Glacier Geoengineering, a human solution for a human problem?
Geophysics is an instrumental field for understanding and mitigating the effects of climate change, and one fast-increasing region of criticality are polar ice sheets. As global temperatures rise, which they already have done by 1 degree Celsius, the destabilisation and melting of glaciers contributes significantly to sea-level rise, particularly those in polar regions. One controversial approach to addressing this issue is glacier geo-engineering, which brings with it technical, political, and philosophical challenges. The Thwaites Glacier poses the most significant looming threat with regards to sea level rise, due to its noted weakness to surrounding warm waters and potential to raise global sea levels by 65 centimetres.
Geo-engineering is a relatively new term used to describe interventions aimed at altering the natural progression of global systems, most commonly undoing the effects of climate change. For glacier geo-engineering, interventions have been suggested on a basal and oceanic level: basal interventions focus on increasing the friction between the ice sheet and the underlying continental basement to slow down the glacier's flow towards the sea, for example by pumping water from the base or using thermosyphons to remove heat; oceanic interventions aim to prevent warm water from reaching the glacier's base most commonly by reducing water flow rates. The primary objective of glacier geo-engineering is to slow the retreat of critical glaciers like Thwaites and Pine Island in Antarctica, as well as smaller but still vulnerable glaciers in Greenland. Thwaites Glacier, in particular, is of significant concern to the community due to its being larger than Florida, and it retreating at a rate of half a kilometre per year. It also acts as a buttress to the rest of the West Antarctic Ice Sheet, so would be a tipping point in the fight against rising sea levels.
Geophysics plays a crucial role in understanding glacier dynamics, and therefore the feasibility of geo-engineering interventions. Techniques such as satellite remote sensing, ground penetrating radar (GPR) and seismic surveys can provide detailed insights into the glacier's structure, movement, and underlying geology. Interferometric Synthetic Aperture Radar (InSAR) has been pivotal in monitoring the dynamics of the Thwaites Glacier. Radar waves are reflected off of the changing surface of the glacier, and so measures the displacement of the glacier surface revealing the rates of ice flow and grounding line retreat. InSAR has also revealed that the height of the glacier seems to align with the tides, increasing at high tide, indicating that there are likely waves pushing underneath the glacier during high-tide of the Amundsen Sea. Seismic and GPR are also used, particularly by the GHOST (Geophysical Habitat of Subglacial Thwaites) investigation, which is mapping the bedrock and subglacial environment. These methods help identify subglacial ridges and other features that influence the glacier's stability. For example, a subglacial ridge 70 km inland from the current grounding line, the line at which beyond the glacier is separated from the basement by water, may offer some resistance to the glacier's retreat. The dip-direction of the basement rock is pivotal to the rate of retreat of the glacier's grounding line, as it is easier for the glacier to retreat when the underlying rock is in retrograde. Hence, finding future ridges could help direct the spatial coordination of any possible geoengineering projects.
The scientific and environmental community are divided on the feasibility and ethical implications of glacier geo-engineering. Proponents, such as John Moore of the University of Lapland, argue that such interventions could buy time for humanity to reduce greenhouse gas emissions and avoid catastrophic sea-level rise. Critics, such as Twila Moon of the National Centre for Snow and Ice, warn that focusing on geo-engineering could divert attention and resources from the essential task of reducing emissions, and so human interaction with scientific progress is brought into question.
Implementing these methods on the whole expanse of the Thwaites Glacier, or even just the Thwaites Ice Shelf (the region that sits directly above warm sea water) would be among the largest civil engineering projects undertaken by humanity so far, comparable to the Three Gorges Dam in likely cost. This is largely due to the remote environment of Thwaites, being 700km from the nearest permanent research station and hence only available to be worked on during the 3-month field-season. The methodology itself contains many technical challenges beyond remoteness, for example maintaining sub-zero temperatures in boreholes to prevent refreezing. The energy requirements for basal drilling are also substantial, and environmental limitations prevent solar-power from being used, meaning it would be instrumental to weigh up the emissions cost of running such a program using fuel.
Ethically, the debate centres on the potential for geo-engineering to cause unintended, but predictable, harm to local ecosystems and indigenous communities. Geo-engineering has a psychological allure as a distraction from the harder but more permanent and wide-reaching solution of emission reduction. The harms from geo-engineering and ice-sheet retreat need to be compared to one another, and then each geo-engineering method needs to be compared in turn with simple hard and fast emission reduction, so a global conclusion can be made.
The potential for informed decision making could be increased by using effective public engagement and transparent policy discussions, such as that at Stanford. Creating a geo-engineering plan for the Thwaites Glacier, even if acknowledged by scientists to not be a full solution, may be perceived by policy-makers as the right course of action in a panicked turning point moment that could arise in the future. If such an event were to happen, the best way to ensure that rapid action is not more damaging to the environment is to make assessments from many different fields as to the benefits of geo-engineering. This includes marine ecology, sociology, the political and geographic science of the Antarctic Treaty, the list goes on.
