Coastal erosion could amplify climate warming

A study of sediment samples from the Sea of Okhotsk on the eastern coast of Russia concludes that loss of Arctic permafrost deposits via coastal erosion could amplify climate warming through the greenhouse effect.

Conclusions of the study by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, were published on Sept. 10 by EurekAlert, an online journal of the American Association for the Advancement of Science.

Researchers found that the loss of Arctic permafrost at the end of the last glacial period led to repeated sudden increases in the carbon dioxide concentration in the atmosphere. They said the exact magnitude of the future increase in greenhouse gas concentrations is an unknown, in part because carbon dioxide is not only produced by people burning gas, coal and oil, but can come into the atmosphere as a result of natural environmental processes.

Researchers were able to show that several thousand years ago large quantities of carbon dioxide were released from Arctic permafrost, due to a rapid rise of sea level. Permafrost soils preserve huge quantities of dead biomass, mainly plant remains. When that permafrost thaws, bacteria start degrading the ancient biomass, and their metabolisms release the greenhouse gases carbon dioxide and methane.

Scientists know that about 11,500, 14,600 and 16,500 years ago there were significant and sudden rises in the carbon dioxide level in the atmosphere, but the reasons for these changes are poorly understood. AWI researchers noted that about 11,500 and 14,600 years ago, particularly intense melting of the ice sheets led to what are known as meltwater pulses, and each time the sea level rose by up to 20 meters within a few centuries.

“We assume that this resulted in severe erosion of the permafrost coast in the Sea of Okhotsk and the North Pacific, a phenomenon that we can observe in the Arctic today,” said Professor Gesine Mollenhauer.