DEEPOCEANGLACIALCO2

Using deep-sea corals to test the role of the deep Southern Ocean in ocean circulation and the regulation of atmospheric carbon dioxide

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 Obiettivo del progetto (Objective)

'The convective circulation of the world's ocean exerts important controls on two key aspects of the climate system: the transport of heat around the Earth and the degree to which the oceans sequester greenhouse carbon dioxide away from the atmosphere. Models of the past circulation predict variations in its strength that have been implicated in climate change. Marine sediments record changes in ocean chemistry that can be used to test these models. This approach has been pursued with great success in the North Atlantic. The Southern Ocean, on the other hand, is much less studied because of a lack of suitable sediments that record ocean chemistry. And yet, the Southern Ocean and its circulation system may be the key to both heat transport and isolation of a deep ocean carbon reservoir. This proposal seeks to provide key constraints on some of these issues using a unique set of deep-sea coral samples from the Pacific sector (70°S) of the Southern Ocean provided by the British Antarctic Survey and the Alfred Wegener Institute. Specifically we aim to use the radiocarbon ages of the corals, coupled with their calendar ages, to investigate the degree of isolation of the deep Southern Ocean carbon reservoir from the atmosphere, and therefore the extent to which this isolation might explain low atmospheric CO2 during recent glacial periods in Earth history. We also seek to use them to provide basic chemical information on the deep Southern Ocean, information that is key to many studies that use the chemistry of the past North Atlantic Ocean to try to understand ocean circulation.'

Introduzione (Teaser)

Scientists may have resolved a longstanding mystery concerning the storage and release of carbon dioxide by the Earth's oceans. The answer lies among the coral deep in the Southern Ocean.

Descrizione progetto (Article)

The amount of carbon dioxide (CO2) in the atmosphere varied long before mankind arrived on the scene. It is well known that the oceans play an important role in the uptake and cycling of carbon. It is thought that oceans may exhale large amounts of stored CO2 when the conditions are right, while at other times they may inhale it and store it in deep reservoirs.

This theory is being put to the test using sediment cores from the Atlantic Ocean. Unfortunately, this technique doesn't work everywhere, but a new approach using corals found deep in the Southern Ocean is being developed with the aid of EU funding. The project is called 'Using deep-sea corals to test the role of the deep Southern Ocean in ocean circulation and the regulation of atmospheric carbon dioxide' (DeepoceanglacialCO2).

Coral samples were collected during a research cruise in the Southern Ocean and dated using special radioisotopes. Measurements of the coral's growth rate at different times in the past have provided feedback regarding the amount of CO2 in the seawater. This enabled the research team to construct a time series of dissolved CO2. In addition, information about the origin of the seawater has been obtained that sheds light on aspects of global ocean circulation.

The new methodology shows promise and work is already underway to further refine it. Unlocking the secrets of how the oceans regulated atmospheric CO2 concentrations in the past will help scientists better understand what will happen in the future as anthropogenic emissions complicate the picture.