In contrast to the seismic and infrasonic energy released from quiescent and erupting volcanoes, which have long been known to manifest episodes of highly periodic behavior, the spectral properties ...of volcanic gas flux time series remain poorly constrained, due to a previous lack of high‐temporal resolution gas‐sensing techniques. Here we report on SO2 flux measurements, performed on Mount Etna with a novel UV imaging technique of unprecedented sampling frequency (0.5 Hz), which reveal, for the first time, a rapid periodic structure in degassing from this target. These gas flux modulations have considerable temporal variability in their characteristics and involve two period bands: 40–250 and 500–1200 s. A notable correlation between gas flux fluctuations in the latter band and contemporaneous seismic root‐mean‐square values suggests that this degassing behavior may be generated by periodic bursting of rising gas bubble trains at the magma‐air interface.
Key Points
Distinct periodic structure in volcanic degassingCorrelation between gas flux fluctuations and contemporaneous seismic RMS valuesPeriodic bursting of rising gas bubble trains at the magma‐air interface
We report here on a UV-camera based field experiment performed on Stromboli volcano during 7 days in 2010 and 2011, aimed at obtaining the very first simultaneous assessment of all the different ...forms (passive and active) of SO2 release from an open-vent volcano. Using the unprecedented spatial and temporal resolution of the UV camera, we obtained a 0.8Hz record of the total SO2 flux from Stromboli over a timeframe of ∼14h, which ranged between 0.4 and 1.9kgs−1 around a mean value of 0.7kgs−1 and we concurrently derived SO2 masses for more than 130 Strombolian explosions and 50 gas puffs. From this, we show erupted SO2 masses have a variability of up to one order of magnitude, and range between 2 and 55kg (average ∼20kg), corresponding to a time integrated flux of 0.05±0.01kgs−1. Our experimental constraints on individual gas puff mass (0.03–0.42kg of SO2, averaging 0.19kg) are the first of their kind, equating to an emission rate ranging from 0.02 to 0.27kgs−1. On this basis, we conclude that puffing is two times more efficient than Strombolian explosions in the magmatic degassing process, and that active degassing (explosions+puffing) accounts for ∼23% (ranging from 10% to 45%) of the volcano's total SO2 flux, e.g., passive degassing between the explosions contributes the majority (∼77%) of the released gas. We furthermore integrate our UV camera gas data for the explosions and puffs, with independent geophysical data (infrared radiometer data and very long period seismicity), to offer key and novel insights into the degassing dynamics within the shallow conduit systems of this open-vent volcano.
► High spatial and temporal resolution UV-camera measurement performed on Stromboli. ► First assessment of all the different forms of SO2 release from a volcano. ► Explosive Strombolian activity contributes to 7±1.5% of the total SO2 flux. ► Puffing release twice more SO2 than Strombolian explosions. ► Explosion and puffing play a key role in modulating a cyclic SO2 degassing behaviour.
The UV camera is becoming an important new tool in the armory of volcano geochemists to derive high time resolution SO sub(2) flux measurements. Furthermore, the high camera spatial resolution is ...particularly useful for exploring multiple-source SO sub(2) gas emissions, for instance the composite fumarolic systems topping most quiescent volcanoes. Here, we report on the first SO sub(2) flux measurements from individual fumaroles of the fumarolic field of la Fossa crater (Vulcano Island, Aeolian Island), which we performed using a UV camera in two field campaigns: in November 12, 2009 and February 4, 2010. We derived ~ 0.5 Hz SO sub(2) flux time-series finding fluxes from individual fumaroles, ranging from 2 to 8.7 t d super(-1), with a total emission from the entire system of ~ 20 t d super(-1) and ~ 13 t d super(-1), in November 2009 and February 2010 respectively. These data were augmented with molar H sub(2)S/SO sub(2), CO sub(2)/SO sub(2) and H sub(2)O/SO sub(2) ratios, measured using a portable MultiGAS analyzer, for the individual fumaroles. Using the SO sub(2) flux data in tandem with the molar ratios, we calculated the flux of volcanic species from individual fumaroles, and the crater as a whole: CO sub(2) (684 t d super(-1) and 293 t d super(-1)), H sub(2)S (8 t d super(-1) and 7.5 t d super(-1)) and H sub(2)O (580 t d super(-1) and 225 t d super(-1)).
