Oceans & marine

Cultivating algae for export to Japan, Zanzibar

Oceans & marine

Seaweed and macro algae cultivation

The potential of carbon sequestration by marine based plants such as mangroves, seagrass and algae, often referred to as blue carbon, and the importance of better understanding it, has clearly been recognised (Mcleod et al. 2011). The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (2019) concluded blue carbon can play an important role in both climate regulation and adaptation. The term algae groups together several kinds of marine photosynthetic organisms. These are often subdivided into very small microalgae like phytoplankton, and larger macroalgae like kelp and seaweed. Although there is still large uncertainty about the total amount of carbon sequestered by these marine organisms, a recent estimate by Duarte et al. (2022) indicated that all macroalgae took in as much CO2 as the Amazon rainforest.

Coastal Archipelago Park of the South Coast ("Sørlandet") of Norway, colors at the shoreline (1)

Oceans & marine

Artificial downwelling

Artificial downwelling (AD) is an idea to pump upper layer water deeper down into the ocean.

Oceans & marine

Ocean fertilization

Ocean fertilization schemes seek to increase the amount of available nutrients in the top layer of the ocean to stimulate the growth of phytoplankton.

Ringed plovers (Charadrius hiaticular) arriving from the Arctic on Tromlingen, Raet National Park

Oceans & marine

Ocean Alkalinity enhancement

Carbon uptake in the ocean mainly occurs directly through ocean-atmosphere interaction or through weathering processes. Due to this uptake of carbon, the oceans turn more acidic overtime, and since the start of the industrial revolution oceans have become 30% more acidic. This has all sorts of effects as it, for example, impacts marine biochemistry, and prevents certain organisms from successfully growing.

River Ölfusá just North of Selfoss, South Iceland

Oceans & marine

River Liming

The pH of water is lowered when it takes up atmospheric carbon. Given that the Earth’s oceans serve as a major carbon sink, there is increasing interest in the possibility to artificially increase the alkalinity of water to restore pH to previous levels, and/or increase carbon uptake potential.

Cape Petrel (Daption capense), Antarctic Peninsula

Oceans & marine

Reflective foams and bubbles on oceans

Sea water has a low albedo of around 0.1 and therefore absorbs most of the incoming solar energy. Since water covers over two thirds of the Earth’s surface, changes to this albedo can potentially cause significant changes in global temperatures.

Oceans & marine

Re-oxygenating the Baltic

The deep waters in the Baltic are severely deoxygenated. Although the causes of the current state are complex, this is mainly a result of increased eutrophication from sewage and agricultural runoff from surrounding lands, which leads to extreme bioproductivity (Rolff et al. 2022). Some species manage to survive in the upper water layers, but many organisms living on the seafloor are severely impacted by the hypoxia, thereby influencing the health of a wide network of ecosystems and biochemical processes. There are attempts to reduce nutrient runoff into the Baltic (see for example: https://helcom.fi/baltic-sea-action-plan/). However, some argue these will be insufficient and argue for engineering solutions to the issue.

A school of juveniles of the Dusky spinefoot Siganus luridus (second)

Oceans & marine

Artificial upwelling

Artificial upwelling (AU) is an idea to increase carbon uptake of upper ocean layers by fertilizing it with pumped-up colder nutrient-rich waters from the deep, which would encourage the biological sequestration of carbon through photosynthesis (NASEM 2022).

Fishing boat in between icebergs, Disco Bay, Greenland

Oceans & marine

Improved fishing practices and management

Fisheries contribute to global CO2 emissions by the extraction of fish, disturbance of coastal and oceanic blue carbon ecosystems, and the use of fossil fuels as their main energy source. Fishing vessels are moreover a major source of short-lived climate forcers like black carbon (McKuin and Campbell 2016), which can have a major effect in Arctic and Northern regions (see Black carbon reduction).

Oceans & marine

Enhancing oceanic light availability below the photic layer

Ocean bioproductivity through photosynthesis stops beyond the photic layer as no more energy from the sun can penetrate beyond that point.

Oceans & marine

Promoting ocean calcifiers to sequester atmospheric carbon

Biotic processes play an important role in oceanic carbon uptake, with most attention going to carbon-consuming photosynthesising organisms. Moore et al. (2023) argue that the potential role of shellfish and other calcifiers in carbon sequestration is significantly overlooked in the CDR literature.

High waves at Tromøy shore, "Rollingstone" (Raet) National Park in planning, Arendal

Oceans & marine

Hydrological system modification - Ocean current modification

Hydrological systems play an important role in energy distribution in the climate system. For the Arctic and Northern region the clearest example of this is the habitability of the European Arctic thanks to the Gulf Stream. Furthermore, there are several access points to the Arctic ocean that play an important role in shaping local geophysical conditions.