The cryosphere is composed of all parts of Earth where water is frozen, whether on the surface (snow, ice, sea ice) or below the surface (permafrost). Notice that Mexico is a beige- to yellow-colored region with no snow or ice near the bottom of Fig. 13.1B.

1. What is the order in which you would encounter different parts of the cryosphere if you traveled overland from Mexico to the North Pole? While continental glaciation occurs only in Greenland and Antarctica today, mountain glaciers and ice caps occur in many places, including Canada, Russia, Alaska, the Rocky Mountains, the Andes, the Alps, and the Himalayas. Some mountain glaciers exist very close to the equator.

2.How do you think it is possible for glaciers to exist at the equator?

3. How do the changes in Arctic sea ice extent over time compare with the Antarctic changes? If they are different, why do you think that might be? Consider as many possibilities as you can.

Map of Regional Variations in the Cryosphere A ICE SHELF: A sheet of ice attached to the land on one side but afloat on the ocean on the other side. SEA ICE: A sheet of ice that originates from the freezing of seawater. South Pole Antarctica Asia Arctic Ocean North Pole North America Mexico Greenland SEASONAL SNOW: Snow and ice may accumulate here in winter, but it melts over the following summer. PERMAFROST CONTINUOUS: The ground is permanently frozen over this entire area. PERMAFROST DISCONTINUOUS: The ground is permanently frozen in isolated patches within this area. MOUNTAIN GLACIERS AND ICE CAPS: This area contains permanent patches of ice on mountain sides (cirques), river-like bodies of ice that flow down and away from mountains (valley and piedmont glaciers), and dome-shaped masses of ice and snow that cover the summits of mountains so that no peaks emerge (ice cap). ICE SHEET: A pancake-like mound of ice covering a large part of a continent (more than 50,000 km).