Climate is one of the most important drivers of ecosystems; it defines the landscape and what can live on it. Globally, the Arctic is almost entirely covered by water, much of it frozen. Some frozen features, such as glaciers and icebergs, are freshwater. In fact, the glaciers and icebergs in the Arctic make up about 20% of Earth’s supply of freshwater. Other sources of freshwater are the many Arctic lakes and rivers.

Most of the Arctic, however, is the liquid saltwater of the Arctic Ocean basin. Some parts of the ocean’s surface remain frozen all or most of the year as sea ice. Sea ice helps determine Earth’s climate. It has a very bright surface, or albedo, that reflects about 80% of sunlight that strikes sea ice is reflected back to space. The dark surface of the liquid ocean, however, absorbs about 90% of solar radiation. This dynamic of reflecting or absorbing sunlight is an important driver of climate. The decrease in sea ice means that more sunlight (and heat) is absorbed by the ocean, which accelerates warming. The Arctic is warming more than twice as fast as the global average due to these positive feedbacks, also called polar amplification.

What was the glacial extent in Alaska and the Arctic during the Pleistocene? Check out this atlas of Alaska's (and Arctic Canada) Paleo glaciers.

For more information about the Arctic climate, see the National Snow and Ice Data Center for current conditions, trends, data, and maps.

Tundra

Tundra is the coldest of biomes and it’s name comes from the Finnish word tunturia, meaning treeless plain. There are two types of tundra: arctic tundra is above latitudinal treeline and alpine tundra is above elevational treeline. The mountains of the Brooks Range have both kinds of tundra. Tundra is defined by its frost- or ice-molded landscapes, very low temperatures, little precipitation, poor nutrients, and short growing seasons. Tundra vegetation is generally low to the ground and wildlife species are specially adapted to live there.

Arctic tundra (high latitude) is located in the northern hemisphere, encircling the north pole and extending south to the coniferous forests of the taiga or boreal forest. The Arctic is known for its cold, desert-like conditions. The growing season ranges from just 50 to 60 days. Arctic tundra is underlain by a layer of permanently frozen soil called permafrost. Permafrost is permanently frozen ground that affects nearly everything in the Arctic ecosystem, including soils, vegetation, water, and wildlife. During summer months, the top layer of soil thaws (known as the active layer) creating a wet landscape with rapid runoff. The striking quilt-like, polygonal pattern of permafrost landscapes is caused by the build-up and thawing of ice in the ground, which produces pits, ponds, and landslides. When water saturates the upper surface, bogs and ponds may form, providing moisture for plants.

Alpine tundra (high elevation) is located on mountain tops throughout the world at high altitude. The growing season is approximately 180 days. The climate and soils of high-elevation alpine tundra prevent tree growth. Alpine tundra is distinguished from Arctic tundra in that alpine tundra typically does not have permafrost and alpine soils are generally more porous than Arctic soils.