Drone's-eye view reveals just how polluted and soot-covered Greenland's glaciers have become

Scott Sutherland

Monday, July 14, 2014, 2:28 PM - The drone's-eye view of the Greenland Ice Sheets shown above should be revealing a near-blinding, but beautiful vista of pristine white snow and glacial blue ice. However, instead it is showing us just how dark the snow there has become, and this has serious implications for global warming and for sea level rise in years to come.

The above video was shot by scientists working with the Dark Snow project, a team that is currently camping out on the ice sheets while they investigate an alarming drop in the reflectiveness (aka 'albedo') of Greenland over the past several years.

Greenland, despite its name, is mostly white, due to over three-quarters of the island's land-area being covered in glacial ice and snow (even in summer). All that ice and snow plays an important part in Earth's climate. Not only is it a massive store of freshwater, which helps keep our oceans at the levels we're currently used to (and what our coastal cities and infrastructure currently depend on), but it helps regulate the planet's thermostat, both through influencing local weather patterns and by reflecting a significant amount of the sun's light back into space. It's this last part, the albedo of the ice and snow, that's the latest concern when it comes to global warming and climate change.

When the Sun's light (short-wave radiation) reaches Earth, about three-fifths of it makes it straight through the atmosphere to the ground without stopping, while the rest is either absorbed or reflected by clouds. At the ground, some is reflected (about one twelfth of the total), with the remainder absorbed by the surface. The surface gets heated by this, and that heat is radiated as long-wave radiation, and while greenhouse gases - carbon dioxide, methane, water vapour, etc - aren't too partial to short-wave radiation, they 'gobble up' long-wave radiation. This traps that radiation in the atmosphere, forcing it to take a much longer route than it normally would before finally working its way back to the top of the atmosphere, to be radiated away into space. The trace amounts of these greenhouse gases that are in our atmosphere have been just enough to give Earth a warm, hospitable environment for life, which is why our current trend of pumping billions of tons of carbon dioxide into the atmosphere every year is such a big concern. Levels are currently 40 per cent higher than they were before the start of the Industrial Revolution, and they're rising, which means that more of that radiation is going to be trapped as times goes on.

The increase in greenhouse gas concentrations is just one part of this, though. If the albedo of the planet changes, that changes how much short-wave solar radiation is converted to long-wave radiation, and thus how much long-wave radiation there is for the greenhouse gases to absorb. While every surface has some ability to reflect incoming sunlight, the best reflectors are ice and snow. A glacier with fresh snow on top of it, for example, directly reflects around 90 per cent of the Sun's rays. By comparison, a shallow pond of water that has formed from melting snow and ice on the surface of that glacier only reflects back about 40 per cent (at the most), and the deeper the water, the less it reflects back (oceans reflect only around 6 per cent). With the Greenland Ice Sheet suffering an extreme low in albedo back in 2012, this was partly due to ponds and lakes appearing on the ice sheet, as nearly every surface of it experienced at least some melting that summer.

Credit: J. Box/Geological Survey of Denmark and Greenland

However, as the researchers with the project discovered, it wasn't just about these ponds and lakes. The ice itself was losing its albedo, as it was gathering a layer of soot from forest fires and industrial pollution, as well as organic matter (algae) that was feeding off this soot and pollution. Just from the short flight of the drone the project is using, you get scenes like this:

Credit: Dark Snow Project

We aren't directly to blame for most forest fires, as many of them are set off by natural events (lightning, mostly). However, global warming and climate change are making them more frequent, and worse, by making the conditions that favour them (ie: drought) more common in some areas. Add to that all the pollution our industries emit, and we're can't consider ourselves completely blameless for what's going on in Greenland right now.

It's going to take more study of the ice sheets to see exactly how bad the effects of all this 'darkening' are going to be, but since we know the cause of it, that's something we can work on right away.

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