Ocean Dead Zones Swirl Off Africa, Threatening Coastlines with Mass Fish Kills

The world ocean is now a region of expanding oxygen-deprived dead zones.

It’s an upshot of a human-warmed ocean system filled with high nutrient run-off from mass, industrialized farming, rising atmospheric nitrogen levels, and increasing dust from wildfires, dust storms, and industrial aerosol emissions. Warming seas hold less oxygen in solution. And the nutrient seeding feeds giant algae blooms that, when they die and decompose, further rob ocean waters of oxygen. Combined, the two are an extreme hazard to ocean health — symptoms of a dangerous transition to stratified, or worse, Canfield Ocean states.

Coastal Dead Zones -- No Fish Left

(Geographical extent of more than 405 coastal dead zones worldwide. New dead zones discovered by scientists are now traversing mid-ocean regions. Image source: No Fish Left.)

In total, more than 405 dead zones now occupy mostly coastal waters worldwide. Covering an area of 95,000 square miles and expanding, these anoxic regions threaten marine species directly through suffocation or indirectly through the growth of toxin-producing bacteria which thrive in low-oxygen environments.

Mobile, Anoxic Underwater Cyclones

Now, according to new research published in Biogeosciences, it appears that some of these dead zones have gone mobile.

The report finds zones of very low oxygen covering swirls of surface water 100-150 kilometers in diameter and stretching to about 100 meters in depth. The zones churn like whirlpools or eddies. Encapsulated in their own current of water with oxygen levels low enough to induce fish kills, these ‘dead pools’ have been discovered swirling off the coast of Africa in recent satellite photos.

The ‘dead pools’ form as strong ocean eddies break off from West African ocean currents. The eddies create mixing environments near the surface which fuels algae blooms (seen as the light blue coloration in the image below). Large algae blooms are trapped in the eddy and as the algae die, they rob the water column of oxygen. The flows of the eddy form as a kind of wall to mixing with higher oxygen surrounding waters. As a result, the oxygen readings within the dead pool plummets.

Dead Pool Eddy 2

(Newly discovered ocean dead pools like the one shown above are propagating off the coast of West Africa. These eddies are mobile dead zones of low oxygen water. A new phenomena, they represent a unique threat to ocean health in addition to the 405 other, mostly stationary, dead zones in the world’s coastal waters. Image source: Biogeosciences.)

According to lead-author Johannes Karstensen, a researcher at GEOMAR, the Helmholtz Centre for Ocean Research Kiel, in Kiel, Germany:

“The fast rotation of the eddies makes it very difficult to exchange oxygen across the boundary between the rotating current and the surrounding ocean. Moreover, the circulation creates a very shallow layer – of a few tens of meters – on top of the swirling water that supports intense plant growth. From our measurements, we estimated that the oxygen consumption within the eddies is some five times larger than in normal ocean conditions.”

Researchers found levels in these swirls to be less than 0.3 millilitres of oxygen per litre of seawater or about 1/100th the oxygen content of surrounding ocean. These are readings low enough to produce mass fish kills and to support production of toxin-producing bacteria harmful to oxygen dependent life.

Azores Downrange of Dead Pools

The zones were observed moving through the Tropical North Atlantic west of Africa. They propagated toward the north and west, finally petering out about 100 kilometers north of the Azores. This puts that East Atlantic archipelago directly in the line of fire of these new, low-oxygen eddies. A cause for concern. If one of these eddies were to enter the Azores the result could be a massive fish die off around the island chain.

Karstensen notes:

“…it is not unlikely that an open-ocean dead zone will hit the islands at some point. This could cause the coast to be flooded with low-oxygen water, which may put severe stress on the coastal ecosystems and may even provoke fish kills and the die-off of other marine life.”

