New Study Tracks Permafrost Carbon Carried by Rivers to the Arctic Ocean
(14 September 2015)
Durham University scientists worked with colleagues from Woods Hole Oceanographic Institute, Institut de Physique du Globe de Paris, NERC Radiocarbon Facility, Stockholm University and Université Paris-Sud, and discovered that as many as 2.2 million metric tons of organic carbon per year are carried by the Mackenzie river in Canada to the Arctic Ocean. They found that the carbon from soils was buried rapidly on the seafloor, locking carbon away from the atmosphere for many thousands of years. The natural process helps to stabilize the Earth's CO2 levels over time.
The team collected river sediments over three years from one of the largest rivers in the Arctic, the Mackenzie River basin, when the river was in flood and when water levels were lower. They measured radiocarbon (the Carbon 14 isotope) to assess the source of organic carbon in the Mackenzie River for the first time, correcting for carbon eroded from rocks (which does not impact CO2 levels over thousands of years). They were able to determine that carbon eroded from soils was up to 8000 years old and eroded from very old, deep soils, likely in areas of permafrost degradation.
The research team compared the river sediments carried by the Mackenzie River to a sediment core obtained from the Arctic Ocean seabed. They found that a significant amount of the biospheric carbon is swept into storage offshore, helping to stabilising Earth's CO2 levels over thousands of years. However, it is not all good news. The research shows that the natural process it is too slow to counter the current CO2 emissions from burning fossil fuels. It is also about 10 - 20 times too slow to offset the predicted release of CO2 if the frozen soils thaw due to warming over the next 100 years.
The work was supported by grants from the Natural Environment Research Council UK (NERC Radiocarbon Facility Allocation 1611.0312), WHOI Arctic Research Initiative, an Early Career Research Grant by the British Society for Geomorphology, a Royal Society University Fellowship, and a grant from the National Science Foundation (OCE-0928582).