Ocean Dynamics

, 55:68 | Cite as

Variability of dense water formation in the Ross Sea

  • Karen M. AssmannEmail author
  • Ralph Timmermann
Original paper


This paper presents results from a model study of the interannual variability of high salinity shelf water (HSSW) properties in the Ross Sea. Salinity and potential temperature of HSSW formed in the western Ross Sea show oscillatory behaviour at periods of 5–6 and 9 years superimposed on long-term fluctuations. While the shorter oscillations are induced by wind variability, variability on the scale of decades appears to be related to air temperature fluctuations. At least part of the strong decrease of HSSW salinities deduced from observations for the period 1963–2000 is shown to be an aliasing artefact due to an undersampling of the periodic signal. While sea ice formation is responsible for the yearly salinity increase that triggers the formation of HSSW, interannual variability of net freezing rates hardly affects changes in the properties of the resulting water mass. Instead, results from model experiments indicate that the interannual variability of dense water characteristics is predominantly controlled by variations in the shelf inflow through a sub-surface salinity and a deep temperature signal. The origin of the variability of inflow characteristics to the Ross Sea continental shelf can be traced into the Amundsen and Bellingshausen Seas. The temperature anomalies are induced at the continental shelf break in the western Bellingshausen Sea by fluctuations of the meridional transport of circumpolar deep water with the eastern cell of the Ross Gyre. In the Amundsen Sea, upwelling due to a persistently cyclonic wind field carries the signal into the surface mixed layer, leading to fluctuations of the vertical heat flux, anomalies of brine release near the sea ice edge, and consequently to a sub-surface salinity anomaly. With the westward flowing coastal current, both the sub-surface salinity and deep temperature signals are advected onto the Ross Sea continental shelf. Convection carries the signal of salinity variability into the deep ocean, where it interacts with modified circumpolar deep water upwelled onto the continental shelf as the second source water mass of HSSW. Sea ice formation on the Ross Sea continental shelf thus drives the vertical propagation of the signal rather than determining the signal itself.


Numerical modelling BRIOS Ross Sea Amundsen Sea Interannual variability High salinity shelf water (HSSW) 



We would like to thank Hartmut Hellmer, Stan Jacobs and Olaf Klatt for interesting discussions, and two anomymous reviewers for their constructive and helpful comments. All of these really helped to improve the manuscript. The NCEP atmospheric forcing data were received via the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado (


  1. Assmann KM (2003) The effect of McMurdo Sound topography on water mass exchange across the Ross Ice Shelf front. Annual report of the Filchner-Ronne Ice Shelf Program (FRISP), no. 15. (Available online at assmann.pdf)
  2. Assmann K, Hellmer HH, Beckmann A (2003) Seasonal variation in circulation and watermass distribution on the Ross Sea continental shelf. Ant Sci 15(1):3–11. DOI:10.1017/S0954102003001007Google Scholar
  3. Baines PG, Condie S (1998) Observations and modelling of Antarctic downslope flows: a review. Antarct Res Ser 75:29–49Google Scholar
  4. Beckmann A, Timmermann R (2001) Circumpolar influences on the Weddell Sea: indication of an Antarctic circumpolar coastal wave. J Climate 14:3785–3792CrossRefGoogle Scholar
  5. Beckmann A, Hellmer HH, Timmermann R (1999) A numerical model of the Weddell Sea: large scale circulation and water mass distribution. J Geophys Res 104(C10):23375–23391CrossRefGoogle Scholar
  6. Botnikov VN, Chuguy IV (1989) The major features of water circulation and spatial distribution of the Ross Gyral. Polar Geogr Geol 13(3):212–224Google Scholar
  7. Comiso JC, Gordon AL (1998) Interannual variability in summer sea ice minimum, coastal polynyas and bottom water formation in the Weddell Sea. Antarct Res Ser 74:293–315Google Scholar
  8. Fahrbach E, Knoche M, Rohardt G (1991) An estimate of water mass transformation in the southern Weddell Sea. Mar Chem 35:25–44CrossRefGoogle Scholar
  9. Fischer H (1995) Vergleichende Untersuchungen eines optimierten dynamisch–thermodynamischen Meereismodells mit Beobachtungen im Weddellmeer [Comparison of an optimized dynamic–thermodynamic sea ice model with observations in the Weddell Sea.]. Berichte zur Polarforschung 166, Alfred-Wegener-Institute, Bremerhaven, 130 ppGoogle Scholar
  10. Foster TD, Carmack EC (1976) Frontal zone mixing and Antarctic bottom water formation in the southern Weddell Sea. Deep Sea Res 23(4):301–317Google Scholar
  11. Gordon AL, Martinson DG, Taylor HW (1981) The wind-driven circulation in the Weddell-Enderby Basin. Deep Sea Res 28A:151–163Google Scholar
  12. Gouretski VV (1999) The large-scale thermohaline structure of the Ross Gyre. In: Spezie G, Manzella GMR (eds) Oceanography of the Ross Sea. Springer, Berlin Heidelberg New York, pp 77–102Google Scholar
  13. Gouretski V, Jancke K, Reid J, Swift J, Rhines P, Schlitzer R, Yashayaev I (1999) WOCE Hydrographic Programme Special Analysis Centre, Atlas of Ocean Sections CD-ROM, 1999. [Available at SACserver/SACHome.htm.]
  14. Greischar LL, Bentley CR, Whiting LR (1992) An analysis of gravity measurements on the Ross Ice Shelf, Antarctica. Antarct Res Ser 57:105–155Google Scholar
  15. Haidvogel DB, Wilkin JL, Young RE (1991) A semi-spectral primitive equation ocean circulation model using vertical sigma and orthogonal curvilinear horizontal coordinates. J Comput Phys 94:151–185CrossRefGoogle Scholar
  16. Heap JA (1964) Pack ice Antarctic research. In: Pristley R, Adie R, Robin G (eds) Buterworths, pp 308–317Google Scholar
  17. Hellmer HH, Jacobs SS, Jenkins A (1998) Oceanic erosion of a floating Antarctic glacier in the Amundsen Sea. Antarct Res Ser 75:83–99Google Scholar
  18. Hibler WD (1979) A dynamic-thermodynamic sea ice model. J Phys Oceanogr 9(4):815–846CrossRefGoogle Scholar
  19. Jacobs SS, Comiso JC (1989) Sea ice and oceanic processes on the Ross Sea continental shelf. J Geophys Res 94:18195–18211Google Scholar
  20. Jacobs SS, Giulivi CF (1998) Interannual ocean and sea ice variability in the Ross Sea. Antarct Res Ser 75:135–150Google Scholar
  21. Jacobs SS, Amos AF, Bruchhausen PM (1970) Ross sea oceanography and Antarctic bottom water formation. Deep Sea Res 17:935–962Google Scholar
  22. Jacobs SS, Hellmer HH, Jenkins A (1996) Antarctic ice sheet melting in the Southeast Pacific. Geophys Res Lett 23:957–960CrossRefGoogle Scholar
  23. Jacobs SS, Giulivi CF, Mele PA (2002) Freshening of the Ross Sea during the late 20th century Science 297:386–389CrossRefPubMedGoogle Scholar
  24. Jeffries MO, Li S, Jana RA, Krause HR, Hurst-Cushing B (1998) Late winter first-year ice floe variability, seawater flooding and snow ice formation in the Amundsen and Ross Seas. Antarct Res Ser 74:69–88Google Scholar
  25. Johnson MR, Smith AM (1997) Seabed topography under the southern and western Ronne Ice Shelf, derived from seismic surveys. Antarct Sci 9:201–208Google Scholar
  26. Klatt O, Fahrbach E, Hoppema M, Rohardt G (2005) The transport of the Weddell Gyre across the Prime Meridian. Deep-Sea Research (in press)Google Scholar
  27. Ledley TS, Huang Z (1997) A possible ENSO signal in the Ross Sea. Geophys Res Lett 24:3253–3256CrossRefGoogle Scholar
  28. Leppäranta M (1983) A growth model for black ice, snow ice, and snow thickness in subantarctic basins. Nord Hydrol 14:59–70Google Scholar
  29. Locarnini RA (1994) Water masses and circulation in the Ross Gyre and environs. PhD Thesis, Texas A & M University, 87 ppGoogle Scholar
  30. Martinson DG, Iannuzzi RA (2003) Spatial/temporal patterns in Weddell gyre characteristics and their relationship to global climate. J Geophys Res 109(C4). DOI: 10.1029/2000JC000538Google Scholar
  31. Orsi AH, Whitworth T III, Nowlin WD (1995) On the meridional extent and fronts of the Antarctic Circumpolar Current. Deep Sea Res 42:641–673CrossRefGoogle Scholar
  32. Owens WB, Lemke P (1990) Sensitivity studies with a sea ice-mixed layer-pycnocline model in the Weddell Sea. J Geophys Res 95(C6):9527–9538CrossRefGoogle Scholar
  33. Pacanowski RC, Philander SGH (1981) Parameterization of vertical mixing in numerical models of tropical oceans. J Phys Oceanogr 11:1443–1451CrossRefGoogle Scholar
  34. Parkinson CL, Washington WM (1979) A large-scale numerical model of sea ice. J Geophys Res 84(C1):311–337Google Scholar
  35. Reid JL (1986) On the total geostrophic circulation of the South Pacific ocean: flow patterns, tracers and transports. Prog Oceanogr 16:1–61CrossRefGoogle Scholar
  36. Semtner AJ Jr (1976) A model for the thermodynamic growth of sea ice in numerical investigations of climate. J Phys Oceanogr 6(3):379–389CrossRefGoogle Scholar
  37. Smith WHF, Sandwell DT (1997) Global sea floor topography from satellite altimetry and ship depth soundings. Science 277:1956–1962CrossRefGoogle Scholar
  38. Timmermann R, Hellmer HH, Beckmann A (2002b) Simulation of ice-ocean dynamics in the Weddell Sea. Part II: interannual variability 1985–1993. J Geophys Res 107(C3). DOI: 10.1029/2000JC000472Google Scholar
  39. Timmermann R, Beckmann A, Hellmer HH (2002a) Simulation of ice-ocean dynamics in the Weddell Sea. Part I: model configuration and validation. J Geophys Res 107(C3). DOI: 10.1029/2000JC000471Google Scholar
  40. Toggweiler JR, Samuels B (1995) Effect of sea ice on the salinity of Antarctic bottom waters. J Phys Oceanogr 25:1980–1997CrossRefGoogle Scholar
  41. Whitworth III T, Peterson RG (1985) The volume transport of the Antarctic circumpolar current from three-year bottom pressure measurements. J Phys Oceanogr 15:810–816CrossRefGoogle Scholar
  42. Yuan X, Martinson DG (2000) Antarctic sea ice extent and its global connectivity. J Clim 13:1697–1717CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Alfred Wegener Institute for Polar and Marine ResearchBremerhavenGermany
  2. 2.Bjerknes Centre for Climate Research BergenNorway

Personalised recommendations