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̽��ֱ��team, involving 20 researchers from seven countries, used long-range drones kitted out with a range of lightweight sensors to study the Manam volcano - one of the most active volcanoes in Papua New Guinea.

Their , published in the journal Science Advances, show how combined measurements from the air, earth and space can be used to understand volcanic contributions to the global carbon cycle, key to sustaining life on Earth.

One of the best ways to detect signs of an impending eruption is to ‘breathalyze’ a volcano by taking regular measurements of volcanic gases. Any change in the ratio of sulfur and carbon dioxide released can warn of an impending eruption. But sampling more remote or hazardous volcanoes like Manam is more challenging. ��

When the volcano last erupted between 2004 and 2006 the entire island was evacuated - crops were destroyed and water supplies contaminated. ̽��ֱ��islanders only started to return five years ago.

Previous studies have shown that Manam is one of the world’s biggest emitters of sulphur dioxide, but nothing was known of its CO₂ output.

Measuring volcanic CO₂ emissions is more challenging because it is already present in high concentrations in the atmosphere. ̽��ֱ��only way to get accurate readings is to take samples from close to active vents.��

Collecting samples on Manam would be incredibly risky - not only is the vent flanked by precarious slopes, the volcano is also unmonitored so there would be little warning if an eruption struck.

Using drones equipped with miniaturised gas sensors, spectrometers and sampling devices the team piloted flights right into the plume emerging from Manam’s vent. ̽��ֱ��measurements captured gas composition, temperature and humidity in real-time.

̽��ֱ��project - Aerial-Based Observations of Volcanic Emissions (ABOVE) – saw the first global collaboration between scientists, remote-sensing specialists, engineers and pilots.

Project lead Dr Emma Liu of ̽��ֱ�� College London, who carried out the research while based at Cambridge’s Department of Earth Sciences, said: “these aerial measurements are pushing the frontiers of the current state-of-the-art in volcano monitoring - from the existing satellite data we know that Manam is a significant source of volcanic emissions, but that data came with a lot of uncertainty because it was measured at a distance.

“ ̽��ֱ��resources of the in-country volcano monitoring institute are small and the team has an incredible workload, but they really helped us make the links with the community living on Manam island.”

Following the fieldwork, the researchers raised funds to buy computers, solar panels and other technology to enable the local community – who have since put together a disaster preparedness group - to communicate via satellite from the island, and to provide drone operations training to Rabaul Volcanological Observatory staff to assist in their monitoring efforts.

ABOVE was part of the Deep Carbon Observatory (DCO), a global community of scientists on a ten-year quest to understand more about carbon in Earth.

“Volcanic emissions are a critical stage of the Earth’s carbon cycle - the movement of carbon between land, atmosphere, and ocean – but CO₂ measurements have so far been limited to a relatively small number of the world’s estimated 500 degassing volcanoes,” said co-author Professor Marie Edmonds, also from Cambridge's��Department of Earth Sciences. “Aerial gas measurements, collected along transects through the plume, together with ground-based and satellite data show that Manam is a major volcanic emission source on a global scale, which ranks fifth in terms of its carbon flux.”

Co-author Professor Alessandro Aiuppa ( ̽��ֱ�� of Palermo) described the findings as ‘a real advance in our field’, adding: “Ten years ago you could have only stared and guessed what Manam’s CO₂ emissions were.

“If you take into account all the carbon released by global volcanism, it’s less than a percent of the total emission budget, which is dominated by human activity. In a few centuries, humans are acting like thousands of volcanoes. If we continue to pump carbon into the atmosphere, it will make monitoring and forecasting eruptions using aerial gas observations even harder.”

“In order to understand the drivers of climate change you need to understand the carbon cycle in the Earth,” said co-author Professor Tobias Fischer from the ̽��ֱ�� of New Mexico. “We wanted to quantify the carbon emission from this very large carbon dioxide emitter. We had very few data in terms of carbon isotope composition, which would identify the source of the carbon and whether it is the mantle, crust or sediment. We wanted to know where that carbon comes from.”

“Drones are changing not only the way we monitor volcanoes – they also help us to understand what causes eruptions, and how carbon moves between the Earth’s interior and atmosphere,” said Edmonds. “If we know how volcanic emissions interacted with the climate in the past, we are closer to understanding controls on our present-day climate and how it may respond to future human-driven impacts.”

ABOVE was funded by Alfred P. Solan Foundation

Reference:
E.J. Liu et al. ‘’ Science Advances (2020). DOI: 10.1126/sciadv.abb9103.