Figure 17.23: The vast taiga is known for its small, hardy, and widely-spaced trees. This
photo is of the Alaska Range in Alaska. ( 31 )
Polar Climates (Group E)
In the polar regions, winters are entirely dark and bitterly cold. In the summer, days are
long, but the sun is low on the horizon. Summers are cool with the average temperature
of the warmest month at less than 10°C (50°F). Winters are extremely cold, so the annual
temperature range is large. Polar climates receive less than 25 cm (10 inches) precipitation,
mostly during the summer. This climate is found across the continents that border the
Arctic Ocean, Greenland and Antarctica.
Polar Tundra (ET)
Thepolar tundraclimate is continental, with severe winters (Figure17.24). Temperatures
are so cold that a layer of permanently frozen ground, calledpermafrostforms below the
surface. This frozen layer can extend hundreds of meters deep. The average temperature
of the warmest months is above freezing, so summer temperatures defrost the uppermost
portionofthepermafrost. Inwinter, thepermafrostpreventswaterfromdrainingdownward.
In summer, the ground is swampy. Although the precipitation is low enough in many places
to qualify as a desert, evaporation rates are also low, so the landscape receives more usable
water than a desert.
The only plants that can survive the harsh winters and soggy summers are small ground-
hugging plants like mosses, lichens, small shrubs and scattered small trees that make up the
tundra(Figure17.25). Due to the lack of ice-free land near the South Pole, there is very
little tundra in the Southern Hemisphere. The area surrounding the Arctic Ocean is the
only part of the globe with much tundra.