Influence of the Indonesian Throughflow on the Circulation of Pacific Intermediate Water

Julian P. McCreary Jr. International Pacific Research Center, University of Hawaii, Honolulu, Hawaii

Search for other papers by Julian P. McCreary Jr. in
Current site
Google Scholar
PubMed
Close
and
Peng Lu Oceanographic Center, Nova Southeastern University, Dania, Florida

Search for other papers by Peng Lu in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

A 4½ layer model is used to study intermediate-water circulation in the Pacific Ocean. Solutions are forced by annual-mean winds. They are also driven by a prescribed inflow of water through the southwestern corner of the basin [12 Sv (Sv ≡ 106 m3 s−1)] and a compensating outflow in layers 1, 2, and 3 through the western boundary just north of the equator; this mass exchange simulates the Pacific interocean circulation (IOC), in which intermediate water enters the South Pacific, and the same amount of upper water exits via the Indonesian passages. The water in each subsurface layer is formed by specific processes, and hence can be interpreted as corresponding to a distinct water-mass type. The types are thermocline water generated by subtropical subduction (layer 2), upper-intermediate and lower-thermocline water generated by midlatitude subduction in the North and South Pacific (NPIW and SPLTW, respectively; layer 3), and lower-intermediate water that corresponds to Antarctic Intermediate Water (AAIW; layer 4).

Solutions are compared for different throughflow vertical structures and without the IOC. For all solutions, the amount of NPIW that moves into the Tropics is almost unchanged (∼4 Sv), indicating that it is remotely determined by midlatitude processes. If the layer 3 outflow is sufficiently large (≳4 Sv), most of the tropical NPIW exits the basin in the throughflow, and SPLTW fills the northern tropical ocean, consistent with the observed circulation. If it is small, however, most of the tropical NPIW recirculates in the northern Tropics, and no SPLTW enters this region. With the IOC, AAIW crosses into the Northern Hemisphere (3.8 Sv), and more than half eventually moves into subpolar ocean. Without the IOC, the transport of AAIW into the Northern Hemisphere is an order of magnitude less (0.37 Sv), and NPIW occupies most of the tropical ocean in both hemispheres, properties that differ markedly from observations. These results suggest that the Indonesian Throughflow is a possible reason why intermediate waters of Southern Hemisphere origin fill the tropical Pacific and spread to higher northern latitudes.

Corresponding author address: Dr. Julian P. McCreary Jr., IPRC, SOEST, University of Hawaii, 2525 Correa Road, POST 401, Honolulu, HI 96822.

Email: jay@soest.hawaii.edu

Abstract

A 4½ layer model is used to study intermediate-water circulation in the Pacific Ocean. Solutions are forced by annual-mean winds. They are also driven by a prescribed inflow of water through the southwestern corner of the basin [12 Sv (Sv ≡ 106 m3 s−1)] and a compensating outflow in layers 1, 2, and 3 through the western boundary just north of the equator; this mass exchange simulates the Pacific interocean circulation (IOC), in which intermediate water enters the South Pacific, and the same amount of upper water exits via the Indonesian passages. The water in each subsurface layer is formed by specific processes, and hence can be interpreted as corresponding to a distinct water-mass type. The types are thermocline water generated by subtropical subduction (layer 2), upper-intermediate and lower-thermocline water generated by midlatitude subduction in the North and South Pacific (NPIW and SPLTW, respectively; layer 3), and lower-intermediate water that corresponds to Antarctic Intermediate Water (AAIW; layer 4).

Solutions are compared for different throughflow vertical structures and without the IOC. For all solutions, the amount of NPIW that moves into the Tropics is almost unchanged (∼4 Sv), indicating that it is remotely determined by midlatitude processes. If the layer 3 outflow is sufficiently large (≳4 Sv), most of the tropical NPIW exits the basin in the throughflow, and SPLTW fills the northern tropical ocean, consistent with the observed circulation. If it is small, however, most of the tropical NPIW recirculates in the northern Tropics, and no SPLTW enters this region. With the IOC, AAIW crosses into the Northern Hemisphere (3.8 Sv), and more than half eventually moves into subpolar ocean. Without the IOC, the transport of AAIW into the Northern Hemisphere is an order of magnitude less (0.37 Sv), and NPIW occupies most of the tropical ocean in both hemispheres, properties that differ markedly from observations. These results suggest that the Indonesian Throughflow is a possible reason why intermediate waters of Southern Hemisphere origin fill the tropical Pacific and spread to higher northern latitudes.

Corresponding author address: Dr. Julian P. McCreary Jr., IPRC, SOEST, University of Hawaii, 2525 Correa Road, POST 401, Honolulu, HI 96822.

Email: jay@soest.hawaii.edu

Save
  • Bingham, F., and R. Lukas, 1994: The southward intrusion of North Pacific Intermediate Water in the Mindanao Coast. J. Phys. Oceanogr.,24, 142–154.

  • ——, and ——, 1995: The distribution of intermediate water in the western equatorial Pacific during January–February, 1986. Deep-Sea Res.,42, 1545–1573.

