In
mid-August 2014 seismic monitoring stations in Iceland began to
record small Earth-tremors beneath the Bárðarbunga Volcano, which
rises through the Vatnajökull Glacier in northern Iceland, Such
seismic events are considered highly significant by volcanonolgists
as they are often caused by magma moving into chambers beneath the
volcano, and can therefore be an indicator of forthcoming eruptions.
These tremors grew in size and frequency throughout the month, until
on 31 August lava began to erupt from vents at the Holuhraun Lava
Field (part of the Bárðarbunga-Veiðivötn Volcanic Complex) to the
north of the Vatnajökull Glacier. This eruption continued through
September 2015, producing a continuous eruption along a 1.5 km
fissure with fountains of lava reaching 100 m in height. During the
second half of the month the eruptive activity declined and became
restricted to four craters along the fissure. Lava continued to be
erupted from these craters at a declining rate until the end of
February 2015. This eruption produced about 1.5 km3
of lava covering an area of about 85 km2.
This is the third recorded eruption at the Holuhraun Lava Field
(previous eruptions having occurred in 1797 and 1862–1864), and the
first flood lava eruption in Iceland since the Laki eruption of
1783-84.
In
a paper published in the Journal of Geophysical Research: Atmospheres on 21 August
2015, a team of scientists led by Anja Schmidt of the School of Earth and Environment at the University of Leeds describe the results of a
study of sulphur dioxide emissions during the 2014-15 Holuhraun Lava
Field eruption, and discuss the implications of this for future
policy making in Europe.
Remote
sensing of the volcanic emissions, both from ground stations and from
satellites, detected Sulphur Dioxide plumes rising as high as 3 km
above the visible eruption, and suggest that an average of 35
kilotons being emitted per day throughout the eruptive episode, with
emissions in September 2014 reaching as high as 120 kilotons per day.
This implies that throughout the eruptive episode the Holuhruan Lava
Field was emitting more sulphur dioxide than the total produced by
all 28 members European Environmental Agency from all sources
including shipping during the entire of 2010. It also significantly
outperformed other volcanoes noted for their high long term sulphur
dioxide emissions, such as Kilauea in Hawaii (which emits about 2-8
kilotons of sulphur dioxide per day on average) and Mount Etna in
Italy (which emits an average of 3.5 kilotons of sulphur dioxide per
day). This represents the largest output of sulphur dioxide by a
single volcano since the 2000-2003 Miyake-jima eruption in Japan,
which was in turn thought to have been the largest emitter of sulphur
dioxide since the Laki eruption of 1783-84, which caused a
significant period of climatic stress and cooling in Europe in the
1780s.
Schmidt
et
al.
attempted to model the progress of emissions from Holuhraun towards
Europe in September 2014 using the NAME computer modelling system,
which has previously been used by the London Volcanic Ash AdvisoryCentre to model emissions from the 2008 Kasatochi eruption, the 2009
Sarychev eruption and the 2010 Eyjafjallajökull eruption. They used
data from air quality measuring stations operated by the Irish Environmental Protection Agency, the Department for Environment, Foodand Rural Affairs, the Scottish Environment Protection Agency, the
Finnish Meteorological Institute and the Netherlands NationalInstitute for Public Health and the Environment to determine sulphur
dioxide in levels in Ireland, the UK, Finland and the Netherlands
during this period.
This
simulation suggested that sulphur dioxide from Holuhraun reached
areas 3000 miles from the eruption itself, and heights of 4500 m in
the atmosphere. The emissions were driven eastwards by a series of
anticyclones (expand); in early September an anticyclone moving
eastwards from the UK to Scandinavia initially produced northerly
winds (i.e. winds from the north) which propelled sulphur dioxide
towards Ireland, then westerly winds that drove emissions from
Iceland towards northern Finland, later in the month two anticyclones
over the North Atlantic and the UK coalesced, forming a ridge of high
pressure over the UK which drove emissions through the UK and into
the Netherlands.
Schmidt
et
al.
compared these simulation results to data obtained by the OzoneMonitoring Instrument on the Aurora satellite and the InfraredAtmospheric Sounding Interferometer instruments on the MetOp-A and MetOp-B satellites, finding a close comparison between the calculated
position of Sulphur Dioxide emissions and the observed positions,
with discrepancies occurring on only two days (5 and 21 September).
Comparison
of satellite-retrieved and satellite-simulated SO2
vertical column densities (VCDs) for 5–6 and 20–21 September
2014. For the comparison of the model simulations to the Ozone
Monitoring Instrument (OMI) the model output was sampled at OMI
overpasses and the column operator was applied, and for the
comparison to the Infrared Atmospheric Sounding Interferometer (IASI)
the model was sampled at IASI overpasses between 08:00 UTC and 15:00
UTC. Both the OMI and IASI data have been gridded onto the same
regular 0.5° by 0.5° longitude-latitude grid as the model
simulations. Schmidt et
al
(2015).
