Temporal Variability in Gas Emissions at Bagana Volcano Revealed by Aerial, Ground, and Satellite Observations

Bagana is a remote, highly active volcano, located on Bougainville Island in southeastern Papua
New Guinea. The volcano has exhibited sustained and prodigious sulfur dioxide gas emissions in recent
decades, accompanied by frequent episodes of lava extrusion. The remote location of Bagana and its persistent
activity have made it a valuable case study for satellite observations of active volcanism. This remoteness has
also left many features of Bagana relatively unexplored. Here, we present the first measurements of volcanic
gas composition, achieved by unoccupied aerial system (UAS) flights through the volcano's summit plume,
and a payload comprising a miniaturized MultiGAS. We combine our measurements of the molar CO2/SO2
ratio in the plume with coincident remote sensing measurements (ground- and satellite-based) of SO2 emission
rate to compute the first estimate of CO2 flux at Bagana. We report low SO2 and CO2 fluxes at Bagana from
our fieldwork in September 2019, ∼320 ± 76 td −1 and ∼320 ± 84 td −1, respectively, which we attribute to
the volcano's low level of activity at the time of our visit. We use satellite observations to demonstrate that
Bagana's activity and emissions behavior are highly variable and advance the argument that such variability is
likely an inherent feature of many volcanoes worldwide and yet is inadequately captured by our extant volcanic
gas inventories, which are often biased to sporadic measurements. We argue that there is great value in the
use of UAS combined with MultiGAS-type instruments for remote monitoring of gas emissions from other
inaccessible volcanoes.

BMK, EJL, and AA acknowledge the
financial support of the Alfred P Sloan
foundation, awarded via the Deep Carbon
Observatory. TR acknowledges funding
via the CASCADE programme, EPSRC
Programme Grant EP/R009953/1. CIS
acknowledges the financial support of the
New Zealand Earthquake Commission.

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