Glacier Geoengineering May Have Unintended Consequences for Marine Ecosystems and Fisheries

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2025AV001732

Authors

Mark James Hopwood, Sascha Schiøtt, Hilde Oliver

First published: 19 August 2025

https://doi.org/10.1029/2025AV001732

Abstract

Numerous proposed geoengineering schemes to mitigate climate change and its consequences are now widely discussed in the scientific literature. Sea level rise is a clear example of the implications of climate change with a further committed rise of at least 2–3 m embedded within the Earth System from +1.5°C of global warming. A bold suggestion to reduce sea level rise is to install underwater barriers to reduce the inflow of oceanic heat around Antarctica and Greenland. Inflow of warm, saline water masses drives ice melt and the destabilization of tidewater glaciers. Whilst the basic theory that barriers would stem oceanic heat flow is uncontroversial, the extent to which barriers might reduce future ice mass loss is less certain. There are numerous concerns about the viability and side-effects of this proposed intervention. We use existing field observations and representative fjord-scale models for the Greenland's largest glacier, Sermeq Kujalleq in the Ilulissat Icefjord, to suggest that there is already sufficient evidence to conclude that artificial barrier installation would have negative regional implications for marine productivity. The effects on fisheries are a concern as negative implications for Greenland's regional fisheries are unlikely to be socially acceptable. Increasing “geoengineeringization” of the Earth Sciences is likely to continue in coming decades as society grapples with the challenges of slowing climate change and mitigating its consequences. To produce beneficial results, the technical and social viabilities of geoengineering concepts need to be considered in parallel, with the latter determined in a complex social, economic and cultural nexus.

Plain Language Summary

Around Antarctica and Greenland, the melting of marine-terminating glaciers and ice shelves is often driven by heat from the inflow of warm seawater. This is leading to the destabilization of ice and driving faster rates of global sea level rise. A widely discussed geoengineering concept is that the construction of artificial underwater barriers at strategic locations could be used to reduce the inflow of warm saline waters and possibly help stabilize sensitive ice sheet outflows into the ocean. This would theoretically reduce future sea level rise, although there are presently large uncertainties predicting to what extent ice melt would be reduced. Apart from the numerous engineering challenges in any such polar geoengineering scheme, there are critical concerns about the resulting side-effects. In a case study for Greenland's largest marine-terminating glacier, we use a combination of model results, field observations, and local knowledge to suggest that artificial barriers would negatively affect marine productivity. Negative impacts on fisheries raise critical questions about the social viability of any such scheme which need to be considered in parallel with, rather than after, the technical viability of barrier installation and function.

Key Points

Proposed geoengineering schemes to mitigate sea level rise include artificial sills/curtains to restrict flow of warm water toward glaciers

Field observations and representative models for Ilulissat Icefjord suggest this would likely have negative effects on regional fisheries

The social implications of geoengineering concepts for stakeholders need to be considered in parallel with the technical aspects

Source: AGU

[Renaud de RICHTER]

phys.org /news/2025-09-underwater-glacier-walls-unintended-consequences.html

Underwater glacier-guarding walls could have unintended consequences

Saima May Sidik 15/09/2025

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Warm water flowing into fjords and beneath ice shelves will continue to be a prime cause of glacial melting as global temperatures rise. This melting will, in turn, contribute to sea level rise and increasing inundation of coastal areas.

As emission reductions fall short of international goals, scientists and some members of the public are discussing possibilities for using geoengineering to mitigate coastal flooding and other detrimental effects of climate warming.

One proposal involves building barriers in the ocean to block warm water from reaching glaciers. For example, some scientists have proposed placing a floating steel curtain or an underwater rock wall around parts of the Greenland ice sheet to limit the influx of warm, ice-melting currents.

Such barriers would be difficult to construct, and it's not clear how effective they would be, Mark Hopwood and colleagues point out in a recent commentary in AGU Advances focusing on the potential effects of this method on Greenland's largest glacier, Sermeq Kujalleq.

What's more, underwater walls are likely to come with substantial downsides for marine ecosystems. Modeling suggests that such barriers would interrupt a process by which glacial runoff pulls nutrient-rich water up from the deep ocean. This disruption, in turn, would reduce phytoplankton levels near the surface and the fish populations that depend on them—ultimately affecting the Greenlanders that rely on these fish for their livelihoods.

Walls might also disrupt fish migration patterns, adding to the problem. The side effects of underwater walls are "unlikely to be socially acceptable," the authors write. Walls built to protect Antarctic glaciers would have similar effects on local ecosystems, they suggest.

The researchers note that although glacier-guarding barriers are both hypothetical and unrealistic at this point, interest in geoengineering is likely to grow in the coming decades. Thus, it is important to keep the unintended consequences of such projects in mind.

Some researchers have suggested that geoengineering approaches should be tested so that policymakers can assess their costs and benefits on the basis of real-world data. But before they seriously consider these techniques, write Hopwood and colleagues, it's crucial that scientists have conversations with local stakeholders to understand how the potential trade-offs could affect their lives and livelihoods.

More information: Mark James Hopwood et al, Glacier Geoengineering May Have Unintended Consequences for Marine Ecosystems and Fisheries, AGU Advances (2025). DOI: 10.1029/2025AV001732

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