Coastal Namibia’s Hydrogen Sulfide Emissions

April 1, 2010 by Brad Barrick

Authors:

Brad Barrick

Figures:

Legend:

Satellite true-color image of hydrogen sulfide emissions off the coast of Namibia. Image is taken by MODIS onboard EOS Terra Satellite on March 13th, 2010 at 9:35 UTC. The hydrogen sulfide emissions vary in color from pale green to milky white.

Temporal Information:

Sat, 03/13/2010 - 09:35

Data Description:

The original data for this image, MOD021KM.A2010072.0935.005.2010072191835.hdf, can be obtained from MODIS data server at LAADS web located at Goddard Space Flight Center http://ladsweb.nascom.nasa.gov/data/add.html. Current image is taken from MODIS rapid response system http://rapidfire.sci.gsfc.nasa.gov/ and modified using Google Earth.

Background:

Hydrogen sulfide eruptions have long been common occurrences on the coastal shelf along the coast of Namibia. These eruptions can stretch 200km and envelop several square kilometers [1]. Ocean currents move fertile water from great depths to the surface along the coast. The nutrient-rich waters provide sustenance for phytoplankton and other free-floating marine life. As the plants die and fall to the ocean floor, bacteria quickly feed on them and multiply quickly [3]. This causes the oxygen levels in the water to gradually disappear, allowing anaerobic bacteria to begin breaking down the dead organisms. This anaerobic bacteria gives off hydrogen sulfide as it breaks down the plant remains. The gas accumulates on the ocean floor until it suddenly wells up to the surface. The hydrogen bonds with oxygen to form water, leaving the sulfur behind to sink and causing the oxygen-poor water to turn white and toxic [3].

Relevance:

Although the foul smell of hydrogen sulfide has come to be a part of life for Namibians living near the coast, the extent of the toll this natural phenomenon takes on the area is just being fully understood. To compound the effects of oxygen-starved water on the marine life in coastal Namibia, hydrogen sulfide is a respiratory toxin and fishing is the nation’s third largest industry [2]. Three of the most economically important species of fish to the region, (the pilchard, horse mackerel, and Cape hake) prefer to breed in the area most prone to hypoxic and sulfur-rich water. Even the species of fish that have evolved to survive in oxygen-poor water are susceptible to the high sulfur content present in the water during these events [1]. Additional research can be done to determine if changes in climate influence these hydrogen sulfide events in the Atlantic.

Reference:

[1]Bruchert, Volker, Bronwen Currie, and Kathleen R. Peard. “Hydrogen Sulfide and Methane Emissions on the Central Nambian Shelf.” Progress in Oceanography 83 (2009) 169-179. Science Direct. Web. 25 Mar. 2010.

[2]Tenenbaum, David. “Giant Oceanic Belch.” The Why Files. (2002). http://whyfiles.org/shorties/097ocean_belch/ 25 Mar. 2010.

[3]Weeks, Scarla J., Bronwen Currie, and Andrew Bakun. "Satellite imaging: Massive emissions of toxic gas in the Atlantic." Nature 415.6871 (2002): 493+. Academic OneFile. Web. 25 Mar. 2010.

Citation:

Coastal Namibia’s Hydrogen Sulfide Emissions , Brad Barrick, Journal of Earth Science Phenomena, 2010, 26.

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