Ancient Arctic carbon is pouring into the sea, but the seabed captures most of it

The Arctic’s frozen ground contains enormous stores of organic carbon. As permafrost thaws and coastlines erode, some of that carbon is carried into the ocean. There, microorganisms can break it down and release greenhouse gases that contribute to climate change.

Until now, scientists have had limited information about how much of this carbon returns to the atmosphere and how much remains trapped in the ocean. Researchers from the Alfred Wegener Institute and MARUM – Centre for Marine Environmental Sciences at the University of Bremen have now examined this process along the permafrost coast of Qikiqtaruk (Herschel Island) in Canada. By studying sediment cores, the team found that large amounts of carbon from land are preserved in the seafloor. They also discovered that marine microorganisms behave like selective eaters, favoring fresh carbon from the ocean over older carbon released from permafrost. The findings were published in Nature Geoscience.

The movement of carbon from land into the ocean may affect more than greenhouse gas emissions. It can also change the chemistry and biology of coastal waters that support food resources for local communities. Sediment released by coastal erosion can reduce the amount of sunlight entering the water. Freshly eroded fragments make the coastal ocean cloudy, while dissolved organic carbon can darken the water. That loss of light can affect single-celled organisms such as algae, which need sunlight to produce biomass and oxygen. This primary production supports a wider food web that includes fish, crustaceans and seals.

Source: Science Daily