In 2017, 100 million Pacific cod disappeared off southern Alaska’s coast. This 70% reduction (over 2 years), represents an unprecedented crash of fishery worth $100 million annually, and it was caused by an increase in ocean temperatures. By Francesca Young
The culprit? “The Blob,” a 4 million square kilometre expanse of ocean water 2.5°C warmer than usual (Cornwall, 2019). This change in temperature, although seemingly small, has wreaked havoc on marine ecosystems. With ocean temperatures reaching unprecedented highs, marine heatwaves like “The Blob” are becoming increasingly common (Saunders, 2023). As we approach critical thresholds, scientists look towards extreme measures - could ‘turning down the sun’ save our marine life from the rising heat?
Ecosystems in crises
“The Blob”, a marine heatwave, began disrupting at the base of the marine food web with phytoplankton, the microscopic plants which all life relies on. In Alaska, warmer temperatures altered circulation and nutrient flow, reducing phytoplankton populations (Cornwall, 2019). As the food chain’s foundation weakened, population crashes of larger marine creatures, from fish to whales, followed (NOAA Fisheries, 2019).
Moreover, marine heatwaves are driving fish migration poleward toward cooler waters, as well as creating dead zones — areas with insufficient oxygen for marine life to survive (Woods Hole Oceanographic Institution, 2019). The doubling of marine heatwave days has led to a 4.1% global decline in marine food sources, with some regions seeing 90% reductions (Oliver et al., 2018; Free et al., 2019; Cornwall, 2019). These changes disrupt commercial fisheries contributing $230 billion to the global economy, crucial for food security particularly, especially in less developed countries and indigenous communities (Barange et al., 2014; Allison et al., 2009). The future is worse; even in optimistic emissions scenarios, projections unanimously forecast further declines in marine biomass, with proliferations of ‘Blobs’ predicted globally (Lotze et al., 2019). Without intervention, these heat waves will grow in duration and intensity, forcing the collapse of marine life, along with the fisheries and economies that depend on them (Cornwall, 2019).
A controversial path to cooling the planet
As an emergency resort, scientists propose climate manipulation strategies like solar radiation management (SRM), which aims to reflect sunlight and cool the planet quickly at low cost. One SRM method, stratospheric aerosol injection (SAI), involves injecting a layer of reflective particles, e.g. sulphate, into the stratosphere to reduce solar radiation reaching Earth (Tracy et al., 2022). Models suggest SAI could stabilise global temperatures at safe target values (1.5°C) and curb marine heatwaves, potentially halting fishery biomass declines (Hueholt et al., 2023).
However, not all models agree; some predict that SAI, by altering precipitation and circulation patterns, could disrupt phytoplankton growth and therefore overall ocean productivity (Tracy et al., 2022; Lauvset et al., 2017). Moreover, SRM’s impacts exhibit great variation, benefitting some regions’ fisheries while harming others (Lauvset et al., 2017). This patchwork effect raises serious concerns about localised food security and exacerbating climate inequalities.
Beyond temperature control: SRM’s ‘blind spot’
One thing that is certain however, is that SRM fails to address a key contributor to marine ecosystem collapse: ocean acidification. Ocean acidification occurs when the ocean absorbs atmospheric CO2, lowering seawater pH, which harms marine life, especially coral reefs. Coral reefs are important as they recycle nutrients for phytoplankton and feed fish that support commercial and subsistence fisheries (Crossland et al., 1991). Even if SRM lowers global temperatures, CO2 build-up would still acidify oceans, potentially causing 90% coral reef loss by 2045, threatening marine ecosystems and dependent economies (Woods Hole Oceanographic Institution, 2019).
Moreover, sudden ocean cooling may also alter ocean circulation, accelerating and broadening ocean acidification, potentially acidifying the entire ocean (Tjiputra et al., 2016). Dr Kelsey Roberts, an expert in marine conservation, stated, “if you lower the temperature globally, but you don’t do anything about the existing CO2 in the atmosphere, you could end up with a cooler but more acidic ocean, which will create a whole new set of problems” (Roberts, 2023).
Roberts emphasises that SAI should only be considered alongside industrial-scale Carbon Dioxide Removal (CDR) strategies, which suck and capture CO2 from the atmosphere. This combination is crucial for tackling both the symptoms (rising temperatures) and the root cause (CO2 emissions) of climate change. Without addressing the latter, SAI alone could prove to be far more detrimental than traditional emissions reductions.
