Reflective foams and bubbles on oceans

Oceans & marine

Cape Petrel (Daption capense), Antarctic Peninsula

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.

Taking inspiration from the naturally occurring whitecaps on ocean water, several scholars have raised the idea to artificially enhance ocean albedo. Such ideas roughly fall under two categories: the (often mechanical) production of microbubbles, and the chemical production of foam (Evans et al. 2010). The main study on foams is by Aziz et al. (2014), who experimented with non-toxic biodegradable additives and found that they had lifetimes beyond three months in a tank. There have been more studies on the albedo enhancement potential bubbles. Seitz’s (2011) exploratory paper is often cited and suggests mechanically produced micro bubbles could provide a long-lasting method of ocean albedo enhancement. A similar idea for a small floating device that injects nanobubbles in the water has more recently been suggested under the name FizzTop (see Clarke 2022). Another often mentioned method focuses on the possible utilization of ships that already sail the oceans, mainly through a modification of their wake (Crook et al. (2016). Ortega and Evans (2017) consider such deployment to be most likely because it would require far less energy to maintain a coverage as compared to other measures. Haley and Nicklas (2021) conceived of a foam or bubble-like structure that could also function as a material for floating tiles which could be released onto sea surface. They furthermore suggest these tiles could be coated with fertilizers or alkalizers to raise oceanic pH and increase oceanic carbon drawdown. However, as they mainly study releasing these in the Atlantic Gyre, an area that falls beyond the geographical scope of this study, these will not be covered further.

Technological Readiness Level (TRL)

Low 1

There have been a few idealized experiments with bubbles and foams in experimental tanks. The long lifetimes reported by Seitz (2011) and Aziz et al. (2014) in such tanks are, however , probably not accurate depictions of their behavior in open seas and significantly overestimate their lifetime (Crook et al, 2016). Several smaller organizations, like Reflective Earth ( https://www.reflectiveearth.org/our-work), who have a portfolio of actions and activities, are studying ocean surface albedo modification. Apart from technical issues, there are large uncertainties around potential radiative forcing effects (Cvijanovic et al 2015) and effects on marine biochemistry. Gattuso et al. (2018) therefore label the technological readiness of ocean surface albedo enhancement as low.

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

This is highly uncertain as the technology does not yet exist. Some authors are very optimistic (see especially Seitz, 2011), and the potential to utilize the already large surface area covered by ocean going ships might raise high expectations. However, as Crook et al (2016) show, there have to be many adjustments to make ship’s wake modification have a significant impact.

Scalability

Physically somewhat scalable; linear efficiency

Timeliness for near-future effects

Unknown 0

Because the technology does not yet exist, and there are several different possible technologies to be developed, this is hard to say at this point.

Northern + Arctic potential

Unknown 0

Crook et al’s (2016) model study reveals that ocean surface cooling could potentially have a large impact in the Northern regions, as they find significantly greater cooling and radiative forcing effects in the Northern Hemisphere. Cvijanovic et al (2015) however argue that surface albedo modification generates very different cooling than global TOA reduction through, for example, SAI, as the former would generate local cooling that would then diffuse to other areas, while the latter would cause a more uniform global cooling. Their model study furthermore shows that local albedo modification might to some degree restore Arctic sea ice, but that this effect would not be enough to save the ice permanently if global temperatures continued to rise. The local specificities of the Arctic would furthermore mean that the distribution of any technology would face significant difficulties (see also sea ice albedo enhancement). It is for example unclear how a bubble producing device or a chemical additive would behave in Arctic sea ice waters, and also the modification of ships’ wakes might be less effective in the North as the region is less traversed (Crook et al, 2016).

Global potential

Unknown 0

Seitz (2011) suggest that the albedo of certain parts of the planet’s oceans could be increased by as much as 0.2 if these bubbles with a radius of 1 µm could in the right concentration. He furthermore writes of ideal potential global cooling of ‘a few degrees K’, which would mean that relatively modest energy inputs could be enough ‘to offset petawatts of CO2 induced radiative forcing.' Gabriel et al (2017) model simulation also showed that the introduction of a reflective layer on certain areas of the ocean could ‘reduce global mean surface temperature relative to RCP6.0 by 0.6 K’, and achieve a global average forcing of −1.5 W m−2. Gattuso et al. (2018) ocean based climate solutions summary report equally estimated its potential as high. There could moreover be cooling effects from cloud interactions, as Evans (2010) noted that artificial whitecaps would increase the amount of salt aerosols in the air, and thereby encourage the formation of reflective clouds that could hopefully reduce even more radiation. ///However, to all these estimates it has to be added that the required technology does not exist, and Crook et al (2016) therefore also emphasize their simulation’s significant global mean radiative forcing of −0.9 Wm−2 and a 0.5°C reduction of global mean surface temperature where only a result of them enhancing 'wake albedo by 0.2 and increasing wake lifetime by ×1440'. ///Zhao et al (2020) modeling study moreover found that another technology Marine Cloud Brightening, could have a 40% greater forcing efficacy than ocean surface albedo modification, and that this technology could also be extra beneficial because it would reflect radiation higher up in the atmosphere, and not at the surface, which has extra benefits of reducing shortwave heating of the lower atmosphere.

