Nine things you need to know about polar sea ice

http://www.theguardian.com/vital-signs/2014/dec/11/arctic-antarctic-sea-ice-explainer?utm_source=twitter&utm_medium=post&utm_term=antarctic,arctic&utm_campaign=Polar&__surl__=IgeKn&__ots__=1419021867143&__step__=1