The deeper layers of the ocean are greatly unsaturated in CO and its dissolved forms, carbonic and bicarbonic acid, and their salts. At depths greater than 3 km, CO becomes liquefied and sinks to the seafloor due to it being higher density than the surrounding seawater. Mathematical models have shown that CO stored in deep sea sediments beyond 3 km could provide permanent geological storage even with large geomechanical perturbations. Deep ocean storage can present a potential sink for large amounts of anthropogenic CO. Other deep water carbon storage techniques currently being explored include, seaweed farming and algae, ocean fertilization, artificial upwelling, and basalt storage.
The deep blue carbon terminology has been used in passing as early as 2017. The Ocean Frontier Institute has made it a centrepiece of their participation at COP27. It is investing significant resources into deep blue carbon research. In terms of net-new-carbon sequestration deep blue carbon offers an estimated 10-20 times higher potential than coastal blue carbon to achieve net-zero goals. There is still a lack of data in this area along with financial, ecological and environmental concerns. Advancements in research and technical capabilities are raising international interest in this kind of storage.