Tracing anthropogenically emitted carbon dioxide into the ocean

The net atmosphere-to-ocean carbon flow rates for total carbon (and hence for ΔC), anthropogenically

Through fossil fuel combustion, deforestation, and other industrial and agricultural activities, humans have raised global atmospheric carbon dioxide (CO2) levels to more than 415 parts per million. That concentration represents a 135-parts-per-million increase since preindustrial times in the late 18th century. It is often assumed that this CO2 increase consists entirely of anthropogenically emitted CO2, but a new study challenges that assumption.

To investigate the standard narrative about the fate of anthropogenically emitted carbon, Holzer and DeVries labeled CO2 as it was emitted and tracked it with a data-assimilated ocean circulation model. This method allowed them to partition the net changes in atmospheric and oceanic carbon inventories as either anthropogenically emitted or natural carbon. The model followed the journey of emitted carbon from 1780 to 2020 using what is called a linear labeling tracer. Researchers have used this labeling technique in other applications but never to track anthropogenic carbon.

The modeling revealed that only 45% of the increase in atmospheric carbon over the past few centuries originated as emitted carbon and that outgassed natural carbon from the ocean accounts for the other 55%. The researchers also found that the ocean has accumulated nearly twice as much emitted carbon as previously assumed.

Aaron Sidder,, 17 October 2022. Press release.

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