Skip to main content

Advertisement

SpringerLink
Log in

Large dunes on the outer shelf off the Zambezi Delta, Mozambique: evidence for the existence of a Mozambique Current

  • Original
  • Published:
Geo-Marine Letters Aims and scope Submit manuscript

Abstract

The existence of a continuously flowing Mozambique Current, i.e. a western geostrophic boundary current flowing southwards along the shelf break of Mozambique, was until recently accepted by oceanographers studying ocean circulation in the south-western Indian Ocean. This concept was then cast into doubt based on long-term current measurements obtained from current-meter moorings deployed across the northern Mozambique Channel, which suggested that southward flow through the Mozambique Channel took place in the form of successive, southward migrating and counter-clockwise rotating eddies. Indeed, numerical modelling found that, if at all, strong currents on the outer shelf occurred for not more than 9 days per year. In the present study, the negation of the existence of a Mozambique Current is challenged by the discovery of a large (50 km long, 12 km wide) subaqueous dune field (with up to 10 m high dunes) on the outer shelf east of the modern Zambezi River delta at water depths between 50 and 100 m. Being interpreted as representing the current-modified, early Holocene Zambezi palaeo-delta, the dune field would have migrated southwards by at least 50 km from its former location since sea level recovered to its present-day position some 7 ka ago and after the former delta had been remoulded into a migrating dune field. Because a large dune field composed of actively migrating bedforms cannot be generated and maintained by currents restricted to a period of only 9 days per year, the validity of those earlier modelling results is questioned for the western margin of the flow field. Indeed, satellite images extracted from the Perpetual Ocean display of NASA, which show monthly time-integrated surface currents in the Mozambique Channel for the 5 month period from June–October 2006, support the proposition that strong flow on the outer Mozambican shelf occurs much more frequently than postulated by those modelling results. This is consistent with more recent modelling studies comparing the application of slippage and non-slippage approaches—they suggest that, when applying partial slippage, a western boundary current can exist simultaneously with the southward migrating eddies. Considering the evidence presented in this paper, it is concluded that a quasi-persistent, though seasonally variable Mozambique Current does exist.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10

Similar content being viewed by others

References

  • Ashley G (1990) Classification of large-scale subaqueous bedforms: a new look at an old problem. J Sediment Petrol 60:160–172

    Article  Google Scholar 

  • Bartholdy J, Bartholomä A, Flemming BW (2002) Grain-size control of large compound flow-transverse bedforms in a tidal inlet of the Danish Wadden Sea. Mar Geol 188:391–413

    Article  Google Scholar 

  • Bassetti MA, Jouet G, Dufois F, Berné S, Rabineau M, Taviani M (2006) Sand bodies at the shelf edge in the Gulf of lions (western Mediterranean): deglacial history and modern processes. Mar Geol 234:93–109

    Article  Google Scholar 

  • Beiersdorf H, Kudrass H-R, von Stackelberg U (1980) Placer deposits of ilmenite and zircon on the Zambezi shelf. Geol Jahrb D36:5–85

    Google Scholar 

  • Chevane CM, Penven P, Nehama FPJ, Reason CJC (2016) Modelling the tides and their impacts on the vertical stratification over the Sofala Bank, Mozambique. Afr J Mar Sci 38:465–479

    Article  Google Scholar 

  • Darbyshire M (1966) Agulhas current. In: Fairbridge RW (ed) The encyclopedia of oceanography. Reinhold, New York, pp 23–28

    Google Scholar 

  • Davis RA Jr, Flemming BW (1991) Time-series study of mesoscale tidal bedforms, martens plate, Wadden Sea, Germany. In: Smith DG, Reinson GE, Zaitlin BA, Rahmani RA (eds) Clastic Tidal Sedimentology, Can Soc petrol Geol mem, vol 16, pp 275–282