  • Chen, L.-G., and W. Dewar, 1993: Intergyre communication in a three-layer model. J. Phys. Oceanogr.,23, 855–878.

  • Fine, R. A., 1985: Direct evidence using tritium data for the throughflow from the Pacific to the Indian Ocean. Nature,315, 478–480.

  • ——, R. Lukas, F. Bingham, M. Warner, and R. Gammon, 1994: The western equatorial Pacific: A water mass crossroads. J. Geophys. Res.,99, 25 063–25 080.

  • Godfrey, J. S., 1989: A Sverdrup model of the depth-integrated flow for the World Ocean allowing for island circulation. Geophys. Astrophys. Fluid Dyn.,45, 89–112.

  • Gordon, A. L., 1986: Interocean exchange of thermocline water. J. Geophys. Res.,91, 5037–5046.

  • Harrison, D. E., 1989: On climatological monthly mean wind stress and wind stress curl fields over the World Ocean. J. Climate,2, 57–79.

  • Hellerman, S., and M. Rosenstein, 1983: Normal monthly wind stress over the World Ocean with error estimates. J. Phys. Oceanogr.,13, 1093–1104.

  • Hirst, A. C., and J. S. Godfrey, 1994: The response to a sudden change in Indonesian Throughflow in a global GCM. J. Phys. Oceanogr.,24, 1895–1910.

  • Hu, D., M. Cui, T. Qu, and Y. Li, 1991: A subsurface current off Mindanao identified by dynamic calculation. Oceanography of Asian Marginal Seas, K. Takano, Ed., Elsevier Oceanography Series, Vol. 54, Elsevier, 359–365.

  • Johnson, G. C., and D. W. Moore, 1997: The Pacific Subsurface Countercurrents and an inertial model. J. Phys. Oceanogr.,27, 2448–2459.

  • ——, and M. McPhaden, 1999: Interior pycnocline flow from the subtropical to the equatorial Pacific Ocean. J. Phys. Oceanogr.,29, 3073–3089.

  • Lu, P., J. P. McCreary, and B. A. Klinger, 1998: Meridional circulation cells and the source waters of the Pacific Equatorial Undercurrent. J. Phys. Oceanogr.,28, 62–84.

  • McCartney, M. S., 1977: Subantarctic mode water. A Voyage of Discovery: George Deacon 70th Anniversary Volume, M. Angel, Ed., Pergamon Press, 103–119.

  • ——, 1982: The subtropical recirculation of Mode Water. J. Mar. Res.,40 (Suppl.), 427–464.

  • McCreary, J. P., and P. Lu, 1994: Interaction between the subtropical and the equatorial ocean circulations: The subtropical cell. J. Phys. Oceanogr.,24, 466–497.

  • Pedlosky, J., 1984: Cross-gyre ventilation of the subtropical gyre: An internal mode in the ventilated thermocline. J. Phys. Oceanogr.,14, 1172–1178.

  • Reid, J. L., 1997: On the total geostrophic circulation of the Pacific Ocean: Flow patterns, tracers, and transports. Progress in Oceanography, Vol. 39, Pergamon, 263–352.

  • ——, and A. W. Mantyla, 1978: On the mid-depth circulation of the North Pacific Ocean. J. Phys. Oceanogr.,8, 946–951.

  • Rhines, P. B., and W. R. Young, 1982: A theory of the wind-driven circulation. I: Mid-ocean gyre. J. Mar. Res.,40 (Suppl.), 559–596.

  • Talley, L. D., 1993: Distribution and formation of North Pacific Intermediate Water. J. Phys. Oceanogr.,23, 517–537.

  • ——, G. Fryer, and R. Lumpkin, 1998: Physical oceanography of the tropical Pacific. Geography of the Pacific Islands, M. Rapaport, Ed., Bess Press, 19–32.

  • Toggweiler, J. R., K. Dixon, and W. S. Broecker, 1991: The Peru upwelling and the ventilation of the South Pacific thermocline. J. Geophys. Res.,96, 20 467–20 497.

  • Tsuchiya, M., 1975: Subsurface countercurrents in the equatorial Pacific Ocean. J. Mar. Res.,33 (Suppl.), 145–175.

  • ——, 1981: The origin of the Pacific equatorial 13°C water. J. Phys. Oceanogr.,11, 794–812.

  • ——, 1991: Flow path of Antarctic Intermediate Water in the western equatorial South Pacific Ocean. Deep-Sea Res.,38 (Suppl. 1), 273–279.

  • ——, and L. D. Talley, 1996: Water-property distributions along an eastern Pacific hydrographic section at 135°W. J. Mar. Res.,54, 541–564.

  • Wijffels, S. E., M. M. Hall, T. Joyce, and D. J. Torres, 1998: Multiple deep gyres of the western North Pacific: A WOCE section along 149°E. J. Geophys. Res.,103, 12 985–13 009.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 391 211 3
PDF Downloads 96 28 2