1995 Fiscal Year Final Research Report Summary
A Study on deep convection related to deep water formation in the Antarctic region
| Project/Area Number |
05402018
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
IMASATO Norihisa Kyoto Univ., Geophysics, Professor., 大学院・理学研究科, 教授 (40025391)
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| Co-Investigator(Kenkyū-buntansha) |
AKITOMO Kazunori Kyoto Univ., Geophysics, Instructor, 大学院・理学研究科, 助手 (10222530)
AWAJI Toshiyuki Kyoto Univ., Geophysics, Associate Professor, 大学院・理学研究科, 助教授 (40159512)
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| Project Period (FY) |
1993 – 1995
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| Keywords | Deep Conuection / Antarctic Ocean / thermobaricity / deep water / Continental shelf slope / Lagrangian transport |
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| Research Abstract |
We have investigated the effect of thermobaricity of sea water on properties of deep convection at high latitudes by the scaling argument and numerical experiments. Thermobaricity is not so effective in a homogeneous ocean. On the contrary, it causes drastic changes in a two-layr ocean which is typical at high latitudes. That is, the water column abruptly overturns when deep convection occurs. The properties of deep convection such as its scale, velocity are proportional to the square root of the difference of potential temperature between the two layrs. From analysis of observatinal data, the two-layr type of deep convection can occur in the Antarctic region whreas the homogeneous-ocean type in the Greenland seas. The effect of wind on the onset of deep convection has been also investigated. The onset is explained by the linear stability theory and after then deep convection occurs intermittently.
Next, we have investigated the other type of deep convection flowing down along a continental shelf slope. Dense water flows maimly in the bottom Ekman layr and its volume transport is determined not only by the pressure gradient due to density deviation but also by the surface pressure gradient induced by the geostrophic adjustment against the depth-mean current flowing along the isobaths. When these two pressure gradients are in opposite direction and comparable to each other, the significant oscillation occurs in the vertical two-dimensional experiment, and the instability in the three-dimensional experiment. Associated with such flow variations, the descending dense water effectively entrains the interior water above the slope to become bottom and deep waters.
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