sea ice

Around the North Pole, temperatures are so cold that parts of the ocean turn into solid ice called "sea ice." It's also happening near the South Pole, where oceans surrounding Antarctica freeze and thaw with the seasons. The forming and melting of sea ice at both poles plays an important role in Earth's climate. In turn, Earth's changing climate has an impact on sea ice. Long-term studies show that Arctic Ocean sea ice is slowly shrinking.

Image credits: main image, National Science Foundation.