The Meridional Oceanic Transports of Heat and Nutrients in the South Atlantic

Jürgen Holfort Institut für Meereskunde an der Universität Kiel, Kiel, Germany

Search for other papers by Jürgen Holfort in
Current site
Google Scholar
PubMed
Close
and
Gerold Siedler Institut für Meereskunde an der Universität Kiel, Kiel, Germany

Search for other papers by Gerold Siedler in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Meridional transports of mass, heat, nutrients, and carbon across coast-to-coast WOCE and pre-WOCE sections between 11°S and 45°S in the South Atlantic are calculated using an inverse model. Usually salt preservation is used as a condition in the inverse model, and only in the case of heat transport the condition of zero total mass transport is taken instead. Other constraints include silica conservation, prescribed southward fluxes of salt and phosphate, and transports in the southward Brazil Current and in the northward Antarctic Bottom Water flow obtained from WOCE moored current meter arrays. The constraints set the underdetermined system of linear equations of the inverse model whose solutions depend on weights, scales, and matrix ranks. The discussion emphasizes the sensitivity of the fluxes to changes in the model input. The transports given in the following are obtained as the means of “reasonable” solutions at 30°S. The error numbers in parentheses include uncertainties due to wind stress and temporal variability, the numbers without parentheses do not contain these terms:0.53 ± 0.03 (0.09) Tg s−1 mass to the south, 0.29 ± 0.05 (0.24) PW heat to the north, 15 ± 120 (500) kmol s−1 oxygen to the south, 121 ± 22 (75) kmol s−1 nitrate to the south, 64 ± 110 (300) silica to the north, and 1997 ± 215 (600) kmol s−1 dissolved inorganic carbon to the south. The above errors in transports are obviously dominated by uncertainties in wind stress and temporal variability. The divergence in meridional heat and mass transport is consistent with integral surface flux changes between corresponding zonal bands. The mass compensation of southward flowing North Atlantic Deep Water occurs to a greater extent in the warm surface waters than in the Antarctic Intermediate Water below. If one follows the arguments of earlier authors on the relation between meridional fluxes and the significance of the two possible pathways for the global thermohaline circulation, the warm water path south of Africa seems to be somewhat more important than the cold water path through Drake Passage.

* Current affiliation: Institut für Meereskunde an der Universität Hamburg, Hamburg, Germany.

Current affiliation: Instituto Canario de Ciencias Marinas, Telde, Grand Canary, Spain.

Corresponding author address: Dr. Jürgen Holfort, Institut für Meereskunde, Universität Hamburg, Troplowitzstraße 7, D-22529 Hamburg, Germany.

Abstract

Meridional transports of mass, heat, nutrients, and carbon across coast-to-coast WOCE and pre-WOCE sections between 11°S and 45°S in the South Atlantic are calculated using an inverse model. Usually salt preservation is used as a condition in the inverse model, and only in the case of heat transport the condition of zero total mass transport is taken instead. Other constraints include silica conservation, prescribed southward fluxes of salt and phosphate, and transports in the southward Brazil Current and in the northward Antarctic Bottom Water flow obtained from WOCE moored current meter arrays. The constraints set the underdetermined system of linear equations of the inverse model whose solutions depend on weights, scales, and matrix ranks. The discussion emphasizes the sensitivity of the fluxes to changes in the model input. The transports given in the following are obtained as the means of “reasonable” solutions at 30°S. The error numbers in parentheses include uncertainties due to wind stress and temporal variability, the numbers without parentheses do not contain these terms:0.53 ± 0.03 (0.09) Tg s−1 mass to the south, 0.29 ± 0.05 (0.24) PW heat to the north, 15 ± 120 (500) kmol s−1 oxygen to the south, 121 ± 22 (75) kmol s−1 nitrate to the south, 64 ± 110 (300) silica to the north, and 1997 ± 215 (600) kmol s−1 dissolved inorganic carbon to the south. The above errors in transports are obviously dominated by uncertainties in wind stress and temporal variability. The divergence in meridional heat and mass transport is consistent with integral surface flux changes between corresponding zonal bands. The mass compensation of southward flowing North Atlantic Deep Water occurs to a greater extent in the warm surface waters than in the Antarctic Intermediate Water below. If one follows the arguments of earlier authors on the relation between meridional fluxes and the significance of the two possible pathways for the global thermohaline circulation, the warm water path south of Africa seems to be somewhat more important than the cold water path through Drake Passage.

