Warmer Oceans = More Atmospheric Carbon Dioxide
Monday, 29. October 2007, 11:01:25
In the global carbon cycle the sea absorbs a proportion of the atmospheric CO2 but also releases CO2 into the atmosphere again. About half of the man made emission of CO2 is absorbed naturally by the oceans. It is therefor important to understand how the exchange of CO2 between the ocean and the atmosphere functions with regard to a world that is warming up. A newly available study shows that the ocean was able to store more CO2 during the ice age than it can today.
To find out how the situation has changed compared to the last ice age, researchers studied mud from the sub-Arctic Pacific Ocean lying approximately one metre below the present sea bed and about 20,000 years old, and thus from the ice age. The Wisconsin (in North America), Devensian (in the British Isles), Midlandian (in Ireland), Würm (in the Alps), and Weichsel (in northern central Europe) glaciations, which ended around 10,000 BC, are the world's most recent glaciations (periods during which the ice caps extend towards the equator). The maximum extent was reached about 18,000 years ago.
Foraminifera, microscopic floating organisms that live in shells, in Earth's oceans hold clues to global climate change. See Image.
Tiny single-celled organisms with limestone shells known as foraminifera were selected from this mud under a microscope and afterwards measured with mass spectrometers. These foraminifers locked in the carbon isotope signature of the seawater of their day. The research team has now been able to measure the 14C content precisely. This enabled them to show that the water in the ocean depths exchanged less CO2 with the atmosphere than at present. They found unusually clear evidence that this water captured more CO2 from the atmosphere than the water at the present day. The latest research results show that the oceans are generally able to fix more CO2 when they are cold. Or said the other way round: Oceans that warm up as a result of climate change release more CO2 into the atmosphere. The more CO2 we emit to the atmosphere, the more CO2 the oceans also release to the atmosphere.
Reference: Galbraith et al. Carbon dioxide release from the North Pacific abyss during the last deglaciation, Nature, 449, 890-894. Abstract.
To find out how the situation has changed compared to the last ice age, researchers studied mud from the sub-Arctic Pacific Ocean lying approximately one metre below the present sea bed and about 20,000 years old, and thus from the ice age. The Wisconsin (in North America), Devensian (in the British Isles), Midlandian (in Ireland), Würm (in the Alps), and Weichsel (in northern central Europe) glaciations, which ended around 10,000 BC, are the world's most recent glaciations (periods during which the ice caps extend towards the equator). The maximum extent was reached about 18,000 years ago.
Foraminifera, microscopic floating organisms that live in shells, in Earth's oceans hold clues to global climate change. See Image.Tiny single-celled organisms with limestone shells known as foraminifera were selected from this mud under a microscope and afterwards measured with mass spectrometers. These foraminifers locked in the carbon isotope signature of the seawater of their day. The research team has now been able to measure the 14C content precisely. This enabled them to show that the water in the ocean depths exchanged less CO2 with the atmosphere than at present. They found unusually clear evidence that this water captured more CO2 from the atmosphere than the water at the present day. The latest research results show that the oceans are generally able to fix more CO2 when they are cold. Or said the other way round: Oceans that warm up as a result of climate change release more CO2 into the atmosphere. The more CO2 we emit to the atmosphere, the more CO2 the oceans also release to the atmosphere.
Reference: Galbraith et al. Carbon dioxide release from the North Pacific abyss during the last deglaciation, Nature, 449, 890-894. Abstract.
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