The Arctic is the Earth's northern polar region, centred on the geographic north pole, which is surrounded by the frozen Arctic Ocean. There are differences of opinion on how to define the extent of the Arctic. Some consider everything north of the Arctic Circle, a line of latitude, as being the Arctic.
The Arctic includes Greenland's vast ice sheet. It is the second largest glacier on Earth after the vast Antarctic ice sheet.
Scientists from around the world are studying the effects of manmade climate change on the Greenland ice sheet, the region's sea ice and permafrost. Oil, gas and other resources lying below the Arctic Ocean and Greenland ice sheet are also being investigated by companies and nations planning to extract them as the ice retreats.
Image: The point where the Sermeq Kujalleq glacier reaches the sea, near Illuissat, Greenland (credit: J.P.Danvoye, Publiphoto Diffusion/SPL)
Time-lapse shows the dramatic changes brought about by spring's arrival.
Two different techniques manipulate the spectacle of change over time in this clip. Taken at intervals of several weeks, a short sequence of still satellite images is blended together to show change over a much larger timescale. Down at ground level, a sophisticated computer driven tracking system took regular shots in a specific location to create a time-lapse sequence of growth close up.
A methane surge in the oceans 55 million years ago warmed the Earth.
Professor Iain Stewart explains how a surge in methane, a greenhouse gas, emitted from the oceans 55 million years ago caused global warming. He describes how the rise of the Himalayas helped to bring this cooling to an end - weathering of this mighty mountain range took carbon dioxide out of the atmosphere. The exact cause of the methane surge 55 million years ago is uncertain.
Many of the world's glaciers are retreating.
Dr Iain Stewart describes the retreat of many of the Earth's glaciers and the break up of polar ice sheets.
Extreme seasonal change in the world's greatest wilderness.
With the melting sea ice becoming unreliable and impossible to walk on, the sequence had to be filmed largely from the air. The heligimbal camera system allowed for stabilised tracking shots over the fragmenting sea ice and the glacial waterfalls. Shooting from so high above prevents the polar bear's normal behaviour from being disturbed. Time-lapse illustrates the constant flux of the ice as it breaks up.
The Arctic (pron.: /ˈɑrktɪk/ or /ˈɑrtɪk/) is a polar region located at the northernmost part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Denmark (Greenland), Norway, the United States (Alaska), Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost. The area can be defined as north of the Arctic Circle (66° 33'N), the approximate limit of the midnight sun and the polar night. Alternatively, it can be defined as the region where the average temperature for the warmest month (July) is below 10 °C (50 °F); the northernmost tree line roughly follows the isotherm at the boundary of this region.
Socially and politically, the Arctic region includes the northern territories of the eight Arctic states, although by natural science definitions much of this territory is considered subarctic. The Arctic region is a unique area among Earth's ecosystems. The cultures in the region and the Arctic indigenous peoples have adapted to its cold and extreme conditions. In recent years the extent of the sea ice has declined. Life in the Arctic includes organisms living in the ice,zooplankton and phytoplankton, fish and marine mammals, birds, land animals, plants and human societies.