SIO 210 Talley Topic 7: Equatorial and eastern boundary circulation

Reading and study questions

Reading (on reserve):

Tomczak and Godfrey: pp. 141-146 (mechanism and Peru/California Currents), pp. 272-278 (Benguela and Canary Currents), pp. 217-220 (Leeuwin Current)

See also: Ocean Circulation, section 4.4 (mechanism and Canary Current)

Other useful reading on eastern boundary currents:

Sverdrup et al (text), pp. 701-706 (Peru Current and El Nino), pp. 724-727 (California Current).

Lynn, R.J. and J.J. Simpson, 1987. The California Current system: the seasonal variability of its physical characteristics. J. Geophys. Res., 92, 12947-12966.

Luyten, J.R. and J.C. Swallow, 1976. Equatorial undercurrents. Deep-Sea Res., 23, 999-1001.

Pickard and Emery text: pp.235-252 (Pacific), pp. 270-274 (Indian).

Talley, L. D., G. Fryer, and R. Lumpkin, 1997. Physical oceanography of the tropical Pacific. In Geography of the Pacific Islands, ed. M. Rapaport. Bess Press, Honolulu, HI. In press.

Tomczak and Godfrey text: review chap. 4, pp. 121-130 (Pacific), pp. 259-263 (Atlantic)

Ocean Circulation text: chap. 5

Study questions:

1. What causes large-scale upwelling along a coast? How deep does it reach? What sort of simple current does the wind create in theory? How does this differ from reality?

2. What is the usual overall structure of an eastern boundary current region, down to about 500 meters? What is interesting (somewhat unexpected) about the usual current structure just below the surface, at about 200 meters?

3. Name all of the eastern boundary currents of the subtropical gyres. What is different about the Leeuwin Current? Any reason why?

4. What are the major "permanent" currents and which way do they flow in the upper ocean in the equatorial Pacific and Atlantic? What is different about the Indian Ocean?

5. What is thought to drive the Equatorial Undercurrent?

6. Where does the water in the Equatorial Undercurrent come from?

7. What are the similarities between currents in the eastern boundary current regions and the equatorial region?

8. What characterizes the vertical structure of equatorial currents to the bottom? How does this vertical structure change with increasing distance from the equator?

Further reading and sources of viewgraphs:

Bakun, A. and C.S. Nelson, 1991. The seasonal cycle of wind-stress curl in subtropical eastern boundary current regions. J. Phys. Oceanogr., 21, 1815-1834.

Brink, K.H., J.S. Allen and R. L. Smith, 1978. A study of low frequency fluctuations near the Peru coast. J. Phys. Oceanogr., 8, 1025-1041.

Brink, K.H. and T.J. Cowles, 1991. The Coastal Transition Zone Program, J. Geophys. Res., 96, 14,637-14,648. (one of many papers in an issue devoted to the coastal transition zone)

Brockmann, C., A. Huyer and R.L. Smith, 1980. The poleward undercurrent along the Peru coast: 5 to 15S. Deep-Sea Res., 27, 847-856.

Kosro, P.M. et al., 1991. The structure of the transition zone between coastal waters and the open ocean off northern California, winter and spring 1987. J. Geophys. Res., 96, 14707-14730.

Reid, J.L., G.I. Roden, J.G. Wyllie, 1958. Studies of the California Current System. Progress Report, SIO New Series No. 998.

Saur, J.F.T., 1980. Surface salinity and temperature on the San Fransisco-Honolulu Route, June 1966-December 1970 and January 1972 - December 1975. J. Phys. Oceanogr., 10, 1669-1680.

Smith, R.L., 1978. Poleward propagating perturbations in the currents and sea level along the Peru coast. J. Geophys. Res., 86, 6083-6092.

Smith, R.L., A. Huyer, J.S. Godfrey and J.A. Church, 1991. The Leeuwin Current off Western Autralia, 1986-1987. J. Phys. Oceanogr., 21, 323-345.

Strub, P.T., P. M. Kosro, and A. Huyer, 1991. The nature of the cold filaments in the California Current system. J. Geophys. Res., 96, 14743-14768. Excellent description of the meandering CCS.

Equatorial circulation:

Bryden, H.L. and E.C. Brady, 1985. Diagnostic model of the three-dimensional circulation in the upper equatorial Pacific Ocean. J. Phys. Oceangr., 15, 1255-1273.

Firing, E., 1989. Mean zonal currents below 1500 m near the equator, 159W. J. Geophys. Res., 94, 2023-2028.

Knox, R.A. and D.L.T. Anderson, 1985. Recent advances in the study of the low-latitude ocean circulation. Prog. Oceanogr., 14, 259-317.

Leetmaa, A. and P. Spain, 1981. Results from a velocity transect along the equator from 125 to 159W. J. Phys. Oceanogr., 11, 1030-1033.

Tsuchiya, M., 1981. The origin of the Pacific equatorial 13C water. J. Phys. Oceanogr., 11, 794-812.

Wyrtki, K. and Kilonski, B., 1984. Mean water and current structure during the Hawaii-to-Tahiti shuttle experiment. J. Phys. Oceanogr., 14, 242-253.