Gravity-induced sea ice desalination under low temperature

The Bohai Rim is one of the water-scarce regions in China. But every winter, more than 1 billion m3 of sea ice formed in the sea, about 40% of which distributes within 10 km offshore and is expected to be exploited and utilized as source of freshwater. The salinity of the Bohai sea ice ranges from 4 to 11‰, under suitable ambient temperatures, gravity driven brine drainage and flushing from the melted water can convert sea ice into freshwater ice. To study the influence of ambient conditions on the process, we conducted two experiments on the coast of the Bohai Sea from January to March in 2011. The results showed that ambient temperature was a decisive and controlling factor in gravity-induced sea ice desalination, and that insulation could affect the duration, volume and salinity of the drainage. If the ambient temperature was controlled between − 4.0 and 3.0 °C, the drainage would have a low volume and high salinity. With a rise in the air temperature, the volume of the drainage increased and the salinity decreased. Sea ice desalination and freshwater production were negatively correlated: the higher the freshwater production, the lower the sea ice desalination and vice versa.

► China's Bohai-Rim lacks freshwater, but sea ice is abundant. ► Salinity of sea ice is lower than seawater and easier to be desalinated. ► Gravitational desalination is low energy-consuming and efficient. ► Under the force of gravity, sea ice can be converted into freshwater. ► It's possible to relieve water scarce problem by gravity-induced sea ice desalination.