The tundra biome is a treeless landscape defined by its cold temperatures and harsh conditions. It encompasses vast areas, primarily in the Northern Hemisphere, extending across North America, Europe, and Asia, just below the Arctic ice caps. This environment is also found at high altitudes on mountains worldwide, known as alpine tundra. The name “tundra” originates from the Finnish word “tunturia,” meaning “treeless plain,” describing its vegetation, including low shrubs, sedges, mosses, and lichens, adapted to the cold and short growing seasons.
Tundra Temperature Ranges and Seasonal Shifts
Tundra temperatures vary significantly between seasons, with long, frigid winters and brief, cool summers. In the Arctic tundra, average winter temperatures reach -34°C (-30°F), with lows around -51°C (-60°F). The average annual temperature is around -28°C (-18°F). During the short Arctic summer, which lasts about 50 to 60 days, temperatures range from 3°C to 12°C (37°F to 54°F), allowing for a brief period above freezing. The lowest recorded temperature in the Northern Hemisphere, near the summit of the Greenland ice sheet, reached -69.6°C (-93.3°F) in December 1991.
Alpine tundra, found on mountains globally, experiences similar cold conditions. Winter temperatures in alpine tundra are below freezing, falling below -30°F (-34°C). Summers are also brief, lasting around 180 days, with average temperatures ranging from 3°C to 12°C (37°F to 54°F), similar to the Arctic. Nighttime temperatures in alpine regions remain below freezing even during the summer months. The growing season in alpine tundra is approximately 180 days, compared to the Arctic’s 50 to 60 days.
Influences on Tundra Temperatures
Low temperatures in the tundra are primarily due to its high latitude or high altitude. In Arctic tundra, the high latitude means the sun’s angle is low, resulting in reduced solar radiation reaching the surface. The sun remains below the horizon for extended periods during winter. Even during summer, sunlight is received at oblique angles, further limiting warming.
The albedo effect is another factor, where extensive snow and ice cover reflect a large portion of incoming solar radiation back into the atmosphere. This reflection prevents the ground from absorbing heat, maintaining cold surface temperatures. Cold air masses, often originating from polar regions, also contribute to frigid conditions. These combined atmospheric and geographical elements create an environment where temperatures remain low for most of the year.
Permafrost and Its Connection to Cold
Permafrost is a characteristic of the tundra, referring to ground that remains at or below 0°C (32°F) for at least two consecutive years. This permanently frozen layer can consist of soil, rock, and ice. Permafrost is both a result of and a contributor to the tundra’s cold temperatures, acting as a thermal insulator that helps keep the ground frozen.
The depth of permafrost varies across tundra regions. In much of the Arctic, permafrost can extend to depths ranging from 350 to 650 meters (1,150 to 2,100 feet). In some unglaciated areas of Siberia, permafrost depths can even reach up to 1,450 meters (4,760 feet). This extensive frozen layer prevents water from draining downwards, leading to saturated and boggy conditions in lowlands during the brief summer thaw. The presence of permafrost limits the rooting depth for plants, contributing to the treeless nature of the tundra.