Cost - benefit

Unknown 0

Because there is no certainty on which technology to use, there is as of now no credible costing estimate. Gattuso et al (2018) estimate a low cost efficiency in comparison with other ocean based solutions. Ortega and Evans (2017) furthermore note that energy consumption could be prohibitively high, thereby driving up costs.

Environmental risks

High 1

There have been no detailed studies on the environmental effects of ocean albedo modification, but because this would impact the amount of energy available to marine life, Gattuso et al. (2018) and NASEM, (2021) warn there can be significant effects on biotic processes, which could in turn also reduce carbon drawdown. This is also highlighted in the summary by the geoengineering-skeptic platform GeoengineeringMonitor. Apart from biochemical effects on the oceans, the increased reflection of incoming solar radiation might also impact rainfall patterns, with Gabriel et al’s (2016) simulation showing 'increase in rainfall over land, most pronouncedly in the tropics'.

Environmental risks

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

Community impacts

Unknown 0

A major effect could be that ocean albedo modification would potentially impact local ecosystems by changing the amount of available light for photosynthesis. This would thereby impact communities that rely on fishing. Given the previous protests by indigenous groups against sea ice albedo modification (See sea ice albedo modification), it is not unreasonable to expect similar opposition to ocean albedo modification technologies.

Ease of reversibility

Unknown 0

The technology could likely be switched off easily. A caveat should perhaps be added to the production of foams through chemical agents, which would potentially have to be removed if found faulty.

Risk of termination shock

Medium 2

If stopped, the regular warming rate would likely continue as before the technology was deployed. However, if applied every year, the sudden energy increase after the measure would be halted could cause a shock to local ecosystems.

Risk of termination shock

Medium or relatively significant termination shock or damage

Legality/governance

Medium 2

The usage of chemicals to produce foam would likely be far more problematic than bubbles, but because the technology is in such an early stage, many uncertainties remain with regards to questions of governance.

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

Although several private scholars and engineers have explored the topic, and Crook et al’s (2016) paper was part of a research project at the University of Leeds, ocean albedo modification remains a rather unexplored field that is also largely absent in popular media accounts.

Scientific/media attention

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

References

Aziz, A., Hailes, H. C., Ward, J. M., & Evans, J. R. (2014). Long-term stabilization of reflective foams in sea water. Rsc Advances, 4(95), 53028-53036. https://doi.org/10.1039/C4RA08714C

Crook, J. A., Jackson, L. S., & Forster, P. M. (2016). Can increasing albedo of existing ship wakes reduce climate change?. Journal of Geophysical Research: Atmospheres, 121(4), 1549-1558. https://doi.org/10.1002/2015JD024201

Cvijanovic, I., Caldeira, K., & MacMartin, D. G. (2015). Impacts of ocean albedo alteration on Arctic sea ice restoration and Northern Hemisphere climate. Environmental Research Letters, 10(4), 044020. https://doi.org/10.1088/1748-9326/10/4/044020

Evans, J. R. G., Stride, E. P. J., Edirisinghe, M. J., Andrews, D. J., & Simons, R. R. (2010). Can oceanic foams limit global warming?. Climate Research, 42(2), 155-160. https://doi.org/10.3354/cr008885

Gabriel, C. J., Robock, A., Xia, L., Zambri, B., & Kravitz, B. (2017). The G4Foam Experiment: global climate impacts of regional ocean albedo modification. Atmospheric Chemistry and Physics, 17(1), 595-613. https://doi.org/10.5194/acp-17-595-2017

Garciadiego Ortega, E., & Evans, J. R. (2019). On the energy required to maintain an ocean mirror using the reflectance of foam. Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment, 233(1), 388-397. https://doi.org/10.1177/147509021775044

Gattuso J-P, Magnan AK, Bopp L, Cheung WWL, Duarte CM, Hinkel J, Mcleod E, Micheli F, Oschlies A, Williamson P, Billé R, Chalastani VI, Gates RD, Irisson J-O, Middelburg JJ, Pörtner H-O and Rau GH (2018) Ocean Solutions to Address Climate Change and Its Effects on Marine Ecosystems. Front. Mar. Sci. 5:337. https://doi.org/10.3389/fmars.2018.00337

Geoengineering Technology Briefing Jan 2021 GEOENGINEERINGMONITOR.ORG Analysis and critical perspectives on climate engineering info@geoengineeringmonitor.org Enhanced Microbubbles / Sea Foam. https://www.geoengineeringmonitor.org/wp-content/uploads/2021/04/enhanced_microbubbles.pdf

