In this interview, John Walsh, who is the President’s Professor of Climate Change at the University of Alaska, Fairbanks, talks about how Northern regions will be affected by recent climate change in the Arctic. This is also the topic of Walsh’s contribution under the Bjeknes Days, which are taking place June 1 and 2.
- The Bjerknes Days provide a unique opportunity to highlight the current state of climate and weather research in the location where the seeds of modern atmospheric science were sown. Given the widespread interest in climate change and its implications for the future, I can think of no other setting where the past, present and future of atmospheric science can be bridged so effectively, says Professor Walsh.
Why do you think climate in northern parts of the world will experience more extreme weather in the years to come and how are these changes related to global warming and recent climate change in the Arctic?
The changes of extreme weather that will accompany climate change have large uncertainties, but northern regions can anticipate fewer extremes of low (cold) temperatures and more extremes of high temperatures. The weather data for the past 25 years already indicate that this is happening in northern North America, particularly Alaska. Storms in the Arctic will have more moisture to draw upon as the sea ice cover retreats and the oceans warm, but there will be less temperature contrast between the Arctic and lower latitudes. These opposing contributions to storminess make it difficult to anticipate future changes of storm intensity, although observations do suggest a recent increase in the frequency of strong storms over the Arctic Ocean. Regardless of any change in storm intensity, Arctic coastal communities will be increasingly vulnerable to flooding and erosion as the increase of open water (due to retreating sea ice) allows for the build-up of higher waves.
Should we be expecting a stronger global warming in the Artic compared to the rest of the world?
There is a physical basis for the expectation that the northern latitudes will warm more than the middle and lower latitudes. One reason is the enhancement of solar heating as sea ice and snow cover retreat, reducing the reflectivity (and increasing the absorptivity) of the ocean and land surfaces. In addition, the high latitudes will be receiving more hear and moisture in the inflow of air from middle and lower latitudes. A recent study has shown that this inflow of warmer and moister air may account for up to half of the amplified warming that is projected for the Arctic in greenhouse scenarios.
What are the main consequences of stronger global warming in the Artic?
The main consequences of the warming in higher latitudes include the changes in Arctic sea ice cover, especially during summer, providing increased opportunities for navigation and other offshore activity – especially on the continental shelf areas. Accelerated melt of glaciers and the Greenland ice sheet are likely to contribute to sea level rise and to a freshening of the upper ocean. This freshening may have consequences for the stratification of the northern oceans, and for their ability to sustain the deep mixing (convection) that is a major driver of the global ocean circulation. A major uncertainty is the impact on the warm ocean currents that flow poleward in the North Atlantic.
In addition to the oceanic consequences, the ongoing and projected climate changes imply northward shifts of terrestrial ecosystems. These include shifts of vegetative zones (e.g., northward expansion of shrubs and forests) and the distribution of permafrost. Other possible terrestrial consequences include northward movement of insects and fire regimes associated with warming and/or drying (by increased evapotranspiration).
What is your prospect for the Intergovernmental Panel on Climate Change's ongoing assessment, particularly, with concern to the Polar regions chapter?
The Intergovernmental Panel on Climate Change (IPCC) is including a chapter on the Polar Regions in its Fourth Assessment Report, which is now under review by the various nations of the world. This Report is scheduled for publication in 2007. Because the Arctic Climate Impact
Assessment addressed Arctic changes through 2003, the IPCC polar sections are emphasizing the most recent (post-2003) findings, and also the findings for Antarctica that have emerged since 2001. Some of the results from the IPCC model simulations made for the 2007 Report have already been published in scientific journals, including the projections of 21st-century changes in Arctic sea ice coverage. These published results show that all the IPCC models project a shrinkage of Arctic sea ice, although the rates of retreat vary widely among models. Because the summer ice minimum decreases more rapidly than the winter ice maximum, the seasonal sea ice coverage (so-called “first-year ice) is actually projected to increase over the 21st century.
About Bjerknes Days
| Facts/John Walsh |
| John Walsh is the President’s Professor of Global Change at the University of Alaska, Fairbanks. He is also the Director of the Cooperative Institute for Arctic Research and the Center for Global Change at the University of Alaska. He was a lead author of the Arctic Climate Impact Assessment (2001-2005), and is a lead author for the Polar Regions chapter of the Intergovernmental Panel on Climate Change’s ongoing assessment. |