe uses a more complex thermodynamic model based on numerical solution of the heat equation.
It too is highly variable, however its value is more difficult to determine since changes in temperature may cause some of the brine to be ejected or move within the layers, particularly in new ice.
Cox and Weeks provide the following formula determining the ratio of total ice salinity between temperatures, T1 and T2 where T2 < T1:[14] where c=0.8 kg m−3 is a constant.
As the ice goes through constant warming and cooling cycles it becomes progressively more porous, through ejection of the brine and drainage through the resulting channels.
The motion of the ice is driven primarily by ocean currents, though to a lesser extent by wind.
Note that stresses will not be in the direction of the winds or currents, but rather will be shifted by Coriolis effects—see, for instance, Ekman spiral.