Haley, J. T., & Nicklas, J. M. (2021). Damping storms, reducing warming, and capturing carbon with floating, alkalizing, reflective glass tiles. London Journal of Research in Science: Natural and Formal, 21, 11-20. Available at: https://journalspress.com/LJRS_Volume21/Damping-Storms-Reducing-Warming-And-Capturing-Carbon-with-Floating-Alkalizing-Reflective-Glass-Tiles.pdf [Accessed 18 July 2024]

Clark, S. 2022. Planetary Restoration Blog. More Climate Solutions. https://planetaryrestoration.net/f/sev-clarke-more-climate-solutions [Accessed 16 July 2024]

National Academies of Sciences, Engineering, and Medicine (NASEM 2021). A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. https://doi.org/10.17226/26278

Seitz, R. (2011). Bright water: hydrosols, water conservation and climate change. Climatic Change, 105(3), 365-381. https://doi.org/10.1007/s10584-010-9965-8

Zhao, M., Cao, L., Duan, L., Bala, G., & Caldeira, K. (2021). Climate more responsive to marine cloud brightening than ocean albedo modification: a model study. Journal of Geophysical Research: Atmospheres, 126(3), e2020JD033256. https://doi.org/10.1029/2020JD033256

Related ideas

Oceans & marine

Ocean fertilization

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 like ocean-atmosphere interaction and weathering processes, and biotically, mainly through carbon consuming photosynthesising organisms.

Autumn at Mykland after forest fire 5 years ago

Land-based measures

Wildfire management

Fire is important to the healthy functioning of boreal ecosystems. However, as wildfires increase, they release greater amounts of GHGs into the atmosphere, contributing to climate change. While boreal fires typically contribute 10% of global CO2 emissions, in 2021, an extreme fire year, they accounted for 23% of global emissions (Zheng et al. 2023). Particulate matter in wildfire smoke (soot or black carbon, see also Black carbon mitigation) can also reduce albedo on sea ice and glaciers, enhancing ice melt (e.g., Aubry-Wake et al. 2022). Wildfires are projected to increase in both frequency and intensity over the coming decades (UNEP 2022). By 2050, wildfires in North American boreal forests alone could contribute close to 12 Gt CO2, almost 3% of the remaining global CO2 emissions to keep temperatures to below 1.5oC (Phillips et al. 2022a).

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).

Land-based measures

Agricultural soil management

Terrestrial carbon can be stored in biomass above or below the ground, and in soils themselves. Soil organic matter can form differently, and have different amounts of plant and microbial components depending on the availability of water (Cotrufo and Lavallee, 2022). The large amounts of the Earth that have been brought under cultivation over the past 12.000 years have significantly degraded soil carbon levels, and have released some 110 billion metric tons of carbon (Sanderman et al. 2017). Soil security and health is increasingly being recognised as essential for planetary health (Kopittke et al. (2022).

Land-based measures

Enhancing permafrost refreezing with air pipes

Large areas of the Northern and Arctic regions consist of permafrost, almost permanently frozen soil. As global temperatures rise, these permafrost areas are thawing at an ever faster rate. This thawing leads to massive amounts of GHGs being released into the atmosphere, as carbon stored in the permafrost is converted into methane by bacteria. Because methane is a very potent GHG, the thawing of the permafrost is considered a major tipping point in the climatic system. Permafrost preservation is of the utmost importance because Arctic terrestrial regions alone hold up to 1500 Pg C (Schuur et al. 2015), and although there is large uncertainty about the total amount of emissions from permafrost (Miner et al. 2022), especially when it comes to nonlinear abrupt thawing (Turetsky et al. 2020), significant amounts of carbon release is to be expected as the Northern regions warm.

Atmosphere / solar radiation

Arctic Marine Cloud Brightening

Roughly one-third of the incoming solar radiation is directly reflected back into space by the Earth’s atmosphere and surface albedo. Clouds play an important role in this, although their role is double as water droplets can also interfere with outgoing longwave radiation, thereby contributing to the greenhouse effect. Over open water clouds can make a particularly big difference as the albedo of the water is below 0.1, thereby absorbing most of the sun’s energy.

Sea ice melting, North of Dickson, Taymyr, Russia

Sea ice & icebergs

Pykrete usage

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.

Industry

Arctic methane capture and usage

Methane is a highly potent greenhouse gas and its reduction is given ever greater priority in international emission reduction policies. Given the increasing, and potentially catastrophic rate of methane release from the thawing Arctic and Northern permafrost, these regions are crucial in this endeavor. Apart from the methane release from microbial activity in thawing permafrost on land, methane also escapes in the form of hydrates which have been formed under sediments beneath the sea.