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第 140 回 大気海洋圏物理系セミナー のおしらせ
日 時: 11月 18日(木) 午前 9:30
場 所:低温科学研究所 2階 講義室
発表者:二橋 創平 研究員 (低温科学研究所 寒冷海洋圏科学部門 )
題 目:Observational evidence of a hemispheric-wide ice-albedo feedback effect on Antarctic sea-ice decay
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Observational evidence of a hemispheric-wide ice-albedo feedback effect on Antarctic sea-ice decay (二橋 創平 研究員) 発表要旨 :
The effect of ice-albedo feedback on sea-ice decay is demonstrated for the entire Antarctic Ocean from an analysis of satellite-derived hemispheric sea-ice maps and ERA-40 atmospheric data for the period 1978-2001. Wind-forced ice drift at the beginning of the melt season (November) correlate with ice concentration at the time of most active melt (December). Standard deviations of ice concentration are amplified as sea-ice melts toward the time of maximum melt. These findings can be explained as follows: once ice concentration is decreased (increased) by the divergent (convergent) wind at the beginning of the melt season, solar heating through the increased (decreased) open water fraction is enhanced (reduced), leading to (suppressing) a further decrease in ice concentration by the heat. A simple ice-ocean coupled model also supports this hypothesis. This positive feedback mechanism can partly explain the large interannual variability of the sea-ice cover in the summer Antarctic Ocean.
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