| Project/Area Number |
09640516
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
OHSHIMA Keiichirou Hokkaido Univ., Inst.of Low Temp.Sci., Asso.Prof, 低温科学研究所, 助教授 (30185251)
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| Co-Investigator(Kenkyū-buntansha) |
FUKAMACHI Yasushi Hokkaido Univ., Inst.of Low Temp.Sci., Inst., 低温科学研究所, 助手 (20250508)
浮田 甚郎 地球フロンティア研究システム, 国際北極圏研究センター, サブリーダー
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| Project Period (FY) |
1997 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1999: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | melting of sea ice / heat budget / shortwave radiation / ice / ocean coupled model / ice albedo feedback / Antarctic Ocean / microwave radiometer / ocean mixed layer / 季節海氷域 / アイスアルベドフィールドバック / 熱交換係数 / 海氷 / 海氷-海洋相互作用 / SSM / I |
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| Research Abstract |
The heat budget analyses show that the net heat input at the water surface reaches 1OO-150 W m^<-2> in the active ice melting season due to large solar heating, while that at the ice surface is nearly zero because of the difference in surface albedo. The temporal variation of the heat input to the upper ocean corresponds well to the melting rate of sea ice. These results suggest that melting of sea ice in the Antarctic Ocean is mostly accomplished by the heat input to the upper ocean through the open water area.
In the Antarctic Ocean, the anomalies in ice concentration in the retreat season are highly correlated with those in the next advance season. In the retreat season, net heat input into the upper ocean from the atmosphere is maximum and is mainly determined by ice concentration. We suggested that the anomaly in the heat input is memorized in the ocean and then affects the next advance of sea ice. This positive feedback can partly explain the interannual variation of the sea ice cover.
We propose a simple ice upper ocean coupled model in which sea ice melts only by the ocean heat supplied from the air. The model shows that the relation between ice concentration and upper ocean temperature converges to a certain asymptotic curve with time, which well explains the observations in the Antarctic summer. The model also roughly reproduces meridional retreat of the Antarctic sea ice. The model can describe the following ice albedo feedback effect ; once the ice concentration is decreased by the divergent wind field, the heat input to the upper ocean is enhanced, leading to further decrease of ice concentration. This mechanism can partly explain the year to year variation of the sea ice retreat.
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