Ships can monitor the ocean's carbon sink
4 December 2009, by Sara Coelho
The oceans can take up carbon dioxide from the atmosphere and counter the damaging effects of rising emissions - but to what extent? Now, a group of scientists has devised a cheap and precise way to monitor exactly how much carbon the oceans are able to store.
Devices on a network of commercial vessels gathered the data.
The new method turns the fleet of commercial ships that criss-cross the seas into floating labs, with custom-made sensors in the engine rooms. The devices analyse how much carbon dioxide is dissolved in the water taken in from the ocean to cool the engine.
Putting commercial ships to good use 'seemed an obvious way to go,' says Professor Andrew Watson, from the University of East Anglia. 'This is a cheap, cost-effective way to measure the flux of carbon between the atmosphere and the oceans.'
Half of the carbon dioxide emitted from burning fossil fuels is absorbed by natural sinks such as the oceans and land vegetation. But the oceans' ability to take up carbon varies and up to now scientists didn't have precise, large-scale measurements of the uptake of carbon dioxide by the oceans.
Watson and his international team took the measurements recorded by five ships in 2005 and developed a model to extrapolate the data collected along the shipping routes to the whole of the North Atlantic Ocean.
They found that during this year the North Atlantic took up 250 million tonnes of carbon from the atmosphere, which is about 10 per cent of the total carbon absorbed by the oceans.
'This is the first time we observe carbon uptake directly over a large region and with accuracy,' says Watson.
Routes of the ships used in the study
The findings, reported yesterday in Science, also show that 'the north Atlantic carbon sink is variable, much more than we would have thought a few years ago.'
Watson believes that the method could be applied to monitor the carbon uptake in every ocean, as long as there are commercial routes and ships available to be fitted with the sensors.
'We ought to do it,' Watson says. 'Monitoring carbon in the oceans is a responsible and sensible thing to do.'
The ship-driven global monitoring system could also be the canary in the coal mine of global warming as scientists believe that a sudden drop in the ocean's capacity to take up carbon is the first signal of pronounced climate change.
The idea of using commercial vessels for climate research goes back a long way. 'Actually, these ships do a surprising amount of scientific work,' says Watson. Many ships record atmospheric conditions every four hours, others monitor plankton as they sail.
The breakthrough came when Watson, then at the Plymouth Marine Laboratory, developed a sensor that can be installed in the engine room to measure the concentration of carbon dioxide in the cooling water.
Andrew J. Watson et al. Tracking the Variable North Atlantic Sink for Atmospheric CO2. Science 4 December 2009: 1391-1393. DOI: 10.1126/science.1177394
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