The formation of a cold-core eddy in the East Australian Current
Cold-core eddies (CCEs) frequently form in western boundary currents and can affect continental shelf processes. It is not always clear, however, if baroclinic or barotropic instabilities contribute more to their formation. The Regional Ocean Modelling System (ROMS) is used to investigate the ocean...
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Published in | Continental shelf research Vol. 114; pp. 72 - 84 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier Ltd
15.02.2016
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Subjects | |
Online Access | Get full text |
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Summary: | Cold-core eddies (CCEs) frequently form in western boundary currents and can affect continental shelf processes. It is not always clear, however, if baroclinic or barotropic instabilities contribute more to their formation. The Regional Ocean Modelling System (ROMS) is used to investigate the ocean state during the formation of a CCE in the East Australian Current (EAC) during October 2009. The observed eddy initially appeared as a small billow (approx. 50km in length) that perturbed the landward edge of the EAC. The billow grew into a mesoscale CCE (approx. 100km in diameter), diverting the EAC around it. A ROMS simulation with a realistic wind field reproduced a similar eddy. This eddy formed from negative vorticity waters found on the continental shelf south of the EAC separation point. A sensitivity analysis is performed whereby the impact of 3 different wind forcing scenarios, upwelling, downwelling, and no winds, are investigated. A CCE formed in all wind scenarios despite the wind induced changes in hydrographic conditions in the continental shelf and slope waters. As such, the source of energy for eddy formation did not come from the interactions of wind with the continental shelf waters. Analysis of strain and energy transformation confirms this by showing that the prevailing source of CCE energy was kinetic energy of the offshore EAC. These results clearly link the formation of the CCE to the swift flowing EAC and barotropic instabilities.
•ROMS is used to investigate a cold-core eddy in the East Australian Current (EAC).•The eddy formed on the edge of continental shelf in waters of negative vorticity.•A sensitivity analysis on wind shows that wind has little effect on eddy formation.•The prevailing source of energy for eddy formation was from the EAC. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0278-4343 1873-6955 |
DOI: | 10.1016/j.csr.2016.01.002 |