british and Norwegian oil companies have announced plans to bury carbon dioxide under the bed of the North Sea. Though they claim they are trying to inhibit climate change, the actual purpose is more mundane increased exploration of oil and gas reserves. Experts have expressed environmental concerns about such sequestering schemes. They feel carbon dioxide is going to seep out to the atmosphere anyway, so this is a stop-gap option to control climate change. What is worse is, according to them, such schemes will bring about ecological imbalance in marine life. Third, it distracts from investment in renewable energy technologies.
Carbon sequestration under the earth or sea has long been regarded, especially by the us, as a solution to mitigate effects of global warming. It involves power stations and oil rigs holding on to their emissions of gases and then pumping them underground to keep them out of the atmosphere.
According to Atul Jain, professor of atmospheric sciences at the University of Illinois, Urbana Champaign, sequestering could lead to an imbalance of carbon dioxide concentration in oceans and atmosphere. "Considering the impact of the climate change in future (climate feedback), the ocean circulation could affect the retention period of carbon dioxide. It may alter oceanic carbon storage and atmospheric carbon dioxide concentration," says Jain.
To investigate the possible effects of feedbacks between global climate change, ocean carbon cycle and oceanic carbon sequestration, Jain and his colleagues developed an atmosphere-ocean climate-carbon cycle model. The study found that climate change has a big impact on oceans' ability to store carbon dioxide and the effect was most pronounced in the Atlantic Ocean. According to Jain, "Injecting carbon dioxide in the Atlantic Ocean is more effective than injecting it in either the Pacific or the Indian Ocean."
Climate change may affect both the intake of carbon dioxide in the ocean basins and the ocean circulation pattern, says Jain. "As sea-surface temperatures increase, the density of water decreases and thus slows down the ocean thermohaline (temperature-salinity) circulation. So, the ocean's ability to absorb carbon dioxide also decreases. This, eventually, leaves more carbon dioxide in the atmosphere. At the same time, reduced ocean circulation will decrease the ocean mixing, which further decreases the ventilation to the atmosphere of carbon injected," says Jain. Sequestering excess carbon dioxide is not a permanent solution. "Carbon dioxide dumped in the oceans will eventually percolate to the surface and into the atmosphere," he adds.
Marine life is highly sensitive to deep sea changes in carbon dioxide. In a study, Monterey Bay Aquarium Research Institute ecologist Brad Seibel and Patrick Walsh of the University of Miami, found how deep-sea animals respond to the physiological stress caused by increased carbon dioxide. "Increased carbon dioxide causes a decrease in seawater ph, creating an acidic environment." Decreased ph can result in metabolic suppression that can inhibit growth and reproduction. Previous studies have established that deep-sea fish and invertebrates have low metabolic rates. Consequently, they lack the metabolic machinery required to compensate body fluid p changes.
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