Circulation, Renewal, and Modification of Antarctic Mode and Intermediate Water

Bernadette M. Sloyan Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

Search for other papers by Bernadette M. Sloyan in
Current site
Google Scholar
PubMed
Close
and
Stephen R. Rintoul Antarctic CRC, University of Tasmania, and CSIRO Division of Marine Research, Hobart, Australia

Search for other papers by Stephen R. Rintoul in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Nine hydrographic sections are combined in an inverse box model of the Southern Ocean south of ∼12°S. The inverse model has two novel features: the inclusion of independent diapycnal flux unknowns for each property and the explicit inclusion of air–sea fluxes (heat, freshwater, and momentum) and the water mass transformation they drive. Transformation of 34 × 106 m3 s−1 of Antarctic Surface Water by air–sea buoyancy fluxes, and cooling and freshening where Subantarctic Mode Water outcrops, renews cold, fresh Antarctic Intermediate Water of the southeast Pacific and southwest Atlantic. Relatively cold, fresh mode and intermediate water enter the subtropical gyres, are modified by air–sea fluxes and interior mixing, and return poleward as warmer, saltier mode and intermediate water. While the zonally integrated meridional transport in these layers is small, the gross exchange is approximately 80 × 106 m3 s−1.

The air–sea transformation of Antarctic surface water to intermediate water is compensated in the Southern Ocean by an interior diapycnal flux of 32 × 106 m3 s−1 of intermediate water to upper deep water. The small property differences between slightly warmer, saltier intermediate water and cold, fresh Antarctic Surface Water results in a poleward transfer of heat and salt across the Polar Front zone.

Mode and intermediate water are crucial participants in the North Atlantic Deep Water overturning and Indonesian Throughflow circulation cells. The North Atlantic Deep Water overturning is closed by cold, fresh intermediate water that is modified to warm, salty varieties by air–sea fluxes and interior mixing in the Atlantic and southwest Indian Oceans. The Indonesian Throughflow is part of a circum-Australia circulation. In the Indian Ocean, surface water is converted to denser thermocline and mode water by air–sea fluxes and interior mixing, excess mode water flows eastward south of Australia, and air–sea fluxes convert mode water to thermocline water in the Pacific.

Current affiliation: NOAA/Pacific Marine Environmental Laboratory/Ocean Climate Research Division, Seattle, Washington.

Corresponding author address: Dr. Bernadette Sloyan, NOAA/PMEL/OCRD, Bldg. 3, 7600 Sand Point Way NE, Seattle, WA 98115-6349.

Email: sloyan@pmel.noaa.gov

Abstract

Nine hydrographic sections are combined in an inverse box model of the Southern Ocean south of ∼12°S. The inverse model has two novel features: the inclusion of independent diapycnal flux unknowns for each property and the explicit inclusion of air–sea fluxes (heat, freshwater, and momentum) and the water mass transformation they drive. Transformation of 34 × 106 m3 s−1 of Antarctic Surface Water by air–sea buoyancy fluxes, and cooling and freshening where Subantarctic Mode Water outcrops, renews cold, fresh Antarctic Intermediate Water of the southeast Pacific and southwest Atlantic. Relatively cold, fresh mode and intermediate water enter the subtropical gyres, are modified by air–sea fluxes and interior mixing, and return poleward as warmer, saltier mode and intermediate water. While the zonally integrated meridional transport in these layers is small, the gross exchange is approximately 80 × 106 m3 s−1.

The air–sea transformation of Antarctic surface water to intermediate water is compensated in the Southern Ocean by an interior diapycnal flux of 32 × 106 m3 s−1 of intermediate water to upper deep water. The small property differences between slightly warmer, saltier intermediate water and cold, fresh Antarctic Surface Water results in a poleward transfer of heat and salt across the Polar Front zone.

Mode and intermediate water are crucial participants in the North Atlantic Deep Water overturning and Indonesian Throughflow circulation cells. The North Atlantic Deep Water overturning is closed by cold, fresh intermediate water that is modified to warm, salty varieties by air–sea fluxes and interior mixing in the Atlantic and southwest Indian Oceans. The Indonesian Throughflow is part of a circum-Australia circulation. In the Indian Ocean, surface water is converted to denser thermocline and mode water by air–sea fluxes and interior mixing, excess mode water flows eastward south of Australia, and air–sea fluxes convert mode water to thermocline water in the Pacific.

Current affiliation: NOAA/Pacific Marine Environmental Laboratory/Ocean Climate Research Division, Seattle, Washington.

Corresponding author address: Dr. Bernadette Sloyan, NOAA/PMEL/OCRD, Bldg. 3, 7600 Sand Point Way NE, Seattle, WA 98115-6349.

