Antarctic Sea Ice
Sea ice is frozen sea water. The ocean around Antarctica freezes each winter, and the ice can be 2 metres or more thick in places. Sea ice plays an important part in Earth's climate because sea ice is grey/white and so it reflects sunlight. Sea ice forms a stable cover on parts of the ocean, reducing heat transfer between the ocean to the atmosphere.
When sea ice forms, salty water sinks, which drives ocean turnover that is a vital part of Earth's climate system. The freezing of Antarctic sea ice in winter and melting in the summer is one of the largest geophysical changes on Earth: sea ice extent reduces from around 18 million square kilometres in winter to around 3 million square kilometres in summer.
Antarctic sea ice also provides food and habitat animals and plants such as penguins and algae.