* Current affiliation: Institut für Meereskunde an der Universität Hamburg, Hamburg, Germany.

Current affiliation: Instituto Canario de Ciencias Marinas, Telde, Grand Canary, Spain.

Corresponding author address: Dr. Jürgen Holfort, Institut für Meereskunde, Universität Hamburg, Troplowitzstraße 7, D-22529 Hamburg, Germany.

Save
  • Baumgartner, A., and E. Reichel, 1975: Die Weltwasserbilanz. Oldenburg Verlag, 179 pp.

  • Bennet, A. F., 1978: Poleward heat fluxes in Southern Hemisphere oceans. J. Phys. Oceanogr.,8, 785–798.

  • Boddem, J., and R. Schlitzer, 1995: Interocean exchange and meridional mass and heat fluxes in the South Atlantic. J. Geophys. Res.,100, 15 821–15 834.

  • Boebel, O., C. Schmid, and W. Zenk, 1997: Flow and recirculation of Antarctic Intermediate Water across the Rio Grande Rise. J. Geophys. Res.,102, 20 967–20 986.

  • Böning, C. W., 1992: Transportprozesse im subtropischen Nordatlantik: Untersuchungen mit wirbelauflösenden Modellen der windgetriebenen und thermohalinen Zirkulation. Postdoctoral thesis, University of Kiel, 173 pp.

  • Brewer, P. G., C. Goyet, and D. Dryssen, 1989: Carbon dioxide transport by ocean currents at 25°N latitude in the Atlantic Ocean. Science,246, 477–479.

  • Bryan, K., 1962: Measurements of meridional heat transport by ocean currents. J. Geophys. Res.,67, 3403–3414.

  • Bunker, A. F., 1988: Surface energy fluxes of the South Atlantic Ocean. Mon. Wea. Rev.,116, 809–823.

  • Byrne, D. A., A. L. Gordon, and W. F. Haxby, 1995: Agulhas eddies:A synoptic view using Geosat ERM data. J. Phys. Oceanogr.,25, 902–917.

  • Coachman, L. K., and K. Aagaard, 1988: Transports through Bering Strait: Annual and interannual variability. J. Geophys. Res.,83, 15 535–15 539.

  • Fu, L., 1981: The general circulation and meridional heat transport of the subtropical South Atlantic determined by inverse methods. J. Phys. Oceanogr.,11, 1171–1193.

  • Ganachaud, A., and C. Wunsch, 1998: Large scale oceanic nutrient and oxygen fluxes. Int. WOCE Newslett.,32, 12–15.

  • Gordon, A. L., 1985: Indian–Atlantic transfer of thermocline water at the Agulhas Retroflection. Science,227, 1030–1033.

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

  • Hall, M. M., and H. L. Bryden, 1982: Direct estimates and mechanisms of ocean heat transport. Deep-Sea Res.,29, 339–359.

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

  • Hogg, N. G., P. Biscaye, W. Gardner, and W. J. Schmitz, 1982: On the transport and modification of Antarctic Bottom Water in the Vema Channel. J. Mar. Res.,40 (Suppl.), 231–263.

  • ——, W. B. Owens, G. Siedler, and W. Zenk, 1996: Circulation in the Deep Brazil Basin. The South Atlantic: Present and Past Circulation, G. Wefer, W. H. Berger, G. Siedler, D. J. Webb, Eds., Springer-Verlag, 249–260.

  • ——, G. Siedler, and W. Zenk, 1999: Circulation and variability at the southern boundary of the Brazil Basin. J. Phys. Oceanogr.,29, 145–157.

