![]() ![]() In the winter when solar heating is at a minimum and air temperatures are lowest, the sea ice insulates the ocean from losing heat to the atmosphere above. ![]() The presence of sea ice near the poles changes this relationship. Ocean-atmosphere interactions therefore generally serve to dampen the seasonal cycle the oceans delay the cooling of the atmosphere in the autumn and, conversely, delay the warming of the atmosphere in the spring. This increased 'memory' of heat means that the seasonal cycle of the ocean is roughly three months behind that of the atmosphere. The ocean is able to retain heat from the Sun more efficiently than the atmosphere (the ocean has a higher 'heat capacity'). Importance of sea ice in the climate system Sea ice overview on the composition and behaviour of sea ice is available. At least 15% of the ocean is covered by sea ice at some point during the year. Then, as the surface cools in the autumn, the ocean starts to freeze again leading to an increased sea ice cover through the winter months. As the Earth's surface at the poles warms in summer more than half the sea ice melts to reveal the open ocean below. They see little or no sunlight during their winters and almost continuous daylight through their summers. The amount of sea ice present in the Arctic (and Antarctic) changes throughout the year as a consequence of the solar heating the polar regions receive. As sea ice is formed from frozen seawater and floats on the sea surface, melting of the ice does not contribute to sea level rise (unlike for melting glaciers and ice sheets which are stores of frozen water on land that add water to the ocean when they melt). Sea ice is also a major component of polar ecosystems because plants and animals at all levels of the food chain live in or around sea ice. It also provides a barrier to the exchange of freshwater, gases and aerosols (tiny, airborne solid and liquid particles). Sea ice is an important component of the climate system because it regulates the transfer of heat and momentum between the atmosphere and the ocean. It is formed in high latitude regions where there is little or no sunlight in the winter and so atmospheric conditions are cold enough for the ocean to freeze. Sea ice is frozen seawater which floats on the surface of the ocean. ![]()
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