Re-oxygenating the Baltic

Oceans & marine

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.

There have been several different ideas to oxygenise the Baltic (Conley 2009). The most discussed technique, which will be the focus here too, aims to directly increase available oxygen to the deep waters by pumping cold oxygenated water down from higher levels (Stigebrandt and Gustafsson 2007). This oxygenation can lead to changes in GHG sinks and sources. There are several potential pumping technologies that are currently being explored, but Liu et al. (2020) find that a wind-powered system would probably work best in the Baltic.

Technological Readiness Level (TRL)

Low 1

Although there remain uncertainties around downwelling techniques (Ollikainenen et al, 2016), Liu et al (2020) say they are rapidly advancing. Model and experimental studies show that it is possible to artificially increase oxygen levels in this way (Stigebrandt et al, 2015; Stigebrandt and Andersson, 2022), and the Baltic deepwater OXygenation project (BOX) conducted a field trial in the Swedish fjord Byfjord and found it had a desired effect there (Forth et al, 2015). It is however questionable if the field trial was too small to serve as a useful analogue for the scale of the entire Baltic, and many questions remain about the ultimate effects of pumping oxygen (Conley, 2012; Ollikainenen et al, 2016). Conley et al (2009) for example note that the effects of physical mixing and circulation processes are still too poorly understood.

Technological Readiness Level (TRL)

A technology with a TRL of 1-3: TRL 1 – Basic; TRL 2 – Concept formulated; TRL 3 – Experimental proof of concept

Scalability

Medium 2

Although the project’s advocates are positive, there are questions about the potential of this technique to be effective at the scale of the Baltic beyond the small areas that have been the subject of field trials (Conley, 2012; Ollikainenen et al, 2016).

Scalability

Physically somewhat scalable; linear efficiency

Timeliness for near-future effects

Medium 2

There have already been some field trials, and a pumping system should probably not be beyond current technological capabilities. However, Conley et al (2009) conclude: 'that these large-scale attempts at remediation are unlikely to substantially improve the short-term conditions in the Baltic Sea'.

Timeliness for near-future effects

Implemented in time to make some difference, although questionable

Northern + Arctic potential

Unknown 0

For ecosystems and communities around the broader Baltic region, this could potentially be of great importance. However it is unknown what kinds of climate effects this measure would have, as oxygenating hypoxic waters can lead to various changes with regards to emissions and uptake of GHG like methane and CO2.

Global potential

Low 1

The effects of oxygenation would be complex, yet it seems unlikely that it would lead to significant global effects.

Global potential

Insignificant to be detected at a global scale

Cost - benefit

Unknown 0

Stigebrandt and Gustafsson (2007) estimate that the installment costs of some 100 wind-powered pump stations would be about 200 million Euros. This is relatively low compared to other engineering projects. However, it has to be noted that no feasible pumps exit as of yet. Ollikainenen et al (2016) cost benefit analysis of pumping in the gulf of Finland concludes that it could be net-beneficial for the coastal areas, but that it is highly doubtful that it could have a net positive effect in the open seas, even under the most optimistic scenario.

Environmental risks

High 1

Conley et al (2009) and Conley (2012) highlight the many environmental risks related to such a scheme, and warn of large scale impacts on ecosystems and even of a reintroduction of toxins that rest on the ocean floor into the food system. One major issue of concern would also be cod reproduction (Conley, 2012), which is a highly complex issue already (Rak et al, 2020).

Environmental risks

Major, serious risks with a high disaster potential; multiple and cascading risks

Community impacts

Beneficial 3

The current state of the Baltic has major consequences for local communities, and a potentially more oxygenated Baltic could prove a boom for those who rely on fishing. However, there are potentially also risks that could make the situation even worse (Conley et al, 2009).

Community impacts

Significant benefits to communities

Ease of reversibility

Unknown 0

If the pumping would be stopped while the cause of the problem remains, it is likely that the system will revert to a low-oxygen state.

Risk of termination shock

Medium 2

There could be significant negative effects if the artificial mixing of water levels suddenly halted (see Artificial Upwelling and Artificial Downwelling).

Risk of termination shock

Medium or relatively significant termination shock or damage

Legality/governance

Medium 2

This could partially be done in waters that fall under States’ exclusive sovereignty, however, given the probable regional and Baltic wide effects, international collaboration would likely be required.

Legality/governance

Fits within existing structures to a certain degree, but some policy changes are needed to deploy at scale

Scientific/media attention

Medium 2

There has been some scientific attention for this project and it has been featured several times in popular media too.

