Ice and Salt Keep Arctic Ocean Alive

The circumpolar oceans – the Arctic Ocean and the Southern Ocean – are still not well understood. Yet it's here, in the interaction of ice, water and sunlight, where our future could be determined.

The circumpolar oceans are primarily characterised by temperatures of around zero degrees, so they involve large quantities of sea ice . Some of the sea ice melts during the summer, and when the ocean surface freezes up again in the autumn, quite a lot of salt is shed from the new ice. The water right below this ice is consequently very salty and so also very heavy, sinking to the bottom. The heaviest water that exists anywhere in the oceans is the result of this process, and it is part of the global abyssal circulation. Unlike the more well-known surface currents such as the Gulf Stream, the abyssal circulation is particularly "fuelled" by specific weight differences between volumes of water.

Because of the huge ice masses, the circumpolar oceans are still the most unknown ocean regions, as genuine exploration was not initiated until after World War II. Today, there is much focus on these ocean regions, because they are expected to include major natural resources such as oil and minerals beneath the ocean floor. Today, oil and raw material producers are engaged in tapping into the resources.

Around the ice front, the ocean is productive. The formation of ice produces heavy water, and so, a circulation results which carries nutritious water to the sur-face. In combination with the large quantity of sunlight in the summer, the result is a major primary production in the shape of plant plankton. The tiny organisms form the basis of a food chain for fish, birds, and mammals that is adapted to the special polar conditions.

The circumpolar oceans are among the regions where climate change is most obvious. Changes of sea ice extension and thickness are clear. The sea ice plays a central role ice albedo feedback. Albedo is a measure of a surface’s ability to reflect visible light. When the extension of the ice is reduced due to heating, the reflection ability is reduced, resulting in absorption of more sunlight and so in more heating.