The Arctic Tundra Flashcards
What is the extent of the Arctic tundra?
The Arctic tundra occupies approximately 8 million km² in northern Canada, Alaska, and Siberia. It extends from the northern edge of the boreal coniferous forest to the Arctic Ocean.
What is the climatic limit of the tree line in the Arctic tundra?
The 10°C July isotherm approximates the southern limit of the Arctic tundra. It signifies the climatic limit beyond which trees cannot grow.
What are the climatic conditions in the Arctic tundra?
Climatic conditions in the tundra are severe, with average monthly temperatures below freezing for eight or nine months of the year. The ground is permanently frozen, with only the top meter or so thawing during the Arctic summer.
What is permafrost, and what role does it play in the water cycle of the tundra?
Permafrost is a layer of permanently frozen ground that underlies much of the tundra. It acts as an important feature of the region’s water cycle by impeding infiltration, percolation, recharge, and groundwater flow.
What is the vegetation like in the Arctic tundra?
The tundra has low biodiversity and is mostly treeless, except for a few dwarf species. In the southern areas, vegetation provides a continuous ground cover, while in the High Arctic, plant cover is discontinuous, with extensive areas of bare ground.
What are the main features of the water cycle in the tundra?
The main features of the water cycle in the tundra include low annual precipitation (50-350 mm), with most of it falling as snow. The low temperatures result in limited transpiration and low rates of evaporation. Groundwater and soil moisture stores are limited, and wetlands, ponds, and lakes form during the summer due to permafrost impeding drainage.
How does permafrost affect the carbon cycle in the tundra?
Permafrost is a vast carbon sink, estimated to contain 1600 GT of carbon globally. The low temperatures in the tundra slow the decomposition of dead plant material, leading to the accumulation of carbon in the permafrost. The amount of carbon in tundra soils is five times greater than in the above-ground biomass.
What is the net primary productivity (NPP) in the tundra?
The net primary productivity (NPP) in the tundra is less than 200 grams/m²/year. The short growing season and low temperatures limit plant growth and productivity.
What are the factors contributing to the carbon flux in the tundra?
The carbon flux in the tundra is concentrated during the summer months when the active layer thaws. Plant growth occurs rapidly during the short summer, increasing carbon uptake. Even in winter, pockets of unfrozen soil and water in the permafrost act as sources of carbon dioxide (CO₂) and methane (CH₄).
What are the potential impacts of global warming on the carbon cycle in the tundra?
Global warming has raised concerns about the tundra becoming a carbon source rather than a sink. While outputs of carbon from the permafrost have increased in recent decades, higher temperatures have also stimulated plant growth and increased carbon uptake. The balance of the carbon budget in the tundra remains uncertain.
What are the physical factors influencing the water cycle in the tundra?
The water cycle in the tundra is influenced by temperature, relief, and rock permeability. Average temperatures are well below freezing for most of the year, resulting in water storage as ground ice in the permafrost layer. Relief is minimal, contributing to waterlogging, and rock permeability plays a minor role due to the impermeability of permafrost and the dominant crystalline rocks in the tundra.
What is the role of temperature in the water cycle of the tundra?
Average temperatures in the tundra are below freezing for most of the year, leading to the storage of water as ground ice in the permafrost layer. During the short summer, the shallow active layer thaws, allowing liquid water to flow on the surface.
How does relief influence the water cycle in the tundra?
The tundra exhibits minimal relief, with an ancient rock surface that has been eroded and weathered over millions of years, resulting in a gently undulating plain. The lack of significant relief contributes to waterlogging during the summer months, impeding drainage.
What is the role of rock permeability in the water cycle of the tundra?
Rock permeability has limited influence on the water cycle in the tundra. The impermeability of permafrost and the dominance of crystalline rocks, such as in Arctic and sub-Arctic Canada, restrict the flow of water through the rocks. Porosity and mineral composition have minimal impact on the water and carbon cycles.
How is carbon mainly stored in the tundra?
Carbon in the tundra is mainly stored as partly decomposed plant remains frozen in the permafrost. This carbon has been locked away for at least the past 500,000 years.
