In the past few decades, average Arctic temperatures have risen at twice the rate of the rest of the world (3-4 degrees centigrade in the last 50 years in Alaska and northwest Canada). Over the next 100 years they could rise a further 3-5 degrees centigrade over land and up to 7 degrees centigrade over the oceans. This is already leading to melting of the Greenland ice sheet, glaciers and sea ice. Ice and snow reflect a lot of solar energy as they have a high albedo, so when they melt more energy is absorbed and warming increases. In addition:

~The melting of ice could make the Arctic Ocean less saline and warmer. This would weaken the formation of the Arctic conveyor, which draws the warm gulf stream current northwards. The loss of the warm Gulf Stream would cause a dramatic cooling of the climate in northwestern Europe.
~Water from melting ice sheets and glaciers will contribute to rising sea levels globally.

Climate change in the polar regions is likely to be among the largest and most rapid of any on Earth, with major environmental and ecological impacts, and knock-on socioeconomic effects, especially in the Arctic. Note, however, that both positive and negative impacts can be seen.

Impacts on natural systems

Vegetation shifts

Vegetation zones are predicted to shift northwards, with coniferous forests like the Boreal forest encroaching on tundra and on ice deserts. This shift will destabilise existing food webs and increase likelihood of forest fires and insect outbreaks in northern Russia. The longer, warmer growing season will be a benefit to Arctic agriculture, although soils will be a limiting factor.

Thawing of permafrost

Up to 40% of total permafrost is expected to thaw, especially in Siberia. This will release large quantities of methane - itself a greenhouse gas. In some areas, lakes and rivers will drain as the frozen ground beneath them thaws, while rising river flows could create new wetlands in other places. These changes will have an impact on species, particularly freshwater fish such as the Arctic char and lake trout.

Increasing fires and insects

Global warming will increase forest fires and insect-caused tree death, which may have an impact on old-growth forest, a valuable habitat that is rich in lichens, mosses, fungi and birds such as woodpeckers. Alien species may invade, such as red foxes.

Ultraviolet impacts

Increased ultraviolet (UV) radiation will reach the Earth's surface as snow and ice cover is lost. Many freshwater ecosystems are highly sensitive to UV radiation, which destroys phytoplankton at the base of the marine food chain.

Carbon cycle changes

The replacement of Arctic vegetation with more forests will lead to higher primary productivity and increased carbon dioxide uptake, but methane emissions from warming wetlands and thawing permafrost could counterbalance this positive impact.

Other impacts

Increased coastal erosion as thawing permafrost weakens the coast, and there are more waves and storm surges as the protection of sea ice is lost.

Impacts on animal species

Northward species shift

Species will shift north with forests, particularly the Boreal forest, encroaching on the tundra and limiting the habitats of animals evolved to survive there, such as the Arctic fox and the Polar Bear. Some species are likely to suffer major decline.

Marine species

Marine species dependent on sea ice, including polar bears, ice-living seals, walruses and some birds, will decline. Some may face extinction. Numbers of Polar bears have declined by 20% in Hudson Bay, Canada, due to loss of habitat and declining prey (seals). Birds like geese will have different migration patterns.

Land species

land species adapted to the Arctic climate, including lemming, vole, Arctic fox, snowy owl and caribou are at risk. Lemmings and voles have declined as a result of the poor snow conditions, decreasing the prey of one of their predators, the Arctic fox. Furthermore, the thawing of ice and the encroaching Boreal forest is making the Arctic fox easier prey, as their fur is camouflaged to fit in with the tundra environment, not the forest one. The red fox, which lives in the boreal forest, is also a predator of the Arctic fox. As a result of this, the European Arctic foxes now number only around 150 in Sweden, Finland and Norway.

Impacts on society

The ecological and environmental changes described above will mean:

~Loss of hunting culture and decline of food security for indigenous peoples (e.g. Inuits). 80% of Inuit still hunt Caribou, fish and marine mammals. 24 Inuit villages in Alaska are now threatened by flooding.
~Need for herd animals (e.g.reindeer) to change their migration routes.
Decline in northern freshwater fisheries (e.g. threatened Arctic char), but enhanced marine fisheries (e.g. arrival of cod and herring due to warmer water).
~Increasing access for marine shipping, but disruption of land-based transport because of permafrost thawing. In 2007, the Northwest Passage was opened up for marine going vessels.
~Enhanced agriculture and forestry.
~As large areas of snow and ice melt, exposing new land and open sea, the Arctic will become more accessible, and vulnerable to exploitation for oil, gas, fish and other resources. 25% of the world's remaining resources are in the Arctic. 80 % of the population of Greenland think this is a positive impact as it increases economic opportunities.

	Criado por Holly Lovering mais de 10 anos atrás

taken straight from the edexcel as geography textbook, with added facts and figures