By Christopher Krembs Arctic sea ice covers significant portions of the northern marine hemisphere, forming and persisting at temperatures below the freezing point of seawater. As ice crystals grow in the water during the autumn season, small ice platelets begin to accumulate at the ocean surface, inter-link and form a porous structure of ice crystals filled with liquid referred to as brine. The flourishing life within the briny habitat of sea ice is intricately linked to physics.
Temperature controls every physical and chemical aspect of ice, including the availability of light.
The most notable effect of decreasing temperature as winter progresses and the ice solidifies is the reduction of pore space within and the concurrent increase in brine salinity. Studying the capability of organisms to survive such extremes is an active research field of Astrobiology , where wintertime sea ice is used as an analogue for possible extraterrestrial habitats on the frozen surfaces of such solar bodies such as Europa, Ganymede, Mars and Titon. Sea ice constitutes a thermal barrier against the cold winter atmosphere such that the ice-water interface remains at the temperature of seawater. During spring when light begins to be available for photosynthesis and troughout the summer, a large biomass in the form of unicellular photosynthetic algae ice develop within the lowermost sections of the ice. The ice-water interface is therefore critical to polar marine ecosystems.