Arctic geoengineering: Difference between revisions

Temperatures in the Arctic region have tended to increase more rapidly than the global average, and the effects of global warming on the region have been generally well represented in climate models.^[1] Various geoengineering schemes have been suggested to reduce the chance of significant and irreversible effects on global warming and sea level rise.

Several geoengineering proposals have been made which are specific to the Arctic. They are usually hydrological in nature, and principally centre upon measures to prevent Arctic Ice Loss. These are detailed below.

In addition, two general geoengineering techniques, namely marine cloud brightening and stratospheric sulfur aerosols^[2] have been proposed for cooling the Arctic region to save the Arctic sea ice.

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^[3] and Arctic methane release from melting permafrost and methane clathrate^[4]. 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' process could potentially commence as the Arctic region warms, if there is positive feedback with sufficient gain. Professor Tim Lenton suggests that the retreat of sea ice is such a process, and the tipping may have started already^[5]. Geoengineering 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.^{[6][7][unreliable source?]} Additionally, the sea ice has a wider regional climatic role, and acts to maintain permafrost more generally in the region, by insulating the cold winter winds from the warm sea.^[8]

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.^[9] As ice is an insulator, water on the surface of the ice tends to freeze more quickly than that below. River water could be used for this purpose, as salt water tends to resist freezing, and may end up perforating the resulting ice sheet.

Ice sheets can be destabilised by the presence of water between the ice and the rock base.^{[citation needed][unreliable source?][10]} Arctic Explorer David de Rothschild from Sculpt the Future, UK has proposed geoengineering scheme to actively pump water out from under (or from pockets within) the ice sheet in order to stabilise the ice mass (or remove heat and the fallen meltwater that can stay accumulated within ice cavities and fissures). Until recently, moulins were mostly formed near the edge of Greenland's ice sheet draining their water quickly from ice back to the sea when the melting season ends.^[11][12] The seasonal impact moulins that drain themselves fast deserve little attention as their heat effect is not accumulative. However, the melting inreasingly occurs further inland where Greenland's ice sheet has a subglacial topography to take meltwater (and heat in it) inwards, towards subglacial, subsided Greenland interior. These accumulative impact moulins build up a growing layers (or pockets) of water under (or within the ice) that benefit from draining operations to remove meltwater and its heating from within the ice, or, improve the hold of ice sheet against ground as water pools are pumped away and ice rests back onto rough rock terrain rather than floating frictionlessly on meltwater pools. The impact of Greenland's interior moulins is the ultimate greenhouse effect in action as the thick ice is a very good insulator to keep heat trapped almost indefinitely once the melt water and heat in it has fallen under or within the ice sheet through these accumulative impact moulins that can only be remedied by artificial draining.

Thickening ice by spraying seawater onto existing ice has been proposed.^[13] 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.^[14]

Ken Caldeira et al analysed the effect of geoengineering in the Arctic using Stratospheric sulfur aerosols^[15] 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.

• Geological Engineering
• Geological and geophysical engineering
• Environmental geology
• Exploration geophysics
• Engineering geology

• Global Change and the Earth System