EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

A Major Ecosystem Shift in Coastal East African Waters during the 1997/98 Super El Niño as Detected Using Remote Sensing Data

Zoe Jacobs1, Fatma Jebri1, Meric Srokosz1, Dionysios Raitsos2, Stuart Painter1, Francesco Nencioli3, Kennedy Osuka4, Melita Samoilys4, Warwick Sauer5, Mike Roberts1, Sarah Taylor1, Lucy Scott6, Hellen Kizenga7, and Ekaterina Popova1
Zoe Jacobs et al.
  • 1National Oceanography Centre, Marine Systems Modelling, Southampton, United Kingdom of Great Britain – England, Scotland, Wales (
  • 2Department of Biology National & Kapodistrian University of Athens, Greece
  • 3Collecte Localisation Satellites (CLS), 31520 Ramonville Saint-Agne, France
  • 4Coastal Oceans Research and Development–Indian Ocean, Mombasa, Kenya
  • 5Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown 6140, South Africa
  • 6South African Environmental Observation Network, Egagasini Node, Cape Town, South Africa
  • 7Institute of Marine Sciences, Zanzibar, Tanzania

Under the impact of natural and anthropogenic climate variability, upwelling systems are known to change their properties leading to associated regime shifts in marine ecosystems. These often impact commercial fisheries and societies dependent on them. In a region where in situ hydrographic and biological marine data are scarce, this study uses a combination of remote sensing and ocean modelling to show how a stable seasonal upwelling off the Kenyan coast shifted into the territorial waters of neighboring Tanzania under the influence of the unique 1997/ 98 El Niño and positive Indian Ocean Dipole event. The formation of an anticyclonic gyre adjacent to the Kenyan/ Tanzanian coast led to a reorganization of the surface currents and caused the southward migration of the Somali–Zanzibar confluence zone and is attributed to anomalous wind stress curl over the central Indian Ocean. This caused the lowest observed chlorophyll-a over the North Kenya banks (Kenya), while it reached its historical maximum off Dar Es Salaam (Tanzanian waters). We demonstrate that this situation is specific to the 1997/ 98 El Niño when compared with other the super El-Niño events of 1972,73, 1982–83 and 2015–16. Despite the lack of available fishery data in the region, the local ecosystem changes that the shift of this upwelling may have caused are discussed based on the literature. The likely negative impacts on local fish stocks in Kenya, affecting fishers’ livelihoods and food security, and the temporary increase in pelagic fishery species’ productivity in Tanzania are highlighted. Finally, we discuss how satellite observations may assist fisheries management bodies to anticipate low productivity periods, and mitigate their potentially negative economic impacts.

How to cite: Jacobs, Z., Jebri, F., Srokosz, M., Raitsos, D., Painter, S., Nencioli, F., Osuka, K., Samoilys, M., Sauer, W., Roberts, M., Taylor, S., Scott, L., Kizenga, H., and Popova, E.: A Major Ecosystem Shift in Coastal East African Waters during the 1997/98 Super El Niño as Detected Using Remote Sensing Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11951,, 2021.


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