Solar Geoengineering Could Limit Sea-Level Rise from Cryosphere

Of the many impacts caused by climate change, sea-level rise threatens to be one of the most devastating due to the thermal expansion of the oceans and the melting of ice and glaciers on land. These impacts, along with numerous others related to rising global temperatures, may in the future motivate a country, a group of countries, or even a very rich individual to pursue solar geoengineering, a controversial proposal for limiting the amount of solar radiation that reaches the Earth’s surface. A recent study in The Cryosphere assessed the efficacy of such a solar geoengineering attempt at limiting global sea-level rise.

Geoengineering, as it relates to climate change, falls into two categories. The first, atmospheric carbon removal, entails physically removing carbon dioxide from the air to reduce greenhouse gas concentrations and limit temperature rise. The second, solar geoengineering, involves injecting sulfur dioxide or another aerosol into the stratosphere to reflect a portion of incoming solar radiation, again limiting temperature rise.

Because of the temperature-reducing effect of solar geoengineering, research suggests that such a proposal would also reduce sea-level rise. However, just how effective solar geoengineering could be in limiting sea-level rise had not yet received sufficient research, according to Peter Irvine, the lead author of the study, who spoke with GlacierHub. Irvine and his team of scientists hoped to “shed some light on the complexities of the sea-level rise response to solar geoengineering, make an initial evaluation of its efficacy, and to bring this issue to the attention of the cryosphere research community,” Irvine told GlacierHub.

Photo of the sun. Solar geoengineering could limit the amount of sunlight that reaches the Earth’s surface (Source: climatemediat/Twitter).

Initially, the researchers conducted a literature review on the small number of studies that explored the cryosphere’s potential response to solar geoengineering. A 2009 study that examined the Greenland Ice Sheet found that under a scenario where atmospheric concentrations were quadrupled, solar geoengineering could slow or even prevent the collapse of ice sheets. Conversely, a 2015 study determined that while solar geoengineering could slow melting, glaciers and ice sheets would not recover to past states. Lastly, a 2017 study focusing on high-mountain Asia, found that solar geoengineering would stop temperature increases; however, 30 percent of glaciated area would still be lost.

Following the literature review, the researchers evaluated the potential effect of solar geoengineering on three aspects of sea-level rise. The first aspect was thermosteric sea-level rise, or more simply, the thermal expansion of ocean waters. Because temperature is the dominant influence on thermosteric sea-level rise (warmer water is less dense than cooler water), the decrease in solar radiation reaching the Earth’s surface due to solar geoengineering would limit sea-level rise.

Secondly, the researchers examined solar geoengineering’s effect on the surface mass balances of glaciers and ice sheets. Surface mass balance is primarily affected by the surface melt rate, which is the result of the availability of energy at the surface of the ice. Thus, a change in solar radiation reaching the Earth’s surface would likely reduce surface melt. The analysis of large volcanic eruptions offers an analogous example to what might happen to surface melt if solar geoengineering were pursued because the dust and ash released during an eruption blocks some incoming solar radiation.

Photo of Pinatubo eruption Solar geoengineering could have a similar effect to the 1991 eruption of Pinatubo (Source: USGS/Twitter).

One study examined by the researchers showed that surface mass balances in Greenland were at their maxima in the year after the El Chicón and Pinatubo eruptions in 1982 and 1991, respectively. Similarly, another study in Greenland found that in the years following the El Chicón and Pinatubo eruptions, surface runoff was the third lowest and lowest, respectively, between the years 1958 and 2006, further reinforcing the expectation that solar geoengineering would limit surface mass balance reductions.

In addition to its effect on temperature, solar geoengineering would also affect the global hydrologic cycle and subsequently sea-level rise. Warming temperatures due to climate change will likely lead to more precipitation worldwide; however, if solar geoengineering is pursued, this increase could be offset. This precipitation change would affect both Greenland and Antarctica, according to Irvine.

In Greenland, surface melt changes, not precipitation accumulation, are the primary influence on surface mass balances; therefore, solar geoengineering would likely have a positive effect by reducing temperatures, with the decrease in precipitation unlikely to lead to mass balance decline. In Antarctica, on the other hand, increased precipitation due to climate change has had a positive effect on surface mass balance, thus a decrease in precipitation due to solar geoengineering would negatively impact mass balances.

