The observed changes in sea ice on the Arctic Ocean, in the mass of the Greenland Ice Sheet and Arctic ice caps and glaciers over the past ten years are dramatic and represent an obvious departure from the long‐term patterns.
The warming of the Arctic, due to climate change, has been twice as high as the world average since 1980. Surface air temperatures in the Arctic since 2005 have been higher than for any five‐ year period since measurements began around 1880. Arctic summer temperatures have been higher in the past few decades than at any time in the past 2000 years.
This, however, is not the only explanation why the melting of ice and snow in the Arctic have accelerated beyond any expectations in the last decade. There is now evidence that two components of the cryosphere –snow and sea ice – are interacting with the climate system to accelerate warming.
SWIPA: Snow, Water, Ice and Permafrost in the Arctic
This is one of the key messages from the so called "SWIPA assessment", the most comprehensive compilation of scientific knowledge on the impacts of climate change on the frozen parts of the Arctic occurring within the past 6 years.
Hundreds of scientists have worked to produce the assessment organised by Arctic Council's Arctic Monitoring and Assessment Programme (AMAP).
MORE CHANGE TO COME
Virtually all parts of the Arctic frozen components are affected by warming. The extent and duration of snow cover and sea ice have decreased. Temperatures in the permafrost have risen by up to 2 °C, and nearly all glaciers and ice caps in most regions of the Arctic, including the Greenland Ice Sheet, have been declining faster since 2000 than they did in the previous decade. These are all observations.
In the future, average autumn‐winter temperatures in the Arctic are projected to increase even more. By between 3 °C and 7 °C by the late twenty‐first century (2080).
Arctic rain and snow fall are projected to increase in all seasons, but mostly in winter, and at the same time it is projected that the winter season will be shorter.
The Arctic mountain glaciers and ice caps are projected to lose between 10% and 30% of their total mass by 2100.
And the Arctic Ocean is predicted to be nearly ice free in summer during this century. Likely within the next 30 to 40 years.
These are projected possible futures described in the SWIPA assessment.
FEEDBACK MECHANISMS
The accelerated rate of changes in Arctic snow and ice conditions may cause additional warming. The fact that highly reflective snow and ice surfaces are diminishing means that darker land or ocean surfaces are reveals that absorbs more of the sun's energy, and therefore enhances warming of the Earth's surface and the air above.
The sea‐ice feedback has been anticipated by climate scientists, but clear evidence for it has only been observed in the Arctic in the past five years. In regions of the Arctic Ocean where sea ice has disappeared by the end of summer, more of the sun's energy is absorbed and this leads to higher temperatures in the autumn when the heat is released to the atmosphere. Similar effects are seen over land where areas with earlier snow melt in spring experience stronger warming. A number of other potential feedback mechanisms at play in the Arctic have been identified. Of those feedbacks expected to have strong effects, eight lead to further warming, and just one leads to cooling.
GLOBAL IMPACTS
In the future, global sea level is projected to rise by 0.9–1.6 m by 2100 and the loss of ice from Arctic glaciers, ice caps, and the Greenland Ice Sheet will make a substantial contribution to this. It should be noted that high uncertainty surrounds estimates of future global sea level.
Loss of ice and snow in the Arctic enhances climate warming by increasing absorption of the sun's energy at the surface of the planet. It could also dramatically increase emissions of carbon dioxide and methane and change large‐scale ocean currents. The combined outcome of these effects on global climate is not yet known.
LIVING IN THE NEW ARCTIC REALITY
The changes in the Arctic will have fundamental impacts on the livelihood and living conditions for the 9 million inhabitants. The characteristics of ecosystems will change, access to many areas will change, thawing permafrost causes deformation of buildings and infrastructure, some communities will have to relocate.
However there is another side to adapting to climate change in the Arctic: new opportunities. As the Arctic sea ice diminishes during summer, accessibility to the Arctic minerals, energy resources, and sea routes will increase.
The scientific content of the SWIPA assessment was presented and discussed at the international scientific conference "The Arctic as a Messenger for Global Processes ‐ Climate Change and Pollution", 4‐6 May 2011, Copenhagen.
The SWIPA assessment was formally presented to the 7th Arctic Council Ministerial Meeting in Nuuk, Greenland on 12 May 2011
Key findings SWIPA-report
Key finding 1
The past six years (2005–2010) have been the warmest period ever recorded in the Arctic. Higher surface air temperatures are driving changes in the cryosphere.
Key finding 2
There is evidence that two components of the Arctic cryosphere – snow and sea ice – are interacting with the climate system to accelerate warming.
Key finding 3
The extent and duration of snow cover and sea ice have decreased across the Arctic. Temperatures in the permafrost have risen by up to 2 °C. The southern limit of permafrost has moved northward in Russia and Canada.
Key finding 4
The largest and most permanent bodies of ice in the Arctic – multiyear sea ice, mountain glaciers, ice caps and the Greenland Ice Sheet – have all been declining faster since 2000 than they did in the previous decade.
Key finding 5
Model projections reported by the Intergovernmental Panel on Climate Change (IPCC) in 2007 underestimated the rates of change now observed in sea ice.
Key finding 6
Maximum snow depth is expected to increase over many areas by 2050, with greatest increases over Siberia. Despite this, average snow cover duration is projected to decline by up to 20% by 2050.
Key finding 7
The Arctic Ocean is projected to become nearly ice-free in summer within this century, likely within the next thirty to forty years.
Key finding 8
Changes in the cryosphere cause fundamental changes to the characteristics of Arctic ecosystems and in some cases loss of entire habitats. This has consequences for people who receive benefits from Arctic ecosystems.
Key finding 9
The observed and expected future changes to the Arctic cryosphere impact Arctic society on many levels. There are challenges, particularly for local communities and traditional ways of life. There are also new opportunities.
Key finding 10
Transport options and access to resources are radically changed by differences in the distribution and seasonal occurrence of snow, water, ice and permafrost in the Arctic. This affects both daily living and commercial activities.
Key finding 11
Arctic infrastructure faces increased risks of damage due to changes in the cryosphere, particularly the loss of permafrost and land-fast sea ice.
Key finding 12
Loss of ice and snow in the Arctic enhances climate warming by increasing absorption of the sun's energy at the surface of the planet. It could also dramatically increase emissions of carbon dioxide and methane and change large-scale ocean currents. The combined outcome of these effects is not yet known.
Key finding 13
Arctic glaciers, ice caps and the Greenland Ice Sheet contributed over 40% of the global sea level rise of around 3 mm per year observed between 2003 and 2008. In the future, global sea level is projected to rise by 0.9–1.6 m by 2100 and Arctic ice loss will make a substantial contribution to this.
Key finding 14
Everyone who lives, works or does business in the Arctic will need to adapt to changes in the cryosphere. Adaptation also requires leadership from governments and international bodies, and increased investment in infrastructure.
Key finding 15
There remains a great deal of uncertainty about how fast the Arctic cryosphere will change in the future and what the ultimate impacts of the changes will be. Interactions ('feedbacks') between elements of the cryosphere and climate system are particularly uncertain. Concerted monitoring and research is needed to reduce this uncertainty.
No comments:
Post a Comment