Email: sloyan@pmel.noaa.gov

Save
  • Barnier, B., L. Siefridt, and P. Marchesiello, 1995: Thermal forcing for a Global Ocean Circulation using a three year climatology of ECMWF analysis. J. Mar. Syst.,6, 363–380.

  • Baumgartner, A., and E. Reichel, 1975: The World Water Balance. Elsevier, 179 pp.

  • Budd, W. F., P. A. Reid, and L. J. Minty, 1995: Antarctic moisture flux and net accumulation from global atmospheric analyses. Ann. Glaciol.,21, 149–156.

  • Coachman, L., and K. Aagaard, 1988: Transport through Bering Strait: Annual and interannual variability. J. Geophys. Res.,93, 15 535–15 539.

  • da Silva, A. M., C. C. Young, and S. Levitus, 1994: Atlas of Surface Marine Data 1994. Vol. 1: Algorithms and Procedures, NOAA/NESDIS Tech. Rep. 6, 83 pp.

  • Deacon, G. E. R., 1937: The Hydrology of the Southern Ocean. Vol. 15, Cambridge University Press, 3–12.

  • de Ruitjer, W. P. M., A. Biastoch, J. R. E. Drijfhout, S. S. Lutjeharms, R. P. Matano, T. Pichevin, P. J. van Leeu Wen, and W. Weijer, 1999: Indian–Atlantic interocean exchange: Dynamics, estimation and impacts. J. Geophys. Res.,104, 20 885–20 910.

  • Döös, K., and A. Coward, 1997: The Southern Ocean as the major upwelling zone of north Atlantic Deep Water. Int. WOCE Newsl.,27, 3–4.

  • Fahrbach, E., G. Rohardt, M. Schröder, and V. Strass, 1994: Transport and structure of the Weddell Sea. Ann. Geophys.,12, 840–855.

  • Fine, R. A., 1993: Circulation of Antarctic Intermediate Water in the South Indian Ocean. Deep-Sea Res.,40, 2021–2042.

  • Fu, L.-L., 1986: Mass, heat, and freshwater fluxes in the South Indian Ocean. J. Phys. Oceanogr.,16, 1683–1693.

  • Georgi, D. T., 1979: Modal properties of Antarctic Intermediate Water in the southeast Pacific and South Atlantic. J. Phys. Oceanogr.,9, 456–468.

  • ——, 1981: On the relationship between the large-scale property variations and fine structure in the Circumpolar Deep Water. Deep-Sea Res.,86, 6556–6566.

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

  • ——, and E. J. Molinelli, 1982: Southern Ocean Atlas. Columbia University Press, 11 pp., 233 plates.

  • ——, and B. A. Huber, 1990: Southern Ocean winter mixed layer. J. Geophys. Res.,95, 11 655–11 672.

  • ——, R. F. Weiss, W. M. Smethie Jr., and M. J. Warner, 1992: Thermocline and intermediate water communication between the South Atlantic and Indian Oceans. J. Geophys. Res.,97, 7223–7240.

  • Hellerman, 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 Jr., 1982: On the transport and modification of Antarctic Bottom Water in the Vema Channel. J. Mar. Res.,40, 231–263.

  • Holfort, J., 1994: Großräumige Zirkulation und meridionale Transporte im Südatlantik (in German, English abstract). Ph.D. thesis, Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, Nr. 260, 95 pp. [Available from Institute for Marine Research, University of Kiel, Düsternbrooker Weg, 24105 Kiel, Germany.].

  • Jackett, D., and T. J. McDougall, 1997: A neutral density variable for the world’s oceans. J. Phys. Oceanogr.,27, 237–263.

  • Keith, D. W., 1995 Meridional energy transports: Uncertainty in zonal means. Tellus,47, 30–44.

  • Levitus, S., and T. Boyer, 1994: World Ocean Atlas 1994. Vol. 4: Salinity, Tech. Rep. NOAA Atlas NESDIS 4, U.S. Department of Commerce, NOAA, NESDIS, 117 pp.

  • Lutjeharms, J. R. E., and R. C. Van Ballegooyen, 1988: The retroflection of the Agulhas Current. J. Phys. Oceanogr.,18, 1570–1583.

  • Macdonald, A. M., 1993: Property fluxes at 30°S and their implication for the Pacific–Indian throughflow 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.

  • ——, and C. Wunsch, 1996: An estimate of global ocean circulation and heat fluxes. Nature,382, 436–439.

  • Marshall, J., D. Jamous, and J. Nilsson, 1999: Reconciling thermodynamic and dynamic methods of computation of water-mass transformation rates. Deep-Sea Res.,46, 545–572.

