The North Pole and the South Pole are defined by the intersection of the Earth's rotation axis with its surface. In a broader sense, the poles encompass all land and ocean at the high latitudes, where ice, sea ice, and snow are perennial.

Ice and snow are important components of Earth's climate system and are particularly sensitive to local and global climate change. Changes in snow cover and sea ice have immediate effects on land and ocean heating, the strength of major ocean currents, terrestrial and marine ecosystems, [Page 2204]and human activities. As stated in the Fourth Assessment of the International Panel on Climate Change (IPCC), “Warming of the climate is unequivocal, as is now evident from observations of increases in global average air and ocean ...