Modular iceberg creation by submersibles

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.

It has recently been suggested that hollow glass microspheres (HGM, see also see sea ice albedo increase) could be used to increase the albedo of mountain glaciers and thereby slow their melt.

Sea ice thickening is an idea to slow or reverse the decline of Arctic sea ice by artificially thickening it.

In 2019, an Indonesian design team came up with the idea of a submersible device that could take in sea water, desalinate it, and then have it freeze into a solid block they called a “new ice baby” (Griffiths, 2019).

There have been several isolated suggestions to mitigate permafrost thaw or influence the thaw processes in the active layer by physically covering the surface with materials (see for example https://groups.google.com/g/geoengineering/c/u2b9Xb5B0C8/m/aXQia-nNDbcJ) in a similar way to how glaciers might be preserved (see Glacier Insulation, and Passive Radiative Cooling). Although different materials have been suggested, these have not been worked out further, and are likely to be a very costly, and impractical solution.

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.

Direct air carbon capture and storage (DACCS) aims to reduce the amount of carbon dioxide in the atmosphere by taking it directly out of the air, and removing it from the carbon cycle.