Question by Dana1981: What do you make of the new study concluding that global warming causes oceanic dead zones?
“Under the worst scenario [5-7°C warming], warmer seas and a slowdown of ocean circulation would lower marine oxygen levels, creating “dead zones” that could not support fish, shellfish and other higher forms of marine life — and may not revive for 1,500 to 2,000 years.”
“They would start slowly by the end of this century, it’s not something that would happen tomorrow or in the near future but over the next few generations,”
“Lead scientist Gary Shaffer of the Niels Bohr Institute at the University of Copenhagen said it was unclear, in the grim light of this study, whether future generations could look to the oceans as a major reserve of food.”
http://news.smh.com.au/breaking-news-world/study-predicts-ocean-dead-zones-20090126-7pk2.html
The study abstract (published in Nature Geoscience) concludes:
“substantial reductions in fossil-fuel use over the next few generations are needed if extensive ocean oxygen depletion for thousands of years is to be avoided.”
http://www.nature.com/ngeo/journal/v2/n2/abs/ngeo420.html
What are your thoughts on this study?
Best answer:
Answer by jim z
Warm water holds less oxygen. Warming would exacerbate so called dead zones. Human pollution such as sewage, phosphates, nitrates, etc also tend to increase biologic action which increases dead zones. There have always been dead zones but humans have made them worse. We have made great strides in cleaning up our act.
I noticed the nature article took great leaps in logic to come up with their conclusion that CO2 would cause O2 depletion. I couldn’t open their links but their logic is apparently, CO2 causes warming, warming causes O2 depletion, therefore CO2 causes O2 depletion. When I learned geometry, it was important to make sure your first assumption was correct before jumping to your next.
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8 Comments
peter.jungmann
on 21st Jan, 12 04:01pm
If the earth cools it is certain to create dead zones.
And, as none of the “likely” scenarios cooked up by the fear-mongering AGW promoter crowd have come to pass, there’s virtually nothing to fear from warming caused “dead zones.”
Sounds like a desperate attempt to create more fear of something that doesn’t exist.
dirocyn
on 21st Jan, 12 04:01pm
Scary stuff, but not terribly likely. If we get that level of warming, humans will be unable to sustain our present population and energy use. When we quit adding pollution to the system, life is likely to rebound quickly.
It seems highly unlikely that Earth’s oceans will have dead zones for thousands of years–some form of life (probably phytoplankton) will find an advantage to living where there are fewer things to eat them. Phytoplankton will produce oxygen, and the ocean will eventually be restored.
If (as seems likely) the ocean dead zones are caused by sewage and agricultural runoff (which causes blooms, followed by algae death and rotting–which depletes the oxygen) the most logical step would be to quit dumping sewage into the ocean. Just suppose we were able to put that sewage down a depleted oil well, removing all that material from the carbon cycle. Perhaps we could prevent growth in the oceanic dead zones, and over time reduce atmospheric CO2.
eric c
on 21st Jan, 12 04:01pm
He makes a worst case scenario, and then says we should cut back on fossil fuels because of a worst case scenario. Where would society be if we made decisions based on “worst case scenarios”?
J S
on 21st Jan, 12 05:01pm
Wasn’t that already clear from studies of the Permain-Triassic Extinction? Is there something new in this paper?
We already have dead zones from overfertilization (Gulf Coast) and there’s the growing one off the Oregon Coast that scientists haven’t quite figured out yet (believed to be caused by winds affecting ocean mixing, but they don’t seem to know what’s triggered the change now).
Did the papers’ authors specifically explain and dismiss all of the known dead zones that have recently appeared and their potential relationship to global warming, or is their prediction of this being closer to a 2100 issue completely off-the-cuff?
Given the greater-than-expected warming, glacial melting, and CO2 increases observed in recent years, the timeframe estimate could prove to be a little reckless and irresponsible.
littlerobbergirl
on 21st Jan, 12 06:01pm
oh bugger. its the Permian extinction all over again.
what i read that struck home was;
Professor Shaffer [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.
http://www.sciencedaily.com/releases/2009/01/090125142118.htm
and its already happening;
http://www.sciencedaily.com/releases/2008/05/080501143406.htm
oops! i wandered off into cyberspace for hours, and j.s. beat me to the permian reference. but i think its serious. sulphur bacteria yum.
gwens18a
on 21st Jan, 12 06:01pm
My thoughts? What more can be said other than this is another blow to the food supply to the planetary grandchildren. How much more bad news can the future of humanity take?
Welcome to the Anthropocene.
George
on 21st Jan, 12 07:01pm
God disagrees with the study.
Heretic
on 21st Jan, 12 07:01pm
A fairly old notion about marginal boundaries and oceanic thermal memory. It would be a little more interesting if it had mention carbonate platforms and sea level flux other then (shellfish)? Is that really saying anything new.