  • Holfort, J., 1994: Großräumige Zirkulation und meridionale Transporte im Südatlantik. Ber. Inst. Meereskunde Univ. Kiel,260, 96pp.

  • ——, K. M. Johnson, B. Schneider, G. Siedler, and D. W. R. Wallace, 1998: Meridional transport of dissolved inorganic carbon in the South Atlantic Ocean. Global Biogeochem. Cycles,12, 479–499.

  • ——, M. Vanicek, and G. Siedler, 2000: What causes long-term temporal changes in the South Atlantic? Geophys. Res. Lett.,27, 1187–1190.

  • Houry, S., E. Dombrowsky, P. De Mey, and J. F. Minster, 1987: Brunt–Väisälä frequency and Rossby radii in the South Atlantic. J. Phys. Oceanogr.,17, 1619–1626.

  • Josey, S. A., E. C. Kent, D. Oakley, and P. K. Taylor, 1996: A new global air–sea heat and momentum flux climatology. Int. WOCE Newslett.24, 3–5.

  • Keeling, R. F., and T.-H. Peng, 1995: Transport of heat, CO2 and O2 by the Atlantic’s thermohaline circulation. Philos. Trans. Roy. Soc. London,348B, 133–142.

  • Macdonald, A. M., 1993: Property fluxes at 30°S and their implications for the Pacific–Indian Troughflow and the global heat budget. J. Geophys. Res.,98, 6851–6868.

  • ——, 1998: The global ocean circulation: A hydrographic estimate and regional analysis. Progress in Oceanography, Vol. 41, Pergamon, 281–382.

  • Müller, T. J., and G. Siedler, 1992: Multi-year current time series in the eastern North Atlantic Ocean. J. Mar. Res.,50, 63–98.

  • Onken, R., 1994: The asymmetry of western boundary currents in the upper Atlantic Ocean. J. Phys. Oceanogr.,24, 928–948.

  • Reid, J. L., 1989: On the total geostrophic circulation of the South Atlantic Ocean: Flow patterns, tracers and transports. Progress in Oceanography, Vol. 23, Pergamon, 149–244.

  • Rintoul, S. R., 1991: South Atlantic interbasin exchange. J. Geophys. Res.,96, 2675–2692.

  • ——, and C. Wunsch, 1991: Mass, heat, oxygen and nutrient fluxes and budget in the North Atlantic Ocean. Deep-Sea Res.,38 (Suppl.), 355–377.

  • Roach, A. T., K. Aagaard, C. H. Pease, S. A. Salo, T. Weingartner, V. Pavlov, and M. Kulakov, 1995: Direct measurements of transport and water properties through Bering Strait. J. Geophys. Res.,100, 18 443–18 457.

  • Roemmich, D., 1983: The balance of geostrophic and Ekman transports in the tropical Atlantic Ocean. J. Phys. Oceanogr.,13, 1534–1539.

  • Saunders, P. M., and B. A. King, 1995: Oceanic fluxes on the WOCE A11 section. J. Phys. Oceanogr.,25, 1942–1958.

  • Schlitzer, R., 1996: Mass and heat transports in the South Atlantic derived from historical hydrographic data. The South Atlantic: Present and Past Circulation, G. Wefer, W. H. Berger, G. Siedler, and D. J. Webb, Eds., Springer-Verlag, 83–104.

  • Schmitt, R. W., P. S. Bogden, and C. E. Dorman, 1989: Evaporation minus precipitation and density fluxes for the North Atlantic. J. Phys. Oceanogr.,19, 1208–1221.

  • Siedler, G., and W. Zenk, 1992: WOCE Südatlantik 1991, Reise Nr. 15, 30 Dezember 1990–23 März 1991. METEOR-Berichte 92-1, University of Hamburg, 126 pp.

  • ——, W. Balzer, T. J. Müller, R. Onken, M. Rhein, and W. Zenk, 1993: WOCE South Atlantic 1992, Cruise No.22, 22 September 1992–31 January 1993. METEOR-Berichte 93-5, University of Hamburg, 131 pp.

