Oceans Will Become Major Greenhouse Gas Emitter by Century’s End

A new study reports that Earth’s oceans will begin to emit more ozone layer-depleting CFCs than they absorb by 2075.

Acropora corals with colorful bleaching in New Caledonia. (Photo courtesy The Ocean Agency / XL Catlin Seaview Survey)

(CN) — Experts have long believed that the ozone-harming gases known as chlorofluorocarbons, or CFCs, that have been absorbed over the years by Earth’s oceans would have little to no major influence on the planet’s atmospheric health once they have been trapped in the ocean’s depths.

But new research released Monday suggests that, in time, those slumbering gases will be emitted back into the atmosphere faster than the ocean can absorb them — and it will probably happen before the turn of the century.

On top of being home to countless lifeforms and complex ecosystems, the oceans that dominate Earth’s surface also play host to a wide variety of gases that have been claimed by the sea over many years.

Perhaps one of the most famed gases lurking below the ocean are the unique and highly volatile CFCs. For years these gases were widely used as refrigerants and propellants for aircraft and other vehicles before being gradually phased out of common use when their destructive influence on the ozone became more apparent.

Ultimately banned outright in the late 80s by the Montreal Protocol, today Earth has one remaining major collector and supplier of CFCs: the ocean itself.

While this may sound like a potential environmental problem waiting to happen, experts have widely held that any CFC emissions from the ocean are largely trivial and couldn’t amount to a major atmospheric factor — until now.

In a study published Monday in the journal Proceedings of the National Academy of Sciences, researchers used a series of data models to do a deep dive into the likely future of the CFC content of the oceans and found that their environmental role is likely to change dramatically in the future.

Researchers say their models predict that by the year 2075, a specific variant of CFC known as CFC-11 will be so absorbed into Earth’s oceans that the water will gradually become oversaturated with the lingering gas. Once it has become oversaturated, the ocean will have no choice but to begin emitting more CFC-11 than it takes in.

Experts say that after Earth’s oceans can no longer serve as the collective sink for these types of gases, by around 2130 there will enough CFC-11 emissions from the oceans that our manmade detection instruments will begin to pick them up.

“By the time you get to the first half of the 22nd century, you’ll have enough of a flux coming out of the ocean that it might look like someone is cheating on the Montreal Protocol, but instead, it could just be what’s coming out of the ocean,” said Susan Solomon, professor at MIT’s Department of Earth, Atmospheric and Planetary Sciences and co-author of the study, in a statement. “It’s an interesting prediction and hopefully will help future researchers avoid getting confused about what’s going on.”

Researchers say that on top of causing more noticeable CFC-11 ocean emissions, these changes will also result in a longer lifespan for the gases. Once the new emissions from the oceans are taken into account, the data models predict that it will allow CFC-11 to linger in the atmosphere for at least five years longer than it otherwise would.

The temperature of Earth’s oceans are also likely to play a role in this going forward. Experts report that as an ocean gets warmer, it generally becomes a less effective reservoir for gases and will release them back into the atmosphere at a faster rate.

But while rising ocean temperatures as a result of climate change is certainly speeding up the process, it is by no means causing it. The data suggests that as CFCs decay in the atmosphere and become absorbed by the ocean, it is only a matter of time before the ocean becomes imbalanced enough that it will send that gas right back out. A warmer ocean, researchers say, simply quickens the pace.

The study reports that there is still much to be discovered when it comes to this impending shift, including what other oceanic factors could be serving as contributors, but researchers are hopeful that this new data will help policymakers around the world become more aware of the future of this ozone-diminishing gas.

“Some of the next steps would be to do this with higher-resolution models and focus on patterns of change,” said co-author and MIT research scientist Jeffery Scott. “For now, we’ve opened up some great new questions and given an idea of what one might see.”

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