Fire provides an impulsive and stochastic pathway for carbon from the terrestrial biosphere to enter the atmosphere. Despite fire emissions being of similar magnitude to net ecosystem exchange in ...many biomes, even the most complex dynamic vegetation models (DVMs) embedded in general circulation models contain poor representations of fire behaviour and dynamics, such as propagation and distribution of fire sizes. A model-independent methodology is developed which addresses this issue. Its focus is on the Arctic where fire is linked to permafrost dynamics and on occasion can release great amounts of carbon from carbon-rich organic soils. Connected-component labelling is used to identify individual fire events across Canada and Russia from daily, low-resolution burned area satellite products, and the obtained fire size probability distributions are validated against historical data. This allows the creation of a fire database holding information on area burned and temporal evolution of fires in space and time. A method of assimilating the statistical distribution of fire area into a DVM whilst maintaining its fire return interval is then described. The algorithm imposes a regional scale spatially dependent fire regime on a sub-scale spatially independent model; the fire regime is described by large-scale statistical distributions of fire intensity and spatial extent, and the temporal dynamics (fire return intervals) are determined locally. This permits DVMs to estimate many aspects of post-fire dynamics that cannot occur under their current representations of fire, as is illustrated by considering the modelled evolution of land cover, biomass and net ecosystem exchange after a fire.
Surficial enhanced rock weathering (ERW) is a land-based carbon dioxide removal (CDR) strategy that involves applying crushed silicate rock (e.g., basalt) to agricultural soils. However, unintended ...biogeochemical interactions with the nitrogen cycle may arise through ERW increasing soil pH as basalt grains undergo dissolution that may reinforce, counteract, or even offset the climate benefits from carbon sequestration. Increases in soil pH could drive changes in the soil emissions of key non-CO2 greenhouse gases, e.g., nitrous oxide (N2O), and trace gases, e.g., nitric oxide (NO) and ammonia (NH3), that affect air quality and crop and human health. We present the development and implementation of a new improved nitrogen cycling scheme for the Community Land Model v5 (CLM5), the land component of the Community Earth System Model, allowing evaluation of ERW effects on soil gas emissions. We base the new parameterizations on datasets derived from soil pH responses of N2O, NO, and NH3 in ERW field trial and mesocosm experiments with crushed basalt. These new capabilities involve the direct implementation of routines within the CLM5 N cycle framework, along with asynchronous coupling of soil pH changes estimated through an ERW model. We successfully validated simulated “control” (i.e., no ERW) seasonal cycles of soil N2O, NO, and NH3 emissions against a wide range of global emission inventories. We benchmark simulated mitigation of soil N2O fluxes in response to ERW against a subset of data from ERW field trials in the US Corn Belt. Using the new scheme, we provide a specific example of the effect of large-scale ERW deployment with croplands on soil nitrogen fluxes across five key regions with high potential for CDR with ERW (North America, Brazil, Europe, India, and China). Across these regions, ERW implementation led to marked reductions in N2O and NO (both 18 %), with moderate increases in NH3 (2 %). While further developments are still required in our implementations when additional ERW data become available, our improved N cycle scheme within CLM5 has utility for investigating the potential of ERW point-source and regional effects of soil N2O, NO, and NH3 fluxes in response to current and future climates. This framework also provides the basis for assessing the implications of ERW for air quality given the role of NO in tropospheric ozone formation, as well as both NO and NH3 in inorganic aerosol formation.
Here we present a novel spectroscopic approach to capturing, with unprecedented time resolution and accuracy, volcanic SO2 fluxes. This is based on two USB2000 spectrometers, coupled to cylindrical ...lens telescopes, each collecting light which has transited horizontal sections of the rising plume. We report on field data from Stromboli volcano, in which the entire emission rate from the volcano was measured, as well as flux signatures associated with individual crater explosions. The latter were integrated with seismic and thermal data, demonstrating correlations in both cases, and representing the first such geophysical‐geochemical data corroboration on this timescale. Such a holistic empirical capability could significantly expedite our understanding of explosive volcanic processes.