Observations of these dead pools seems to indicate they are a new event. A possible result of nutrient enrichment of the surface waters in West African currents due to increased run-off or surface water nitrogen and dust seeding. As extreme rainfall events related to climate change wash more sediment down rivers and into the oceans, as more nitrogen compounds and particulate matter hit the atmosphere due to fossil fuel emissions, wildfire burning, and dust storms, and as sea level rise starts to flood nutrient-rich low lying areas, it is possible that the Tropical Atlantic dead pools represent an emerging ocean state that will grow more prevalent as time moves forward.

(UPDATED — 2037 EST, 5 May, 2015)


Dead Zones Moving West

Dead Zones Found in Atlantic Open Waters

VIMS: Dead Zones

No Fish Left

Ocean Dead Zones

Through the Looking Glass of the Great Dying

Hat Tip to Colorado Bob

Hat Tip to DT Lange

Hat Tip to Jeremy Beck

Leave a comment


  1. Dead zones off W Africa, drought and conflict zones onshore


  2. rustj2015

     /  May 5, 2015

    Maybe some readers will want to react to this dead zone:
    it’s an e-mail petition:
    Don’t Let Republicans Gut NASA’s Climate Change Research

    and if this is a no-no here, please let me know and pardon me…

  3. Great interpretation of this new phenomenon. Even I can understand it.

    Below a succinct summary of the 200 year “bipolar seesaw” –


  4. Colorado Bob

     /  May 5, 2015

    Another source of nutrient-rich fertilization for these dead zones –

    The Sahara desert is a key source of dust storms, particularly the Bodélé Depression[5] and an area covering the confluence of Mauritania, Mali, and Algeria.[6]

    Saharan dust storms have increased approximately 10-fold during the half-century since the 1950s, causing topsoil loss in Niger, Chad, northern Nigeria, and Burkina Faso. In Mauritania there were just two dust storms a year in the early 1960s, but there are about 80 a year today, according to Andrew Goudie, a professor of geography at Oxford University.[7][8] Levels of Saharan dust coming off the east coast of Africa in June (2007) were five times those observed in June 2006, and were the highest observed since at least 1999, which may have cooled Atlantic waters enough to slightly reduce hurricane activity in late 2007.[9][10][11]

    Bodélé Depression

    Dust storms from the Bodélé Depression occur on average about 100 days per year,[1] one typical example being the massive dust storms that swept over West Africa and the Cape Verde Islands in February 2004.[2][3] As the wind sweeps between the Tibesti and the Ennedi Mountains in Northern Chad, it is channeled across the depression. The dry bowl that forms the depression is marked by a series of ephemeral lakes, many of which were last filled during wetter periods of the Holocene.

    Diatoms from these fresh water lakes, once part of Mega-Lake Chad, now make up the surface of the depression and are the source material for the dust,[1] which, carried across the Atlantic Ocean, is an important source of nutrient minerals for the Amazon rainforest.


  5. Good thorough post, Robert. Another system undergoing profound changes.
    Thanks for being “on top” of things.

    I want to add that atmospheric nutrients, such as nitrogen, feeds algae blooms.
    N, or NOX, deposition in the environment keeps popping up ( I evidence here in PDX, as well.) as a real threat to ecosystems and “ocean biogeochemistry’.

    Geophysical Research Abstracts
    Vol. 17, EGU2015-10209, 2015
    EGU General Assembly 2015

    Impact of increased anthropogenic atmospheric nitrogen deposition on
    ocean biogeochemistry

    n the last century, the strong increase in anthropogenic emissions and agricultural activities brought about a tripling in atmospheric nitrogen deposition (AND) rates to oceans. There is growing evidence for a strong fingerprint of increased AND on aquatic systems. Increases in excess N over P (N*) have been attributed to the growing
    anthropogenically sourced N-deposition in the North western Pacific (Kim et al. 2011) and the North Pacific…
    …We simulate detectable signals in N* in the northern hemisphere
    as well as a complex pattern of increases and decreases in ocean productivity, with the former causing an expansion of oxygen minimum zones and an increase in water column denitrification. The increase in AND also reduces the ecological niches for N2-fixers, causing a substantial decrease in global ocean N-fixation. Despite this increase
    in N-loss by denitrification and decrease in N-gain by N-fixation, the increase in AND has put the global marine N-budget severely out of balance…


    • Atmospheric emissions + agriculture… May need an additional note.

