Ice covers 10 percent of our planet but it’s now disappearing at alarming rates. Using data collected by the Intergovernmental Panel on Climate Change (IPCC), scientists have discovered that ice sheets in Greenland and Antarctica are melting six times faster than in the 1990s. The rise in global temperatures is largely to blame. But scientists have discovered a new phenomenon that could be adding to the problem: dark ice.
Dark ice forms when dust, soot, and algae settle on ice and turn it into a dark, black hue. This change in color causes the ice to absorb more heat than regular, white ice, and melt at faster-than-normal rates.
Scientists predict that dark ice and a warmer climate may cause sea levels to rise so much that by 2100, 400 million people could lose their homes and livelihoods to coastal floods each year.
In this article, we explore why dark ice forms, and what impact it could have on climate change.
What is dark ice?
Dark ice is a phenomenon where the upper layers of an ice sheet or glacier become coated with dark-colored particles known as cryoconites.
Cyroconites are usually powdery dust or soot particles that are carried from wildfires, towns, and cities by the wind. Its name comes from the ancient Greek words κρύον, which means cold or ice and κόνις, which means dust.
In some places, these particles mix with ice algae after they settle on the snow. The algae are photosynthetic microorganisms that turn dark to protect themselves from the harsh sunlight on the ice. As the algae bloom and combine with the black carbon particles, they become embedded in the snow. The darkened surface in turn reduces the ice’s albedo or overall reflectivity.
When this happens, ice begins to absorb more heat than it usually does. This effect is most visible in Greenland, where 586 billion tons of ice melted in 2019.
The darkened ice heats up so rapidly during the summertime heat that rocky coastlines, previously covered in snow, become exposed. Melting glaciers pour water out into the sea and cause sea levels to rise in the area. On the ice sheet itself, streams of freshwater and melt ponds appear as the top layers melt away.
Scientific estimates suggest that between 2000 and 2015, the average ice albedo of Greenland’s ice declined by 5 percent. This small shift has already caused dark snow to melt at a rate that’s 300 percent higher than regular, clean ice.
Is dark ice a sign of climate change?
Yes, dark ice reflects the rate at which our climate is changing. Human activity is causing global average temperatures to rise and the air to become polluted with fossil fuel particles. Both of these changes contribute directly to the formation and melting of dark ice, which reinforces the cycle of climate change.
These changes are significant because ice acts as an “air conditioner” for our planet. Clean, white ice reflects about 70 percent of solar radiation into space. Our polar ice caps help moderate the global climate and keep our northern and southern polar regions cool.
When this ice starts turning dark from cryoconite deposits, the world slowly becomes unable to cool itself. Retreating ice exposes the ocean’s dark surface, which is said to absorb 90 percent of the sun’s heat. Changes in ocean temperatures, plus the addition of freshwater into the North Atlantic, can lead to ocean circulation shifts that destroy ecosystems and create extreme weather patterns, such as El Niños.
The warming of temperatures around the Arctic Sea also causes permafrost to thaw. According to NASA, thawing releases carbon dioxide and methane into the atmosphere, which further contributes to our climate change problem.
Scientists predict that dark ice will continue to cause Greenland’s icecap, along with other parts of the polar ice caps, to thin over the next few decades.
How far is dark ice spreading?
Increasing amounts of soot from fires, ultra-fine particles from car engines, and dust from exposed agricultural soil are traveling thousands of miles from population centers to lodge themselves in ice sheets.
Recent research suggests that dark ice is spreading to places as diverse as the Himalayas and the Arctic.
In Nepal, geologists recorded dark ice forming for a week on the world’s highest glacier, Khumbu. The fine dust particles, blown in by fierce winds, settled on the ice and turned the snow black and brown. The geologists found that the sudden darkening reduced the ice's albedo by 20 percent in a single month.
Just a bit further away, on the Tibetan Plateau, soot from wood-fired cooking stoves has caused a similar darkening of the glaciers. The contaminated ice melts in freshwater quickly, carrying the dirty particles down into the Yangtze, Ganges, Yellow, and Mekong rivers. These rivers serve as the primary source of water for two billion people.
