Arctic climate change
Arctic climate change
Global climate change is having a greater impact in the Arctic than in other parts of the world. Many species are dependent on the sea ice for their survival, and are experiencing dramatic changes in conditions as ice cover decreases. The extent of the sea ice in the Arctic reached a record low in 2012.
Higher temperatures, less ice, more rain and snow
The Earth’s climate is already changing, and the changes are particularly marked in the Arctic. But the impacts of climate change in the Arctic will be felt throughout the world, because changes in physical processes here influence the climate on a global scale. Processes of change in the Arctic can therefore provide a unique insight into the climate change that is already taking place and also act as a forewarning of the future regional and global impacts of these changes.
Rapid temperature rise
The annual mean temperature has been rising about twice as fast in the Arctic as in the rest of the world in the past few decades, though with some variations within the region. In general, temperatures are rising faster in winter than in summer. In Alaska and western Canada, the average winter temperature has risen by 3–4°C in the past 50 years.
Modelling using scenarios developed for the IPCC indicate that average temperature will continue to rise throughout the Arctic.
Melting glaciers contribute to rising sea level
Since the early 1960s, most glaciers and ice sheets in the Arctic have retreated and their volume has shrunk. This trend became more marked in the 1990s. Several of the glaciers in Svalbard have shown a negative mass balance every year since 2000; in other words, there is an annual net loss of ice, and they are shrinking in size.
As more glacier ice melts, a greater volume of water enters the oceans, raising the global sea level. Global models show that Arctic glaciers will make an increasing contribution to the rise in sea level over the next 100 years.
Dramatic loss of sea ice
The extent and thickness of the sea ice has been declining for several years, and there is now very little thick multi-year ice in the Arctic. The thinner, younger sea ice melts more readily.
In 2012, a record level of ice melt was recorded in the Arctic. There has never been so little ice cover since satellite measurements started in 1979. Observations showed 700 000 km2 less sea ice than at the previous minimum in 2007. This satellite image from NASA (NASA/Goddard Scientific Visualization Studio) shows the extent of the sea ice on 12 September 2015. The yellow line shows the average minimum for the last 30 years.
- More information on NASA’s website
- NASA satellite map comparing the situation in 1980 and 2012
- Daily updates of sea ice extent from The National Snow and Ice Data Center
Sea ice cover varies widely from year to year, and this variability is expected to continue. However, the rate of decline is expected to accelerate, and climate models suggest that it may only be a few decades until the Arctic Ocean is ice-free in summer.
The reduction in ice cover will affect the sea surface temperature. Snow-covered ice absorbs only 10–20 per cent of the incoming solar energy, whereas open water absorbs more than 90 per cent. The sun thus warms the sea water, and evaporation from the surface increases. This is an example of a positive feedback loop: greater absorption of solar energy results in accelerating ice melt, which in turn results in even more absorption of solar energy.
Ocean circulation will be affected
Ocean circulation in the Arctic is controlled by the inflow of relatively warm Atlantic water with the Gulf Stream and the outflow of relatively cold, less saline water via the East Greenland current. Ice is mainly transported out of the Arctic Ocean with the East Greenland current.
Scientists have known for a long time that the Greenland Sea is an important area for bottom water formation, which may be one of the main forces driving the Norwegian Atlantic current. Water continuously sinks towards the bottom, and has to be replaced by surface water, which flows in with the Atlantic current. Climate change may influence bottom water formation and ocean currents, with further repercussions on sea ice extent and the climate in Arctic parts of the Nordic region.
Studies of sediment cores from the seabed show that during and just after the last Ice Age, there were large, abrupt changes in temperature in the Arctic. It is estimated that the temperature changed by 5–7°C over a period of only 10 to 100 years. It is possible that this happened because the formation of bottom water ceased, perhaps during periods of rapid ice melt. It is uncertain whether we can expect the current rate of global warming to have such consequences, but recent research indicates that bottom water formation is unlikely to cease in the next 100–200 years.
Rainfall and snowfall expected to rise
Observations sugget that precipitation has risen by about 8 per cent in the Arctic as a whole over the past 100 years. However, this result is somewhat uncertain, both because of sources of error in the measurement of precipitation in a cold Arctic climate and because there is a lack of data from parts of the region.
In the Arctic as a whole, annual precipitation is expected to rise by about 20 per cent during the 21st century, most of this in the form of rain. The greatest rise is expected in coastal areas in autumn and winter. In these areas, an increase of more than 30 per cent is expected.
Major impacts on animals, plants and people
Climate change in the Arctic will have impacts on human society as well as on animal and plant life.
Impacts on animals and plants
Changes in the extent of the sea ice and glaciers will alter living conditions for many organisms. Tiny planktonic organisms are dependent on the ice edge for survial and reproduction, and polar bears use the sea ice to hunt for seals and feed their cubs. The sea ice has already retreated, and polar bears have lost much of their habitat. These are some of the changes that are expected in the years ahead:
- The treeline is expected to shift northwards and upwards, and much of the tundra will become forest. Tundra vegetation will gradually shift into areas that are now polar desert.
- Vegetation will probably become more productive and carbon uptake will therefore increase. However, as snow and ice melts the Earth’s surface will become less reflective. This effect will probably outweigh the extra carbon uptake, resulting in greater global warming.
- Outbreaks of insect pests and forest fires are likely to be more frequent, more serious and more prolonged. This will make it easier for alien species to spread to Norway.
- Shrinking sea ice cover will drastically reduce the area of suitable habitat for polar bears, ice-dependent seals and some seabirds. Some species will be at risk of extinction.
- Climate change will alter the availability of food supplies and suitability of breeding areas and migration routes for reindeer and other terrestrial species.
- The distribution of many terrestrial and marine species is expected to shift northwards. New species will become established in the Arctic, which will affect species already present in the region.
Impacts on people and society
- As the climate changes, so do short-term weather patterns. Extreme weather events are likely to be more frequent, and new areas may become vulnerable to flooding, landslides and avalanches.
- The ice edge and parts of the polar front will retreat northwards, and the area where polar lows are liable to form will also move further north. There will be a lower risk of polar lows forming the coast of North Norway.
- Where the soil is suitable, a longer and warmer growing season will make agriculture possible further north. However, winter temperatures close to 0°C will be more frequent, which will increase the risk of winter damage to crops.
- Health risks are likely to increase because new species that spread to Norway may well be vectors for animal diseases that also affect people, such as West Nile fever.
- Certain fisheries in Arctic seas are of global importance and make a substantial contribution to the regional economy. Some of them will probably become more productive.
Research and monitoring
Most global climate models predict more warming in the polar regions than in the rest of the world. A good deal of research is currently being done on what impacts this may have on the global climate system.
Long-term environmental monitoring
Long-term environmental monitoring is an important basis for a better understanding of the climate. Data should be collected on changes in sea ice cover, ocean circulation, heat balance and glacier mass balance. We also need to learn more about energy exchange process and ocean-atmosphere-sea ice interactions.
Following up the Arctic Climate Impact Assessment
The results of the Arctic Climate Impact Assessment (ACIA) were published in 2004. This was the first comprehensive assessment and analysis of climate change in the Arctic and its consequences for the region and for the world as a whole.
The Norwegian authorities initiated a follow-up project, a Norwegian Arctic climate impact assessment (NorACIA). Its aim was to assess and analyse climate change and its impacts in the Norwegian part of the Arctic. It ran from 2005 to 2009, and a report (in Norwegian) was published in 2010.