    Google Scholar 

  • DiMarco SF, Nowlin WD, Chapman P (1998) Properties and transport of the Mozambique Channel. US WOCE Implementation Rep no 10, pp 34–35

  • DiMarco SF, Chapman P, Nowlin WD Jr, Hacker P, Donohue K, Luther M, Johnson GC, Toole J (2002) Volume transport and property distributions of the Mozambique Channel. Deep Sea Res II: Top Stud Oceanogr 49:1481–1511

    Article  Google Scholar 

  • Duncan CP (1970) The Agulhas Current. PhD thesis, University of Hawaii, Honolulu

  • Flemming BW (1976) Side-scan sonar: a practical guide. Int Hydrogr Rev 53:65–92

    Google Scholar 

  • Flemming BW (1980) Sand transport and bedform patterns on the continental shelf between Durban and Port Elizabeth (southeast African continental margin). Sediment Geol 26:177–198

    Article  Google Scholar 

  • Flemming BW (1981) Factors controlling shelf sediment dispersal along the southeast African continental margin. Mar Geol 42:259–277

    Article  Google Scholar 

  • Flemming BW (1988) Zur Klassifikation subaquatischer, strömungstransversaler Transportkörper. Bochumer Geol Geotech Arb 29:44–47

    Google Scholar 

  • Flemming BW (2000a) The role of grain size, water depth and flow velocity as scaling factors controlling the size of subaqueous dunes. In: Trentesaux a, Garlan T (eds) Marine Sandwave dynamics, 23–24 March 2000, University of Lille 1 (France), proceedings, pp 55–60

  • Flemming BW (2000b) On the dimensional adjustment of subaqueous dunes in response to changing flow conditions: a conceptual model. In: Trentesaux a, Garlan T (eds) Marine Sandwave dynamics, 23–24 March 2000, University of Lille 1 (France), proceedings, pp 61–67

  • Flemming BW (2013) Comment on “large-scale bedforms along a tideless outer shelf setting in the western Mediterranean” by lo Iacono et al. (2010) in continental shelf research vol 30, pp 1802–1813. Cont Shelf Res 52:203–207

    Article  Google Scholar 

  • Flemming BW, Bartholomä A (2012) Temporal variability, migration rates, and preservation potential of subaqueous dune fields on the southeast African continental shelf. Int Assoc Sediment Spec Publ 44:229–247

    Google Scholar 

  • Flemming BW, Davis RA Jr (1992) Dimensional adjustment of subaqueous dunes in the course of a neap-spring semicycle in a mesotidal backbarrier channel environment (German Wadden Sea, southern North Sea). Cour Forschungsinst Senck 151:28–30

    Google Scholar 

  • Flemming BW, Davis RA Jr (1994) Holocene evolution, morphodynamics and sedimentology of the Spiekeroog barrier island system (southern North Sea). Senckenberg Marit 24:117–155

    Google Scholar 

  • Gardner JV, Calder BR, Hughes Clarke JE, Mayer LA, Elston G, Rzhanov Y (2007) Drowned shelf-edge deltas, barrier islands and related features along the outer continental shelf north of the head of De Soto canyon, NE Gulf of Mexico. Geomorphology 89:370–390

    Article  Google Scholar 

  • Harlander U, Ridderinkhof H, Schouten MW, de Ruijter WPM (2009) Long-term observations of transport, eddies, and Rossby waves in the Mozambique Channel. J Geophys Res 114:C02003. doi:10.1029/2008JC004846

    Article  Google Scholar 

  • Harris TFW (1972) Sources of the Agulhas current in the spring of 1964. Deep Sea Res 19:633–650

    Google Scholar 

  • Jaritz W, Ruder J, Schlenker B (1977) Das Quartär im Küstengebiet von Mozambique und seine Schwermineralführung. Geol Jahrb B26:3–93

