Brine channels

Due to the fact that salts cannot be within the ice crystals, they are expelled as the crystals form (Krembs et al. 2000). This forces the blades of ice to be separated by grooves filled with brine that has been expelled.  The brine will either become trapped with in the ice or be released back in the ocean. The process of the brine being released into the ocean forces the underlying water to sink, due to the water being cooled and increased in salinity by the addition of brine. This causes the density of the water to increase, so the water sinks rapidly down. This process is an important component of the ‘Global Thermohaline Conveyor Belt’(Thomas 2004).

The brine that remains in the ice causes the ice to be covered with an intricate labyrinth of channels. The volume of ice to the volume of the brine channels increases as the temperature goes down, resulting in more salt in a smaller space. So the salinity of the brine increases proportionally to the decreases in temperature (Thomas 2008). Ice at the top of the ice floe is normally colder than the ice at the bottom, therefore a gradient of temperature goes down the ice, meaning there is all so a gradient of brine salinity and volume. Due to these characteristics of the ice, the majority of organisms are found in the lower warmer ice due to the more space available (Gradinger 1999). These regions are known as ‘bottom’ sea- ice assemblages. The main primary producers in these channels are the diatoms, which in turn support many metazoan and protozoan species (Janssen and Gradinge 1998).

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