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.
One degree matters — Full movie from European Environment Agency on Vimeo.
Modelling using scenarios developed for the Arctic Climate Impact Assessment (ACIA) indicates that the annual mean temperature will continue to rise throughout the Arctic. The rise is roughly estimated at 3–5°C over land and up to 7°C over the sea by the end of this century.
Winter temperatures are expected to rise considerably more, by about 4–7°C over land and 7–10°C over the sea. Temperatures are likely to rise most over land close to sea areas where a considerable reduction in sea ice cover is expected, for example in northern Russia.
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. Satellite data show that ice melt has speeded up since 1979. 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 16 September 2012. The yellow line shows the average minimum for the last 30 years.
The extent of the sea ice has declined far more in summer than in winter. It is estimated that the winter ice cover has declined by 2.5 per cent every 10 years since 1979, whereas summer ice cover has dropped by about 10 per cent every 10 years.
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.
It has been suggested that global warming may result in cooling at northern latitudes. The reasoning behind this is that weakening of deep-water formation could reduce the strength of the Gulf Stream, which maintains temperatures in Norway at a level 5–8°C higher than would be expected at these latitudes.
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 % 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.
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.
International Polar Year
The fourth polar year, IPY 2007–08, involved field work and data collection from March 2007 to March 2009. Previous polar years were organised in 1957–58, 1932–33 and 1882–83. All the polar years have resulted in the collection of valuable material and data sets and led to advances in scientific knowledge. Analysis of the results continues for many years after the field work.
Climate change was the main focus of IPY 2007–08, which was an intensive, coordinated international and interdisciplinary research programme. The data and samples collected will make it possible to improve climate models and projections.
The Research Council of Norway allocated NOK 288 million to polar research in the period 2007–10. About two-thirds of the funding was for meteorological and climate research. The results of IPY 2007–08 are making an invaluable contribution to knowledge of climate processes in the Arctic and will provide us with a better basis for assessing the impacts of the changes that have already been observed.