This
gave Schmidt et
al.
the confidence to calculate levels of Sulphur Dioxide based upon the
model and satellite observations, coming up with an average figure of
20-60 kilotons per day per day during 6-22 September 2014, rising to
60-120 kilotons per day for the rest of the month. This puts peak
emissions slightly higher than twice the peak emissions recorded from
the Miyake-jima eruption (54 kilotons per day during December 2000),
and suggests that over the course of the eruption Holuhruan may have
erupted a total of 11 teragrams of sulphur dioxide (convert to
something more sensible), less than the 18 teragrams erupted over the
three year period of the Miyake-jima eruption, but more than twice as
much as emitted by Miyake-jima during the first six months of that
eruption.
The
highest concentration of Sulphur Dioxide recorded in Europe during
the Holuhruan eruption occurred at Ennis in the Republic of Ireland
on 4-8 September 2014, with concentrations reaching a high of ~524
μg/m3
between 5.00 and 6.00 pm on 6 September. This is the first time that
sulphur dioxide levels in excess of 400 μg/m3
have been recorded in Europe since 1990, following the introduction
of stringent Europe-wide restrictions on industrial emissions in the
1980s. The second highest levels recorded were in Scotland, where
average levels of ~320 μg/m3
were recorded on 20-25 September. The highest recorded levels in
Finland occurred at Sammaltunturi during the night of 7–8
September, when average sulphur dioxide levels of ~180 μg/m3
were recorded. England and the Netherlands both recorded their
highest sulphur dioxide levels on 22 September 2014, with ~96 μg/m3
recorded in England and ~82 μg/m3
recorded in the Netherlands.
Sulphur
dioxide pollution is known to cause a wide range of health problems,
and the World Health Organisation recommends that exposure to levels
higher than 500 μg/m3
be regarded as hazardous, while the Clean Air for Europe Directive
mandates that if sulphur dioxide levels remain above 500 μg/m3
for
more than three hours then a public health warning must be issued.
During the 2014-15 Holuhruan eruption recorded sulphur dioxide levels
exceeded 500 μg/m3
only once and for only one our at a single monitoring station
(Ennis), but concentrations exceeding 350 μg/m3
were recorded for over 100 hours in total at the same station during
the course of the eruption, the highest sustained sulphur dioxide
concentration recorded in Europe since records began. By contrast on
Iceland the Höfn monitoring station, which is only about 100 km from
the Holuhruan Lava Field, the highest concentration recorded was 3000
μg/m3,
but concentrations exceeding 350 μg/m3
were recorded for only 124 hours in total.
In
the United Kingdom sulphur dioxide levels in excess of 266 μg/m3
are considered 'moderate pollution' by the Department for
Environment, Food and Rural Affairs. This level was not exceeded at
any UK monitoring station during the Holuhruan eruption, but Schmidt
et
al.'s
computer model suggests that this level was exceeded off the northern
coast of Scotland for about eleven consecutive hours.
Sulphur
dioxide monitoring in Europe began in the 1980s in response to high
levels of the gas being produced by industry. Since this time tighter
environmental regulations have almost eliminated this source of
pollution, and many governments are considering cutting back on
monitoring. However the Holuhruan Lava Field eruption has shown that
such stations can be useful in monitoring naturally occurring sulphur
dioxide emissions, which present the same hazard to health, and the
Scottish Environment Protection Agency is now planning to extend
sulphur dioxide monitoring in Scotland as a result of this event.
Schmidt et
al.
also recommend that European agencies look to expand satellite
monitoring of such emissions, which would allow the better prediction
of the movements of clouds of sulphur dioxide, allowing local
authorities to plan for pollution events before they occur.
See
also
Magnitude 5.4 Earthquake beneath the Vatnajökull Glacier in Iceland. The Icelandic Met Office, which also
monitors seismic activity, recorded a Magnitude 5.4 Earthquake at a
depth of 4.1 KM...
Magnitude 5.4 Earthquake beneath the Vatnajökull Glacier in Iceland. The Icelandic Met Office, which also
monitors seismic activity, recorded a Magnitude 5.4 Earthquake at a
depth of 4.1 KM...
The Icelandic Met Office recorded a
Magnitude 5.4 Earthquake at a depth of 3.9 km beneath the Vatnajökull
Glacier slightly before 7.10 am local time (which is...
Lava began to erupt from a fissure in the Holuhraun lava field, no the
north of the Vatnajökull Glacier in central Iceland, late in the evening
of Thursday 28 August, and has continued to do so for the next three
days. The lava field lies to the northeast of Bárðarbunga, a volcano...
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