The third and final sea-level rise aspect examined by the researchers to evaluate the efficacy of solar geoengineering was ice lost through calving and eventual ice-sheet collapse. Calving, the scientific name for icebergs breaking off a glacier at its terminus, depends on the speed at which ice flows, which itself is driven by climatic changes.

Photo of a calving glacier in Greenland A calving glacier in western Greenland (Source: NASA_ICE/Twitter).

In Antarctica, warming water known as circumpolar deep water (CDW) is the primary driver of calving. CDW is pushed below and then up into glacial cavities by surface winds, where the warm water melts the ice. This melting drives calving and leads to the thinning of glaciers.

While solar geoengineering would likely lower air temperatures, it is unlikely to reduce the temperature of CDW and limit melting and subsequent calving from below. In addition, a 2015 study found that solar geoengineering is unlikely to limit the upwelling of CDW and could even increase upwelling. However, this finding has yet to be replicated, according to Irvine, and it is not clear whether the results are exclusive to the model used.

There is also no guarantee that solar geoengineering would be able to prevent glacial collapse due to marine ice sheet instability. This collapse occurs when a glacier retreats past its grounding line (where ice meets underlying bedrock) and continues to retreat inland until it reaches another stabilizing ridge. The process might already be occurring at West Antarctica’s Thwaites and Pine Island glaciers, which are extremely vulnerable due to the sloping topography upon which they rest.

Nevertheless, retreat and possible collapse might be preventable, says a 2016 study. It showed that returning water to cooler conditions reversed glacial retreat. This finding indicates solar geoengineering may be useful to prevent marine glaciers from destabilizing. While encouraging, it remains likely that certain glaciers, especially those in West Antarctica, will continue to experience significant ice loss regardless of whether solar geoengineering is pursued or greenhouse gas emissions are dramatically reduced.

Based on their study, the researchers lay out four areas in need of future research. First is the need to evaluate the sea-level rise response to solar geoengineering scenarios in conjunction with climate change scenarios so that the efficacy of solar geoengineering and greenhouse gas emissions reductions can be compared. Second is the need to employ regional models of surface mass balance in order to assess the effectiveness of solar geoengineering to limit mass balance losses. Third, the researchers recommend additional evaluation of the effect of solar geoengineering on the CDW upwelling and stability of glaciers and ice-shelves. Finally, the researchers recommend the evaluation of sea-level rise risk, alongside the numerous other risks and challenges associated with solar geoengineering.

Diagram of glacier melting from below Diagram depicting a glacier melting from below due to warming ocean currents (Source: EuroGeosciences/Twitter).

The potential for solar geoengineering to limit sea-level rise from the cryosphere is still up for debate, but as this study shows, it may have the potential to reduce temperature and curb some aspects of sea-level rise, including surface mass balance losses and ocean thermal expansion. However, for other aspects, mainly the melting of glaciers from below by warm waters, it may be unlikely that solar geoengineering can limit sea-level rise contributions. Nonetheless, when it comes to the society-altering impact of sea-level rise, solar geoengineering could be a part of humanity’s response.

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Glacial Geoengineering: The Key to Slowing Sea Level Rise?

The rapid collapse of some of the world’s biggest glaciers due to climate change will have devastating consequences for our planet’s coastlines due to sea level rise. Compounding this issue is the fact that many of these coastlines are heavily populated and developed. A recent proposal, first reported in The Atlantic, aims to avert potential catastrophe by turning to geoengineering through the construction of massive underwater walls, called sills, which would be built where glaciers meet the ocean in Antarctica and Greenland.

The idea is the work of Michael Wolovick, a glaciology postdoctoral researcher at Princeton University. The uniqueness of his geoengineering proposal is its focus on a consequence of climate change, in this case sea-level rise, as a result of glacial collapse, rather than a focus on decreasing greenhouse gases (GHG), the root cause of climate change. Many geoengineering proposals attempt to slow down or even reverse the Earth’s rising temperatures as an alternative to GHG mitigation through the addition of aerosols like sulfur dioxide to the atmosphere or increase in the reflectivity of clouds, while others explore ways to capture and subsequently sequester carbon.

Photo of the Jakobshavn glacier in Greenalnd.
The calving front of the Jakobshavn glaicer in western Greenland. The Jakobshavn is a potential site for the proposal’s walls (Source: NASA Goddard Space Flight Center/Creative Commons).

