A weaker carbon pump

Oceans are a key player in the planet’s carbon cycle, but researchers may have found that one way the oceans store carbon is less significant than thought. A team led by researchers from the National Oceanography Centre in Southampton, England, report in an upcoming issue of Geophysical Research Letters on new measurements of the “biological carbon pump,” which sequesters small carbon-rich particles that sink from the ocean’s surface to its depths. Using a version of the radioactive element thorium, which sticks to particles and thus traces their movement, the researchers found that much less carbon was sinking than other, indirect, studies have suggested.