The Hot Zone

Seabed may be too turbulent to store carbon

Posted by Alison Hawkes on January 20, 2011
Category : Climate Science and Scientists, The Oceans

The ocean floor has been eyed as a potential site to sequester carbon, the idea being that we can get CO2 far, far away from human activity by banishing it to the earthly equivalent of the Final Frontier.

But if you get CO2 out of the way of humans, it may instead be smack dab in the middle of natural forces. In an editorial published this week in the journal Nature Geoscience, the fallibility of burying carbon below the sea bed is explored.

The chief point of concern is that the ocean bed is actually a hot bed of volcanic activity, and may have, in fact, influenced the global carbon cycle in the past through large-scale off-gassing of stored methane.

This has apparently been the case in at least several areas of the ocean, including the Gulf of California, where magma has heated organic sediments to the point where methane, instead of being sequestered as previously thought, has been released into the ocean instead.

In another spot, the Juan de Fuca Ridge in the Northeast Pacific Ocean, microbes in hydrothermal vents are converting inorganic carbon into dissolved carbon matter, thereby releasing CO2 into the overlying ocean waters.

Some aspects of this underwater carbon cycle are still unknown and open to further discovery. How much carbon, in sum total, is being emitted? And how reactive is the carbon? The editorial posits that further insight will come from ocean drilling.

Hydrothermal vents may be an important part of the ocean carbon cycle. Photo: NOAA Vents Program

But the situation remains that the sea floor,  “where natural sources of carbon are just being discovered,” is no place to test out carbon sequestration, which must last for hundreds of thousands of years.

“As long as the natural carbon cycle in the deep ocean continues to surprise us, it would probably be unwise to go ahead and disturb it with the deposition of carbon captured from the use of fossil fuels,” the editorial states.

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