Using this graphic and referring to it is encouraged, and please use it in presentations, web pages, newspapers, blogs and reports.
For any form of publication, please include the link to this page and give the cartographer/designer credit (in this case Hugo Ahlenius, UNEP/GRID-Arendal)
Based on NASA Blue Marble NG, with data from the National Snow and Ice Data Centre
Uploaded on Tuesday 21 Feb 2012
Cryosphere - winter seasons, Northern and Southern Hemispheres
Hugo Ahlenius, UNEP/GRID-Arendal
Seasonal variation in the extent of ice and snow cover is greatest in the Northern Hemisphere. Imagine the Earth with white caps on the top and bottom. The top cap increases by a factor of six from summer to winter, while the bottom cap only doubles from summer to winter. This difference is due to snow cover: in the Northern Hemisphere snow cover on land varies from less than 2 million km2 in the summer to 40 to 50 million km2 in the winter3. There is little snow cover in the Southern Hemisphere. In Antarctica, land ice covers about 14 million km2 yearround, with little change from summer to winter. Sea ice cover in the Arctic varies between approximately 7 and 15 million km2 seasonally, while sea ice cover in the Antarctic, though about the same extent at its peak, varies much more – from around 3 million km2 during summer to 18 million km2 in winter. This means that there is less multi-year sea ice in the Antarctic than in the Arctic, where much of the sea ice is older than one year.