Arctic Seabed Acts as Carbon Sink for Thawing Permafrost Erosion

As the Arctic warms at an accelerated pace, the integrity of its frozen landscape is failing. This thermal shift triggers the release of massive organic carbon reservoirs previously locked in permafrost. Current estimates suggest that terrestrial permafrost ecosystems hold 1,300 gigatonnes of organic carbon, with another 400 gigatonnes residing in river deltas and marine sediments. Research led by the Alfred Wegener Institute (AWI) and the University of Bremen focuses on Qikiqtaruk (Herschel Island), Canada, to determine the fate of this material as it enters the Beaufort Sea.

The Trajectory of Eroded Carbon

Coastal erosion and river discharge currently deposit approximately 0.02 gigatonnes of organic carbon into the ocean annually. Projections indicates this volume could surge by 70 to 150 percent by the year 2100. Dr. Manuel Ruben and his team analyzed sediment cores representing 50 years of accumulation to track where this carbon goes. The data reveals a surprising stabilization: only about ten percent of the organic carbon in these sediments is converted into gas by microorganisms.

The vast majority of the terrestrial material remains sequestered within the seafloor rather than entering the active carbon cycle. While the sea transports immense quantities of land-based carbon, the seabed serves as a long-term storage vault, preventing a massive, immediate release of greenhouse gases into the atmosphere.

Microbial Preferences and Isotopic Indicators

The study, published in Nature Geoscience, utilized carbon isotopes to identify the specific "diet" of marine microbes. By analyzing 13C and 14C isotopes in sediment pore water, researchers distinguished between ancient permafrost carbon and modern organic matter. The findings suggest that marine bacteria act as selective consumers, favoring fresh algae over the degraded, ancient carbon from thawing land.