Arctic geoengineering

Arctic sea ice coverage as of 2007 compared to 2005 and also compared to 1979-2000 average

Arctic Geoengineering is the attempt to influence arctic climate conditions using the methods and principles of geoengineering. As a proposed solution to climate change it is relatively new and has not yet been implemented at large scale. It is based on the principle that Arctic albedo plays a large role in regulating the Earth's temperature and that there are large-scale solutions that can preserve this. Advocates for Arctic geoengineering cite that projections of sea ice loss adjusted to account for recent rapid Arctic shrinkage suggest that the Arctic will likely be free of summer sea ice sometime between 2059 and 2078 thus it would be necessary to take actions to slow or stop this.

Current proposed methods include using sulfate aerosols to reflect sunlight, pumping water up to freeze on the surface, and using Hollow Glass Micro-spheres to increase albedo. These methods are hotly debated, and criticisms have been published that these methods are 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. Later, in 1965, the Johnson administration 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 Lowell Wood advanced the proposition of bombarding the Arctic stratosphere with sulfates to build up an ice sheet which would “suck heat in from the mid-latitude heat bath”. Other plans have since been proposed including the use of Hollow Glass Micro-spheres (HGMs).

Motivation

The Arctic region plays an important role in the regulation of the Earth's climate. Conditions in the Arctic may suggest the existence of tipping points, including ice–albedo feedback from melting Arctic sea ice and Arctic methane release from thawing permafrost and methane clathrate. The speed of future retreat of the Arctic sea ice is contentious. 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, the ice has since undergone unexpectedly significant retreat, reaching a record low area in summer 2007 before recovering somewhat in 2008.

A tipping point process could potentially commence as the Arctic region warms, if there is positive feedback with sufficient gain. Tim Lenton suggests that the retreat of sea ice is such a process, and the tipping may have started already. 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.

Preventing such ice loss is important for climate control, as the Arctic ice regulates global temperatures by virtue of its albedo, and also by restraining methane emissions from permafrost near the shoreline in the Arctic region. Additionally, the sea ice has a wider regional climatic role since it acts to maintain permafrost in the general region through its ability to insulate cold winter winds from the warm sea.

Proposed geoengineering methods

Stratospheric sulfate aerosols

The idea to inject sulfate aerosols into the stratosphere comes from simulating volcanic eruptions. Sulfate particles found in the atmosphere are used to scatter sunlight, which increase 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. This technique is not specific to the Arctic region. He found that At high latitudes, there is less sunlight deflected per unit albedo change but climate system feedbacks operate more powerfully there. These two effects largely cancel each other, making the global mean temperature response per unit top-of-atmosphere albedo change relatively insensitive to latitude.

Building thicker sea ice

Mechanics

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. Sea ice is an effective thermal insulator, and thus freezing takes place much more rapidly on the top surface of the ice sheet than on the bottom. Thicker sea ice is more structurally stable and is more resistant to melting due to its increased mass. An additional 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.

Wind power pumps to build thicker sea 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 that use wind power to drive them have been successfully used in the South pole 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.

Concerns

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 spreading glass over new ice works because the new ice is formed in the months were there is little sunlight, thus the effectiveness of the glass beads can not 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.

Influencing ocean temperature and salinity

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.

Further reading

• Steffen, Will; Sanderson, A.; Jäger, Jill; et al. (September 2005). Global Change and the Earth System: A Planet Under Pressure. Springer. p. 150. ISBN 978-3-540-26594-8.