When Glaciers Get Dirty
by Paige Brown, Museum Blogger-in-Residence.
If you’ve ever jumped up from a chair or a car seat that was too hot because it had been exposed to the summer sun, you might be familiar with the fact that dark-colored materials absorb more heat than light-colored materials. Your black t-shirt or dark-colored leather car seat absorbs more heat from the summer rays than does your white t-shirt or tan-colored car seat.
While you might never have had the pleasure of walking on top of a glacier in Greenland or Antarctica, if you’ve experienced the enhanced heat absorption of dark materials in the sun, you already know something about what is making glaciers melt so quickly in today’s climate. Along with warming of our planet’s climate attributed to both natural forces and man-made greenhouse gas emissions, a black substance called cryoconite is causing glaciers all over the world to melt more quickly today than in the past.
Cryoconite is powdery windblown dust made of a combination of small rock particles, soot and bacteria. The dark dust, which is spread over glaciers in Greenland and other icy areas of the world by wind and rain, is composed of mineral dust from warmer regions of the world, rock particles from volcanic eruptions, and soot from fires, the emissions of our cars and coal-fired power plants. While many of the materials in cryoconite are natural materials, human activities based on coal use have increased the amount of black soot in cryoconite since the substance was first discovered in 1870. The increasing amount of black soot in cryoconite has caused glaciers to darken in a phenomenon scientists call “biological darkening,” as the gritty substance builds up on snow, glaciers and icecaps. While clean white ice helps to reflect the sun’s rays, soot-containing cryoconite increases the absorption of heat by the ice surface, making snow and glaciers melt more quickly.
The combination of global warming and biological darkening of glaciers due to cryoconite build-up is creating a vicious cycle of glacial melting. As glaciers melt more than normal, the water normally trapped inside the ice flows into the sea and global sea levels rise. With sea level rising, people living in coastal environments, for example on the coastal plain of North Carolina or along the coast in the Gulf of Mexico, are at risk from flooding and losing their land to the ocean.
Cryoconite does other strange things to the ice. As the black substance causes the ice surface to melt, it causes round melt holes filled with water to form. As the cryoconite sinks and creates a black layer at the bottom of these holes, the holes continue to melt deep down into the ice. The holes also harbor bacteria and other small organisms that produce energy and contribute to the growth of the holes.
Cryoconite Holes, Greenland.
World-renowned photographer James Balog and other scientists who study glaciers around the world have played an important role in documenting cryoconite build-up and glacial melting in scientific evidence and photographs.
If you want to learn more about what is making glaciers melt, and what cryoconite holes look like, check out James Balog’s documentary film “Chasing Ice.” The film is both beautiful and heart-wrenching, showing how glaciers of enormous proportions are being melted largely by human influences.
You can also learn about what ice tells us about the climate by interacting with the exhibits on the second floor of the Nature Research Center.