2007 Fiscal Year Final Research Report Summary
Investigation of reemergence of winter sea surface temperature and its relation to interdecadal climate variation
| Project/Area Number |
17540408
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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 | Tohoku University |
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Principal Investigator |
HANAWA Kimio Tohoku University, Graduate School of Science, Professor (40142921)
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| Project Period (FY) |
2005 – 2007
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| Keywords | reemergence / sea surface temperature / Aleutian Low / North Pacific Subtropical Mode Water / North Pacific Eastern Subtropical Mode Water / climate variation / subtropical gyre / Kuroshio |
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| Research Abstract |
The purpose of the present study is to investigate the reemergence phenomenon of the North Pacific Subtropical Mode Water (NPSTMW) in detail and to clarify its relation to the 20-year period Pacific Oscillation. The present research result can be summarized as follows.
1. The NPSTMW has both co-located reemergence in the formation area and remote reemergence in the central North Pacific due to the advection of part of NPSTMW.
2. It is found that the Eastern Subtropical Mode Water shows no reemergence phenomenon mainly due to quick change in water properties by the vigorous mixing of salt-finger type convection and weak heat input in the warming season.
3. Remote emergence phenomenon has 20-year periodicity, the reason of which is 20-year periodicity of the Aleutian Low activity.
The above result strongly suggests that the remote reemergence phenomenon of the NPSTMW Pacific sector. The scenario of the 20-year periodic climate variation is as follows. The strengthened Aleutian Low causes the spin-up of the subtropical gyre, and resultantly the NPSTMW is formed more with some time delay. Then, the remote emergence occurs in the central North Pacific and sea surface temperature (SST) is warmed there. This SST change would cause the weakening of the Aleutian Lows. The same process with a sign reversed would follow. The period to close one cycle is about 20 years.
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