Annual Rossby Wave in the Southern Indian Ocean: Why Does It “Appear” to Break Down in the Middle Ocean?

Liping Wang Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland

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Chester J. Koblinsky Ocean and Ice Branch, Laboratory for Hydrospheric Processes, NASA Goddard Space Flight Center, Greenbelt, Maryland

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Stephan Howden Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland

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Abstract

Using both altimetry data (TOPEX/Poseidon and Geosat) and Levitus climatology and a linear reduced-gravity model, the authors studied the annual Rossby waves in the southern Indian Ocean from 19° to 9°S. The most striking feature from the data analysis is that the westward phase propagation of the annual variability appears to break up in the midocean, which results in two local maxima for annual variability in both the sea level and the depth of the 18°C isotherm, with one in the eastern basin and the other in the western basin. Separating the two maxima is a midocean minimum. Decomposition of the annual variability into Rossby waves and localized response indicates that the two local maxima of the annual variability simply result from the constructive interference between the localized response and the Rossby waves in the eastern and western basin. On the other hand, the midocean local minimum results from the destructive interference between the Rossby waves and the localized response. Modeling results suggest that the bulk of the annual variability in the study domain is driven by wind forcing, while forcing by throughflow through eastern boundary radiation is of minor importance. Dissipation is found to have a much greater impact on the Rossby waves than on the local response.

Corresponding author address: Dr. Liping Wang, ESSIC, University of Maryland, College Park, MD 20742.

Abstract

Using both altimetry data (TOPEX/Poseidon and Geosat) and Levitus climatology and a linear reduced-gravity model, the authors studied the annual Rossby waves in the southern Indian Ocean from 19° to 9°S. The most striking feature from the data analysis is that the westward phase propagation of the annual variability appears to break up in the midocean, which results in two local maxima for annual variability in both the sea level and the depth of the 18°C isotherm, with one in the eastern basin and the other in the western basin. Separating the two maxima is a midocean minimum. Decomposition of the annual variability into Rossby waves and localized response indicates that the two local maxima of the annual variability simply result from the constructive interference between the localized response and the Rossby waves in the eastern and western basin. On the other hand, the midocean local minimum results from the destructive interference between the Rossby waves and the localized response. Modeling results suggest that the bulk of the annual variability in the study domain is driven by wind forcing, while forcing by throughflow through eastern boundary radiation is of minor importance. Dissipation is found to have a much greater impact on the Rossby waves than on the local response.

Corresponding author address: Dr. Liping Wang, ESSIC, University of Maryland, College Park, MD 20742.

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  • Barnier, B., 1988: A numerical study on the influence of mid-Atlantic ridge on nonlinear first mode baroclinic Rossby wave generated by seasonal winds. J. Phys. Oceanogr.,18, 417–433.

  • Chelton, D., and M. Schlax, 1996: Global observation of oceanic Rossby waves. Science,272, 234–238.

  • da Silva, A., C. Young, and S. Levitus, 1994: Atlas of Surface Marine Data 1994. NOCD, NOAA/NESDIS E/OC21.

  • Donguy, J., and G. Meyers, 1995: Observations of geostrophic transport variability in the western tropical Indian Ocean. Deep-Sea Res.,42, 1007–1028.

  • Fu, L., and R. Smith, 1996: Global ocean circulation from satellite altimetry and high-resolution computer simulation. Bull. Amer. Meteor. Soc.,77, 2625–2636.

  • Hastenrath, S., and L. Greischer, 1991: The monsoonal current regimes of the tropical Indian Ocean: Observed surface flow fields and their geostrophic and wind-driven components. J. Geophys. Res.,96, 12 619–12 633.

  • Huang, R., and J. Pedlosky, 1999: Climate variability inferred from a layered model of the ventilated thermocline. J. Phys. Oceanogr.,29, 786–798.

  • Jacobs, G., G. Born, and W. Emery, 1993: Rossby waves in the Pacific Ocean extracted from Geosat altimetric data. J. Phys. Oceanogr.,23, 1155–1175.

  • ——, H. Hurlburt, J. Kindle, E. Metzger, J. Mitchell, W. Teague, and A. Wallcraft, 1994: Decadal scale trans-Pacific propagation and warming effects of an El Nino anomaly. Nature,370, 360–363.

  • Kelly, K., M. Caruso, and J. Austin, 1993: Wind-driven variations in sea surface height in the northeast Pacific Ocean. J. Phys. Oceanogr.,23, 2391–2411.

  • Kessler, W., 1990: Observations of long Rossby waves in the northern tropical Pacific. J. Geophys. Res.,95, 5183–5217.

