Scientists are actively researching several important questions about how change will continue to unfold in the Arctic how these changes may affect other parts of the planet. More time and data are needed to fully answer these questions.
Will sea ice loss affects weather patterns in middle latitudes?
There is concern that that through influencing the contrast in atmospheric temperature between the Arctic and lower latitudes, the outsized warming in the Arctic will alter weather patterns in the middle latitudes of the Northern Hemisphere. The basic idea is that changing the temperature contrast alters the strength of the westerly winds high in the atmosphere (winds from west to east) in turn altering the character of the polar vortex. (See What is the polar vortex? for a fuller discussion.) While some scientists think that such effects have already occurred, the connection between sea ice loss and weather patterns is still highly controversial and the subject of considerable scientific debate.
Barnes, Elizabeth A. 2013. Revisiting the evidence linking Arctic amplification to extreme weather in midlatitudes. Geophysical Research Letters 40, 1–6, doi:10.1002/grl.50880.
Francis, J.A., S. J. and Vavrus. 2012. Evidence linking Arctic amplification to extreme weather in mid-latitudes. Geophysical Research Letters 39, L06801, doi:10.1029/2012GL051000.
Overland, J.E., and M. Wang. 2010. Large-scale atmospheric circulation changes are associated with the recent loss of Arctic sea ice. Tellus 62(1): 1-9, doi: 10.1111/j.1600-0870.2009.00421.x.
When might the Arctic become virtually ice free in summer, and what impacts will result?
Arctic sea ice extent at the end of the summer melt season has declined sharply during the past 30 years. Summers with an essentially ice-free (under 1 million square kilometers of extent) Arctic Ocean are likely to be realized well within this century, perhaps as early as 2030. Ice extent for September 2012 was the lowest observed in the satellite record (1979 to present), and the six lowest September extents during the period of satellite coverage have all occurred in the past six years. While the trend is clearly downwards, there is large year to year variability in ice conditions, and there are many undertainties as to when a seasonally ice free ocean will be become a reality.
Stroeve, J.C., V. Kattsov, A. Barrett, M.. Serreze, T. Pavlova, M. Holland and W.N. Meier. 2012. Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations. Geophys. Res. Lett., 39 , Art. No. L16502, issn: 0094-8276, ids: 995JM, doi: 10.1029/2012GL052676.
Will Arctic warming lead to further warming through a carbon cycle feedback?
Most Arctic land areas are underlain by permafrost – perennially frozen ground. There is a great deal of carbon stored in these permafrost soils. The concern is that, as the Arctic warms, and this permafrost begins to thaw, microbial activity in the soil will increase, with respiration leading to a release of some of this stored carbon back to the atmosphere, leading to further warming. There is a great deal of uncertainty regarding both when this climate feedback might kick in and how important it will be.
Schaefer, K., T. J. Zhang, L. Bruhwiler, and A. P. Barrett. 2011. Amount and timing of permafrost carbon release in response to climate warming. Tellus 63(2): 165-180, doi:10.1111/j.1600-0889.2011.00527.x.
Lawrence, David M., and Andrew G. Slater. 2005. A projection of severe near-surface permafrost degradation during the 21st century. Geophysical Research Letters 32, December 2005, doi:10.1029/2005GL025080.
Environmental change and hazards
How fast is fresh water being added to the world’s oceans due to melting of ice sheets and glaciers, and how much is sea level rising?
Global mean sea level has increased throughout the 20th century and continues to rise in the 21st Century. The estimated increase in global mean sea level for the period 1901 to 2010 is between 0.17 meter and 0.21 meter (6.7 inches to 8.3 inches). It is likely that the rate of increase in sea level has increased in recent decades.
Thermal expansion of the oceans and shrinking land ice account for most of this sea level rise. Natural and human-induced changes in water storage on the land as groundwater or in reservoirs are small by comparison with these two major contributors. In the past, much of the contribution from land ice has been from small glaciers and ice caps. These small glaciers and ice caps, referred to here as glaciers, are all land ice that is not part of the Greenland and Antarctic ice sheets. The term ice sheet is used only for the Greenland and Antarctic ice sheets. However, since 1990, the Greenland and Antarctic ice sheets have begun to contribute more. The contributions to sea level rise from the two ice sheets are currently roughly the same. Smaller glaciers and ice sheets will continue to contribute to sea level rise in the future.
Almost all glaciers worldwide are shrinking. Ice lost from glaciers ultimately end up in the oceans. Glaciers in Alaska, the Canadian Arctic, the Russian Arctic, around the periphery of Greenland, and Svalbard make up 56% of the total glacier area on the globe. These Arctic glaciers are contributing to sea level at a rate of 164 ± 20 gigatons per year. The contribution from all glaciers in the world between 2005 and 2009 was 301 ± 135 gigatons per year. By contrast, between 2002 and 2011 the Greenland ice sheet contributed between 157 gigatons per year, and 274 gigatons per year, with a mean of gigatons per year. Over the same period, Antarctica contributed between 72 gigatons per year and 221 gigatons per year with a mean of 147 gigatons per year.
IPCC. 2013. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp. http://www.ipcc.ch/report/ar5/wg1/#.UvFYh_biy0E