When asked about the inspiration behind his distinct work, Wolovick told GlacierHub he has been fascinated by the large scale societal implications that glacial collapse could have, given the relatively small scales of the glaciers themselves. The so called “doomsday glacier,” the Thwaites of West Antarctica, is only around 100 km wide, for example, but its collapse would swiftly destabilize large parts of the West Antarctic ice sheet, potentially leading to sea level rise of up to 13 feet in some parts of the world.

So how does Wolovick’s plan work? It starts with an engineering project of unprecedented scale, the construction of large underwater walls, composed of an inner layer like sand and an outer layer of boulders. These walls would be strategically built at the grounding line, where a glacier’s leading edge meets the ocean, of the world’s most unstable glaciers. These walls would be built primarily in Antarctica and Greenland where many glaciers extend beyond the land to float on the ocean.

Figuredetailing how ocean ending glaciers are melted from below
Figure detailing how ocean-ending glaciers are melted from below. The walls from this proposal would be placed in front of the grounding line pictured here (Source: Smith et al.).

Glaciers that extend from land into the ocean are exposed to both warming air and water temperatures. Warmer sea water melts these glaciers from below in addition to the melting that occurs from the air above, causing them to melt faster than glaciers solely confined to land. This is where the walls built on the ocean-floor would come into play. Once in place, the purpose of these barriers would be “to block warm water so you could reduce the melting rate, and also to provide pinning points that the ice shelf could reground on as it thickens,” according to Wolovick. In addition, because the glaciers are already floating, the walls would prevent warm water from moving further inland and increasing melting rates there.

Would these walls work in actuality? Wolovick’s computer modelling is in its early stages, but some models show glaciers stabilizing after walls are put in place, with some glaciers actually gaining in mass. This possible stabilization would buy some time to act decisively on adaptation to sea level rise and perhaps allow the prevention of disastrous ice sheet collapse altogether. Still, Wolovick admits a lot more work needs to be done in the future including the development of better ocean models to see if the walls would block warmer water in the way intended, allowing a glacier to stabilize.

Photo of a calving front of a glacier in West Antarctica
The calving front of a glacier in West Antarctica (Source: NASA Goddard Space Flight Center/Creative Commons).

While the proposal has the potential to slow glacial melting, Lukas Arenson, principal geotechnical engineer at BGC Engineering Inc. who spoke with GlacierHub about the proposal, says it is still in its very early stages, and there are many questions that need to be answered before implementation. One of Arenson’s principle concerns is “the enormous costs for building such a sill or a dike in a stable manner in these areas as it requires some major engineering and construction efforts.” Wolovick recognizes that his proposal would require placing a massive amount of material in front of glaciers, especially for wide ones such as the Thwaites.

There are also a plethora of engineering matters that need to be addressed. First, the foundations for the walls would need to be well protected. This protection could take the form of boulders and concrete elements or additional sills built in front of or at an angle to the main sill to redirect currents that could compromise its effectiveness, according to Arenson. Secondly, the seafloor on which the walls would be built could be “quite unstable and soft at places so that placing additional fill for a sill may be extremely challenging, potentially causing some local instabilities,” Arenson added. Finally, Wolovick states that it may be necessary to build the wall “underneath floating ice shelves, or in the vicinity of dense iceberg melange.” These efforts would further complicate what would already be a mega-engineering project.

Photo of an iceberg in Pine Island Bay
An iceberg floats in West Antarctica’s Pine Island Bay where the Thwaites glacier ends Source: NASA Goddard Space Flight Center/Creative Commons).

In addition to the technical aspects of the proposal, there are other issues to consider. There is also the question of where the material for the walls would come from and whether the walls might have detrimental impacts on sensitive Antarctic sea floor environments.

However, despite the many challenges ahead, the time is right to take action. As climate change progresses and glaciers around the world continue to melt, global sea levels creep up. One recent study projects an increase of 80 to 150 cm (close to five feet) by 2100, which would flood land currently inhabited by 153 million people. This geoengineering proposal will by no means solve every problem associated with climate change, like unabated human emissions of greenhouse gases, but with millions living along the coasts, it could provide humanity with something always in short supply, time.

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Researchers turn to geoengineering to save Chile’s glaciers

https://www.flickr.com/photos/deepblue66/364369665/
Chile’s glaciers, like the one seen above, are under threat from mining and global climate change. Some researchers are trying to geoengineer a way to save them.
(Dietmar Temps/Flickr)

When you think of geoengineering, you may be imagining huge mirrors in space, or iron filings being dumped into the ocean. Geoengineering, though, can occur on a smaller scale. Some researchers are proposing small-scale fixes as in an effort to save some of Chile’s 3,100 glaciers.

