At What Point Does Acidifying Ocean Become Net CO2 Source, Rather Than Sink?

[hatrack]

THE ocean is becoming more acidic because it is struggling to absorb the amount of carbon dioxide (CO2) we‘re putting up into the atmosphere – and no one knows when the “tipping point” will come, when the ocean starts to expel CO2. That‘s the chilling warning from department of environment affairs (Deat) climate change specialist Dr Ashley Johnson, who addressed a packed public meeting – organised by Deat, the Wildlife and Environment Society and Bayworld – in Port Elizabeth last week.

The ocean is Earth‘s biggest sink or natural absorber of CO2, a major ingredient of emissions from heavy industry and one of the chief greenhouse gases responsible for climate change, he explained. “The wind blows over the ocean, carrying this CO2, and it is trapped and vertically mixed into the sea.

“How much more can it take? That‘s the million-dollar question. That is why we urgently need more research to understand the role of the ocean better. There are so many questions around its relationship to climate change. Like when will the tipping point come when CO2 starts to get expelled. “What we do know is that if this point is reached, there will be an exponential increase in the level of CO2 in the atmosphere – and climate change will accelerate dramatically.”

It has long been recognised that ocean and climate are “coupled”, he said. A global oceanic conveyor belt of currents transports heat from the tropics to the poles, and this vast movement of water and temperature is reflected in the atmosphere. In a parallel process, oceanic plant life produces oxygen which helps to balance the gas content of the sea and to sustain its sink capability, he explained. “So if mankind continues to pollute the ocean and destroy its biological diversity, if we continue to take no heed of pesticides running off farmland into rivers and then into the sea, if we somehow damage the oceanic conveyor belt – we will undermine the ocean‘s sink capability, and its capacity to act as a buffer against climate change.”

EDIT

http://www.theherald.co.za/herald/news/n15_21102008.htm

[Barrett808]

1. This may be happening already:

Is the ocean carbon sink sinking?
http://www.realclimate.org/index.php/archives/2007/11/is-the-ocean-carbon-sink-sinking/langswitch_lang/en