1. Life in ice? Life in ice Life in ice?

2. Life in ice The cryosphere The portion of the Earth’s surface covered in ice is known as the cryosphere. This includes ice caps, ice sheets, glaciers and sea ice. It also includes areas with permanently frozen ground (permafrost). Snow cover is part of the cryosphere, but is seasonal not permanent. Snow can cover up to 50 million km 2 of land in the northern hemisphere winter. Seasonal snow cover in Iceland

3. Life in ice? Life in ice The size of the cryosphere Several parts of the cryosphere vary markedly by season. This includes ice on rivers, lakes and the sea. Sea-ice cover in the northern hemisphere is more variable than in the southern hemisphere. Snow and ice extent varies because of the timing of seasons in the northern versus the southern hemisphere Cryosphere component Million km 2 Snow cover47–4 (winter to summer) Ice caps and glaciers 1 Ice sheets16 Permafrost25 River and lake ice1 Sea ice28–19 (winter to summer)

4. Life in ice? Life in ice Extreme environments Traditionally, the cryosphere has been grouped with other extreme areas such as hyper-arid deserts and areas of bare rock (see table). These environments were seen as essentially unproductive in terms of biological productivity. Notice that in the table ‘Extreme desert, rock, sand, ice’ is the third largest environment by area. However, it is the least productive in terms of NPP. Extent and productivity of global biomes

5. Life in ice? Life in ice Ice life-forms Recent research suggests there is more life in the cryosphere than once thought. Most of this life is very simple, consisting of algae. This includes Chlamydomonas nivalis which looks red/pink and creates ‘watermelon snow’ and Melosira arctica which is a type of algae that lives on the underside of floating sea ice. There are, rarely, more complex life-forms that live in ice such as Alaskan ice worms Mesenchytraeus solifugus

6. Life in ice? Life in ice Food webs The algae that live in ice form the basis of food webs. The algae photosynthesise, and so produce carbohydrate. Living and dead algae can be released from ice during melting. This means glacial meltwater in rivers, and ice melt from sea ice, contains food for other organisms. This, simple life forms on ice can be an important component of food webs.