Swedish researchers pinpoint scary climate feedback loop
By Summit Voice
SUMMIT COUNTY — Instead of absorbing heat-trapping gases, Arctic near-shore seas are becoming sources of carbon dioxide, accorindg to researchers from Sweden’s University of Gothenburg. With careful measurements, the scientists found that the amount of CO2 being absorbed by the oceans is decreasing.
That leads to an increase of greenhouse gases in the atmosphere and an increased rate of warming in the Arctic in a self-reinforcing climate feedback loop that includes some unexpected factors. For example, increased coastal erosion carries more organic matter into the sea, where it breaks down and releases even more CO2.
About half of the carbon dioxide from fossil fuel combustion was absorbed by the oceans up until 1994. But as the amount of carbon dioxide in the oceans rises, their capacity to absorb the gas falls, and it remains in the atmosphere.
“The greenhouse gases raise the temperature of the Earth and this increase is particularly noticeable in the Arctic. It is even more pronounced in Siberia and its coastal seas,” said marine chemistry researcher Iréne Wåhlström.
The increase in temperature has an impact on the environment in the Arctic – the cover of sea ice is lower, for example, and the supply of water from rivers increases, the permafrost thaws and the rate of coastal erosion increases.
“One consequence is that organic matter that has been stored in soil is carried to the seas, where it is partially broken down to carbon dioxide,” Wåhlström said.
Wåhlström studied the Laptev Sea and the East Siberian Sea, working on a ship to collect extensive samples and in the lab to model the changes she observed.
“The level of marine photosynthesis is high in these waters during the summer, and carbon dioxide is consumed. This leads to the level in the sea being lower than in the air, and the sea absorbs carbon dioxide from the air,” Wåhlström said.
The western East Siberian Sea receives also a major contribution from rivers, both directly from the land and from the neighbouring Laptev Sea.
“The river water contains high levels of organic matter, which is partially broken down to carbon dioxide in the sea. This leads to the level in the sea being higher than in the air, and thus carbon dioxide flows from the sea into the air, accelerating climate change.”
The Laptev Sea had an excess of carbon dioxide during the late summer of 2008 that was of the same order of magnitude as the western East Siberian Sea, probably caused by the breakdown of organic matter from the land.
The results suggest that the Laptev Sea has changed from being a sink for atmospheric carbon dioxide to become a source of carbon dioxide during the late summer. This will probably be reinforced by a higher air temperature, particularly if parts of the large reservoir of stored organic matter in the Arctic tundra thaw and are carried to the sea. This will further increase the rate of temperature rise of the Earth.