  • McCartney, M. S., 1977: Subantarctic Mode Water. Deep-Sea Res.,24, 103–119.

  • ——, 1982: The subtropical recirculation of Mode Waters. J. Mar. Res.,40, 427–464.

  • McIntosh, P. C., and S. R. Rintoul, 1997: Do box inverse models work? J. Phys. Oceanogr.,27, 291–208.

  • Metzl, N., B. Moore, and A. Poisson, 1990: Resolving the intermediate and deep advective flows in the Indian Ocean by using temperature, salinity, oxygen and phosphate data: The interplay of biogeochemical and geophysical tracers. Geochemical Variability in the Oceans, Ice and Sediments, L. P. Labeyrie and C. Jeandel, Eds., Vol. 89, Palaeogeography, Palaeoclimatology, Palaeoecology (Global and Planetary Change Section), Elsevier Science, 81–111.

  • Molinelli, E. T., 1981: The Antarctic influence on Antarctic Intermediate Water. J. Mar. Res.,39, 267–293.

  • Munk, W. H., 1966: Abyssal recipes. Deep-Sea Res.,13, 707–730.

  • Nurser, A. J. G., R. Marsh, and R. G. Williams, 1999: Diagnosing water mass formation from air–sea fluxes and surface mixing. J. Phys. Oceanogr.,29, 1468–1487.

  • Orsi, A. H., T. Whitworth III, and W. D. Nowlin Jr., 1995: On the meridional extent and fronts of the Antarctic Circumpolar Current. Deep-Sea Res.,42, 641–673.

  • Peterson, R., 1992: The boundary currents in the western Argentine Basin. Deep-Sea Res.,39, 623–644.

  • ——, and L. Stramma, 1991: Upper-level circulation in the South Atlantic Ocean. Progress in Oceanography, Vol. 26, Pergamon, 1–73.

  • Piola, A. R., and D. T. Georgi, 1982: Circumpolar properties of Antarctic Intermediate Water and Subantarctic Mode Water. Deep-Sea Res.,29, 687–711.

  • ——, and A. L. Gordon, 1989: Intermediate water in the southwestern South Atlantic. Deep-Sea Res.,36, 1–16.

  • Polzin, K. L., and E. Firing, 1997: Estimates of diapycnal mixing using LADCP and CTD data from I8S. Int. WOCE Newsl.,29, 39–42.

  • Reid, J. L., 1986: On the total geostrophic circulation of the South Pacific Ocean: Flow patterns, tracers and transports. Progress in Oceanography, Vol. 16, Pergamon, 1–61.

  • ——, 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 J. L. Bullister, 1999: A late winter hydrographic section from Tasmania to Antartica. Deep-Sea Res.,46, 1417–1454.

  • Robbins, P. E., and J. M. Toole, 1997: The dissolved silica budget as a constraint on the meridional overturning circulation of the Indian Ocean. Deep-Sea Res.,44, 879–906.

  • Sætre, R., and A. J. da Silva, 1984: The circulation of the Mozambique Channel. Deep-Sea Res.,31, 485–508.

  • Saunders, P. M., and B. R. King, 1995: Oceanic fluxes on the WOCE A11 Section. J. Phys. Oceanogr.,25, 1942–1957.

  • 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.

  • Schmitz, W. J., Jr., 1995: On the interbasin-scale thermohaline circulation. Rev. Geophys.,33, 151–173.

  • ——, 1996: On the World Ocean Circulation. Vol. II: The Pacific and Indian Oceans/A global update. Tech. Rep. WHOI-96-08, Woods Hole Oceanographic Institute, 237 pp. [Available from Woods Hole Oceanographic Institute, Woods Hole, MA 02543.].

  • ——, and P. L. Richardson, 1991: On the sources of the Florida Current. Deep-Sea Res.,38, 389–409.

  • Sloyan, B. M., 1997: The circulation of the Southern Ocean and the adjacent ocean basins determined by inverse methods. Ph.D. thesis, Institute of Antarctic and Southern Ocean Studies, University of Tasmania, 479 pp. [Available from IASOS, University of Tasmania, GPO Box 252-77, Hobart, Tasmania 7001, Australia.].

  • ——, and S. R. Rintoul, 2000: Estimates of area-averaged diapycnal fluxes from basin-scale budgets. J. Phys. Oceanogr.,30, 2320–2341.

  • ——, and ——, 2001: The Southern Ocean limb of the global deep overturning circulation. J. Phys. Oceanogr.,31, 143–173.

  • Speer, K., and E. Tziperman, 1992: Rates of water mass formation in the North Atlantic Ocean. J. Phys. Oceanogr.,22, 93–104.

