Medieval and recent SO2 budgets in the Reykjanes Peninsula: implication for future hazard

Abstract

Exposure to volcanic SO 2 can have adverse effects on human health, with severe respiratory disorders documented on short-and long-term timescales. Here, we use melt inclusion and groundmass glass data to calculate potential syneruptive SO 2 emissions during medieval and recent (2021-2024) eruptions across the Reykjanes Peninsula, the most populated area of Iceland, which has recently undergone magmatic reactivation with the 2021-2024 eruptions at Fagradalsfjall and Svartsengi. We target 16 individual eruptions from the medieval volcanic cycle at the Reykjanes Peninsula, the 800-1240 AD Fires, along with the 2021-2023 Fagradalsfjall eruptions and the 2023-2024 eruptions at Sundhnúksgígar. We calculate potential SO 2 emissions across the RP for the individual eruptions to be in the range of 0.004-6.3 Mt. These estimates correspond to mean daily SO 2 emissions in the range of 1000-111,000 t/day, higher than the mean SO 2 measurements of 5240 ± 2700 t/day during the 2021 Fagradalsfjall eruption. By using pre-eruptive sulfur values preserved in undegassed melt inclusions, we develop an empirical approach to calculate best-and worst-case potential SO 2 emission scenarios of any past or ongoing Reykjanes Peninsula eruption of known effusion rate. We conclude that the potential sulfur emissions across the RP can be significantly higher than observed during the 2021 Fagradalsfjall eruption, mainly because of the more evolved nature and higher sulfur contents of magmas erupted during the medieval period. Based on dominant NW wind directions on the Reykjanes Peninsula, eruptions in Brennisteinsfjöll pose the greatest health hazard to the capital area. Sulfate aerosol produced during long-term eruptions may impact visibility and air quality in the Keflavík Airport area. Our findings enable assessment of SO 2 emission scenarios of future eruptions across the RP and can be used together with gas dispersal models to forecast SO 2 pollution at ground level, and its impact on human health.

Magmatic Controls on Volcanic Sulfur Emissions at the Iceland Hotspot

“…In both cases, the total SO 2 emissions derived from petrological estimates and gas measurements match remarkably well; the petrological estimate of 10.5 Mt SO 2 for Holuhraun (Bali et al, 2018) compares well with the 9.6 (6.7-14.3) Mt SO 2 (Pfeffer et al, 2018) derived from direct plume measurements by differential optical absorption spectroscopy (DOAS). Similarly, for Fagradalsfjall, the petrological method yields 0.9 ± 0.2 Mt SO 2 , matching with 0.97 ± 0.54 Mt SO 2 determined by DOAS (Barsotti et al, 2023;Caracciolo et al, 2024;Pfeffer et al, 2024).…”

“…The petrological method has been previously applied to a selection of historical and recent Icelandic eruptions (Bali et al, 2018;Caracciolo et al, 2024;Devine et al, 1984;Haddadi et al, 2017;Hartley et al, 2014;Métrich et al, 1991;Óskarsson et al, 1984;Palais & Sigurdsson, 1989;Sigmarsson et al, 2013;Sigurdsson, 1982;Thordarson et al, 1996Thordarson et al, , 2001Thordarson et al, , 2003. These studies reveal the massive atmospheric SO 2 loading resulting from large historical basaltic fissure eruptions in Iceland, exemplified by the Eldgjá 939 CE (∼200 Mt SO 2 ; Palais & Sigurdsson, 1989;Thordarson et al, 2001) and Laki 1783 CE fires (∼120 Mt SO 2 ; Óskarsson et al, 1984;Sigurdsson, 1982;Thordarson et al, 1996).…”