Ice melts each summer and refreezes each winter in the Arctic Ocean. Summer sunshine only melts part of the sea ice, but the amount that melts has increased dramatically over the last few years, especially since 2007. The extent of sea ice at its summer minimum (which usually occurs in September) is now little more than half of where it was in the 1980s, and the minimum ice volume (which considers both extent and thickness) has dropped by more than 60%.
Experts differ on how quickly Arctic sea ice will continue to melt, with some projections leading to summer periods that are virtually free of ice by the 2020s or even sooner. Ice will continue to refreeze each winter, but the increased areas of open ocean will affect human activities and wildlife and may influence regional climate in ways now being studied. Also, the dark ocean can absorb more heat than brighter, more reflective sea ice, which helps foster a vicious cycle of more melting and more warming.
Unlike ice that’s melting on land, the loss of ice floating in the ocean doesn’t raise sea level, since the ice will take up less space once it melts (just as ice melting in a glass of lemonade doesn’t cause the glass to overflow).