Scientists believe the Arctic sea ice, or the floating ice cover of the Arctic Ocean, has reached its minimum extent for the year, shrinking to the second lowest extent since record-keeping began in 1978. The Arctic sea ice cover shrank to 1.44 million square miles (3.74 million square kilometers) by September 15, the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder announced Monday. This is only 135,000 square miles (350,000 square kilometers) higher than the lowest extent reached in 2012.