The Deep Ocean Might Store Way Less Carbon Than We Hoped

With 39,000 gigatons of carbon dioxide stored up in the seas right now, which is almost 50 times more than what is currently flowing in the atmosphere, the oceans are one of the most significant carbon sinks on our planet.

However, because we are manufacturing too much extra CO2 too rapidly, we can't rely on carbon capture and storage to resolve our climate crisis issue.

Furthermore, according to a recent research, the deep ocean isn't able to store nearly as much carbon as was previously believed.

Researchers studied the carbon cycle, which involves small plants on the water's surface absorbing carbon and letting it float to the seafloor.

It turns out that this mechanism is "leakier" and retains less carbon over the long term than prior predictions, according to new particle tracking models.

"The ocean is an important carbon sink, and the depth to which biological carbon sinks affects how much atmospheric carbon dioxide the ocean stores," according to Chelsey Baker, an ocean biogeochemical model analyst from the National Oceanography Center in the UK.

"In this study, we show that the longevity of carbon storage in the deep ocean may be considerably less than what's generally assumed." 

To be on a timeline that is important to climate change, carbon must be sequestered for 100 years.

It was previously believed that any carbon trapped below 1,000 meters (3,250 feet) in depth would be kept hidden from the planet for several millennia by the deep ocean's circulation routes.

Only 66% of the carbon that reaches a depth of 1,000 meters (3,250 feet) or more in the North Atlantic Ocean would, on average, be retained for a century or longer, according to the calculations employed by the researchers.

Although the effectiveness of CO2 capture varied depending on factors such as ocean currents and temperature, carbon needed to reach a depth of 2,000 meters (6,500 feet) to be almost certain of remaining stored for more than 100 years. At that depth, the simulations showed, 94 percent of carbon stayed put for a century or more.

"These findings have implications for estimates of future predictions of carbon sequestration by global biogeochemical models, which may be overstated, as well as for carbon management strategies," write the researchers in their report.

Models will need to be revised when the ocean and climate change. According to experts, as the oceans warm, they will become more stratified, which will result in less mixing between layers and less carbon sinking to the bottom.

Furthermore, the more accurate our models are, the better we are able to predict what will happen and, if required, how we might be able to avoid it. The amount of CO2 we are making, how much the ocean can store, and how long it will likely stay trapped in the earth's atmosphere must all be known to scientists with as much accuracy as possible.

More carbon may be removed from the atmosphere's circulation by enhancing the natural carbon cycle in a variety of ways, but in order to do so, we must first understand how effective and efficient the deep ocean is as a carbon sink.

"Our findings could be important because artificially enhanced carbon storage by the ocean is one avenue being explored to help us achieve net zero by 2050. For example, by ocean schemes for carbon dioxide removal, such as iron fertilization," Baker explains.

"The effectiveness of such nature-based solutions is often dependent on the assumption that carbon reaching the deep ocean will be stored for hundreds of years, something our work suggests may not be so simple."

The research has been published in Global Biogeochemical Cycles.