Ocean geoengineering scheme no easy fix for global warming

(National Oceanography Centre, Southampton (UK)) Pumping nutrient-rich water up from the deep ocean to boost algal growth in sunlit surface waters and draw carbon dioxide down from the atmosphere has been touted as a way of ameliorating global warming. However, a new study led by Professor Andreas Oschlies of the Leibniz Institute of Marine Sciences in Kiel, Germany, pours cold water on the idea.

"Computer simulations show that climatic benefits of the proposed geo-engineering scheme would be modest, with the potential to exacerbate global warming should it fail," said study co-author Dr Andrew Yool of the National Oceanography Centre, Southampton (NOCS). …

The aim would be to mimic the effects of natural ocean upwelling and increase drawdown of atmospheric carbon dioxide by phytoplankton through the process of photosynthesis. Some of the sequestered carbon would be exported to the deep ocean when phytoplankton die and sink, effectively removing it from the system for hundreds or thousands of years.

A previous study, of which Yool was lead author, used an ocean general circulation model to conclude that literally hundreds of millions of pipes would be required to make a significant impact on global warming. But even if the technical and logistical difficulties of deploying the vast numbers of pipes could be overcome, exactly how much carbon dioxide could in principle be sequestered, and at what risk?

In the new study, the researchers address such questions using a more integrated model of the whole Earth system. The simulations show that, under most optimistic assumptions, three gigatons of carbon dioxide per year could be captured. This is under a tenth of the annual anthropogenic carbon dioxide emissions, which currently stand at 36 gigatons per year. A gigaton is a million million kilograms. … when the simulated pumps were turned off, the atmospheric carbon dioxide levels and surface temperatures rose rapidly to levels even higher than in the control simulation without artificial pumps. This finding suggests that there would be extra environmental costs to the scheme should it ever need to be turned off for unanticipated reasons. …

Ocean geoengineering scheme no easy fix for global warming

Technorati Tags: global warming,climate change,algae bloom,carbon dioxide,ocean,ocean fertilization,carbon sequestration

Ocean fertilization: dead in the water?

Study casts doubt on iron-induced carbon sequestration.

by Quirin Schiermeier

The theory that adding iron to the oceans can help suck up atmospheric carbon dioxide cheaply and efficiently has received a further blow. A study¹ published in this week's issue of Nature (see page 577) finds that the potential of iron-induced carbon sequestration is far lower than previously estimated.

During the CROZEX experiment in 2004 and 2005, scientists on board the British vessel RSS Discovery observed the impact of natural iron fertilization on algal growth and carbon export near the Crozet Islands, an archipelago some 2,000 kilometres southeast of South Africa. The team found that, relative to one unit of added iron, the amount of carbon sequestered to 200 metres' depth, where it will stay for a couple of decades, was almost 80 times smaller than the amount that scientists had determined during a similar study in the nearby Kerguelen region².

"Ecosystem response and carbon export seem to vary very substantially from region to region," says Ulrich Bathmann, a biological oceanographer at the Alfred Wegener Institute (AWI) for Polar and Marine Research in Bremerhaven, Germany, who was not involved in the new study. "And the closer you look, the more complex the story gets."

Ocean fertilization: dead in the water?
Thu, 29 Jan 2009 17:51:38 GMT

Technorati Tags: ocean fertilization,carbon sequestration