Fisheries at a crossroads: The uncertain future of SRM
Marine ecosystems are fragile, and SRM’s ecological impacts are largely unknown. Before deploying SRM, further research is crucial for assessing all potential effects on ecosystems. Moreover, political and ethical complications question SAI’s viability as a climate solution. Whilst it offers quick fixes to ocean surface temperatures, can we ethically justify a solution that might benefit some regions while severely harming others?
Whilst the need for action is indisputable, our best course may be to commit to significant emissions reductions and focus on adapting to the inevitable consequences of our alterations to the planet, as further manipulating our environment could potentially lead to more harm than good.
References
Cover Image Credit: Pexels, https://www.pexels.com/photo/dead-fish-on-shore-11658911/
Allison, E.H., Perry, A.L., Badjeck, M.C., Adger, W.N., Brown, K., Conway, D., et al. (2009) 'Vulnerability of national economies to the impacts of climate change on fisheries', Fish and Fisheries, 10(2), pp. 173–196.
Barange, M., Merino, G., Blanchard, J.L., Scholtens, J., Harle, J., Allison, E.H., et al. (2014) 'Impacts of climate change on marine ecosystem production in societies dependent on fisheries', Nature Climate Change, 4(3), pp. 211–216.
Cornwall, W. (2019) 'Ocean heat waves like the Pacific’s deadly "Blob" could become the new normal', Science. Available at: https://www.science.org/content/article/ocean-heat-waves-pacific-s-deadly-blob-could-become-new-normal (Accessed: 12 January 2024).
Crossland, C.J., Hatcher, B.G. and Smith, S.V. (1991) 'Role of coral reefs in global ocean production', Coral Reefs, 10(2), pp. 55–64.
Free, C.M., Thorson, J.T., Pinsky, M.L., Oken, K.L., Wiedenmann, J. and Jensen, O.P. (2019) 'Impacts of historical warming on marine fisheries production', Science, 363(6430), pp. 979–983.
Hueholt, D., Barnes, E.A., Hurrell, J.W., Richter, J.H. and Sun, L. (2023) 'Assessing outcomes in stratospheric aerosol injection scenarios shortly after deployment', Earth's Future, 11(5), e2022EF002981.
Lauvset, S.K., Tjiputra, J. and Muri, H. (2017) 'Climate engineering and the ocean: effects on biogeochemistry and primary production', Biogeosciences, 14(24), pp. 5675–5691.
Lotze, H.K., Tittensor, D.P., Bryndum-Buchholz, A., Eddy, T.D., Cheung, W.W.L., Galbraith, E.D., et al. (2019) 'Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change', Proceedings of the National Academy of Sciences, 116(26), pp. 12907–12912.
NOAA Fisheries (2019) 'Looking Back at The Blob - Chapter 2: Marine Heat Wave Intensifies, "Completely Off the Chart"', NOAA. Available at: https://www.fisheries.noaa.gov/feature-story/looking-back-blob-chapter-2-marine-heat-wave-intensifies-completely-chart (Accessed: 12 January 2024).
Oliver, E.C.J., Donat, M.G., Burrows, M.T., Moore, P.J., Smale, D.A., Alexander, L.V., et al. (2018) 'Longer and more frequent marine heatwaves over the past century', Nature Communications, 9, Article number: 1324.
Roberts, K. (2023) Interview with Kelsey Roberts [Interview], 18 December. Available at: https://www.climateinterventionbiology.org/author/kelsey-roberts/ (Accessed: 12 January 2024).
Saunders, T. (2023) '2023 on track to be world’s hottest year on record, temperatures exceed 1.5°C above pre-industrial levels for first time', ABC News. Available at: https://www.abc.net.au/news/2023-09-11/global-temperatures-pass-1-5c-above-pre-industrial-levels/102836304 (Accessed: 12 January 2024).
Tjiputra, J.F., Grini, A. and Lee, H. (2016) 'Impact of idealized future stratospheric aerosol injection on the large‐scale ocean and land carbon cycles', Journal of Geophysical Research: Biogeosciences, 121(1), pp. 2–27.
Tracy, S.M., Moch, J.M., Eastham, S.D. and Buonocore, J.J. (2022) 'Stratospheric aerosol injection may impact global systems and human health outcomes', Elementa: Science of the Anthropocene, 10(1), p. 00066.
Woods Hole Oceanographic Institution (2021) 'Ocean Warming'. Available at: https://www.whoi.edu/know-your-ocean/ocean-topics/climate-weather/ocean-warming/ (Accessed: 12 January 2024).
