In the past 10 days, the Arctic ocean has been losing as much as 150,000 square kilometres of sea a day, said Mark Serreze, director of the NSIDC. "The extent [of the ice cover] is going down, but it is also thinning. So a weather pattern that formerly would melt some ice, now gets rid of much more. There will be ups and downs, but we are on track to see an ice-free summer by 2030. It is an overall downward spiral."