Is Climate Change Sapping Oceans of Oxygen?
Around the globe, the effects of climate cannot be ignored. The world is facing some of the biggest environmental challenges the present generations have ever seen. The impact of the climate includes severe heat waves, rising seas, increased insect outbreaks. It is even possible the oxygen may be drained out of the world’s oceans. The loss of ocean oxygen is scary. What will happen to humanity if the world’s oceans are dead?
But are the world’s oceans really running out of oxygen?
A new study has interesting answers to this question, and adds more questions. The study reveals that deoxygenation or a drop in the amount of oxygen dissolved in the oceans due to climate change is already detected in some parts of the world. However, widespread loss of ocean oxygen will be even more evident across large parts of the ocean between 2030 and 2040.
The research team, led by climate scientist Matthew Long, found that deoxygenation caused by climate change could already be detected in the Atlantic basins, southern Indian Ocean and parts of the eastern tropical Pacific. And the bad news is, more widespread detection of deoxygenation caused by climate change is possible between 2030 and 2040.
Climate Change Causing the Deoxygenation of Oceans?
Scientists have asserted that a warming climate can gradually drain oceans of oxygen, endangering marine life.
Matthew Long, one of the climate scientists at the National Center for Atmospheric Research (NCAR), said loss of oxygen in the ocean is one of the serious impacts of a warming atmosphere, and is a major threat to marine life.
It is a known fact that warm waters may result in less oxygen absorption. In warm water, the oxygen that is absorbed has a more difficult time going deeper into the ocean. The scientists explained that as water heats up, it expands, becoming lighter than the water below it and is less likely to sink.
Climate Change May not Be the Culprit For Oxygen Drain
Although there is evidence that deoxygenation of the ocean was caused by warming climate, it is not enough to conclude that climate change is the main culprit of the oxygen drain. The study pointed out that in some parts of the ocean, including areas off the east coasts of Africa, Australia, and Southeast Asia, deoxygenation caused by climate change may not be evident even by 2100.
There is an important factor to consider. One is the natural variability of oxygen concentrations in the world’s oceans.
In addition, Dr. Long said ocean oxygen concentrations naturally vary depending on variations in winds and temperature at the surface.
“It’s been challenging to attribute any deoxygenation to climate change.” – Dr. Long
That is why the study was conducted to determine the impact from climate change to overwhelm the natural variability.
Considering the natural variability
The flow of oxygen in the ocean is interesting and complex. The ocean gets its oxygen supply from the surface from the atmosphere or from phytoplankton, which release oxygen into the water through photosynthesis.
Interestingly, natural warming and cooling is attributed to constantly changing oxygen concentrations at the sea surface. These changes can linger for years or even decades deeper in the ocean. This means cold water would allow the ocean surface to absorb a large amount of oxygen, then flow deeper. The oxygen may then stay in the deep of the ocean for years.
In contrast, hot weather could lead to natural “dead zones” in the ocean. This is where fish, crabs, and other marine life cannot survive.
Study Uses NCAR-based Community Earth System Model to Cut through Natural Variability
To cut through this natural variability and probe the impact of climate change, the research team relied on the NCAR-based Community Earth System Model.
By using output from a project that ran the model more than two dozen times for the years 1920 to 2100, the climate scientists can determine when ocean deoxygenation due to climate change is likely to become more evident than at any point in the modeled historic range.