Artificial downwelling

Oceans & marine

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

Oceans play an important role in global heat transfer and carbon storage processes. As global temperatures and atmospheric carbon levels rise, some have suggested artificially modifying the vertical movement of water to enhance these processes.

Artificial downwelling (AD) is an idea to pump upper layer water deeper down into the ocean. This has also been suggested as a means to increase oxygen levels at deeper layers (see Oxygenating the Baltic), but in the following AD will be considered in terms of its proposed functionality of carbon transportation from upper layers to the deeper ocean. Although questions remain about the efficacy of AD for the purpose of carbon transportation to deep waters, the assumption is that it can artificially mimic a natural process in which carbon-saturated surface water can be pumped down to deeper levels where carbon levels are lower. The idea to use AD for this purpose was first suggested by Zhou and Flynn (2005), but has received relatively little further attention afterwards due to the very high associated costs and limited efficacy (GESAMP 2019). Multiple techniques have been suggested to pump ocean water up or down (Pan et al. 2016), and small scale tests have been conducted with physical pumps (Stigebrandt et al. 2015), with at least 60 different technologies currently patented (Liu et al. 2020). However, most of these technologies are designed to oxygenate deep water, and it is unclear if these techniques could feasibly be used to increase carbon uptake in the deep ocean at scale. The GESAMP (2019) report notes that some authors have previously suggested to artificially cool areas at high latitudes to increase thermohaline circulation and enhance downwelling, but that these techniques have not since been considered.

Technological Readiness Level (TRL)

Low 1

As a CDR measure AD is currently not considered or developed in major research projects, and there is no clarity on how to actually downwell water at scale (GESAMP, 2019). The Swedish company Desert Ocean writes that they want to develop AD but provide no further information (https://www.desertocean.se/technology). ///This lack of research stands in contrast to the relative frequency and prominence with which AD is referred to in lists of ocean based climate interventions like NASEM (2022). This can probably be explained by the linkage of AD with artificial upwelling, and because some of these studies include the research into AD as a measure to increase oxygen levels in the deep ocean.

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

Scalability

Physically somewhat scalable; linear efficiency

Timeliness for near-future effects

Low 1

Timeliness for near-future effects

Implemented too late to make a significant difference

Northern + Arctic potential

Low 1

AD has been sometimes suggested to be deployed in the Arctic through an amplification of already existing downwelling thermohaline processes (GESAMP, 2019).

Northern + Arctic potential

No noticeable extra positive effect beyond the global average; technology is unsuited to the Arctic

Global potential

Low 1

The CDR potential of AD is considered to be very low (Zhou and Flynn, 2005; Lenton and Vaughan, 2009).

Global potential

Insignificant to be detected at a global scale

Cost - benefit

High 1

Zhou et al (2005) damningly conclude that: ‘[t]he estimated cost for the most favorable case is so high compared to alternatives with less uncertainty that the pursuit of this alternative for carbon sequestration is not attractive.’

Cost - benefit

Cost of investment comparable to cost of avoided damage

Environmental risks

Medium 2

Although there are no specific studies on the environmental impacts of AD for CDR purposes, NASEM (2022) outlines certain risks for both AD and artificial upwelling, and Conley (2012) warns specifically of significant consequences of AD proposals in the Baltic.

Environmental risks

More widespread and possibly regional impacts that extend beyond the immediate solution deployment location

Community impacts

Neutral 2

Community impacts

Unnoticeable or negligible positive or negative effects

Ease of reversibility

Easy 3

Ease of reversibility

Easily reversible naturally

Risk of termination shock

High 1

Risk of termination shock

High or very significant termination shock or damage

Legality/governance

Medium 2

Webb et al (2022) note that both AD and artificial upwelling would fall under national governance and legal frameworks, as well as international conventions like the United Nations Convention on the Law of the Sea, the Convention on Biological Diversity, the Convention on the Prevention of Marine Pollution by Dumping of Waste and Other Matter, and the Protocol to that Convention.

Legality/governance

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

Scientific/media attention

Low 1

Although AD is being developed for other purposes, and some reviews note it as an option, as a CDR measure AD is not seriously considered after initial estimates by Zhou and Flynn (2005) judged it as infeasible (GESAMP, 2019).

Scientific/media attention

Very low attention from individuals and/or abandoned ideas; low media attention; no commercial interest.

References

Conley, D. J. (2012). Save the Baltic Sea. Nature, 486(7404), 463-464. https://doi.org/10.1038/486463a

Lenton, T. M., & Vaughan, N. E. (2009). The radiative forcing potential of different climate geoengineering options. Atmospheric Chemistry and Physics, 9(15), 5539-5561. https://doi.org/10.5194/acp-9-5539-2009

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

National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. https://doi.org/10.17226/26278.

Pan, Y., Fan, W., Zhang, D., Chen, J., Huang, H., Liu, S., ... & Chen, Y. (2016). Research progress in artificial upwelling and its potential environmental effects. Science China Earth Sciences, 59, 236-248. https://doi.org/10.1007/s11430-015-5195-2

Romany M. Webb, Korey Silverman-Roati, and Michael B. Gerrard. 2022. Removing Carbon Dioxide Through Artificial Upwelling and Downwelling: Legal Challenges and Opportunities, Sabin Center for Climate Change Law, May 2022. Available at: https://scholarship.law.columbia.edu/faculty_scholarship/3337/ [Accessed 18 July 2024]

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