Climate Change - Arctic Climate Change,
Economy and Society

Quantification of the impacts of climate change on economic sectors and the evaluation of associated risks requires a profound knowledge of the state of the Arctic climate system. The future development of the Arctic sea-ice, atmosphere, and ocean needs to be assessed. Especially, the rapid changes in sea-ice extent, thickness, and age as well as other properties have an impact on all economic activities. Iceberg drift, the regional and temporal changes in weather patterns, and extreme weather events like polar lows are also important processes in this respect.

 

The Arctic has experienced substantial and rapid changes in recent years. Most prominent among these was the minimum Arctic sea-ice extent in summer 2007. It far exceeded the previous minimum observed in September 2005. These changes are most likely caused by a combination of natural variability of the high-latitude climate system, anthropogenic changes in the radiation balance and subsequently in atmospheric and oceanic heat transports, and feedbacks in the air/sea-ice/ocean coupled system. There is much evidence that the rapid retreat of the summer Arctic sea-ice cover from 2005 onwards was a response to at least three decades of thinning, resulting in a sea-ice cover which partly disintegrated during summer melt and allowed increased heat absorption by the near-surface ocean. Solar heating of the oceanic mixed layer and subsequent release of the heat to the atmosphere in the autumn delay the freezing up of sea-ice and influence the atmospheric circulation. Increased absorption of solar radiation in the surface ocean and decreased sea ice cover reflecting less solar radiation back into space are the main factors for the polar amplification of global warming, enhanced bottom melting of sea-ice and sea ice thinning.

The 4^th International Polar Year provided key observations of the atmosphere, the ocean and sea-ice. The young ice (first and second year ice), was expanding surprisingly fast at the expense of the old (multi-year) ice. Mean sea-ice drift velocities increased. In the atmosphere, the Arctic Oscillation understood to be the dominant mode of sea-level pressure variability in the Arctic during the 1980s and 1990s, has been replaced by a dipole characterized by a low pressure system extending over Siberia and the Aleutians and a high pressure system extending over North America and Greenland. Other Arctic cryospheric components such as Greenland ice and permafrost appear to be largely influenced by Arctic Ocean warming and retreating sea ice.

Climate scenarios and current climate models are unable to reproduce these recent changes in the Arctic environment. Sea-ice is vanishing faster than in all coupled climate model scenario calculations. None of those calculations anticipated the 2007 drastic sea ice retreat. Models that feature sudden sea-ice extent reductions put them later in the 21^st century. To improve scenarios and climate models, a number of measures are necessary. In ACCESS, we will monitor the current status and changes of the Arctic sea-ice to provide a baseline against which to compare projected future changes and to maintain the critical measurements that are needed to confirm and determine the trends in ocean, ice and atmospheric change. Projections and estimates of uncertainties for future developments on time scales of up to several decades will be provided by our own simulations as well as from other sources. These include regionally differentiated scenarios for the development of sea-ice and its variability on interannual to sub-seasonal scale; changes in the frequency, locality, and intensity of extreme weather events; and potential changes in oceanic current systems and hydrography. Furthermore, ACCESS will develop improved scenarios for environmental changes that could result from increased economic activity in the Arctic and feed them into Earth System Models to produce enhanced climate projections.

 

The WP dedicated to the Arctic environment in the context of climate change is an overarching activity of the ACCESS project. The other activities of ACCESS, including the economic sectors of fisheries, oil and gas extraction and marine transportation, depend on this work package. It is indeed very important to realize that all the other activities of ACCESS are preempted in the context of Arctic climate changes.

 

 

Objectives

• Building an infrastructure for quantitative network design for observing the Arctic system
• Provide the project with information on the current status and changes of the Arctic sea ice during the duration of the project
• Analyzing past changes and current state of the Arctic Ocean
• Mapping atmospheric circulation changes over the Arctic
• Provide the other WPs with projections and estimates of uncertainties for future developments on time scales of up to several decades
• Evaluation of the impact of airborne and deposited soot aerosols on climate, of improved sea-ice representation and increased atmospheric model resolution
• Assessment of the contribution of local and remote anthropogenic and natural sources on air pollution, acidification and climate in the Arctic
•  Assessment of future short-term forecasting capabilities.