2002 Fiscal Year Final Research Report Summary
Ice albedo feedback on sea ice/ocean coupled system
| Project/Area Number |
12640414
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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 Kay I. Hokkaido Univ., Institute of Low Temperature Science, Asso.Prof., 低温科学研究所, 助教授 (30185251)
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| Project Period (FY) |
2000 – 2002
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| Keywords | shortwave radiation / seasonal ice zone / sea ice melting / heat budget / Antarctic Ocean / ice-ocean coupled system / ocean mixed layer / microwave radiometer |
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| Research Abstract |
First we analyze upper-ocean/sea-ice dataset collected by several icebreakers over the whole Antarctic Ocean, along with the satellite microwave radiometer data. These analyses suggest that sea ice melts mostly on the bottom and lateral faces by the heat input (mainly solar radiation) through the open water area. Further, it is found that the negative (positive) anomalies in ice concentration in the retreat season lead to the negative (positive) anomalies in the next advance season with strong correlation, which can be regarded as ice-albedo feedback in a coupled ice-ocean system.
We propose a simple ice-upper ocean coupled model in which sea ice melts only by the ocean beet supplied from the air. The model well explains the relation between ice concentration and upper-ocean in the Antarctic summer. By fitting of the model result and observation, the beat transfer coefficient between upper-ocean and sea ice can be determined. With use of this coefficient value, the model can roughly reproduce meridional retreat of sea ice.
When the model is extended to two-dimensional in the meridional direction with the inclusion of the wind-drift effects, reproduction of the sea ice retreat has further progressed. This two-dimensional 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 in the Antarctic Ocean. However, some observed results cannot be explained only by the ice-ocean coupled system, which requires the understanding of the feedback system including the atmosphere.
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