    • And updated. Thanks for the additional material DT, CB, and Beck.

      • Thanks, Robert.
        And I add another possible aspect to the dynamic of the hypooxia, and nutrients for algae blooms — that of the decay of marine life corpses caused by the hypoxia. The decay may provide nutrients. I don’t know the answer but as a general rule in nature: where there is death there is decay — and so on. ?


    • F3s in Germany. Now there’s a rather uncommon event.

      We have instability due to a trough running out of the Arctic and very warm weather over the Med. Kinda the same dynamic that happens in the Great Plains of the US with Arctic air over Canada and tropical air in the Gulf colliding. Usually the Gulf Stream prevents this sort of thing for Europe. But this year the Gulf Stream is plugged up in the North Atlantic with a very hot pool off the US East Coast.

      Odd and ugly weather pattern. Adding in El Nino makes this thing a real bit of work for rational forecasting.

  6. Colorado Bob

     /  May 5, 2015

    Climate drives ‘new era’ in Arctic Ocean

    Changes in the Arctic Ocean are so profound that the region is entering what amounts to “a new era”, according to Norwegian scientists


    • Colorado Bob

       /  May 5, 2015

      “Typically, there’s much less life underneath first year ice – multiyear ice is more complex, with more ridging and typically has more animal life,” he said.

      “So what has been seen around the Arctic is these animals that live underneath the ice – crustaceans, amphipods, and copepods – the biodiversity has gone down and their abundance and biomass have also gone down in the areas that have been measured.

      “That is a very serious concern because these animals are important prey items for sea birds feeding on the ice edge and for the marine animals that feed on them.”

  7. Colorado Bob

     /  May 5, 2015

    Melting Arctic ice changing weather patterns, scientists say

    As ice melts the open water is absorbing more heat. That makes it harder for Arctic cod to survive. The cod thrive on cold water at about 3C. The fish feeds the seals that feed polar bears.

    But scientists predict by the end of the century, Arctic sea temperatures could rise to 10C to 13C, dramatically affecting that crucial food chain.

    “Warm water is not good for cod and that will have real consequences for other marine mammals,” said Dr. Ed Farley with NOAA’s Alaska Fisheries Science Center. Farley points out scientists are already seeing polar bears hunting for other types of food.

    “More polar bears, because of loss of sea ice, are resorting to more land-based food and that land-based food has been determined as more junk food. It’s not as high in fat content as their normal prey [seals] are,” Farley told reporters.


    • Arctic waters warming by 10 to 13 C and there are still some that expect no hydrate feedback? That is just an outrageous amount of warming. Greenland melt will tamp down some of it. But nowhere near enough ice in the North to provide enough negative feedback for all.

      Goodness what an absolute mess.

  8. Griffin

     /  May 5, 2015

    Another effect of changing ocean currents, disruption of the bacteria that feed on methane seeps. Not hard to guess that this will have some sort of an impact on the amount of gas that makes it to higher levels in the water column somewhere.

    • Griff —

      That’s a good bit of research. But the long term trend, under warming, would tend to be for a slowing of ocean currents. So that may be a bit of a silver lining. That said, I doubt the methanophiles would be enough to cap all the methane in bottom zones that will be under threat in a business as usual or possibly even a mid-range scenario. Huge threat for more anoxia as well.

