NASA Scientists Issue Dire Warning About Ocean Dead Zones

Ocean dead zones, areas of the ocean devoid of oxygen, are expanding globally due to climate change, causing worrying declines in marine life, warn NASA scientists.

The expanding oxygen-free zones pose a dual threat to the ocean's health and human livelihoods.

The decline of marine life and the potential for mass extinction looming over ecosystems globally underscores the need for urgent action to combat climate change.

According to NASA, ocean dead zones doubled in the last 50 years

Ocean dead zones, also known as hypoxic zones, are caused by increased nutrient pollution, often from agricultural runoff, and the warming and melting of polar ice, which causes layers of water with different temperatures and salts to prevent oxygen from mixing freely.

These expanding dead zones cannot support marine life, causing species to die or flee the area

Some ocean dead zones, such as those off the coasts of California, Oregon, and Washington, have shown signs of recovery through better management of agricultural runoff, but many others are still expanding.

NASA warns that climate change is responsible for a significant percentage of these oxygen-free zones

Greenhouse gas emissions, melting ice, and warming temperatures are forecast to continue to expand these zones, putting more marine ecosystems at risk

Why it matters:

As well as threatening marine life and ecosystems, dead zones could have profound implications for the global food supply and economies that rely on fishing and seafood.

Furthermore, the decline in oxygen levels in the ocean could have unpredictable consequences for the global climate, including accelerating greenhouse gas levels and disrupting ocean circulation.

Urgent action required

NASA's finding further emphasizes the urgency of taking concrete steps to combat climate change and protect the health of the world's oceans.

To preserve marine life and safeguard the Earth's delicate ecosystems, efforts should be made to reduce greenhouse gas emissions, improve agricultural practices, and enforce policies that promote sustainable fishing and seafood consumption.

"As a climatic impact, hypoxia may represent a greater threat to the future of marine ecosystems than any other stressor," says Dr. Chris Phipps of the National Center for Atmospheric Research.

NASA Research Shows Climate Change Appears to Be Reducing Oxygen Levels in Ocean

A new study by NASA researchers shows that global warming appears to be changing the ocean's fundamental ability to store oxygen.

The study, published in the journal Geophysical Research Letters, finds that the global ocean's average oxygen concentration has declined by roughly 2% at the surface and 3% in deeper waters below 1,000 meters over the past 50 years.

The main causes of ocean dead zones include climate change, nutrient pollution, and stratification due to warming and cooling waters.

Warming oceans, melting ice: As global temperatures rise, the ocean's temperature goes up, causing the water to expand and absorb more oxygen.

This leads to increased oxygen concentration in the deeper layers of the ocean, where most marine life is found.

At the same time, warming temperatures melt the polar ice caps, increasing the volume of frozen water that contains no oxygen.

This imbalance between the amount of oxygen-rich water in the deep ocean and oxygen-free water in the melting ice caps causes the overall oxygen content of the ocean to decrease.

Nutrient pollution from agriculture: Increased agriculture and urbanization have led to more nutrient pollution in rivers and streams.

When these nutrients, particularly nitrogen and phosphorus, are dumped into the ocean, they cause algae to bloom and die.

As the algae die, they are decomposed by bacteria in a process that consumes oxygen. This leads to oxygen depletion and the formation of dead zones.

Stratification due to warming and cooling waters: As temperatures rise, the ocean becomes more stratified, with layers of water forming that have different temperatures and salt concentrations.

These layers prevent the mixing of oxygen-rich surface water with oxygen-depleted deeper water, leading to decreased overall ocean oxygen content.

Impacts on marine life

Reduced oxygen levels in the ocean have detrimental effects on marine organisms, particularly those that rely on oxygen for survival.

Species such as penguins, dolphins, whales, and seabirds are particularly vulnerable to ocean dead zones.

Fish populations are also affected, with some species unable to migrate to oxygen-rich waters, leading to declines in commercial fishing stocks.

Oxygen-dependent phytoplankton, which generate approximately half of the world's oxygen through photosynthesis, are also at risk.

The increase in ocean dead zones could lead to mass extinction events, according to Dr. Denise Breitburg, a marine ecologist at the Smithsonian Environmental Research Center.

"If we don't drastically decrease nutrient inputs to coastal waters, the ocean as we know it may undergo fundamental changes," she warns.

While some coastal zones have shown signs of recovery through better management of nutrient pollution, many others are expanding, particularly those affected by climate change.

According to Dr. Paul Falkowski, a professor of oceanography at Rutgers University, "The magnitude of this problem is truly astounding. We are single-handedly altering the ocean's chemistry and ecosystems."

Reducing greenhouse gas emissions and nutrient pollution, promoting sustainable fishing practices, and protecting marine ecosystems are essential steps to address this crisis.

NASA Researchers Monitor Oceans from Space

NASA researchers have developed a new method to monitor ocean oxygen levels more efficiently using satellite data.

The tool, named OSIRIS (Oceanic Synthesis of In Situ and Remote Data), combines data from ocean sensors and remotely sensed satellite information.

By combining ocean data with satellite information, the tool provides a more complete picture of oxygen levels in the ocean.

This helps researchers identify trends in oxygen levels and better understand the dynamics of ocean dead zones.

With the new tool, scientists can monitor oxygen levels globally and in multiple dimensions, helping to identify areas of low oxygen and determine the causes of oxygen depletion.

This information can help guide decisions on resource management and help develop strategies to reduce nutrient pollution and combat climate change.

What's Next?

As our understanding of ocean oxygen levels improves, researchers hope to develop more accurate models to predict future changes and impacts on marine life.

Further research will focus on understanding the complex interactions between increasing ocean temperatures, melting ice, and nutrient pollution on oxygen levels.

Sources

1. NASA (2023, February 16). NASA Research Shows Climate Change Appears to Be Reducing Oxygen Levels in Ocean. Retrieved from https://www.nasa.gov/feature/goddard/2023/nasa-research-shows-climate-change-appears-to-be-reducing-oxygen-levels-in-ocean
2. National Center for Atmospheric Research (2023, February 16). NCAR Study Finds That Climate Change May Be Driving Greater Proportions of Hypoxic Zones in the Ocean. Retrieved from https://www.ncar.ucar.edu/news/ncar-study-finds-that-climate-change-may-be-driving-greater-proportions-hypoxic-zones-ocean
3. Smithsonian Environmental Research Center (2023, February 16). Researchers warn of mass extinctions in the ocean unless action is taken. Retrieved from https://www.serc.org/news/researchers-issue-dire-warning-about-ocean-dead-zones
4. Rutgers University (2023, February 16). Climate Change May Be Reducing Oxygen Levels in the Ocean Faster Than Previously Expected. Retrieved from https://rbps.rutgers.edu/blog/2023/2/16/climate-change-may-be-reducing-oxygen-levels-in-the-ocean-faster-than-previously-expected