Dead Zones Fuel Global Warming

Photo courtesy NASA

Fight disinformation: Sign up for the free Mother Jones Daily newsletter and follow the news that matters.


A new paper in the journal Science reveals that oxygen-deprived (hypoxic) dead zones in the oceans have a far bigger impact than killing fish in local waters. The increased amount of nitrous oxide (N2O) produced in hypoxic waters can elevate N20 in the atmosphere—fueling more global warming and growing bigger atmospheric ozone holes.

Nitrous oxide is a highly potent greenhouse gas and is becoming a key factor in stratospheric ozone destruction. Dead zones are a result of climate change, eutrophication, and changes in ocean currents. The author of the study, oceanographer Louis Codispoti of the Horn Point Laboratory, says:

“As the volume of hypoxic waters move towards the sea surface and expands along our coasts, their ability to produce the greenhouse gas nitrous oxide increases. With low-oxygen waters currently producing about half of the ocean’s net nitrous oxide, we could see an additional significant atmospheric increase if these ‘dead zones’ continue to expand.”

Currently, the number and size of dead zones worldwide is doubling every decade (405 worldwide, last count)—including dead zones covering nearly all of the eastern and southern coasts of the US. The drivers behind most of these dead zones are human activities (fertilizers, livestock farming, burning fossil fuels).

The chemistry goes like this:

  • As dissolved oxygen levels decline in ocean waters, N2O production occurs.
  • In healthy well-oxygenated waters, microbes produce N2O at low rates.
  • But as oxygen concentrations decrease to the point of hypoxic levels, N2O production takes off.

When suboxic (little or no oxygen) waters occur at depths of less than 300 feet, the combination of high microbial respiration rates, plus a process called denitrification, can drive N2O production rates 10,000 times higher than average for the open ocean. Because the ocean is a net producer of N20, much of it will be lost to the atmosphere, driving up the climate impact. The future of marine N2O production depends critically on what will happen to the roughly 10 percent of the ocean volume that’s currently hypoxic and suboxic:

“Nitrous oxide data from many coastal zones that contain low oxygen waters are sparse, including Chesapeake Bay,” says Codispoti. “We should intensify our observations of the relationship between low oxygen concentrations and nitrous oxide in coastal waters.”
 

WE'LL BE BLUNT:

We need to start raising significantly more in donations from our online community of readers, especially from those who read Mother Jones regularly but have never decided to pitch in because you figured others always will. We also need long-time and new donors, everyone, to keep showing up for us.

In "It's Not a Crisis. This Is the New Normal," we explain, as matter-of-factly as we can, what exactly our finances look like, how brutal it is to sustain quality journalism right now, what makes Mother Jones different than most of the news out there, and why support from readers is the only thing that keeps us going. Despite the challenges, we're optimistic we can increase the share of online readers who decide to donate—starting with hitting an ambitious $300,000 goal in just three weeks to make sure we can finish our fiscal year break-even in the coming months.

Please learn more about how Mother Jones works and our 47-year history of doing nonprofit journalism that you don't find elsewhere—and help us do it with a donation if you can. We've already cut expenses and hitting our online goal is critical right now.

payment methods

WE'LL BE BLUNT

We need to start raising significantly more in donations from our online community of readers, especially from those who read Mother Jones regularly but have never decided to pitch in because you figured others always will. We also need long-time and new donors, everyone, to keep showing up for us.

In "It's Not a Crisis. This Is the New Normal," we explain, as matter-of-factly as we can, what exactly our finances look like, how brutal it is to sustain quality journalism right now, what makes Mother Jones different than most of the news out there, and why support from readers is the only thing that keeps us going. Despite the challenges, we're optimistic we can increase the share of online readers who decide to donate—starting with hitting an ambitious $300,000 goal in just three weeks to make sure we can finish our fiscal year break-even in the coming months.

Please learn more about how Mother Jones works and our 47-year history of doing nonprofit journalism that you don't find elsewhere—and help us do it with a donation if you can. We've already cut expenses and hitting our online goal is critical right now.

payment methods

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate