1997 Fiscal Year Final Research Report Summary
On roles of mesoscale variability and fresh water flux on deep water formation
| Project/Area Number |
07459001
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
広領域
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
IKEDA Motoyoshi Hokkaido Univ., Guraduate School of Environmental Earth Science, Pro., 大学院・地球環境科学研究科, 教授 (50261227)
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| Co-Investigator(Kenkyū-buntansha) |
HIBIYA Noriyuki Tokyo Univ., Center for International Cooperation, Ocean Research Institute, Ass, 海洋研究所, 助教授 (80192714)
OSHIMA Keiichiro Hokkaido Univ., Institute of Low Temperature Science, Asso.Pro., 低温科学研究所, 助教授 (30185251)
YASUDA Ichiro Tokyo Univ., Guraduate School of Science, Asso.Pro., 大学院・理学系研究科, 助教授 (80270792)
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| Project Period (FY) |
1995 – 1997
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| Keywords | Deep water formation / Mesoscale Phenomena / Ice-ocean interaction / Coupled ice-ocean model |
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| Research Abstract |
As a time scale becomes longer, the ocean plays more important roleson climate variability. The North Atlantic Deep Water formed in the Greenland Sea originates the global conveyor belt in the deep ocean, andits presence and formation rates influence global climate. The surface layr of the Greenland Sea could not become dense enough to be convected with the lower layr, depending on the amount of fresh water plus sea ice from the Arctic Ocean. However, brine rejection from ice formation may increase the surface layr density and yield deepconvection. The surface layr is not horizontally uniform, but contains variability at spatial scales of 10-100km. The horizontal variability is another important aspect for deep convection, because convection can occur in more weakly stratified areas. In addition to open water deepconvection, dense water is formed over the shelf regions, leading to the Arctic Water at the mid-depth.
A coupled ice-ocean model was constructed in the present study. We aimed at reconstructing dense water formation in the model as well as understanding several important processes such as convection, mesoscale eddies and internal waves. The model was applied to the Labrador Shelf and the Okhotsk Sea, for simulating seasonal formation/decay of sea ice along with dense water formation. Using a nonhydrostatic model, we examined vertical mixing caused by ice formation in open leads and polynyas. The dense water is dependent on sizes, distribution and movement of the open water areas. It was suggested that baroclinic instability plays a major role in transporting dense water to the offshore region. Internal waves were found to be important for vertical mixing in a stably stratofied ocean. These results provide useful information for predicting global climate change.
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