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Two-layer gap-leaping oceanic boundary currents: experimental investigation

Published online by Cambridge University Press:  10 January 2014

Joseph J. Kuehl  and
V. A. Sheremet
Joseph J. Kuehl*
Affiliation:
Graduate School of Oceanography, University of Rhode Island, 215 South Ferry Road, Narragansett, RI 02882, USA
V. A. Sheremet
Affiliation:
Graduate School of Oceanography, University of Rhode Island, 215 South Ferry Road, Narragansett, RI 02882, USA
*
†Present address: Geochemical and Environmental Research Group, Texas A&M University, 833 Graham Road, College Station, TX 77845, USA. Email address for correspondence: [email protected]
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Abstract

The problem of oceanic gap-traversing boundary currents, such as the Kuroshio current crossing the Luzon Strait or the Gulf Stream traversing the mouth of the Gulf of Mexico, is considered. Systems such as these are known to admit two dominant states: leaping across the gap or penetrating into the gap forming a loop current. Which state the system will assume and when transitions between states will occur are open problems. Sheremet (J. Phys. Oceanogr., vol. 31, 2001, pp. 1247–1259) proposed, based on idealized barotropic numerical results, that variation in the current’s inertia is responsible for these transitions and that the system admits multiple states. Generalized versions of these results have been confirmed by barotropic rotating-table experiments (Sheremet & Kuehl, J. Phys. Oceanogr., vol. 37, 2007, 1488–1495; Kuehl & Sheremet,J. Mar. Res., vol. 67, 2009, pp. 25–42). However, the typical structure of oceanic boundary currents, such as the Gulf Stream or Kuroshio, consists of an upper-layer intensified flow riding atop a weakly circulating lower layer. To more accurately address this oceanic situation, the present work extends the above findings by considering two-layer rotating table experiments. The flow is driven by pumping water through sponges and vertical seals, creating a Sverdrup interior circulation in the upper layer which impinges on a ridge where a boundary current is formed. The $\beta $ effect is incorporated in both layers by a sloping rigid lid as well as a sloping bottom and the flow is visualized with the particle image velocimetry method. The experimental set-up is found to produce boundary currents consistent with theory. The existence of multiple states and hysteresis, characterized by a cusp topology of solutions, is found to be robust to stratification and various properties of the two-layer system are explored.

JFM classification

Geophysical and Geological Flows: Geophysical and Geological Flows Geophysical and Geological Flows: Quasi-geostrophic flows Geophysical and Geological Flows: Stratified flows
Type
Papers
Information
Journal of Fluid Mechanics , Volume 740 , 10 February 2014 , pp. 97 - 113
Copyright
©2104 Cambridge University Press 

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References

Arnold, V. I. 2004 Catastrophe Theory. Springer.Google Scholar
Caruso, M. J., Gawarkiewicz, G. G. & Beardsley, R. C. 2006 Interannual variability of the Kuroshio intrusion in the South China Sea. J. Oceanogr. 62, 559–575.CrossRefGoogle Scholar
Charney, J. G. 1955 The gulf stream as an inertial boundary layer. Proc. Natl Acad. Sci. USA 41, 731–740.CrossRefGoogle ScholarPubMed
Cho, Y. K., Beardsley, R. C. & Sheremet, V. A. 2002 On the cause of Scotian shelf water crossovers. Geophys. Res. Lett. 29, 2212.Google Scholar
Fratantoni, P. S., Lee, T. N., Podesta, G. P. & Muller-Karger, F. E. 1998 The influence of loop current perturbations on the formation and evolution of tortugas eddies in the southern straits of Florida. J. Geophys. Res. 103, 24759–24779.CrossRefGoogle Scholar
Gill, A. E. & Smith, R. K. 1970 On similarity solutions to the differential equation ${\psi }_{zzzz} + {\psi }_{x} = 0$. Proc. Camb. Phil. Soc. 67, 163–171.Google Scholar
Kuehl, J. & Sheremet, V. A. 2009 Identification of a cusp catastrophe in a gap-leaping western boundary current. J. Mar. Res. 67 (1), 25–42.CrossRefGoogle Scholar
Lu, J. & Liu, Q. 2013 Gap-leaping Kuroshio and blocking westward-propagating Rossby wave and eddy in the Luzon Strait. J. Geophys. Res. 118, 1170–1181.Google Scholar
Morgan, G. W. 1956 On the wind-driven ocean circulation. Tellus 8, 301–320.Google Scholar
Nan, F., Xue, H., Chai, F., Shi, L., Shi, M. & Guo, P. 2011a Identification of different types of Kuroshio intrusion into the South China Sea. Ocean Dyn. 61, 1291–1304.CrossRefGoogle Scholar
Nan, F., Xue, H., Xiu, P., Chai, F., Shi, M. & Guo, P. 2011b Oceanic eddy formation and propagation southwest of Taiwan. J. Geophys. Res. 116, C12045.CrossRefGoogle Scholar
Oey, L. Y. 2008 Loop current and deep eddies. J. Phys. Oceanogr. 38, 1426–1449.Google Scholar
Pichevin, T. & Nof, D. 1997 The momentum imbalance paradox. Tellus 49A, 298–319.Google Scholar
Sheremet, V. A. 2001 Hysteresis of a western boundary current leaping across a gap. J. Phys. Oceanogr. 31, 1247–1259.Google Scholar
Sheremet, V. A. & Kuehl, J. 2007 Gap leaping western boundary current in a circular tank model. J. Phys. Oceanogr. 37, 1488–1495.CrossRefGoogle Scholar
Sheu, W.-J., Wu, C.-R. & Oey, L.-Y. 2010 Blocking and westward passage of eddies in the Luzon Strait. Deep-Sea Res. (II) 57, 1783–1791.Google Scholar
Stommel, H. 1965 The Gulf Stream: a Physical and Dynamical Description. Cambridge Univesity Press.Google Scholar
Stommel, H. 1982 Is the South Pacific helium-3 plume dynamically active? Earth Planet. Sci. Lett. 61, 63–67.Google Scholar
Stommel, H. & Yoshida, K. 1972 Kuroshio, Its Physical Aspects. Univesity of Tokyo Press.Google Scholar
Thom, R. 1972 Stabilite Structurelle et Morphogenese. Benjamin.Google Scholar
Thom, R. 1975 Structural Stability and Morphogenesis. Benjamin-Addison Wesley (translated by D. H. Fowler).Google Scholar
Yuan, D. & Wang, Z. 2011 Hysteresis and dynamics of a western boundary current flowing by a gap forced by impingement of mesoscale eddies. J. Phys. Oceanogr. 41, 878–888.Google Scholar