• Furthermore, because sea ice contains less salt than sea water, when sea ice is formed the salt content (salinity) and density of the surface layer of the ocean is increased.

• This is because the models project that a higher flow of fresh water into the North Atlantic from increased high latitude precipitation will reduce the salinity of the surface water and cause an estimated 50 % decrease in the rate of deep water formation by 2100.

• These two causes are not independent as the formation of the Atlantic deep water - the driver of the oceanic circulation - depends on the ocean 's temperature and salinity, which are themselves dependent on atmospheric conditions: wind, rain and insolation.