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Content archived on 2023-03-02

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New information on how oceans operate as carbon sinks

Research conducted by scientists from the Universities of Bremen and Hanover in Germany and Newcastle in the UK have identified some of the very slow processes that make oceans carbon sinks. Tracing where deposits of organic carbon (carbon from living or once-living things) e...

Research conducted by scientists from the Universities of Bremen and Hanover in Germany and Newcastle in the UK have identified some of the very slow processes that make oceans carbon sinks. Tracing where deposits of organic carbon (carbon from living or once-living things) emerge, the researchers have found that lateral particle transport takes the remains of small sea animals, algae and other living things out to sea, where it is buried in an extremely slow process, taking thousands or millions of years. Their study focused on the coast of south-western Africa, which is considered to have extraordinarily high plankton populations. When the plankton die, their bodies sink to the ocean floor. When living, each takes carbon dioxide from the air, and sequesters it in its body by growing. On a day-by-day basis, the quantity of sequestration may be small, but over millions of years, this represents a vast quantity of sequestered carbon. Taking samples from the ocean, the seabed and core samples from bedrock, the team found that plankton die and sink to clouds at the sea bottom. These clouds drift over large areas until they arrive in deeper waters and become buried at depths of 400 to 1,500 metres. Carbon dating of samples has revealed that this process alone could take thousands of years, and also, importantly, moves the carbon from close to the shoreline where the plankton grew to further away due to currents. This is the key reason why carbon dioxide from the air eventually turns into sequestered carbon in rock 'Depocenters for organic carbon on the shelf rarely persist for long time periods, and thus do not serve as carbon sinks over geologic time. Enrichment of organic matter in deep-marine sediments has a much better chance to enter the geological record, and thus has a sustainable effect on sequestration of carbon from the atmosphere,' reads the report. The report emphasises 'the significance of lateral transport as an important secondary mechanism, effectively transferring carbon from the atmosphere to long-term sequestration in the deep sea, and supporting the deposition of organic carbon-rich sediments with high hydrocarbon potential.' In other words, the plankton that have taken the carbon dioxide from the air over millions of years will eventually transform into rock under the sea, and occasionally become oil. Here, the carbon dioxide is extracted and burnt, releasing that carbon dioxide back into the air again. Interestingly, this research also explains why many oil deposits are found off-shore. Moreover, when you consider that the sea level has fluctuated a great deal over geologic time, then deposits could exist both closer to and further away from the shore compared to today's coastline.

Countries

Germany, United Kingdom