  • ——, T. J. Müller, R. Onken, M. Arhan, H. Mercier, B. A. King, and P. M. Saunders, 1996: The zonal WOCE sections in the South Atlantic. The South Atlantic: Present and Past Circulation, G. Wefer, W. H. Berger, G. Siedler, and D. J. Webb, Eds., Springer-Verlag, 83–104.

  • Speer, K., and W. Zenk, 1993: The flow of bottom water into the Brazil Basin. J. Phys. Oceanogr.,23, 2667–2682.

  • ——, ——, G. Siedler, J. Pätzold, and C. Heidland, 1992: First resolution of flow through the Hunter Channel in the South Atlantic. Earth Planet. Sci. Lett.,113, 287–292.

  • ——, J. Holfort, T. Reynaud, and G. Siedler, 1996: South Atlantic heat transport at 11°S. The South Atlantic: Present and Past Circulation. G. Wefer, W. H. Berger, G. Siedler, D. J. Webb, Eds., Springer-Verlag, 105–120.

  • Stramma, L., 1989: The Brazil Current transport south of 23°S. Deep-Sea Res.,36, 639–646.

  • STS/ODF, 1992a: South Atlantic Ventilation Experiment (SAVE). Chemical, physical and CTD data report, legs 1, 2 and 3. SIO Reference No. 92-9. [Available from Scripps Institution of Oceanography, La Jolla, CA 92037.].

  • ——, 1992b: South Atlantic Ventilation Experiment (SAVE). Chemical, physical and CTD data report, Legs 4 and 5. SIO Reference No. 92-10. [Available from Scripps Institution of Oceanography, La Jolla, CA 92037.].

  • ——, 1992c: HYDROS leg 4. Physical, chemical and CTD data, R/V Melville 13 March–19 April 1989. SIO Reference No. 92-12. [Available from Scripps Institution of Oceanography, La Jolla, CA 92037.].

  • Tarbell, S., R. Meyer, N. Hogg, and W. Zenk, 1994: A moored array along the southern boundary of the Brazil Basin for the Deep Basin Experiment—Report of a joint experiment 1991–1992. Ber. Inst. Meereskunde Univ. Kiel,243, 97 pp.

  • van Bennekom, A. J., 1996: Silica signals in the South Atlantic. The South Atlantic: Present and Past Circulation. G. Wefer, W. H. Berger, G. Siedler, D. J. Webb, Eds., Springer-Verlag, 345–354.

  • ——, and G. W. Berger, 1984: Hydrography and silica budget of the Angola Basin. Neth. J. Sea Res.,17, 149–200.

  • Warren, B. A., 1999: Approximating the energy transport across oceanic sections. J. Geophys. Res.,104, 7915–7919.

  • ——, and K. G. Speer, 1991: Deep circulation in the eastern South Atlantic Ocean. Deep-Sea Res.,39, 1273–1298.

  • Wijffels, S. E., R. W. Schmidt, H. L. Bryden, and A. Stigebrandt, 1992: Transport of freshwater by the ocean. J. Phys. Oceanogr.,22, 155–162.

  • Wunsch, C., 1978: The North Atlantic general circulation west of 50°W determined by inverse Methods. Rev. Geophys. Space Phys.,16, 583–620.

  • Wust, G., 1932: Das ozeanographische Beobachtungsmaterial (Serienmessungen). Vol. 4, Wissenschaftliche Ergebnisse der deutchen Atlantischen Expedition “Meteor” 1925–1927. Verlag von Walter de Gruyter, 290 pp.

  • ——, 1996: The Ocean Circulation Inverse Problem. Cambridge University Press, 442 pp.

  • Zenk, W., and T. J. Müller, 1995: WOCE studies in the South Atlantic, cruise no. 28, 29 March–14 June 1994. METEOR-Berichte 95-1, University of Hamburg, 193 pp.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 584 168 8
PDF Downloads 245 57 3