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December 15, 2000 
Under the tuteladge of Program Director Motoyoshi Ikeda, scientists Dr. Poryakov and others in the International Arctic Research Center, a division of the FRSGC, established as a joint project, by NASDA (President: Mr. Shuichiro Yamanouchi) and JAMSTEC (President: Mr. Takuya Hirano), have presented a new explanation for the decreasing area of Arctic sea ice over the past 30 years. Using a mathematical model, they reproduced the fact that the decrease is not only caused by commonly known global warming, but also due to the strengthening of counter-clockwise winds (polar vortex) existing within the polar circle. Their findings were printed in Geophysical Research Letters, published on December 15, 2000. Background Typically, the decreasing of sea ice in the Arctic has been attributed to global warming due to the increase in greenhouse gases such as carbon dioxide, which would increase the temperature in the Arctic circle and reduce sea ice. This would make it more difficult for albedo to occur, thereby r promoting a further increase in temperatures, and further melting of sea ice. (reference 1) The findings presented here are given as an another important cause of the melting of sea ice. Findings and Consideration Using a mathematical model, the scientists were able to reproduce polar vortexes and polar temperature changes caused by natural phenomena over a period of several decades, resulting in changes in sea ice. From this, by eliminating the effects of repeating natural variations, we can accurately estimate the amount of sea ice decreased that was caused by an increase of carbon dioxide accompanied by an increase in temperature. In a future task, in order to utilize the size of the sea ice area in the Arctic Ocean as an index of global warming, it is necessary for us to promote research on atmospheric model, sea ice oceanic model, and climatic data analysis among others. References ref. 1. Sea ice decrease due to global warming(positive feedback) ref. 2. Mechanism of sea ice decrease ref. 3. Distribution of atmospheric pressure and the movement of sea ice(Comparison between those of 30 years ago and of present days) ref. 4. Atmospheric pressure difference between the coast of the England and Iceland (a), and index of polar vortex(b) ref. 5. Index of the North Atlantic Oscillation (NAO) ref. 6. Sea-ice depth calculated by the model Reference JAMSTEC/NASDA Joint Promotion Office of the FRSGC: Contact: Mr. Hishida, Mr. Kawasaki TEL:+81-3-5404-7852(Hishida),+81-3-5765-7100(Kawasaki) Homepage: http://www.frontier.esto.or.jp JAMSTEC, Public relations division, Administration Dept TEL:+81-468-67-5547 Homepage: http://www.jamstec.go.jp NASDA Public relations office TEL:+81-3-3438-6111 Homepage: http://yyy.tksc.nasda.go.jp 
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