Two maps of Arctic sea ice extent in (a) September 1980 and (b) September 2012. The figure shows the physical landforms (grey) and ocean areas (dark blue) centred around the North Pole with the sea ice extent shown in white. Hence most of the oceanic Arctic region in the centre of the picture appears white. The sea ice extent and concentration are greater in September 1980 than September 2012. The median line for 1981-2010 is also shown, which encompasses most of the Arctic Ocean. For the 1980 the map the sea ice extent is slightly larger than the median line while for the 2012 map the extent is consistently smaller than the median. The figure has labels indicating the extent is 7.9 million sq km in September 1980 and 3.6 million sq km in September 2012.