  9. Colorado Bob

     /  May 5, 2015

    A week of deluge and severe weather
    After years of intense drought, the plains of West Texas are soaking up one of their best episodes of spring rainfall in years. Several rounds of storms overnight produced 24-hour rainfall totals of 3 – 5” from the Lubbock area south toward Midland, and one cooperative observer in the town of Tahoka reported 9.10”. Four of the last six years gave Lubbock less than 13” of rain each, so apart from localized flash flooding, this is a much-appreciated dousing. As energy dives in and out of the upper-level low over the Southwest, the corridor of repeated storm development will shift only very slowly eastward over the next few days. This will keep the tap running from Texas across Oklahoma and Kansas as well as northeast Colorado, where atmospheric moisture is at near-record levels for this time of year.


    • Colorado Bob

       /  May 6, 2015

      ” As system nears a tipping point , it moves to it’s extremes. From one extreme to the next .”

      The drought at Tahoka, and most of Texas , was marked by the most extreme rain events Lubbock ever saw, and then the rain stopped. And this last drought in Texas beat every other drought like a drum.

      Now these crazy lazy lows drift into the region , and rains like Oregon in Dec. Hour after hour. The rain in West Texas used to come with big towering clouds . And in 30 mins. it was gone and the sun came out.

      Not anymore. But this system is going to cure a lot of peoples problems , so I’m not beefing, it’s just so usual, and strange.

    • There’s your subtropical jet. Big moisture plume off our, now moderate, El Nino. Near record levels apparently.

  10. Andy in San Diego

     /  May 6, 2015

    It almost appears as though new micro environments are forming which have no precedence in our known history and form because nature does what nature does. Could this be the start of the “new world” ecosystems developing?

    Hyper hypoxia zones that favor anaerobic lifeforms. Other such deltas from our norm occurring in both ocean and on land, gradually forming the new earth bio systems. One that will favor successful species, of which we may or may not be one.

    • If you’re going to low oxygen life, then you’re going back in time. Back before the oxygen crisis in the 2.4-2.5 billion year ago interval. All the way back to the Archean.

      You’re talking ancient, ancient life. And much of it is pretty toxic to existing forms.

      • Andy in San Diego

         /  May 6, 2015

        I could see oceanic areas (small ecosystems, subsections) becoming less oxygen rich, others perhaps more. Some areas becoming acidic, others not (deltas and run-off). Land based changes such as high temps and full light in the summer, dark in the winter (arctic). Desert, dry, infrequent catastrophic rainfalls. New locales for which there are no proxies today, or very limited.

        We see things in human terms from our experience. When perhaps we are creating alien environments on our planet.

      • Add in a lid of fresh water expanding from the poles, diverting salty, warm tropical waters to the basal zones. Add in a rising chemocline, with nasty toxins upwelling and painting waters in neons or just matt black. Add in an ocean that is basically upside down, with cool, fresh water at the surface in the meridional and polar zones and warm water at the ocean bottom. Add in sea creatures that cling to a thin veil of oxygenated waters at the surface. Add that to your patchwork of fragmented ecosystems and we might be getting a decent picture of it, Andy.

    • Don’t look now, but WWB in the West Pacific just kicked up a notch. Broad zone that is likely a gale along the equator now. Seems to be emerging as modeled.

      Wili, Tom, if you’re lurking, may want to take a look at nullschool. Rather decent fetch as well.

      • Phil

         /  May 6, 2015

        One comment on Neven’s site that GFS is now forecasting possibility of a much stronger and longer WWB event as well. Will be interesting to see if this continues and if it does actually eventuate.

      • Tom

         /  May 6, 2015

        Thanks robert, i read your blog every day, especially the comments. By now it’s abundantly clear where we’re headed.

    • Cheers, Kevin. Thanks for the link.

    • That said. We are looking at SLR now. And we just have one study showing 4.4 mm per year, which is a substantial uptick in our current context. We have other references showing near 4 mm per year increases since 2009. And we are in the context of what appears to be a time of rapidly destabilizing ice sheets.

      So this is worth a good hard look. And, no, this is not something that is easy to pin down because the Earth system can tend to deviate from the neat curves when perturbed.