Cedomir Marangunic, a glaciologist in Chile, saw the retreat of the country’s glaciers due to mining and global warming as an opportunity to test techniques for creating new glaciers and slowing the retreat of exiting ones.

How do you make a glacier? You can transport tens of thousands of tons of ice from a place where retreat is fast to a pre-prepared location where retreat is slower; you can set up barriers around an existing ice field, increasing snow accumulation and transforming the area into a small glacier; or you can cover an existing one with a “geotextile” sheet or rocky debris to slow ablution. A minimum of three years is required for some of these methods, according to Marangunic,

While stimulating the growth of new glaciers or slowing the retreat of established ones sounds great, project must simulate a “natural process” and avoid damage to local ecosystems, according to Marangunic, who claims this as a priority for his projects.

Others are not so convinced.

The head of Greenpeace Chile, Matias Asun, doubts that Marangunic’s techniques are “viable, sufficient, successful, and cost effective technologies.” Asun’s priority is promoting actions that protect and save existing glaciers, pointing out that despite the threat of climate change and industry, Chile’s glaciers are not protected by law. A bill in parliament proposes a registry of glaciers and a legal definition for them. The bill might increase awareness to their disappearance, but does little to protect them.

Currently, under the Chile’s water code, water rights are a private resource and can be bought, leading to the question of whether glaciers will be similarly purchasable. Environmentalists believe that that interpretation could allow mining interests to purchase rights to glaciers in order to degrade them with impunity.

Those 3,100 Chilean glaciers hold 82 percent of Latin America’s freshwater reserves – water that is crucial for industry and agriculture in the region. Government and business have an obvious and compelling imperative to save and restore the glaciers, but will leaders look to geoengineering or conservation? The window to conserve is closing, while the door to geoengineering is opening.

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If you build (an artificial glacier), they will come

https://www.flickr.com/photos/kenlund/1291996844/in/photolist-2YaPDE-fPdsWr-ittKQX-itumwT-itsxUL-itrYTq-ituePJ-ittBbL-itsgrX-ittfKc-ittvb6-itsg6s-itu4Hy-itsYCA-itsuWm-itsV3t-itsFUH-ittYPp-ittigf-ittfAg-its3D2-itsBpT-itsa6j-ittA8T-ittcTo-itt7qE-fPdsr2-nzqaKJ-itv23E-itrRLk-qUWW3-nB4wcJ-e8ifEq-itsoGB-e8czy6-e8ifx5-e8czvR-e8ifsm-e8ifkA-e8if3w-e8ieZA-e8ieX7-ittYjz-ituc9A-ituDUC-ittZkf-ittHK6-itvgZL-ittjBy-ittNDK/
Oregon’s Mount Hood has seen the decline of three of its glaciers, Flickr/Ken Lund

The concept of geoengineering artificial glaciers is starting to gain traction among glacier communities around the world. Advocates recently hosted a presentation on “Artificial Glaciers in the Northwest”

The presentation, delivered in April 2014 in Hood River, Oregon by Emily Smith and Tom Bennett of Portland State University, discussed the possibility of importing those techniques to the north side of Mount Hood. The mountain has seen the decline of its Eliot, Coe and Langille glaciers, and the presentation organizers hope that the method can offset the loss of those glaciers.

That method was created by Chewang Norphel, a civil engineer in Ladakh, India, who pioneered a way to “grow” glaciers in the Himalayas. A short film about Norphel’s mission to create small glaciers in Nepal, “Beyond Prayer”, shows the retired engineer describing his technique, which relies on the redirection of streams in the winter to cool areas, and constructing breaks to slow the flow of water. The water freezes along the mountain slope at regular intervals. During the winter, an ice sheet covers these frozen pools, creating small, artificial glaciers.

https://www.flickr.com/photos/jace/4337244484/
Civil engineer Chewang Norphel created a technique to restore melting glaciers. (Flickr/Kiran Jonnalagadda)

Norphel had the irrigation of villages in mind when he developed the artificial glaciers, so it is unclear if it will be used in Oregon. That low cost geoengineering techniques from Nepal are finding their way to glacier communities of the Pacific Northwest U.S. speaks to the common challenges and threats faced by communities throughout the world, and to the growing awareness within these communities that they can benefit from more contact with each another.

BEYOND PRAYER from SPOTFILMS on Vimeo.

 

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