Dramatic expansion of dead zones in the oceans

January 25, 2009

Unchecked global warming would leave ocean dwellers gasping for breath. Dead zones are low-oxygen areas in the ocean where higher life forms such as fish, crabs and clams are not able to live. In shallow coastal regions, these zones can be caused by runoff of excess fertilizers from farming. A team of Danish researchers have now shown that unchecked global warming would lead to a dramatic expansion of low-oxygen areas zones in the global ocean by a factor of 10 or more.

Whereas some coastal dead zones could be recovered by control of fertilizer usage, expanded low-oxygen areas caused by global warming will remain for thousands of years to come, adversely affecting fisheries and ocean ecosystems far into the future. The findings are reported in a paper 'Long-term ocean oxygen depletion in response to carbon dioxide emissions from fossil fuels' published on-line in the scientific journal Nature Geoscience.

Professor Gary Shaffer of the Niels Bohr Institute, University of Copenhagen, who is the leader of the research team at the Danish Center for Earth System Science (DCESS), explains that "such expansion would lead to increased frequency and severity of fish and shellfish mortality events, for example off the west coasts of the continents like off Oregon and Chile".

Large extinction events

He adds that "if, as in many climate model simulations, the overturning circulation of the ocean would greatly weaken in response to global warming, these oxygen minimum zones would expand much more still and invade the deep ocean." Extreme events of ocean oxygen depletion leading to anoxia are thought to be prime candidates for explaining some of the large extinction events in Earth history including the largest such event at the end of the Permian 250 million years ago.

Series of changes

Furthermore, as suboxic zones expand, essential nutrients are stripped from the ocean by the process of denitrification. This in turn would shift biological production in the lighted surface layers of the ocean toward plankton species that are able to fix free dissolved nitrogen. This would then lead to large, unpredictable changes in ocean ecosystem structure and productivity, on top of other large unpredictable changes to be expected from ocean acidification, the other great oceanic consequence of high atmospheric carbon dioxide concentrations from fossil fuel burning.

Professor Shaffer warns that as a result, "the future of the ocean as a large food reserve would be more uncertain. Reduced fossil fuel emissions are needed over the next few generations to limit ongoing ocean oxygen depletion and acidification and their long-term adverse effects".

Paper: Nature Geoscience Advanced Online Publication: www.nature.com/ngeo/journal/va … /ncurrent/index.html

Source: University of Copenhagen

Explore further: Uncharted waters: Scientists to explore Indian Ocean depths

Related Stories

Uncharted waters: Scientists to explore Indian Ocean depths

January 24, 2019

Scientists prepared Thursday to embark on an unprecedented, years-long mission to explore the Indian Ocean and document changes taking place beneath the waves that could affect billions of people in the surrounding region ...

Tiny killer threatens giant clam, aquatic emblem of the Med

January 25, 2019

With wing-shaped shells lined with iridescent mother-of-pearl and producing the fibres of rare and delicate sea silk, the noble pen shell clam is one of the most emblematic species in the Mediterranean and a bellwether for ...

Recommended for you

The powerful meteor that no one saw (except satellites)

March 19, 2019

At precisely 11:48 am on December 18, 2018, a large space rock heading straight for Earth at a speed of 19 miles per second exploded into a vast ball of fire as it entered the atmosphere, 15.9 miles above the Bering Sea.

Revealing the rules behind virus scaffold construction

March 19, 2019

A team of researchers including Northwestern Engineering faculty has expanded the understanding of how virus shells self-assemble, an important step toward developing techniques that use viruses as vehicles to deliver targeted ...

OSIRIS-REx reveals asteroid Bennu has big surprises

March 19, 2019

A NASA spacecraft that will return a sample of a near-Earth asteroid named Bennu to Earth in 2023 made the first-ever close-up observations of particle plumes erupting from an asteroid's surface. Bennu also revealed itself ...

Nanoscale Lamb wave-driven motors in nonliquid environments

March 19, 2019

Light driven movement is challenging in nonliquid environments as micro-sized objects can experience strong dry adhesion to contact surfaces and resist movement. In a recent study, Jinsheng Lu and co-workers at the College ...


