Respuestas
Even though sea ice occurs primarily in the polar regions, it influences our global climate. Sea ice has a bright surface, so much of the sunlight that strikes it is reflected back into space. As a result, areas covered by sea ice don't absorb much solar energy, so temperatures in the polar regions remain relatively cool. If gradually warming temperatures melt sea ice over time, fewer bright surfaces are available to reflect sunlight back into space, more solar energy is absorbed at the surface, and temperatures rise further. This chain of events starts a cycle of warming and melting. This cycle is temporarily halted when the dark days of the polar winter return, but it starts again in the following spring. Even a small increase in temperature can lead to greater warming over time, making the polar regions the most sensitive areas to climate change on Earth.
Sea ice also affects the movement of ocean waters. When sea ice forms, most of the salt is pushed into the ocean water below the ice, although some salt may become trapped in small pockets between ice crystals. Water below sea ice has a higher concentration of salt and is more dense than surrounding ocean water, and so it sinks. In this way, sea ice contributes to the ocean's global "conveyor-belt" circulation. Cold, dense, polar water sinks and moves along the ocean bottom toward the equator, while warm water from mid-depth to the surface travels from the equator toward the poles. Changes in the amount of sea ice can disrupt normal ocean circulation, thereby leading to changes in global climate (for more information, see Sea Ice and Global Climate).
Too much or too little sea ice can be a problem for wildlife and people who hunt and travel in polar regions. In the Arctic, sea ice can be an obstacle to normal shipping routes through the Northern Sea route and Northwest Passage. See the Environment section to learn more about the impact of sea ice changes on people and wildlife.