Magma recharge at Manam volcano, Papua New Guinea, identified through thermal and SO2 satellite remote sensing of open vent emissions

Abstract

Abstract Manam is one of the most frequently active volcanoes in Papua New Guinea and is a top contributor to global volcanic volatile emissions due to its persistent open vent degassing. Here, we present a multi-year time series (2018-2021) of thermal and SO2 emissions for Manam from satellite remote sensing, which we interpret in the context of open vent feedbacks between magma supply, reservoir pressure, and outgassing. We classify the time series into four phases based on the varying SO2 flux and observe a transient, yet substantial, increase in time-averaged SO2 flux from background levels of ~0.6 kt day-1 to ~4.72 kt day-1 between March and July 2019. We also identify a transition from temporally-coupled to decoupled gas and thermal emissions during this period which we explain in the context of a magma recharge event that supplied new, volatile-rich magma to the shallow plumbing system beneath Manam. We infer that the arrival of this recharge magma triggered the series of eruptions between August 2018 and March 2019. These explosive events collectively removed 0.18 km3 of degassed residual magma and signalled the onset of a renewed period of unrest that ultimately culminated in a major eruption on 28 June 2019. We quantify the magnitude of “excess” degassing at Manam after the removal of the inferred residual magma. SO2 emissions reveal that ~0.18 km3 of magma was supplied but only ~0.08km3 was erupted between April 2019 and December 2021. We highlight how multi-parameter remote sensing observations over months to years enables interpretation of open vent processes that may be missed by short duration campaign measurements.