Adjust slider to filter visible comments by rank

Display comments: newest first

2.4 / 5 (14) Jan 25, 2009
Global warming is a hoax. So are these so-called "dead zones". The oceans are huge and filled with life. How can mere humans even begin to affect it in any significant way?
3.4 / 5 (5) Jan 25, 2009
And yet, here:


The same conditions sre causing unprecedented growth in fish and other sea life in the Nile delta, even though the warming there has been about the same or a little more than Oregon. Chile has shown no warming whatsoever in the last thirty years.


Is the science really settled, or do we need thirty or forty more years to get this right?
2.7 / 5 (13) Jan 25, 2009
Good to see the reality denialists are on top of things. Keep up the good work, kerry and MikeB. Big oil and king coal need people like you to spread their gospel of lies, distortions, and obfuscation to keep the American people enslaved to fossil fuels. Maybe they'll send you a coupon some day for all your efforts.
1.5 / 5 (4) Jan 25, 2009
I was totally being sarcastic. I'm not so sure about Mike, though..
3.3 / 5 (12) Jan 25, 2009
science is never settled. Science is THEORY, the only fact of any kind that exists in the universe as a relational aspect for for fleshy humans is that: There Are No Facts -of any kind. PERIOD.

All is theory.

If science exists as established facts, then all you do is set yourself up to fall off the rails at a later date. The idea of scientific facts is a crutch for the feeble minded person who NEEDS to believe in permanence and one who also has black and white values. These types of persons are DANGEROUS--to all of us.

it's too bad that this insanity is what they teach in schools. Law this, Law that. Fuck that shit.

This type of thinking categorically disallows for the new and or the undiscovered and disallows any observations to take place that might even allow for a new thing or new exploration. 'New' -always- changes or disproves the old and the established--this is the nature of discovery.

So please remember that all science is theory and can be changed at the blink of an eye--and then you can allow new thoughts and new ideas to shape your mind, to help you literally walk into the future.

Otherwise, you are dead where you stand.

What does this ahve to do with ocean dead zones? Not much. But shen someone mentions 'scientific facts', I just want get up on the table and just take a giant dump in their cornflakes, for that is what they deserve. Why?

It's what they deserve for not even understanding that nothing is 'real' and there are no facts. Then we can finally move forward into the new.

Something they knew, for the most part when they where young..but the professors (manytimes they are professors because they are incapable of real work in their fields-remember that) then encountered drilled it out them.

Law of this..Law of that. Such horseshit.
3 / 5 (8) Jan 25, 2009
Breaking News: Computer modeling shows that collision of Earth with rogue star would reduce fish population.

Note that we haven't proven such a collision will occur. But if it does, boy will there be some dead zones.

More extrapolation masquerading as science.

Next Week: Invasion by Fire Breathing Venusian Dragons could endanger old growth forests.
4.3 / 5 (6) Jan 26, 2009
This article postulates a POSSIBLE result based on an ASSUMED (and IMHO bogus) "unchecked global warming." Only if you can acknowledge and agree to such very narrow pre-conditions of the study (whether right or wrong), can the result be considered valid FOR THOSE LIMITED CONDITIONS.

Valid or not, this report is so "doomsday" in its assumptions that it tends to seem more like the same old global warming fearmongering and self-fulfilling Chicken Little science. It might help (maybe) if they had at least stated "this report assumes Doomsday pre-conditions".

As if to say that anything humans do (or don't do) could ever prevent nature from doing what nature is going to do. If the earth gets warmer... we adapt. If the earth gets colder, we adapt. if the earth splits into three... well, we better f%#$ing adapt. Until science discovers how humans can predictably control the global thermostat in the face of earth and nature's never-ending dynamic, I won't see it any other way.
1.8 / 5 (5) Jan 26, 2009
The oceans are huge and filled with life. How can mere humans even begin to affect it in any significant way?

90% of big fish in the oceans are gone. We ate them all; that why we have to resort to fish farming for almost half of all fish production.
4 / 5 (4) Jan 26, 2009
Exactly correct Barkster, which is why this kind of approach is so misleading.

Look at the headline: "Dramatic expansion of dead zones in the oceans"

One could reasonably expect an article to follow describing a measured increase in the oceanic 'dead zones', backed by specific data. But the article is not that at all, it is merely another projection that if there is "unchecked global warming" then that might happen. It's like headlining "Dramatic Cure for Cancer Discovered" only to find that the article describes how assuming a cure is found, then hospitals apply it.

