The climate in the Arctic has impact worldwide

Warming in the Arctic has consequences not only for climate developments and Arctic communities (both human and natural), but also throughout the world. First and foremost are the consequences for the climate system itself (and thus also for future climate). In addition, warming will affect sea level, which has a direct impact on people and societies in many parts of the planet.

Projections of global mean sea level rise over the 21st century relative to 1986–2005 from the combination of the CMIP5 ensemble with process-based models, for RCP2.6 and RCP8.5. The assessed likely range is shown as a shaded band. The assessed likely ranges for the mean over the period 2081–2100 for all RCP scenarios are given as coloured vertical bars, with the corresponding median value given as a horizontal line. For further technical details see the Technical Summary Supplementary Material (Table 13.5, Figures13.10 and 13.11; Figures TS.21 and TS.22). Photo: IPPC

The large-scale changes that take place in the arctic climate system exert a strong influence throughout the global climate system. The Arctic plays an important role in balancing the world’s climate. Changes here will therefore rapidly have repercussions in the rest of the world. For example, less sea ice leads to altered temperature and salinity in seawater, which in turn affect global ocean circulation patterns; these patterns play a major role in determining the climate in regions all over the world. Such alterations will also affect biodiversity far outside the Arctic. Inflow of fresh water from melting glaciers, ice caps and sea ice will also affect sea circulation and thus climate.

Deep water formation and the thermohaline circulation are important factors in maintaining temperature balance around the world, and they help keep Europe relatively warm. However, the stability of these processes is a topic of discussion. The increased amount of fresh water observed in the Arctic Ocean could theoretically perturb the thermohaline circulation and ultimately lead to cooling in regions around the North Atlantic. IPCC considers a collapse of the thermohaline circulation to be a ”low probability – high impact” risk associated with global warming. Most model simulations show that the thermohaline circulation is more likely to collapse than merely to weaken.

Weather and climate in the Arctic influence weather and climate in much of the rest of the world. The temperature difference between the cold Arctic and warmer regions in the south during autumn and winter drives the jet stream, which shapes and propels the weather systems of the northern hemisphere. But the temperature difference has decreased, and this affects the speed of the jet stream. One apparent result is that weather systems spend more time over certain regions, leading to extreme snowfall, drought, and heat waves. In addition, the warming of the Arctic allows the jet stream to meander more, bringing cold arctic air to farther south and allowing warm air to penetrate farther north, leading to new record high and low temperatures.

Many extreme weather events were recorded during the winters of 2009-2010 and 2010-2011; unusually high temperatures in the Arctic coincided with severe cold and heavy snowfall in China, the United States and Europe. Such extreme weather events arise owing to the random and unpredictable behaviour of weather systems and the causes are therefore difficult to trace.[1]

Nonetheless, the recent major changes in the Arctic may have contributed to the extreme weather. Such changes in weather patterns will have far-reaching implications; for example, they may threaten global food production.

The effect of thawing permafrost on the carbon cycle is another crucial aspect for how climate evolves worldwide. Permafrost in the Arctic will thaw as a consequence of increasing temperatures in the soil, oceans, rivers and lakes that overlie the frozen ground. Carbon stored in the permafrost can then be released in the form of CO2 and methane, thus increasing the levels of greenhouse gases in the atmosphere and hastening global warming. But warming also affects the carbon content of the permafrost by making the active layer of the permafrost more productive: increased growth means increased carbon sequestration. The arctic permafrost is estimated to contain about 1.7 trillion tonnes of carbon – more than all human activity has generated since the beginning of the industrial revolution. A study in Canada estimated that thawing of the Canadian permafrost alone would release 75 to 560 million tonnes of carbon to the atmosphere before 2100, and increase the earth’s temperature by 0.5°C in addition to the warming that is already projected. However, estimates of the total amount of carbon that can be released from the permafrost remain highly uncertain, which limits the possibility of assessing the potential impact of such emissions. Empiric data and model simulations diverge considerably in terms of the amounts and locations of organic carbon in the permafrost regions, and a great deal of uncertainty remains concerning what role carbon in permafrost will play in the greenhouse gas balance.[2]

The seabed also contains permafrost with huge stores of methane hydrates: the carbon content is estimated to 10 billion tonnes. Methane is twenty times more powerful as a greenhouse gas than CO2.[3] It is still not clear how great a threat release of this carbon store would pose. Not enough is known about the time scale over which marine hydrates can become destabilised. The time scale is probably very long for hydrates in deep sediments, but shorter for hydrates in shallow seas such as the Arctic Ocean. Much uncertainty is related to lack of knowledge concerning the size and location of methane hydrate stores, how rapidly warmth penetrates through seawater and sediments, and the fate of methane in seawater.[4]

Melting of glaciers and ice caps is expected to raise global sea level. Average sea level will continue to rise – and more quickly than in the period 1971-2010. Models show an increase of 0.52-0.98 metres before 2100, but these results depend on warming. So far, most of the rise in sea level has been caused by thermal expansion of seawater (a warmer ocean takes up more space); this effect is expected to continue to contribute 30-50% of the increase in years to come. Changes in the arctic cryosphere (ice on land) will underlie a substantial proportion of the expected increase.

Rising sea level has particularly dire implications for densely populated low-lying areas, including many island nations in the Pacific Ocean. More than a billion people – most of them in Asia – live in flat coastal areas. Within this century, some of these areas can be inundated by rising seas. The inhabitants will be forced to find solutions to the problem. Experts are hard at work trying to determine which regions will be hardest hit, but it is impossible to predict exactly how rising sea level will affect these coasts and island nations; so much depends on how great the changes are and how quickly they come about. Modern dynamic sea level models, which take into account storm winds and waves, paint a much more serious picture of the future for some of the low-lying islands in the Pacific than earlier models.[5]

References

  1. James E. Overland et al. 2011. Warm Arctic—cold continents: climate impacts of the newly open Arctic Sea. Polar Research (30): 15787. DOI:10.3402/polar.v30i0.15787
  2. U. Mishra et al. 2013. Empirical estimates to reduce modeling uncertainties of soil organic carbon in permafrost regions: a review of recent progress and remaining challenges. Environmental Research Letters (Vol. 8 no. 3). DOI:10.1088/1748-9326/8/3/035020
  3. Arctic Monitoring and Assessment Programme (AMAP), 2012. Arctic Climate Issues 2011: Changes in Arctic Snow, Water, Ice and Permafrost. Snow, Water, Ice and Permafrost in the Arctic (SWIPA) 2011 Overview Report.
  4. Fiona M. O'Connor et al. 2010. Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review. Reviews of Geophysics (48): 4. DOI:10.1029/2010RG000326
  5. Curt Storlazziy et al. 2013. Forecasting the Impact of Storm Waves and Sea-Level Rise on Midway Atoll and Laysan Island within the Papahānaumokuākea Marine National Monument—A Comparison of Passive Versus Dynamic Inundation Models. U.S. Geological Survey.