The dark ice phenomenon has even spread to parts of the western United States. Throughout the 2010s, snowpacks of the Colorado Rockies were caked in layers of red dust that caused the snow to melt weeks earlier than normal. The dirt came from the deserts of the Southwest and was carried to the snowpacks by wind storms.
Coupled with rising temperatures, dark ice has accelerated melting in the Sierras and the Cascade Range to the point that researchers found little snow to measure on the mountains during a 2014 expedition.
Dark ice will likely continue to spread as dust storms become bigger and people buy up more fossil fuel cars to drive. We’re already seeing fierce winds sweep dust from the Sahara and north into Britain and Norway. It may not be long before dark ice spreads to parts of Antarctica, which have been previously sheltered from dust.
The scientific community’s efforts to study dark ice
The dark ice phenomenon has garnered a lot of attention lately for its role in speeding up climate change in the Arctic.
In the past decade, several universities and research agencies conducted surveys in Greenland and the Arctic ice cap to measure the spread of dark ice and its impacts on sea levels. Here’s a look at some of the scientific community’s efforts to study dark ice:
The Dark Snow Expedition
Climate scientists Johnny Ryan of Aberystwyth University and Jason Box of the Geological Survey of Denmark and Greenland organized the Dark Snow Expedition in 2014 to measure the albedo of Greenland’s ice sheet.
Using NASA satellites, UAVs, and pyranometers, they discovered that the Arctic ice sheet was 5.6 percent darker than the average recorded between 1981 and 2010. They also sought to understand how the complex composition of soot, algae, and dust on the ice influenced the behavior of the ice.
A French study of the Arctic ice cap
Another study of Greenland’s ice sheet by a team of French government meteorologists has found that dark snow is lengthening the ice’s melting season.
The scientists reported that between 1992 and 2010, the Arctic ice cap lost a staggering 27 billion tonnes of ice per year due to dust deposits on the ice’s surface, on top of the 12.9 billion tonnes lost to warming temperatures. The dark snow caused the ice’s melting season to extend by six to twelve days per decade compared to data recorded in the 1970s.
They also predicted that the continued loss of ice would cause sea levels to rise by several centimeters before the end of the century.
Stanford University study on cryoconite
Researchers at Stanford University’s Atmosphere/Energy Program have discovered that cryoconite “is the second-leading cause of global warming after carbon dioxide”.
The particles, created by emissions from the burning of fossil fuels and wood, were found to accelerate Arctic warming and kill over 1.5 million people prematurely each year.
The researchers said that the best way of slowing warming around the Arctic Sea would be to control the flow of soot to the area.
Ways to limit dark ice
Dark ice can be limited through a reduction in the burning of fossil fuels and forests. Scientists believe that if fewer amounts of soot and dust reach the Arctic ice sheet, cryoconite deposits are less likely to occur.
Cutting soot emissions requires a collective change in the way we live our lives. Environmental policies as simple as installing pollution traps on diesel engines can significantly reduce the number of carbon emissions that cause dark ice.
Here are some ways that dark ice can be limited.
Cut as much carbon dioxide as possible out from our lives
Governments can initiate laws and programs that limit the use of carbon-intensive technologies.
Items like dung-fired stoves were discovered by scientists to be the leading cause of dark ice in places like Nepal and Tibet. These can be replaced with solar stoves that perform the same function without producing destructive soot.
Urban centers also have a role to play in the formation of dark ice. Plumes of smoke from our cars and coal-fired power plants contain ultra-fine carbon particles that can get carried by strong winds to the Arctic glaciers. By switching to electric vehicles and clean energy systems, we can significantly reduce the amount of these particles in our atmosphere.
Prevent deforestation
Slash-and-burn techniques used by farmers to clear forests have long been known to contribute to climate change. The burning of vegetation produces soot and exposes the soil to wind. It also increases the risk of drought as the loss of tree cover reduces the effectiveness of the planet’s water cycle.
Over time, strong winds can carry soot from the fires and dust from the exposed soil to the polar ice caps, creating dark ice. It’s therefore crucial that we keep as much of the world’s land forested through conservation and tree planting efforts.
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