Sea ice is frozen ocean water that melts each summer and refreezes each winter. It typically reaches its smallest "extent" in September and largest in March of each year, and is tracked by the data center, located in Boulder, Colo.
Measurements of sea ice in the Arctic began in 1979.
The monthly average January 2016 sea ice extent was 42,500 square miles less than the previous record low in 2011.
The lack of ice affects wildlife such as polar bears and walruses and also could be changing weather patterns down here over the U.S.