Antarctica's sea ice reaches its lowest level since records began, for the 2nd year in a row

On Feb. 21, Antarctica's sea ice retreated to its lowest extent since satellite records began in 1979.

The amount of sea ice surrounding Antarctica has reached its lowest level since modern records began, for the second year in a row. 

Sea ice is frozen seawater that floats on the ocean's surface around the Earth's polar regions. It forms at much lower sustained temperatures than freshwater ice does, at around 28.8 degrees Fahrenheit (minus 1.8 degrees Celsius). Sea ice builds up during the winter until it reaches its maximum extent, and then melts away in the spring and summer until it reaches its minimum extent.