A New Sulfur and Carbon Degassing Inventory for the Southern Central American Volcanic Arc: The Importance of Accurate Time-Series Data Sets and Possible Tectonic Processes Responsible for Temporal Variations in Arc-Scale Volatile Emissions

This work presents a new database of SO2 and CO2 fluxes from the Southern Central
American Volcanic Arc (SCAVA) for the period 2015–2016. We report 300 SO2 flux measurements from
10 volcanoes and gas ratios from 11 volcanoes in Costa Rica and Nicaragua representing the most
extensive available assessment of this 500 km arc segment. The SO2 flux from SCAVA is estimated at
6,24061,150 T/d, about a factor of three higher than previous estimations (1972–2013). We attribute this
increase in part to our more complete assessment of the arc. Another consideration in interpreting the
difference is the context of increased volcanic activity, as there were more eruptions in 2015–2016 than
in any period since 1980. A potential explanation for increased degassing and volcanic activity is a
change in crustal stress regime (from compression to extension, opening volcanic conduits) following
two large (Mw>7) earthquakes in the region in 2012. The CO2 flux from the arc is estimated at
22,50064,900 T/d, which is equal to or greater than estimates of C input into the SCAVA subduction
zone. Time-series data sets for arc degassing need to be improved in temporal and spatial coverage to
robustly constrain volatile budgets and tectonic controls. Arc volatile budgets are strongly influenced by
short-lived degassing events and arc systems likely display significant short-term variations in volatile
output, calling for expansion of nascent geochemical monitoring networks to achieve spatial and
temporal coverage similar to traditional geophysical networks.