Ice and fire: How burning forests can help melt ice sheets

Ice and fire: How burning forests can help melt ice sheets

On the western edge of the Greenland ice sheet there’s a stretch of dirty grey ice known as the dark zone 400km long and 100km wide this dark zone is melting somewhere between double and ten times the rate of the white ice around it For a while, scientists thought it was a frozen relic from a time in earth’s history when the planet was covered in dust But we now know that the dark zone isn’t just a fossil It’s actually growing To understand what’s happening on the ice we have to start this story a long way from Greenland In many places around the world, forest fires are getting worse: more frequent, more widespread and more ferocious In the last few years in particular North America has suffered record-breaking wildland fires “We have very good empirical evidence that shows that the hotter the climate is, the more likely fires occur and that’s because it’s drying out fuels, it’s creating the fire weather conditions for more wildland fires but more importantly it’s also expanding our fire-prone ecosystems north so areas that didn’t used to burn, now burn” That’s Professor McCarty “My name is Jessica McCarty, and I am an assistant professor of geography at Miami University in Oxford, Ohio” She explained that not only is climate change making fires worse, fires are in turn driving climate change “They can release a lot of CO2 in a very short amount of time So for instance, the fires in British Columbia, which seem to burn every summer now which seem to burn every summer now will release what is equivalent to a small nation’s [annual] amount of CO2 reported to the UNFCCC in a week” But CO2 is only part of the picture Fires also release something called ‘black carbon’ “So black carbon is actually the black part of smoke so you can think of it as soot Colloquially in English we would call it soot Black carbon is a product of burning plant matter or fossil fuels and it’s really good at absorbing heat Compared to its more famous cousin, carbon dioxide the amount of black carbon emitted globally is tiny But its global warming effect is seriously potent These heat-trapping specks of soot are the third or even second largest man-made contributor to climate change depending on who you ask So what’s this got to do with that expanse of grubby ice in Greenland? Although much of the dark zone is dust deposited tens of thousands of years ago it’s now growing, and getting darker in part because new debris is settling on the ice and crucially, that includes black carbon from forest fires Because whereas CO2 can hand around in the atmosphere for up to a century black carbon, being much heavier blows about for just days or weeks before falling back to earth With forest fires, the intense heat from the blaze lifts the black carbon high into the atmosphere where it can be blown thousands of miles before depositing From satellite data we know that black carbon from forest fires in North America can travel all the way to Greenland where it can land on the ice So why does this layer of black carbon cause the ice to melt so much faster? “I’m Alun Hubbard, I’m a professor of glaciology at Tromso and Aberystwyth universities” When we spoke to Professor Hubbard, he had just come off the Greenland ice sheet where researchers have been using drones to study the make up of the sooty mixture on the ice “When you darken the ice sheet you effectively turn up the melt knob by a couple of orders of magnitude so it’s a really really important modulator of melt on the Greenland ice sheet” That’s because of something called the albedo effect Light colours reflect solar energy dark colours absorb it Bright, snow-covered ice reflects up to 90% of the sun’s energy back into space a crucial process for cooling the planet The remaining 10% of the solar energy is absorbed which causes it to melt But in the dark zone, more than 70% gets absorbed rapidly speeding up the melting process But that’s not all that’s going on Not only does the dust and black carbon mixture cause the ice to absorb more of the sun’s rays it provides nutrients for algae which blooms on the ice and darkens it further “So effectively when you put carbon nutrients basically minerals, fertiliser, and water together on the ice sheet it creates the perfect conditions for breeding algae and it’s actually pigmented algae that are actually causing the intensification of the dark zone” Scientists call this a bio albedo effect “It’s effectively pouring baby bio over the ice sheet and then giving it 24-hour sunlight and a bit of moisture” The Greenland ice sheet is already responsible for about 25% of global sea level rise up from 5% in 1993 Hubbard described what’s going on in the dark zone as a ‘wildcard’ a potentially unpredictable factor we urgently need to understand Because the melting caused by the darkened ice isn’t just contributing to rising sea levels it’s increasing the overall warming of the planet By reflecting heat, ice sheets help keep the planet cool so when they melt and shrink, the planet gets warmer and that means fires get more frequent and move north spitting more black carbon onto the ice and making it melt It’s a feedback loop Wildfires are by far the biggest source of black carbon in the Arctic but black carbon is settling on icy regions all over the planet and it comes from agricultural burning, coal plants and ship engines as well as forest fires “Yes, it’s everywhere So we track it in the Andes, the Andean glaciers it happens in the Himalayas in Kenya, there are some glaciers in Kenya It’s happening on Kilimanjaro We know it happens in Antarctica and it definitely happens in the Arctic, so not just Greenland but the Arctic Circle” And here’s the problem We aren’t very good at accurately tracking black carbon A 2013 study concluded that because of gaps in emissions data existing climate models could be underestimating black carbon’s climate-changing contribution by up to a factor of three In fact, the UN guidelines for monitoring carbon emissions from fires don’t currently require countries to track black carbon at all The science on black carbon and the climate is still young and it’s hugely complicated but the more we learn, the clearer it becomes that the rise in global fires is not just a result of climate change Left unchecked, they could accelerate the process

7 thoughts on “Ice and fire: How burning forests can help melt ice sheets

  1. most of the dark zone darkness is biological and black carbon is probably not a nutrient for ice algae. black carbon darkening of Greenland is more important for snow covered areas, just harder to see with our eyes

  2. Good Job Greenpeace. Please consider adding an RSS feed to Unearthed, which is tons better than getting daily emails. And please petition Greenpeace UK to NOT decommission their RSS feeds on Thank you.

  3. Wildfires are also increasing because trees are dying prematurely from absorbing pollution. Ozone is highly toxic to vegetation, especially trees that absorb it season after season. In addition to direct damage, every species becomes more vulnerable to attacks from insects, disease and fungus – all epidemics around the world.

  4. UPDATE: To clear something up, algae don’t actually feed on black carbon (as leading grey ice guy Jason Box points out below). They most likely feed off nutrients tucked inside dust particles – that’s new dust landing on the surface and ancient dust melting through from below. And as Alun Hubbard indicates, but could use extra emphasis, it’s the algae that are the biggest cause of the darkening in the Greenland dark zone. There could be a link between black carbon and ice algae there, but we don’t know yet. And although we know that black carbon does affect albedo in various places all over the Arctic (and the rest of the world), no one has yet quantified the difference it makes in the dark zone. This is a ~very~ live field of research, and we’re told new info on ice and algae in the dark zone is due to be published soon, so watch this space…

  5. This is so heartbreaking….but I know I need to watch all of your videos as soon as possible (only just found you on here). I really worry about what kind of World my 5 year old grandson will be trying to survive in when he is 30

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