Climate change: Arctic sea ice hits 4th lowest level this year - Arctic sea has reached its minimum ice extent for 2015, which is the fourth lowest in the satellite record since observations from space started.
According to the analysis by NASA and the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado at Boulder, the annual minimum extent was 1.70 million square miles (4.41 million square kilometers) on September 11.
This year's minimum is 699,000 square miles (1.81 million square kilometers) lower than the 1981-2010 average.
Arctic sea ice cover is made of frozen seawater floating on top of the ocean. This sea ice cover is important as it plays an important role in regulating the temperature of earth by reflecting solar energy back to space. The sea ice cap grows and shrinks cyclically with the seasons.
Its minimum summertime extent occurs at the end of the melt season and according to experts it has been decreasing since the late 1970s in response to warming temperatures.
In recent years, the decrease in sea-ice minimum extent has been at least in part exacerbated by meteorological factors, but the case was different this year.
Sea ice scientist Walt Meier said though this year is the fourth lowest, people were yet to see any major weather event or persistent weather pattern in the Arctic this summer that helped push the extent lower as often happens.
A powerful August cyclone was witnessed in 2012 - the lowest year on record. The cyclone fractured the ice cover, accelerating its decline.