World's oceans absorbing less carbon dioxide, report says

A massive carbon sink, the world's oceans are unable to absorb all of the carbon dioxide emitted from the burning of fossil fuels, according to a new study.

The world's oceans are, collectively, a massive carbon sink that absorb 93 percent of the world's carbon dioxide.

But the algae, coral and other vegetation in the oceans can't keep up with humanity, and are unable to absorb all of the CO2 emitted from the burning of fossil fuels, according to a new study.

According to the study, published in the current issue of Nature, the oceans have absorbed a smaller proportion of fossil-fuel emissions, nearly 10 percent less, since 2000.

"The release of fossil fuel CO2 to the atmosphere by human activity has been implicated as the predominant cause of recent global climate change1. The ocean plays a crucial role in mitigating the effects of this perturbation to the climate system, sequestering 20 to 35 per cent of anthropogenic CO2 emissions," the study reads. "Our results indicate that ocean uptake of anthropogenic CO2 has increased sharply since the 1950s, with a small decline in the rate of increase in the last few decades."

Led by Columbia University oceanographer Samar Khatiwala, researchers measured the amount of human-caused carbon dioxide emissions absorbed by the oceans since 1765.

Industrial carbon dioxide emissions have been on the rise for decades, but the rate of oceanic absorption slowed after 2000.

Increased concentrations of carbon dioxide can be measured because it turns ocean water more acidic, particularly near the poles. (Carbon dioxide dissolves more readily in cold, dense seawater.)

According to the study, the southern ocean around Antarctica absorbs about 40 percent of the all carbon in the oceans.

Ever-increasing emissions is one suspect.

Previous research on the topic attempted to measure the oceans' carbon sink capacity by assessing the amount of natural carbon in the sea -- a difficult procedure to scale to all the world's oceans.

Coastal marine ecosystems -- made of tidal salt marshes, mangroves, seagreass meadows and kelp forests -- are believed to be more efficient than land-based carbon sinks to mitigate climate change, according to a report by the International Union for the Conservation of Nature.

Similarly, the United Nations estimated in an October report that three to seven percent of current fossil-fuel emissions could be offset in two decades action is taken to prevent marine vegetation loss by runoff pollution and coastal development.

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