Out of the blue: volcanic SO2 emissions during the 2021-2022 Hunga Tonga
- Hunga Ha’apai eruptions
Abstract
The January 15, 2022 phreatomagmatic eruption of the submarine Hunga
Tonga-Hunga Ha’apai (HTHH) volcano (Tonga) generated an explosion of
historic magnitude, and was preceded by ~1 month of
Surtseyan eruptive activity and two precursory explosive eruptions. We
present an analysis of ultraviolet (UV) satellite measurements of
volcanic sulfur dioxide (SO2) between December 2021 and the climactic
January 15, 2022 eruption, comprising an unprecedented record of
Surtseyan eruptive emissions. UV measurements from the Ozone Monitoring
Instrument (OMI) on NASA’s Aura satellite, the Ozone Mapping and
Profiler Suite (OMPS) on Suomi-NPP, the Tropospheric Monitoring
Instrument (TROPOMI) on ESA’s Sentinel-5P, and the Earth Polychromatic
Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR)
are combined to yield a consistent multi-sensor record of SO2 emissions
during the eruptive sequence. We estimate SO2 emissions during the key
phases of the eruption: the initial December 19, 2021 eruption
(~0.01 Tg SO2); continuous SO2 emissions from December
20, 2021-early January 2022 (~0.12 Tg SO2); the January
13, 2022 stratospheric eruption (0.06 Tg SO2); and the paroxysmal
January 15, 2022 eruption (~0.4-0.5 Tg SO2); yielding a
total SO2 emission of ~0.6-0.7 Tg SO2 for the entire
eruptive episode. We interpret the vigorous SO2 emissions observed prior
to the January 2022 eruptions, which were significantly higher than
measured in the 2009 and 2014 HTHH eruptions, as strong evidence for a
rejuvenated magmatic system. High cadence DSCOVR/EPIC SO2 imagery
permits the first UV-based analysis of umbrella cloud spreading and
volume flux in the January 13, 2022 eruption, and also tracks early
dispersion of the stratospheric SO2 cloud injected by the January 15
eruption. The ~0.4-0.5 Tg SO2 discharged by the
paroxysmal January 15, 2022 HTHH eruption is low relative to other
eruptions of similar magnitude, and a review of previous submarine
eruptions of the satellite era indicates that such modest SO2 yield may
be characteristic of these events, with the emissions and atmospheric
impacts likely dominated by water vapor (WV). The origin of the low SO2
loading awaits further investigation but scrubbing of SO2 in the
water-rich eruption plumes and rapid conversion to sulfate aerosol are
highly plausible, given the exceptional WV emission measured in the
January 15, 2022 HTHH eruption.