Arctic geoengineering. Arctic geoengineering is a type of climate engineering in which polar climate systems are intentionally manipulated to reduce the undesired impacts of climate change. As a proposed solution to climate change, arctic geoengineering is relatively new and has not been implemented on a large scale. It is based on the principle that Arctic albedo plays a significant role in regulating the Earth's temperature and that there are large-scale engineering solutions that can help maintain Earth's hemispheric albedo. According to researchers, projections of sea ice loss, when adjusted to account for recent rapid Arctic shrinkage, indicate that the Arctic will likely be free of summer sea ice sometime between 2059 and 2078. Advocates for Arctic geoengineering believe that climate engineering methods can be used to prevent this from happening.

Current proposed methods of arctic geoengineering include using sulfate aerosols to reflect sunlight, pumping water up to freeze on the surface, and using hollow glass microspheres to increase albedo. These methods are highly debated and have drawn criticism from some researchers, who argue that these methods may be ineffective, counterproductive, or produce unintended consequences.

Background

History 
The main goal of geoengineering from the 19th to mid 20th century was to create rain for use in irrigation or as offensive military action. In 1965, the Johnson administration in the US issued a report that brought the focus of geoengineering to climate change. Some of the early plans for geoengineering in the Arctic came from a 2006 NASA conference on the topic of "managing solar radiation" where astrophysicist Lowell Wood advanced the proposition of bombarding the Arctic stratosphere with sulfates to build up an ice sheet. Other arctic geoengineering methods have since been proposed including the use of hollow glass microspheres.

Motivation 
The Arctic's albedo plays a significant role in modulating the amount of solar radiation absorbed by Earth's surface. With the loss of Arctic sea ice and the recent average darkening of Arctic albedo, the Arctic is less able to reflect solar radiation and thus cool Earth's surface. Increased solar radiation causes higher surface temperatures and results in a positive feedback loop where arctic ice melts and albedo decreases further. Such a feedback loop can push temperatures past a tipping point for certain irreversible climate domino effects. This is known as the ice-albedo feedback loop.

Arctic sea ice retreat is further exacerbated by the release of methane, a greenhouse gas that is stored in arctic permafrost in the form of methane clathrate. Excess methane being released into the atmosphere could result in another positive feedback loop in which temperatures continue to rise and more arctic sea ice melts. At the current melting rate, if the global temperature rises 3°C above pre-industrial levels, the top permafrost layers of the arctic could melt at a rate of 30-85% and cause a climate emergency. The IPCC Fourth Assessment Report of 2007 states that "in some projections, Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century." However, arctic late-summer sea ice has since undergone significant retreat, reaching a record low in surface area in 2007 before recovering slightly in 2008. Climate engineering has been proposed for preventing or reversing tipping point events in the Arctic, in particular to halt the retreat of the sea ice.

Goals 
Proponents of arctic geoengineering believe that it may be one way of stabilizing carbon storage in the Arctic. Arctic permafrost holds an estimated 1,700 billion metric tons of carbon, which is about 51 times the amount of carbon that was released globally as fossil fuel emissions in 2019. Permafrost in the Northern Hemisphere also contains about twice as much carbon as the atmosphere, and arctic air temperature has increased at about six times more than the global average over the past few decades. Arctic ecosystems are more sensitive to climate changes and could significantly contribute to global warming if arctic sea ice continues to melt at the current rate. Preventing further ice loss is important for climate control, because the Arctic ice helps regulate global temperatures, by restraining strong greenhouse gasses like methane and carbon dioxide, which trap heat in Earth's atmosphere.

Proponents believe that geoengineering techniques could protect existing sea ice and promote further ice buildup by increasing ice production, reducing the solar radiation that reaches the ice's surface, and slowing the melting of ice. The proposed methods of recovering arctic ice vary in cost and complexity, with some of the more intensive methods requiring significant economic investments and complex infrastructure. One proposed method of increasing Earth's albedo is the injection of sulfate aerosols into the stratosphere. Other proposed geoengineering methods to recover arctic ice include pumping seawater on top of existing ice, and covering existing ice with small hollow glass spheres.

Proposed methods

Stratospheric sulfate aerosols
The idea to inject sulfate aerosols into the stratosphere comes from observations of volcanic eruptions. Sulfate particles found in the atmosphere help scatter sunlight, which increases the albedo, and in theory, produces a cooler climate on earth.