      • Phil

         /  May 6, 2015

        In James Hansen’s interview on Radio national, he mentioned sea level rise of a up to a couple of meters in 30 to 40 years if ice sheet mass loss continues to evolve – is nonlinear and now occurring at a faster and faster rate. Something about a ten year doubling period with this based upon over a decade of satellite observation.

      • At 405 ppm CO2 and 485 ppm CO2e, missing the 2 C mark this century is dependent upon rapidly stopping fossil fuel burning and halting methane emissions so that atmospheric methane falls. It’s also dependent on the global carbon store behaving itself. A lot of ifs. But even in the best case, even if we miss the 2 C mark this century and go to zero human emissions and the global carbon store behaves itself that still gives us at least 2-3 C warming long term unless humans are able to manage things so that we have a falling CO2 curve as well.

        There’s a bit of a window for that, and it also requires luck. Not something I’d place bets on, though. And it’s a window that’s pretty rapidly closing.

        Wouldn’t call him out of touch. Just hopeful.

        Now, when it comes to sea level rise, I think the situation is worse in that the best we can probably hope for now is 15 feet locked in long term. Too many large glaciers moving at this time.

  11. Colorado Bob

     /  May 6, 2015

    The Heartland Inst. is making a major push –

    A. The director of science at the Heartland Inst, is a convicted felon.

    B. Jay Lehr, Ph.D. at the Heartland.

    Is convicted a felon.

    Jay Lehr, Ph.D. (jlehr@heartland.org) is science director at The Heartland Institute, an independent nonprofit organization based in Chicago.


    He pleaded guilty to defrauding the EPA doing ground water studies.

    Jail Sentence Conviction for Defrauding Taxpayers on EPA Contract.

    On April 26, 1991, Jay Lehr was charged for falsifying employee time sheets used to bill the U.S. Environmental Protection Agency during his time as president of the National Water Well Association (NWWA), which was contracted by EPA. Lehr served three months of a six month sentence in a West Virginia prison and NWWA was fined over $200,000, leading to Lehr’s resignation as president of NWWA.[4].


    The director of Science at Heartland is convicted felon.

    Please share this. He padding time cards . What a punk.

    The leading denier group today has a convicted felon as it’s science director.

    As far as I know James Hanson, and Richard Alley have never had a parking ticket.

    • The list of felons serving US conservative orgs and government agencies just grows longer and longer, doesn’t it? Seems he’s been defrauding EPA since jump.

      • Colorado Bob

         /  May 6, 2015

        He’s been there for years. While they attack good people for fraud. Over , and over. He plead out. he’s a real worm in giant can of worms. These people need a taste of their own medicine.

      • I think you’re right…

  12. Colorado Bob

     /  May 6, 2015

    RS release this comment with 2 links, you’ll love it.

  13. http://siberiantimes.com/ecology/opinion/features/f0099-new-warning-about-climate-change-linked-to-peat-bogs/
    A leading Siberian scientist has delivered another stark warning about climate change and said melting peat bogs could speed up the process.

    • rustj2015

       /  May 6, 2015

      Ai yi! Starkness, starkness, as humorta said:

      “Nobel Peace Prize winner Professor Oleg Anisimov said there is now evidence that temperatures are rising four times faster in the frozen region than the rest of the planet.”

      It would mean open water at the top of the world by 2050, with nothing more than a few floating icebergs where the North Pole was once located.”

      and a lot of methane….

  14. jyyh

     /  May 6, 2015

    Dear me, I read the update date to be 2037, est.(imated) 5 May, 20:15 and thought you had a time machine to check if the Azores fishing has ended. But no, this is serious already. Not a thing constructive to contribute, but might these have their origin off Namibian coasts that have had some HAB events with risen H2S and other nasty stuff?

  15. The image of the swirling dead zone is very striking. And the fact it contains only 1% of the oxygen of the surrounding ocean means that it is extremely lethal. It looks as if a cartoonist drew a wormhole to another dimension and pasted it in a satellite image. It looks completely unreal, and totally terrifying.