    Google Scholar 

  • Katoh K, Kume H, Kuroki K, Hasegawa J (1998) The development of sand waves and the maintenance of navigation channels in the Bisanseto Sea. In: edge B (ed) proc 26th Int coastal engineering Conf, ACSE, 22–26 June 1998, Copenhagen, pp 3490–3502

  • Knaapen MAF, Hulscher SJMH (2002) Regeneration of sand waves after dredging. Coast Eng 46:277–289

    Article  Google Scholar 

  • van Landeghem K, Besio G, Niemann H, Mellett C, Huws D, Steinle L, O’Reilly S, Croker P, Hodgson D, Williams D (2013) Amplified sediment waves in the Irish Sea (AmSedIS). In: Van Lancker V, Garlan T (eds) MARID 2013, 4th Int Conf Marine and river dune dynamics, 15–17 April 2013, Bruges, Belgium, Royal Belgian institute of natural sciences and SHOM. VLIZ spec Publ 65, pp 285–290

  • Lo Iacono C, Guillén J, Puig P, Ribó M, Ballesteros M, Palanques A, Lí Farrán M, Acosta J (2010) Large-scale bedforms along a tideless outer shelf setting in the western Mediterranean. Cont Shelf Res 30:1802–1813

    Article  Google Scholar 

  • Lutjeharms JRE (2006) The Agulhas current. Springer, Heidelberg

    Google Scholar 

  • Lutjeharms JRE, Bornman TG (2010) The importance of the greater Agulhas current is increasingly being recognised. S Afr J Sci 106(3/4), art #160. doi:10.4102/sajs.v106i3/4.160

  • Lutjeharms JRE, Biastoch A, van der Werf PM, Ridderinkhof H, de Ruijter WPM (2012) On the discontinuous nature of the Mozambique current. S Afr J Sci 108(1/2), art #428. doi:10.4102/sajs.v108i1/2.428

  • Martin AK (1981) Evolution of the Agulhas current and its palaeo-ecological implications. S Afr J Sci 77:547–554

    Google Scholar 

  • McCave IN (1972) Transport and escape of fine-grained sediment from shelf areas. In: Swift DJP, Duane DB, Pilkey OH (eds) Shelf sediment transport – process and pattern. Dowden Hutchinson & Ross, Stroudsburg, pp 225–248

    Google Scholar 

  • McCave IN (2003) Sedimentary settings on continental margins — an overview. In: Wefer G, Billett D, Hebbeln D, Jørgensen BB, Schlüter M, van Weering T (eds) Ocean margin systems. Springer, Berlin, pp 1–14

    Google Scholar 

  • NASA (2012) http://www.nasa.gov/topics/earth/features/perpetual-ocean.html. NASA, Goddard Space Flight Center, Greenbelt, MD

  • Nehama FPJ, Reason CJC (2014) Morphology of the Zambezi River plume on the Sofala Bank, Mozambique. Western Indian Ocean J Mar Sci 13:1–10

    Google Scholar 

  • Pearce AF (1980) Early observations and historical notes on the Agulhas current circulation. Trans R Soc S Afr 44:205–212

    Article  Google Scholar 

  • Pearce AF, Bang ND (1978) Physical oceanography. In: Heydorn AEF (ed) ecology of the Agulhas current region – an assessment of biological response to environmental parameters in the southwest Indian Ocean. Trans R Soc S Afr 43:156–162

  • Preu B, Spieß V, Schwenk T, Schneider R (2011) Evidence for current-controlled sedimentation along the southern Mozambique continental margin since early Miocene times. Geo-Mar Lett 31:427–435. doi:10.1007/s00367-011-0238-y

    Article  Google Scholar 

  • Quartly GD, de Cuevas BA, Coward AC (2013) Mozambique Channel eddies in GCMs: a question of resolution and slippage. Ocean Model 63:56–67

    Article  Google Scholar 

  • Redding JH (2000) Experimental manipulation of sandwaves to reduce their navigation hazard potential, jade shipping channel, N. Germany. In: Garlan T, Trentesaux a (eds) proc 1st Int Conf Worksh Marine Sandwave dynamics, 23–24 March 2000, University of Lille 1, France, pp 169–176