Scientific/media attention

Some attention within the scientific community, including published research and funding programmes; some media attention; some commercial interest

References

Conley, D. Save the Baltic Sea. Nature 486, 463–464 (2012). https://doi.org/10.1038/486463a

Conley, D. J., Bonsdorff, E., Carstensen, J., Destouni, G., Gustafsson, B. G., Hansson, L. A., ... & Zillén, L. (2009). Tackling hypoxia in the Baltic Sea: is engineering a solution? https://doi.org/10.1021/es8027633

Forth, M., Liljebladh, B., Stigebrandt, A., Hall, P. O., & Treusch, A. H. (2015). Effects of ecological engineered oxygenation on the bacterial community structure in an anoxic fjord in western Sweden. The ISME journal, 9(3), 656-669. https://10.1038/ismej.2014.172

Liu, S., Zhao, L., Xiao, C., Fan, W., Cai, Y., Pan, Y., & Chen, Y. (2020). Review of artificial downwelling for mitigating hypoxia in coastal waters. Water, 12(10), 2846. https://doi.org/10.3390/w12102846

Ollikainen, M., Zandersen, M., Bendtsen, J., Lehtoranta, J., Saarijärvi, E., & Pitkänen, H. (2016). Any payoff to ecological engineering? Cost-benefit analysis of pumping oxygen-rich water to control benthic release of phosphorus in the Baltic Sea. Water Resources and Economics, 16, 28-38. https://doi.org/10.1016/j.wre.2016.11.001

Rolff, C., Walve, J., Larsson, U., & Elmgren, R. (2022). How oxygen deficiency in the Baltic Sea proper has spread and worsened: The role of ammonium and hydrogen sulphide. Ambio, 51(11), 2308-2324. https://doi.org/10.1007/s13280-022-01738-8

Stigebrandt, A. & Andersson, A. (2022). Improving oxygen conditions in periodically stagnant basins using sea-based measures-Illustrated by hypothetical applications to the By Fjord, Sweden. Continental Shelf Research, 244, 104806. https://doi.org/10.1016/j.csr.2022.104806

Stigebrandt, A. & Gustafsson, B. G. (2007). Improvement of Baltic proper water quality using large-scale ecological engineering. AMBIO: A Journal of the Human Environment, 36(2), 280-286. https://doi.org/10.1579/0044-7447(2007)36[280:iobpwq]2.0.co;2

Stigebrandt, A., Liljebladh, B., De Brabandere, L., Forth, M., Granmo, Å., Hall, P., ... & Viktorsson, L. (2015). An experiment with forced oxygenation of the deepwater of the anoxic By Fjord, western Sweden. Ambio, 44, 42-54. https://doi.org/10.1007/s13280-014-0524-9

Related ideas

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).

Industry

Enhanced weathering (on land)

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Ice sheets and glaciers

Pumping water onto ice sheets

One of the potentially most catastrophic effects of contemporary global warming would be the dramatic increase in sea levels as a result of the melting Greenland and Antarctic ice sheets. Even if all current emissions were immediately stopped, sea level rise could still occur because of locked-in warming (ICCI 2022).

Melting glacier ice, Rødefjord, Northeast Greenland National Park

Ice sheets and glaciers

Glacier insulation with fabrics

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Industry

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Industry

Black carbon reduction

Black Carbon (BC), also known as soot, is produced through the incomplete combustion of fossil fuels and biomaterials. Apart from its negative health impacts, BC also has significant climate effects because it generally has a lower albedo than its surroundings, which increases the amount of radiation absorbed both when BC is present in the atmosphere and when it is deposited on land (Stjern et al. 2017). Due to the large albedo differences, the effects of BC are especially significant in areas that are normally covered in snow or ice (Hadley and Kirchstetter 2012; Sand et al. 2016; Kang et al. 2020).

Sea ice, North-West Spitsbergen National Park, Svalbard

Sea ice & icebergs

Sea Ice growth management

Arctic sea ice extent has rapidly decreased over the last few decades, with most multi-year ice disappearing altogether. This has already had major effects on local communities and ecosystems. The disappearance of the relatively reflective sea ice also leads to a dramatic decrease of albedo in the Arctic and subsequent high energy uptakes by the darker water during the Arctic summers.

Oceans & marine

Promoting ocean calcifiers to sequester atmospheric carbon

The oceans are the largest carbon sink for atmospheric carbon and have taken up over 30% of anthropogenic emissions. Carbon uptake occurs abiotically through processes such as ocean-atmosphere interaction and weathering processes. Biotic processes play an important role in oceanic carbon uptake too, with most attention going to carbon-consuming photosynthesising organisms.