Methane is a powerful greenhouse gas produced in wetland
environments via microbial action in anaerobic conditions. If the location and extent of
wetlands are unknown, such as for the Earth many ...millions of years in the past, a model
of wetland fraction is required in order to calculate methane emissions and thus help
reduce uncertainty in the understanding of past warm greenhouse climates. Here we present
an algorithm for predicting inundated wetland fraction for use in calculating wetland
methane emission fluxes in deep-time paleoclimate simulations. For each grid cell in a
given paleoclimate simulation, the algorithm determines the wetland fraction predicted by
a nearest-neighbour search of modern-day data in a space described by a set of
environmental, climate and vegetation variables. To explore this approach, we first test
it for a modern-day climate with variables obtained from observations and then for an
Eocene climate with variables derived from a fully coupled global climate model
(HadCM3BL-M2.2; Valdes et al., 2017). Two independent dynamic vegetation models were used
to provide two sets of equivalent vegetation variables which yielded two different
wetland predictions. As a first test, the method, using both vegetation models,
satisfactorily reproduces modern day wetland fraction at a course grid resolution, similar to those used in
paleoclimate simulations. We then applied the method to an early Eocene climate, testing
its outputs against the locations of Eocene coal deposits. We predict global mean monthly
wetland fraction area for the early Eocene of 8×106 to 10×106 km2 with a
corresponding total annual methane flux of 656 to 909 Tg CH4 yr−1,
depending on which of the two different dynamic global vegetation models are used to
model wetland fraction and methane emission rates. Both values are significantly higher
than estimates for the modern day of 4×106 km2 and around
190 Tg CH4 yr−1 (Poulter et al., 2017; Melton et al., 2013).
Ultraviolet spectroscopy has been implemented for over thirty years to monitorvolcanic SO₂ emissions. These data have provided valuable information concerningunderground magmatic conditions, which ...have been of utility in eruption forecastingefforts. During the last decade the traditionally used correlation spectrometers have beenupgraded with miniature USB coupled UV spectrometers, opening a series of exciting newempirical possibilities for understanding volcanoes and their impacts upon the atmosphere.Here we review these technological developments, in addition to the scientific insightsthey have precipitated, covering the strengths and current limitations of this approach.
ABSTRACT
A deep survey of the Large Magellanic Cloud at ∼0.1–100 TeV photon energies with the Cherenkov Telescope Array is planned. We assess the detection prospects based on a model for the emission ...of the galaxy, comprising the four known TeV emitters, mock populations of sources, and interstellar emission on galactic scales. We also assess the detectability of 30 Doradus and SN 1987A, and the constraints that can be derived on the nature of dark matter. The survey will allow for fine spectral studies of N 157B, N 132D, LMC P3, and 30 Doradus C, and half a dozen other sources should be revealed, mainly pulsar-powered objects. The remnant from SN 1987A could be detected if it produces cosmic-ray nuclei with a flat power-law spectrum at high energies, or with a steeper index 2.3–2.4 pending a flux increase by a factor of >3–4 over ∼2015–2035. Large-scale interstellar emission remains mostly out of reach of the survey if its >10 GeV spectrum has a soft photon index ∼2.7, but degree-scale 0.1–10 TeV pion-decay emission could be detected if the cosmic-ray spectrum hardens above >100 GeV. The 30 Doradus star-forming region is detectable if acceleration efficiency is on the order of 1−10 per cent of the mechanical luminosity and diffusion is suppressed by two orders of magnitude within <100 pc. Finally, the survey could probe the canonical velocity-averaged cross-section for self-annihilation of weakly interacting massive particles for cuspy Navarro–Frenk–White profiles.
Here we present a novel spectroscopic approach to capturing, with unprecedented time resolution and accuracy, volcanic SO sub(2) fluxes. This is based on two USB2000 spectrometers, coupled to ...cylindrical lens telescopes, each collecting light which has transited horizontal sections of the rising plume. We report on field data from Stromboli volcano, in which the entire emission rate from the volcano was measured, as well as flux signatures associated with individual crater explosions. The latter were integrated with seismic and thermal data, demonstrating correlations in both cases, and representing the first such geophysical-geochemical data corroboration on this timescale. Such a holistic empirical capability could significantly expedite our understanding of explosive volcanic processes.
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