  • Ridderinkhof H, de Ruijter WPM (2003) Moored current observations in the Mozambique Channel. Deep Sea Res II: Top Stud Oceanogr 50:1933–1955

    Article  Google Scholar 

  • Rubin DM, McCulloch DS (1980) Single and superimposed bedforms: a synthesis of San Francisco Bay and flume observations. Sediment Geol 26:207–231

    Article  Google Scholar 

  • de Ruijter WPM, Ridderinkhof H, Lutjeharms JRE, Schouten MW, Veth C (2002) Observations of the flow in the Mozambique channel. Geophys Res Lett 29:1401–1403

    Article  Google Scholar 

  • Schulz H, Lückge A, Emeis K-C, Mackensen A (2011) Variability of Holocene to late Pleistocene Zambezi riverine sedimentation at the upper continental slope off Mozambique, 15°–21°S. Mar Geol 286:21–34

    Article  Google Scholar 

  • Shannon LV (1967) The oceanic circulation of South Africa. Division of Sea Fisheries, South Africa, Fish Bull 6:27–33

  • Tinley KL (1985) Mozambique. In: Bird EC, Schwartz ML (eds) The World’s coastline. Van Nostrand Reinhold, New York, pp 669–677

    Google Scholar 

  • Ullgren JE, van Aken HM, Ridderinkhof H, de Ruijter WPM (2012) The hydrography of the Mozambique channel from six years of continuous temperature, salinity, and velocity observations. Deep Sea Res I: Oceanogr Res Pap 69:36–50

    Article  Google Scholar 

  • Ulrich J, Pasenau H (1973) Untersuchungen zur Morphologie des Schelfrandes vor Mozambique nordöstlich der Sambesi-Mündung. Deutsche hydrogr Zeitschrift (Ocean Dynamics) 26:216–225

  • Walford HL, White NJ, Sydow JC (2005) Solid sediment load history of the Zambezi Delta. Earth Planet Sci Lett 238:49–63

    Article  Google Scholar 

  • Wentworth CK (1922) A scale of grade and class terms for clastic sediments. J Geol 30:377–392

    Article  Google Scholar 

  • Wienberg C, Hebbeln D (2005) Impact of dumped sediments on subaqueous dunes, outer Weser estuary, German bight, southeastern North Sea. Geo-Mar Lett 25:43–53. doi:10.1007/s00367-004-0202-1

    Article  Google Scholar 

  • Wiles E, Green AN, Watkeys MK, Jokat W (2017) Zambezi continental margin: compartmentalized sediment transfer routes to the abyssal Mozambique Channel. Mar Geophys Res. doi:10.1007/s11001-016-9301-4

Download references

Acknowledgements

The authors thank the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover (Germany), for permitting access to the original side-scan sonar records from the study area. Tilman Schwenk (University of Bremen, Germany) and the editors are thanked for constructive comments which served to greatly improve the paper.

Author information

Authors and Affiliations

  1. Senckenberg, Südstrand 40, 26328, Wilhelmshaven, Germany

    Burghard W. Flemming

  2. Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, 30655, Hannover, Germany

    Hermann-Rudolf Kudrass

Authors
  1. Burghard W. Flemming
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Hermann-Rudolf Kudrass
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Burghard W. Flemming.

Ethics declarations

Conflict of interest

The authors declare that there is no conflict of interest with third parties.

Additional information

Responsible guest editor: A.N. Green

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Flemming, B.W., Kudrass, HR. Large dunes on the outer shelf off the Zambezi Delta, Mozambique: evidence for the existence of a Mozambique Current. Geo-Mar Lett 38, 95–106 (2018). https://doi.org/10.1007/s00367-017-0515-5

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00367-017-0515-5

Search

Navigation