The tundra biome is a vast, treeless expanse found in Earth’s polar regions and at high altitudes on mountains across the globe. This environment is characterized by perpetually cold conditions, which restrict the growth of trees and tall vegetation. It is one of the planet’s coldest and most challenging biomes.
Defining Climatic Characteristics
The tundra biome is defined by consistently low, year-round temperatures. Average annual temperatures often remain below freezing, directly influencing all other aspects of its climate.
Despite its icy appearance, the tundra receives very little precipitation, often classifying it as a “cold desert.” Annual precipitation, including melted snow, typically ranges from 150 to 250 millimeters (6 to 10 inches), which is less than many of the world’s arid deserts. However, because of the low temperatures, evaporation is minimal, leading to soggy ground in some areas during the warmer months.
A defining feature of the tundra is permafrost, which is ground that remains frozen for at least two consecutive years. This permanently frozen layer can extend to depths of hundreds of meters, significantly impacting water drainage and limiting root penetration for plants. Above the permafrost lies an “active layer” of soil that thaws seasonally.
Strong winds are another characteristic of the tundra climate. These winds contribute to the cold and dry conditions by increasing wind chill and sweeping across the open, treeless landscape. The constant wind also plays a role in redistributing snow, creating areas of bare ground and deep drifts.
Seasonal Climate Patterns
The tundra experiences two primary seasons: a long winter and a short, cool summer. During the extended winter, darkness prevails for significant periods, especially in the Arctic tundra where the sun may not rise for days or even weeks. Winter temperatures are low, with averages often around -28°C (-18°F) and capable of plummeting to -50°C (-58°F) or lower. Precipitation during winter mostly consists of dry snow, which is often redistributed by strong winds.
The brief summer period brings continuous or near-continuous daylight, often referred to as the “land of the midnight sun” in Arctic regions. Temperatures during summer are cool, typically ranging from 3°C to 12°C (37°F to 54°F), though they can occasionally reach 18°C (64°F). This warmer period allows the active layer of soil above the permafrost to thaw, leading to the formation of shallow lakes and bogs as water cannot drain through the frozen ground below. The transition between these seasons is often rapid, with little in the way of traditional spring or autumn.
Variations Across Tundra Types
While sharing overarching characteristics, the climate of the tundra biome varies between its two main types: Arctic and Alpine. Arctic tundra is located at high latitudes, encircling the North Pole across North America, Europe, and Siberia. Its proximity to the Arctic Ocean and flat terrain contribute to long, dark winters and widespread, continuous permafrost.
In contrast, Alpine tundra occurs at high altitudes on mountain ranges worldwide, regardless of latitude. The climate in alpine tundra is influenced by altitude, which causes lower air pressure and often more intense solar radiation during the day. While still cold, alpine tundra typically has a more moderate climate than Arctic tundra, with summer temperatures ranging from 3°C to 12°C (37°F to 54°F) and winter temperatures rarely falling below -18°C (0°F). Precipitation in alpine tundra can be more varied due to topography, and permafrost is often less extensive or discontinuous compared to its Arctic counterpart, allowing for better drainage in some areas.