New ground-based lidar enables volcanic CO2 flux measurements

Abstract

There have been substantial advances in the ability to monitor the activity of hazardous volcanoes in recent decades. However, obtaining early warning of eruptions remains challenging, because the patterns and consequences of volcanic unrests are both complex and nonlinear. Measuring volcanic gases has long been a key aspect of volcano monitoring since these mobile fluids should reach the surface long before the magma. There has been considerable progress in methods for remote and in-situ gas sensing, but measuring the flux of volcanic CO2—the most reliable gas precursor to an eruption—has remained a challenge. Here we report on the first direct quantitative measurements of the volcanic CO2 flux using a newly designed differential absorption lidar (DIAL), which were performed at the restless Campi Flegrei volcano. We show that DIAL makes it possible to remotely obtain volcanic CO2 flux time series with a high temporal resolution (tens of minutes) and accuracy (<30%). The ability of this lidar to remotely sense volcanic CO2 represents a major step forward in volcano monitoring, and will contribute improved volcanic CO2 flux inventories. Our results also demonstrate the unusually strong degassing behavior of Campi Flegrei fumaroles in the current ongoing state of unrest.

New Advances in Dial-Lidar-Based Remote Sensing of the Volcanic CO2 Flux

“…A major breakthrough has recently arisen from the possible application of lidars to remote volcanic CO 2 sensing (Fiorani et al, 2013(Fiorani et al, , 2016Aiuppa et al, 2015;Queißer et al, 2015Queißer et al, , 2016. Aiuppa et al (2015) were the first to report on a DIALlidar-based remote measurement of the volcanic CO 2 flux at Campi Flegrei volcano, but their observations were limited to short (<200 m) measurement distances.…”

“…Aiuppa et al (2015) were the first to report on a DIALlidar-based remote measurement of the volcanic CO 2 flux at Campi Flegrei volcano, but their observations were limited to short (<200 m) measurement distances. Here, we have extended this earlier work to demonstrate that DIAL-lidars can successfully detect volcanic CO 2 at tens of ppmv above the atmospheric background over optical paths up to ≈3 km (Figures 4, 5).…”

“…Our measurements on Stromboli (Figure 1) were obtained using the same DIAL-lidar described in Aiuppa et al (2015) and Fiorani et al (2015Fiorani et al ( , 2016, and realized within the context of the FP7- ERC project Bridge (www.bridge.unipa.it). Only key information is reported here, and the reader is referred to previous studies for a detailed description of the instrument.…”

Ground-Based Remote Sensing of Volcanic CO2 Fluxes at Solfatara (Italy)—Direct Versus Inverse Bayesian Retrieval

“…Optical flow analysis is becoming increasingly popular in conjunction with UV-sensitive cameras to measure SO 2 fluxes in volcanology [32][33][34] and has recently been used in the visible region for CO 2 flux estimation [5]. OF calculates the displacement of image features between subsequent video frames, yielding a displacement vector field for each analyzed pixel by solving…”

“…Carbon dioxide (CO 2 ) is the second most abundant volatile species of degassing magma [1,2]. Measuring CO 2 mass emission rates (fluxes) therefore provides a powerful sampling tool that can be used, for example, to constrain magma crystallization processes related to the magma dynamics [3], learn about the geochemical carbon cycle [4] or for monitoring and early warning of volcanic unrest [5,6]. The nested caldera of Campi Flegrei (CF) is currently in a state of unrest [7,8] and is, as far as immediate human casualties are concerned, perhaps the most dangerous volcano on Earth, since it is located right at the edge of the metropolitan area of Naples in Italy (Figure 1a).…”