  16. Nice to see an emphasis on the oceanic dead zones, one of many aspects of overshoot besides climate that reflect a human population way beyond earth’s capacity to sustain. This sort of readily available information about the myriad dieoffs in the oceans around the world should be enough to stifle the foolish panic about Fukushima radiation in the Pacific, but often isn’t. Of course I am sure you Robert and your readers are familiar with Jeremy Jackson’s valient efforts to educate the public about the Ocean Apocalypse. In his most recent lecture he has turned to emphasizing sea level rise, having despaired that humans care about anything other than immediate, personal threats, so I recommend an earlier version: https://www.youtube.com/watch?v=2zMN3dTvrwY

    • It’s absolutely climate related. But, yes, even if you stop warming and keep loading up the oceans with nitrogen and phosphates, you still have trouble. It’s just much, much worse with warming driving it all.

  17. james cole

     /  May 6, 2015

    Our oceans make earth a habitable planet. Too many people think the oceans can absorb all the pollution and global warming we generate. When ocean food chains start to collapse, when overly warm ocean water generates killer storms, when warm water changes currents that produce climates for regions, when all that happens, we face trouble that politicians are refusing to admit or acknowledge can and will happen.
    Where my family comes from in Sweden, they have lived off of agriculture and fishing since 2,000 BC or earlier. The seas around Sweden are now largely dead, or the fish are small and toxic. By law, a buyer of Baltic or Kattegat fish must be warned of their potential toxic effects. Go into a fish shop in southern Sweden and pick out some fish, and the store clerk should by Swedish law give you a health warning, or it must be posted in the store by size and fish type. The waters of Kattegat, once full of commercial and sport fishing, is a dead sea full of jelly fish.

    • How long has it been this way, James?

      • james cole

         /  May 6, 2015

        Been a problem since the 1950’s growing worse each year. Since the 80’s the Kattegat has gone dead, now it is a corpse.

        • I had heard the EU tried some programs to reduce these dead zones. Apparently, they weren’t too effective.

  18. Robert In New Orleans

     /  May 6, 2015

    So this is another unknown unknown? :-/

  19. Erial A Secas.

     /  May 7, 2015

    Spanish translation of the article:
    Los océanos son ahora una región donde se expanden las zonas muertas privadas de oxígeno.
    ‘Balsas muertas’ recién descubiertas como la mostrada anteriormente se propagan por la costa de África Occidental. Estos remolinos son zonas muertas móviles de agua con poco oxígeno. Un nuevo fenómeno, que representa una amenaza única para la salud del océano, sumada a las otras 405 zonas muertas mayormente inmóviles en las aguas costeras del mundo.

  20. Rotha Jago

     /  May 9, 2015

    Dead Zones around the coasts???
    Could it be the herbicides and industrial chemicals being washed into the oceans and rivers?

    • It’s a combination of warming resulting in lower oxygen content and run off of mostly fertilizers — phosphates and nitrogen rich compounds. In addition, nitrogen + aerosol emissions from smokestacks enhance the effect. The net result is a high nutrient loading of near shore waters. The nutrients feed large algae blooms. The blooms, when they die and decompose further deprive ocean water of oxygen. Added to the net impact of warming and stratification, you get dead zones.

  21. Is there any public or leadership awareness on this issue? Is anything substantial being done to stop or slow it?

  1. Freaky Algae Bloom in North Atlantic Looks Like Dead Zone Eddy | robertscribbler
  2. The Hothouse Breeds More Toxic Waters — Lake Eerie ‘Painted Green’ By Enormous Algae Bloom | robertscribbler
  3. Tumbling Down the Rabbit Hole Toward a Second Great Dying? World Ocean Shows Signs of Coming Extinction. | Basic Rules of Life
  4. NCAR: Global Temperature Increase Depletes Oxygen in Most Ocean Zones by the 2030s | robertscribbler

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