The Thwaites Glacier is the current focal point for discussions on glacier geo-engineering, whilst some locations in Greenland have been highlighted as optimal for earlier tests due to its easier access. The rapid retreat of Thwaites, driven by the influx of warm, salty water beneath the ice, presents a significant challenge for glaciologists. Recent studies using ICEYE satellites and other remote sensing technologies have provided detailed measurements of the glacier's grounding line and the tidal movements of water underneath, which are actually expanding the grounding line into a "grounding zone" which was effectively visualised using the IceFin submersible.
The potential solutions proposed for Thwaites have evolved significantly over time from a sill to block warm water intrusion underneath the glacier, to using flexible buoyant curtains anchored to the seabed to reduce water flow, to even building artificial islands to buttress the glacier in place. These projects have been pushed to evolve due to arguments made to their feasibility, but sometimes it appears that these modifications are made to appease voices not-yet-spoken. Its evident from the research on these technologies that the ecological effect is considered afterwards, and is often the consequential breaker of the potential for ideas to follow through. Further uncertainty is created by the unpredictable consequences of surrounding glaciers, if a method such as ocean curtains were to be deployed, as any diverted warm currents will end up going somewhere.
The scale of the intervention required for Thwaites is unprecedented, as the costs and logistical challenges of such projects are immense. Thwaites was the last part of Antarctica to be mapped on the first continent-wide expedition, and its remoteness has been maintained throughout recent history. Its 700km distance from the nearest dedicated research base means that it is only reached using either ice-breakers over sea, which have had limited success in the past due to thick off-coast ice-sheets, or traverses (large industrial tractors with trailers for equipment) travelling over the icy landscapes. Furthermore, Shaun Fitzgerald from The University of Cambridge has pointed out that the energy needed to bore multiple holes and keep them sub-zero would be "insane", requiring a continuous supply of fuel if the basal method were to be used.
Ultimately, both the feasibility and impact of glacier geo-engineering need to be assessed, largely using geophysics, before further modelling. This has been undertaken by the ITGC's role to map the glacier's internal structure, measure its movement, and model the interactions between ice, water, and bedrock. Geophysical results will inform the design and implementation of any geo-engineering solutions.
Until the ITGC's survey in 2018, no large scale field data collection was collected: this has proved necessary due to the many illuminating differences between what was theorised and what is actually present beneath the Thwaites glacier. Without understanding the current behaviour of the glacier, such as the stratification of fresh-water and sea-water at its basement, or its dependence on the dip of the bedrock, future behaviour of the glacier could be incorrectly predicted. Geophysical investigations have also revealed more concerns to be considered during future assessments, such as the presence of local basins carved out of the underlying continent, which have potential to fill with warm salt-water if the grounding zone retreats far enough, increasing the velocity of iceberg discharge.
Advanced modelling techniques are also being used offsite to simulate the effects of different geo-engineering interventions, such as at The University of Cambridge's Centre for Climate Repair. These models help predict how changes in temperature, water flow, and ice dynamics will impact the glacier and surrounding environment. But as history has shown time and time again, theory can only take you so far. For this reason, talks of glacier geo-engineering so far have maintained the need to only deploy strategies that will be easy to remove again: whilst factually beneficial, policy-makers may view such uncertainty as a type of experimentation of our planet, a view already expressed by some Greenland residents over possible geoengineering on their land.
Effective glacier geo-engineering requires collaboration between geophysicists, climate scientists, engineers and policymakers. This was the philosophy behind the Stanford December 2023 conference: geophysicists contribute their expertise in data analysis and modelling, while other disciplines provide insights into the environmental, technical, and societal aspects of geo-engineering. This is doubly important due to the sensitive nature of the Antarctic Treaty, illustrating how politics and approval will be the ultimate limiting factor behind whether any strategies are implemented. Uniting the 46 countries to agree on these implementations may prove difficult when a group of 52 scientists cannot agree whether or not this conversation should even be happening.
Now that the ITGC research has finished, and a wealth of geophysical data is available for scientists to create better and more accurate models, it would seem we are reaching a point where a decision regarding glacier geo-engineering may soon be made. While ocean curtains and basal freezing do offer potential solutions to slow the melting of the most critical glacier in the world currently, it also raises significant concerns over whether it would be beneficial for the globe, and whether it is feasible to even consider. The data so-far, including many cost-analyses comparing an ocean curtain to seawall defences of cities like New York, seem to suggest that implementation of strategies might be cost effective for the world as a whole. And as the melting process of Thwaites has already begun, as demonstrated by tidal behaviour, it seems that urgent action in addition to emission reduction may be required for the safe-guarding of future generations. Cities like Saint Louis in Senegal are also at risk of the 65 cm sea-level rise that the melting of Thwaites would cause, whilst lacking the funds to support construction of sea-wall defences. Defending Thwaites may be the best use of our resources in this case.
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