Many people only glance through a paper reading the headlines. They will be given the impression that these dead zones are proliferating, and if they glance quickly at the article, that 'global warming' is responsible. Not everyone has the time to scour every source to try to find the truth, and when purportedly scientific publications engage in this kind of chicanery we all lose.

In addition to the trillions of dollars of wealth transfer and power transfer increasingly tied to this fraud, there is the potential for a severe across the board backlash against valid science seeking the truth in all fields. AGW is like Piltdown Man with a huge price tag. If scientists do not come forth and speak against its pernicious falsehoods, we all will stand to lose.
3.8 / 5 (4) Jan 26, 2009
Humans are polluting and fishing the oceans dead, not driving cars to produce too much CO2 and encouraging dead zone growth. If the pro Global Warmers spent as much time re-planting rain forrests as they do concucting theories on how to blames CO2 for all thats wrong with their future, there would be fresher air and happier ppl...
3.1 / 5 (7) Jan 26, 2009
After running the numbers through my HAL-GORE 9000 extrapolation machine, I conclude the following:

Everytime I mash the pedal on my 2.5 ton SUV, 1.2 sparrows fall dead out of the sky. With each and every carbon-dioxide laden breath I take, 0.007 polar bears drown in the arctic ocean. With each explusion of last night's beans, I cause the irreversible loss of 15 mm of glacier.

Of course, I can immediately cause the restoration of each sparrow, polar bear, and ice cap by paying an additional 7% tax to my government.

3.4 / 5 (5) Jan 26, 2009
So Pissorg is now throwing away real science for global warming? I really need to find somewhere else to get my news.

Arkaleus - I think you have it figured out, by golly!
1 / 5 (4) Jan 27, 2009
I don't get what's your problem with global warming or climate change! "The Earth is so big, how could we affect her?" Are you idiots?

The Earth is big, but limited. You don't really think that you can cut forest as much as you like, emit all kind of polluters into the water and the air and still have a working ecosystem that would simply balance your stupidity,right? Maybe in your twisted brains, you can also nuke half the planet and happily live in the other half? Sure, the winds will simply stop blowing in your direction, because you're gonna show them the Bible.

And yes, science is a theory, but the theory best describing the facts and best predicting them. And funnily enough, it's a fact that right where I am, the temperatures are with 20o higher than they are supposed to be at this time of the year. For 2 weeks now. While they are with 20oC lower than they should be in Spain. I wonder why? I guess the gods are just mad on Europe.
5 / 5 (2) Jan 30, 2009
Rubberman I give you credit for recognizing the limitations of the current models and not pushing a "consensus" that the informed realize does not exist.

The economic agenda being pushed certainly raises the stakes. However it should not obscure the fact that much of the ecological argument for AGW is flawed as well.

First, there seems to be an assumption that Earth's ecosystems ought somehow to be frozen in time and henceforth never altered. Rather than a strategy of adapting to change, this clings to a dictum of resisting change at all costs. Is this practical? Is it even possible? Is it wise?

Second, given how little we understand of the immensely complex systems involved, I believe we tend to grossly underestimate homeostatic and reparative mechanisms of the planet. That is an opinion but unless you give it no credence at all, it argues against continually inventing and selling Doomsday scenarios.

Third, in terms of "anthropogenic global warming", the empirical data is still coming in but any honest preliminary appraisal would be that the scare scenarios being pedaled are not bearing out. Far from rising temperatures, rising sea levels, proliferating hurricanes, and all manner of the Chicken Little Buffet the last ten years have shown little or no substantial change as predicted by the AGW alarmists. Instead of asking why the real data is so unimpressive, we are instead treated to more scare scenarios based on data points that aren't there. Co2 has been poured into the atmosphere unabated for a decade; how much has the average global temperature risen?

Fourthly the attempt to suppress dissenting points of view should bring to mind the experience of Gallileo when he claimed facts in evidence that a "consensus" of the thinkers of his day considered heretical. This is not the realm of science but of authoritarian politics. I don't mind at all if you label me a "denier". Feel free to claim that I deny the existance of unicorns as well.

I thank you for your comment, which I found to be of value in spite of our disagreements.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.