Cryoconite refers to soot, dust and other particulate matter (such as heavy metal pollutants) that has landed on snow and ice. They can occur naturally from activities such as dust-storms, volcanic eruptions and forest fires. They can also be due to human activities such as coal mining, manufacturing operations, land-clearing and desertification. Once liberated, the small particles are carried by air and ocean currents around the world and deposited in some of the most remote polar and mountainous regions of the world.
Despite their ubiquity, the impact of cryoconites in the climate change saga has remained largely understated. However, with more and more effort directed towards mitigating and adapting to global climate change, cryoconites have started attracting the attention they deserve as a key player.
This is because cryoconites have been found to accelerate the impacts of climate change. The small particles of dust and soot reduces albedo – or natural reflectivity of snow and ice. Earth’s polar, snow and ice-covered regions act like natural mirrors by reflect incoming solar radiation back into space. Snow has an albedo of 0.9 while sea-ice has an albedo of 0.8. This mean that they reflect 90% and 80% of sunlight respectively.
By contrast, snow and ice that has been discoloured by cryoconites can have an albedo as low as 0.2 (or even lower). The low reflectivity of the darker areas means that the absorb more heat from sunlight and melt much quicker compared to brighter areas. As the particles heat up they form small water-filled holes which further adds to the impacts of climate change. It creates a ‘positive feedback’ loop as the water (sea-water has an albedo of 0.06) absorbs more heat from the sun and accelerates the melting process. In some areas, these holes aggregate and form large pools and streams.
Known as ‘moulins’, the fast flowing melt-water carves its way through the surface of the snow and ice. Eventually, the melt-water burrows through the thick ice and reaches the bottom where it acts like a lubricant making it easier for larger bodies of snow and ice to slide, often into the sea.
Although the loss of sea-ice, snow and glaciers often happen in remote places, their loss has the potential for widespread ecological, cultural and geopolitical ramifications. Greenland, for example is losing an estimated 250 billion tonnes of ice per year. If it was to melt completely, global sea-levels would rise by about six metres. Further, the latest data indicates that the volume of water melting in Greenland caused the underlying tectonic plate to warp. On the opposite end of the world, scientists are concerned about West Antarctic Ice Sheet (known as Larsen C) breaking off. In a matter of days, the rift that is causing the ice-sheet to weaken grew by 11 km.
If the worst case scenario is realised, then the boundaries of many nations will need to be re-drawn. For some nations such as Tuvalu, the Maldives, and the Kiribati the rising sea-levels are already a fact of life. Wealthy nations with large coastal cities are also expected to suffer. Livelihoods which are intimately dependent on the rivers and streams that are fed by glacial melt such as the Mekong, Yangtze and the Ganges will be lost as the snow and ice retreat. And finally, considering that snow and ice account for 75% of global freshwater, their loss will undermine future resource and food security.
In light of the above, there are a number of strategies that have been put forward to drastically reduce the amount of cryoconites being produced due to human activities. Some strategies to do so include:
- Setting higher vehicle emission standards
- Using public transport
- Promoting the rapid transition away from fossil fuels
- Encouraging the government to stop the development of new open-cut mines
- Stopping excessive tree-clearing, particularly, in NSW and QLD
- Supporting and taking part in tree planting activities
- Managing large-scale forest (bush) fires
Cryoconites have long remained on the backstage as the world grappled and continues to grapple with mitigating human induced climate change. However, their presence in snow and ice-covered regions of the world has been found to accelerate their loss. Thankfully, many of the strategies identified to address climate change can also have a positive impact in reducing cryoconites.