Caldeira and Wood analyzed the effect of climate engineering in the Arctic using stratospheric sulfate aerosols. He found that the Earth's average temperature change per unit albedo is unaffected by latitude because climate system feedbacks have a stronger presence in areas of high latitude; where less sunlight is reflected.

Building thicker sea ice
It has been proposed to actively enhance the polar ice cap by spraying or pumping water onto the top of it which would build thicker sea ice. A benefit of this method is that the increased salt content of the melting ice will tend to strengthen downwelling currents when the ice re-melts. Some ice in the sea is frozen seawater. Other ice comes from glaciers, which come from compacted snow, and is thus fresh water ice.

A proposed method to build thicker sea ice is to use wind powered water pumps. These pumps contain a buoy that has a wind turbine attached to it, which functions to transfer the wind energy to power the pump. The buoy also has a tank attached to it to store and release water as necessary. In theory, pumping 1.3 meters of water on top of the ice, at the right time, could increase the ice's thickness by 1.0 meter. The goal of this pump is to increase ice thickness in a way that is energy efficient. Pumps powered by wind have been successfully used in the Antarctic to increase ice thickness.

Glass beads to increase albedo 
Ice911, a non-profit organization whose goal is to reduce climate change, conducted an experiment in a lab. They found that releasing reflective material on top of ice increased its albedo. The reasoning behind this finding is that raising the ice's surfaces reflectivity increases its ability to reflect sunlight and therefore reduces the temperature on the ice's surface. Of the materials used, Ice911 found glass was not only effective in raising the ice's albedo, but it was also financially feasible and environmentally friendly. The team then moved forward and conducted field tests in California, Minnesota, and Alaska. In all field testing locations, the albedo were increased in ice that had the glass beads poured on top of it compared to the ice that didn't have the glass beads added to its surface. The findings indicate the glass beads placed on top of the ice increased the ice's reflectivity.

Decreasing water salinity 
Decreased salinity of ocean water causes it to become less dense, which in turn causes changing ocean currents.  For this reason, it has been suggested  that locally influencing salinity and temperature of the Arctic Ocean by changing the ratio of Pacific and fluvial waters entering through the Bering Strait could play a key role in preserving Arctic sea ice. The purpose would be to create a relative increase of fresh water inflow from the Yukon River, while blocking (part) of the warm and saltier waters from the Pacific Ocean. Proposed geoengineering options include a dam  connecting St. Lawrence Island and a threshold under the narrow part of the strait.

Limitations and risks

Adverse weather conditions 
Because geoengineering is a relatively new concept, there are no real studies on the ramifications of these new technologies and how they may affect weather patterns, ecosystems, and the climate in the long term. Certain methods of arctic geoengineering, such as injecting sulfate aerosol into the stratosphere to reflect more sunlight, or marine cloud brightening, may trigger a chain of events that may be irreversible. For the case of sulfur injection, such effects may include ocean acidification or crop failure due to either delayed precipitation patterns, or by reducing the amount of sunlight needed for them to grow. The latter effects are similar for marine cloud brightening. The process involves using boats to increase sea water aerosol particles in the clouds closest to Earth's surface in order to reflect sunlight.

Rapid Ozone Depletion 
Nobel laureate Paul Crutzen proposed a method of geoengineering in which emitting sulfates into the lower atmosphere would lead to global cooling and theoretically help tackle climate change. The possible downside of this is that injecting sulfates into the stratosphere has the potential to lead to ozone depletion. The process by which this works is that sulfate particles come into contact with atmospheric chlorine and chemically alter them. This reaction is estimated to have the possibility to deplete between one-third and one-half of the ozone layer over the Arctic if it goes into effect. A proposed alternative to prevent this from happening is to swap out sulfates for calcite particles, the idea being that this is the material emitted into the atmosphere during a volcanic eruption. There have not been any prototypes of such an experiment thus far, and while this method would not reverse the damage already done to the environment, it may aid in reducing some of the long-term potential damage.

Effectiveness of reflective particles 
There are concerns surrounding the effectiveness of using glass, and other reflective particles, to increase albedo. A study conducted by Webster and Warren found these particles actually increase the melting rates of sea ice. Webster and Warren argue that spreading glass over new ice works because the new ice is formed during the months with little sunlight; thus, the effectiveness of the glass beads cannot definitively be credited to the beads themselves. Additionally, Webster and Warren argue the glass beads used in the study absorbed dark substances and overall decreased the albedo, which could potentially lead to a faster melting rate of sea ice.

See also
 List of climate engineering topics

References

Planetary engineering
Arctic research
Environment of the Arctic
Climate change policy
Climate engineering