  • ——, and W. Zenk, 1993: The flow of Antarctic Bottom Water into the Brazil Basin. J. Phys. Oceanogr.,23, 2667–2682.

  • Stommel, H., and A. B. Arons, 1960: On the abyssal circulation of the world’s ocean. ii. An idealized model of circulation pattern and amplitude in oceanic basins. Deep-Sea Res.,6, 140–154.

  • Stramma, L., 1992: The south Indian Ocean Current. J. Phys. Oceanogr.,22, 421–430.

  • ——, and R. G. Peterson, 1989: Geostrophic transport in the Benguela Current region. J. Phys. Oceanogr.,19, 1440–1448.

  • ——, and ——, 1990: The South Atlantic Current. J. Phys. Oceanogr.,20, 846–859.

  • ——, and J. R. E. Lutjeharms, 1997: The flow field of the subtropical gyre of the South Indian Ocean. J. Geophys. Res.,102, 5513–5530.

  • ——, R. G. Peterson, and M. Tomczak, 1995: The South Pacific Current. J. Phys. Oceanogr.,25, 77–91.

  • Suga, T., and L. D. Talley, 1995: Antarctic Intermediate Water circulation in the tropical and subtropical South Atlantic. J. Geophys. Res.,100, 13 441–13 453.

  • Talley, L. D., 1996: Antarctic Intermediate Water in the South Atlantic. The South Atlantic: Present and Past Circulation, G. Wefer et al., Eds., Springer, 219–238.

  • Toggweiler, J. R., and B. Samuels, 1993: New radiocarbon constraints on the upwelling of abyssal water to the ocean’s surface. The Global Carbon Cycle, M. Heimann, Ed., Vol. 15, Nato ASI Series I: Global Enviornmental Change, Springer-Verlag, 333–363.

  • Toole, J. M., and B. A. Warren, 1993: A hydrographic section across the subtropical South Indian Ocean. Deep-Sea Res.,40, 1973–2019.

  • Trèguer, P., D. M. Nelson, A. J. Van Bennekorn, D. J. DeMaster, A. Leynaert, and B. Quèguiner, 1995: The silica balance in the world ocean: A reestimate. Science,268, 375–379.

  • Trenberth, K. E., J. Olson, and W. G. Large, 1990: The mean annual cycle in global ocean wind stress. J. Phys. Oceanogr.,20, 1742–1760.

  • Tziperman, E., 1986: On the role of interior mixing and air–sea fluxes in determining the stratification and circulation of the oceans. J. Phys. Oceanogr.,16, 680–693.

  • ——, 1988: Calculating the time-mean oceanic general circulation and mixing coefficient from hydrographic data. J. Phys. Oceanogr.,18, 519–525.

  • Walin, G., 1982: On the relation between sea-surface heat flow and thermal circulation in the ocean. Tellus,34, 187–195.

  • Warren, B., 1981: Transindian hydrographic section at Lat. 18°S: Property distribution and circulation in the South Indian Ocean. Deep-Sea Res.,28, 759–788.

  • Whitworth, T., III, W. D. Nowlin Jr., R. D. Pillsbury, and R. F. Weiss, 1991: Observations of the Antarctic Circumpolar Current and deep boundary current in the Southwest Atlantic. J. Geophys. Res.,96, 15 105–15 118.

  • ——, B. A. Warren, W. D. Nowlin Jr., S. B. Rutz, R. D. Pillsbury, and M. I. Moore, 1999: On the deep western-boundary current in the Southwest Pacific Basin. Progress in Oceanography, Vol. 43, Pergamon, 1–54.

  • Wijffels, S. E., J. M. Toole, H. L. Bryden, R. A. Fine, W. J. Jenkins, and J. L. Bullister, 1996: The water masses and circulation at 10°N in the Pacific. Deep-Sea Res.,43, 501–544.

  • Wunsch, C., 1978: The North Atlantic general circulation west of 50°W determined by inverse methods. Rev. Geophys. Space Phys.,16(4), 583–620.

  • ——, D. Hu, and B. Grant, 1983: Mass, heat, salt and nutrient fluxes in the South Pacific Ocean. J. Phys. Oceanogr.,13, 725–753.

  • Wüst, G., 1935: Die Stratosphäre des Atlantischen Ozeans. Wissenschaftliche Ergebnisse der Deutschen Atlantischen Expedition auf dem Forschungs und Vermessungsschiff, Meteor 1925–1927. (The Stratosphere of the Atlantic Ocean, W. J. Emery, Ed., Amerind, 1978.).

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 1425 384 35
PDF Downloads 695 174 16