The Bay of Bengal is an unexpected weapon against global warming as it helps store vast quantities of terrestrial carbon brought down by the Ganges-Brahmaputra river systems, a study says.
Rivers bring down to the sea carbon in the form of soil and vegetal debris, washed down from slopes, fields and banks. But little is known about what happens to this carbon-rich sediment once it reaches the river's mouth.
Some research-conducted in the churning waters of the Amazon basin-has suggested that 70 percent of this river-borne organic carbon returns to the atmosphere as gas, thus adding to the greenhouse effect from fossil fuels.
But research published on Thursday in the British science journal Nature says the picture is more complex. A team led by Valier Galy of France's Nancy University estimates that around 70-85 percent of the terrestrial carbon that sweeps down the Ganges-Brahmaputra systems from the Himalayas settles to the sea floor rather than escapes to the atmosphere.
The reason: high rates of erosion in the Himalayas cause high rates of sedimentation in the so-called Bengal Fan in the Bay of Bengal. Between a billion and two billion tonnes of sediment are transported each year from the Himalayas to the Bengal coast.
As a result-unlike at the mouths of the Amazon-the thick, fast-growing sediments are not exposed to much oxygen, and this starves microbes of the fuel they need to biodegrade the organic matter. Eventually, powerful currents transfer the sediments to deeper water, where they settle on the ocean bed, safely storing the carbon for potentially millions of years.