Ocean pipes have been proposed as a method for enhancing the growth of oceanic phytoplankton and increasing the uptake of carbon dioxide (CO2) by the ocean. By decreasing the amount (or residence time) of CO2 in the atmosphere, it is suggested that the pipes will decrease global warming.
In a recent publication, James Lovelock and Chris Rapley (2007) proposed that vertical pipes could be placed in the ocean and used to pump up nutrient-rich water from deeper in the ocean. Since phytoplankton growth is limited by the scarcity of nutrients in most parts of the ocean, supplying more nutrients in this way could stimulate phytoplankton growth.
As well as consuming nutrients, the growing phytoplankton will also take up corresponding amounts of carbon as they synthesise new cells. It is proposed that this consumption of DIC in the surface ocean will lead to a flux of CO2 into the ocean from the atmosphere, in order to replace the carbon lost to the new algal cells. Because a fraction of this new material will be transferred into the deep ocean, Lovelock and Rapley suggested that the pipes will accelerate or enhance ocean carbon storage and may help diminish climate change.
You can make a first test of this idea in the carbon model.
- Click on Carbon model on the home page and then click on Model Parameters on the control panel.
- Select the Physical tab and then double KSM to 0.10.
- Apply and Close and then return to the main control panel and run the model.
You will see that atmospheric pCO2 actually increases somewhat, rather than decreases. This is because deep water naturally contains more carbon than surface water (look at the DIC plot on the bottom-left of page 1 of the graphs). Therefore the lifting of deep water to the surface (via pipes) elevates the amount of CO2 and prompts initial outgassing (release of CO2 to the atmosphere).
This was not considered when formulating the pipes proposal and rather drastically reduces the overall efficacy. Pipes could even, potentially, exacerbate the rise of CO2 in the atmosphere. You can repeat this analysis but make it take place in the fossil fuel era. To do this, you need to execute and compare two runs: one with fossil fuels (click on 'Add Fossil Fuels' button on main window) and a standard value of KSM, the other with fossil fuels and a doubled value of KSM.
J.E. Lovelock & C.G. Rapley (2007) Ocean pipes could help the Earth to cure itself. Nature 449, 403 (27 September 2007).
J.G. Shepherd, D. Iglesias-Rodriguez & A. Yool (2007) Geo-engineering might cause, not cure, problems. Nature 449, 781 (18 October 2007).