In parts 1 and 2 of our “Ice is Nice” series, you learned about icebergs and glaciers. They are both formed on land and created by the continuous accumulation of snow and calving. In contrast, a rather simple ice feature at first glance – sea ice – forms, grows and melts in the ocean from salty water. It covers about 7% of the world's surface, or 25 million square kilometers, most of it being enclosed in the polar regions – the Arctic Ocean and the Southern Ocean. This floating ice has a profound influence on climate and wildlife.