Abstract
The role of volcanogenic halogen-bearing (i.e. chlorine and bromine) compounds in stratospheric ozone chemistry and climate forcing is poorly constrained. While the 1991 eruption of Pinatubo resulted in stratospheric ozone loss, it was due to heterogeneous chemistry on volcanic sulfate aerosols involving chlorine of anthropogenic rather than volcanogenic origin, since co-erupted chlorine was scavenged within the plume. Therefore, it is not known what effect volcanism had on ozone in pre-industrial times, nor what will be its role on future atmospheres with reduced anthropogenic halogens present. By combining petrologic constraints on eruption volatile yields with a global atmospheric chemistry-transport model, we show here that the Bronze-Age ‘Minoan’ eruption of Santorini Volcano released far more halogens than sulfur and that, even if only 2% of these halogens reached the stratosphere, it would have resulted in strong global ozone depletion. The model predicts reductions in ozone columns of 20 to >90% at Northern high latitudes and an ozone recovery taking up to a decade. Our findings emphasise the significance of volcanic halogens for stratosphere chemistry and suggest that modelling of past and future volcanic impacts on Earth’s ozone, climate and ecosystems should systematically consider volcanic halogen emissions in addition to sulfur emissions.
Highlights
The role of volcanogenic halogen-bearing compounds in stratospheric ozone chemistry and climate forcing is poorly constrained
It is commonly believed that most of the halogens in explosive volcanic plumes do not enter the stratosphere, because they are removed by hydrometeors in the troposphere[4,5]
Volcanic sulfur emissions are known to play a key role in stratospheric ozone change and climate forcing on annual to decadal timescales[6]
Summary
We determined the volatile fractions released from the melt by subtracting the concentration of volatile species in the matrix glass (post-eruptive melt) from those of glass inclusions (pre-eruptive melt). In our ‘melt + fluid’ degassing scenario, which we consider the most likely one, we assume that the pre-eruptive fluid phase represents 5 wt% of the magma, as explained above. This raises the volatile yield to 36 Tg of S, 675 Tg of Cl, 24 Tg of F, 1.5 Tg of Br and 0.07 Tg of I (Table 3). Some fraction of these volatiles must have crossed the tropopause (~14 km a.s.l. at Santorini’s latitude), since the maximum height of the Plinian column has been estimated as 36 ± 5 km (refs 32 & 33). Recent modelling[34] confirms this value and suggests that the height of the column associated with the last co-ignimbrite phase of the eruption was as high as the Plinian
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