  • Killworth, P., D. Chelton, and R. deSoke, 1997: The speed of observed and theoretical long extra-tropical planetary waves. J. Phys. Oceanogr.,27, 1916–1966.

  • Koblinsky, C., B. Beckley, R. Ray, Y. Wang, L. Tsaoussi, and A. Brenner, 1997: Data processing handbook (unpublished). NASA Ocean Altimeter Pathfinder Project Rep. 1, 50 pp.

  • Levitus, S., and T. P. Boyer, 1994: Temperature. Vol. 4, World Ocean Atlas 1994, NOAA Atlas NESDIS 4, 117 pp.

  • Liu, Z., 1999: Forced planetary wave response in a thermocline gyre. J. Phys. Oceanogr.,29, 1036–1055.

  • Masumoto, Y., and T. Yamagata, 1996: Seasonal variations of the Indonesian throughflow in a general circulation model. J. Geophys. Res.,101, 12 287–12 293.

  • ——, and G. Meyers, 1998: Forced Rossby waves in the southern tropical Indian Ocean. J. Geophys. Res.,103, 12 287–12 293.

  • McCreary, J., P. Kundu, and R. Molinari, 1993: A numerical investigation of dynamics, thermodynamics and mixed-layer processes in the Indian Ocean. Progress in Oceanography, Vol. 31, Pergamon, 181–244.

  • Meyers, G., 1979: On the annual Rossby wave in the tropical North Pacific. J. Phys. Oceanogr.,9, 663–674.

  • ——, R. Bailey, and A. Worby, 1995: Geostrophic transport of Indonesian throughflow. Deep-Sea Res.,42, 1163–1174.

  • Molinari, R., D. Olson, and G. Reverdin, 1990: Surface current distributions in the tropical Indian Ocean derived from compilations of surface buoy trajectories. J. Geophys. Res.,95, 7217–7238.

  • Perigaud, C., and P. Delecluse, 1992: Annual sea level variations in the southern tropical Indian Ocean from Geosat and shallow-water simulations. J. Geophys. Res.,97, 20 169–20 178.

  • ——, and ——, 1993: Interannual sea level variations in the tropical Indian Ocean from Geosat and shallow-water simulations. J. Phys. Oceanogr.,23, 1916–1934.

  • Qiu, B., W. Miao, and P. Muller, 1997: Propagation and decay of Forced and free baroclinic Rossby waves in off-equatorial oceans. J. Phys. Oceanogr.,27, 2405–2417.

  • Qu, T., G. Meyers, J. Godfrey, and D. Hu, 1994: Ocean dynamics in the region between Australia and Indonesia and its influence on the variation of the sea surface temperature in a global general circulation model. J. Geophys. Res.,99, 18 433–18 445.

  • Schott, F., M. Fieux, J. Kindle, J. Swallow, and R. Zantopp, 1988: The boundary currents east and north of Madagascar. Part 2: Direct measurements and model comparisons. J. Geophys. Res.,93, 4963–4974.

  • Wajsowicz, R., 1995: The response of the Indo–Pacific throughflow to interannual variations in the Pacific wind stress. Part I: Idealized geometry and variations. J. Phys. Oceanogr.,25, 1805–1826.

  • Wang, L., and C. Koblinsky, 1994: Influence of mid-ocean ridges on Rossby waves. J. Geophys. Res.,99, 25 143–25 153.

  • ——, ——, and S. Howden, 1998a: Annual and intra-annual, variability in the region of the Kuroshio Extension as observed by the TOPEX/Poseidon and Geosat altimetry. J. Phys. Oceanogr.,28, 692–710.

  • ——, ——, ——, and B. Beckley, 1998b: Large-scale Rossby waves in the midlatitude South Pacific Ocean from altimetry data. Geophys. Res. Lett.,25, 179–182.

  • White, W., 1977: Annual forcing of baroclinic long waves in the tropical north Pacific Ocean. J. Phys. Oceanogr.,7, 50–61.

  • Woodberry, K., M. Luther, and J. O’Brien, 1989: The wind-driven seasonal circulation in the southern tropical Indian Ocean. J. Geophys. Res.,94, 17 985–18 002.

  • Yamagata, T., K. Mizuno, and Y. Masumoto, 1996: Seasonal variations in the equatorial Indian Ocean and their impact on the Lombok throughflow. J. Geophys. Res.,101, 12 465–12 473.

  • Yang, J., L. Yu, C. Koblinsky, and D. Adamec, 1998: Dynamics of the seasonal variations from TOPEX/Poseidon sea surface height and an ocean model. Geophys. Res. Lett.,22, 1915–1918.

  • Yu, L., and M. Rienecker, 1999: Mechanisms for the Indian Ocean warming during the 1997–1998. Geophys. Res. Lett.,26, 735–738.

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