First estimate of volcanic SO 2 budget for Vanuatu island arc

The spatial and temporal coverage of measurements of volcanic gas emissions remains patchy. However, over the last decade, emissions inventories have improved thanks to new measurements of some of the lesser-known volcanic areas. We report on one such region—the Vanuatu island arc, in the Southwest Pacific—for which we now have sufficient systematic observations to offer a systematic emissions inventory. Our new estimate is based on SO2 flux measurements made in the period 2004–2009 with ultraviolet spectroscopy techniques for the following volcanoes: Yasur, Lopevi, Ambrym, Ambae, Gaua and Vanua Lava (from south to north). These are the first ever measurements for Lopevi, Gaua and Vanua Lava. The results reveal the Vanuatu arc as one of Earth's prominent sources of volcanic degassing with a characteristic annual emission to the atmosphere of ~3 Tg of SO2 (representing about 20% of hitherto published global estimates). Our new dataset highlights the sustained prodigious degassing of Ambrym volcano, whose 5 Gg day−1 mean flux of SO2 represents nearly two-thirds of the total budget for the Vanuatu arc. This confirms Ambrym as one of the largest volcanic sources worldwide comparable to Etna, often considered as the most vigorous source of volcanic emission on Earth. We also report a high degassing for Ambae of ~2 Gg day−1 SO2, representing more than 28% of the Vanuatu arc budget. Thus, 90% of the SO2 output from Vanuatu is focused in the central part of the arc (from Ambrym and Ambae) where magmas originate from enriched Indian-type mantle and where peculiar tectonic conditions could favor high magma production rates.