Oceans Absorb Less Carbon Dioxide as Marine Systems Change (Study)

The oceans are by far the largest carbon sink in the world. Some 93 percent of carbon dioxide is stored in algae, vegetation, and coral under the sea.  But oceans are not able to absorb all of the carbon dioxide released from the burning of fossil fuels. In fact, a recent study suggests that the oceans have absorbed a smaller proportion of fossil-fuel emissions, nearly 10 percent less, since 2000. The study, published in the current issue of Nature, is the first to quantify the perceived trend that oceans are becoming less efficient carbon sinks. 

The study team, led by Columbia University oceanographer Samar Khatiwala, measured the amount of human-caused carbon dioxide emissions pumped into the oceans since 1765. "Our method takes as input the relatively well-known atmospheric CO₂ concentration history. Given this history, we calculate the ocean absorption of industrial CO₂ consistent with this history," Khatiwala said.

Industrial carbon dioxide emissions have increased dramatically since the 1950s, and oceans have until recently been able to absorb the greater amounts of emissions. Sometime after 2000, however, the rise in emissions and the oceans' carbon uptake decoupled. Oceans continue to absorb more carbon, but the pace appears to have slowed. The reason is based in part on simple chemistry. Increased concentrations of carbon dioxide have turned waters more acidic, especially nearer to the poles. While carbon dioxide dissolves more readily in cold, dense seawater, these waters are less capable of sequestering the gas as the ocean becomes more acidic. The study revealed that the Southern Ocean, near Antarctica, absorbs about 40 percent of the carbon in oceans.

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Photo courtesy NOAA

Maldives Cabinet Holds Underwater Meeting in Lagoon Off Island of Girifushi

Talk about being creative.  Cabinet ministers in the Maldives held an underwater meeting Saturday to draw attention to the threat global warming poses to the lowest-lying nation on earth. President Mohammed Nasheed and members of his cabinet, dressed in scuba gear, met in a lagoon off the island of Girifushi. They sat at a table anchored to the sand on the floor of the Indian Ocean and signed a document calling on all countries to reduce their carbon dioxide emissions.

Officials from around the world will meet in the Copenhagen, the Danish capital, under UN auspices to hammer out a successor agreement to the Kyoto Protocol, with the aim of reducing greenhouse-gas emissions that are blamed for global warming.

The ministers said that if something isn't done to stem the rate of rising sea levels, the entire archipelago could end up under the water by the end of the century, since the island group is only a couple meters above sea level. Scientists at a meeting in Copenhagen last March predicted that glaciers and ice sheets melting as a result of global warming could boost the level of the world's oceans by as much as a meter by 2100.