Amazon fires could increase glacier melting


Study highlights the impact of black carbon and dust.


Fires burning in the Amazon have a widespread impact, research shows.

NASA

By Natalie Parletta

Smoke plumes from burning rainforests in the Amazon basin could increase melting of tropical Andean glaciers, which have already lost half their ice over just four decades and are a critical water resource for local populations.

Brazilian and French researchers made the connection through a combination of observation and modelling and published their findings in the journal Nature Scientific Reports.

Increasing bushfires around the world are bad news for wildlife, homes, lives, biodiversity and the carbon cycle; the new study adds to other evidence extending their ripple effects to glacier melting.

This occurs because biomass burning releases atmospheric particulate matter including black carbon, light-absorbing particles that can reduce albedo – light reflection – from snow and cause it to melt.

To investigate whether aerosol particles from fires in the southwestern Amazon could impact the Bolivian Zongo Glacier, a team led by Newton de Magalhães Neto, from Rio de Janeiro State University, accessed data collected between 2000 and 2016 on fires, the movement of smoke plumes, rainfall and glacier melting.

They found that airborne particles from the fires – mostly dust and smoke pollution – can be blown to the top of tropical Andean mountains where they land on the snow.

Focussing on the years 2007 and 2010, when fire seasons from August to October were particularly bad due to El Niño-triggered droughts, they estimated reduced snow albedo from black carbon and dust particles, separately and combined.

Modelling showed that black carbon and dust could each potentially increase annual glacier melting by 3%, and by 6% combined when dust concentrations in the snow are low. That could rise to as much as 14% when dust concentrations are high.

These results suggest that the extent of ice melt from Amazon burning depends on the snow’s dust content.

For 2010, the authors report that increased melting of 4.5% above the annual runoff during one of the Amazon’s worst fire seasons corresponded with their estimations.

The findings add to widespread trepidation about increased deforestation in the Amazon due to economic pressures, which is accelerating fire risk and has repercussions beyond its borders.

The impact on communities that rely on the Andean glaciers for water could be dire. Three years ago, the Bolivian government declared a state of emergency during its severest drought for at least 25 years, compounded by the melting glaciers.

“Biomass burning over southwestern Amazonia... cannot be considered a regional issue to be faced,” the authors warn, “but instead has social implications at the continental scale, making use of water by several Andean communities a vulnerability.”

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Natalie Parletta is a freelance science writer based in Adelaide and an adjunct senior research fellow with the University of South Australia.
  1. https://www.newscientist.com/article/2108455-ancient-andes-glaciers-have-lost-half-their-ice-in-just-40-years/
  2. https://doi.org/10.1038/s41598-019-53284-1
  3. https://www.dw.com/en/how-climate-change-is-increasing-forest-fires-around-the-world/a-19465490
  4. https://www.fs.usda.gov/pnw/page/fire-effects-environment
  5. https://www.washingtonpost.com/news/energy-environment/wp/2017/06/26/wildfires-can-cause-glaciers-to-melt-from-over-a-thousand-miles-away-scientists-find/
  6. https://www.nationalgeographic.com/environment/2019/08/amazon-fires-cause-deforestation-graphic-map/
  7. https://www.nationalgeographic.com/environment/2019/08/amazon-fires-cause-deforestation-graphic-map/
  8. https://www.theguardian.com/environment/2016/nov/28/shrinking-glaciers-state-of-emergency-drought-bolivia
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