Grimsvötn volcanic ash and SO2 plumes

21 May 2011 00:00 UTC and 2 November 2004 00:00 UTC

Region

Iceland, Greenland, Atlantic Ocean

Satellites

Meteosat-8, Meteosat-9, GOES, Metop-A

Channels/Products

Sulphur Dioxide Concentration, HRV

EUMETSAT satellites follow Grímsvötn volcanic ash and sulphur dioxide plumes.

Last Updated

24 January 2023

Published on

21 May 2011

By Scott Bachmeier (CIMSS), Sancha Lancaster, Marianne König, HansPeter Roesli and Jochen Kerkmann (EUMETSAT)

Following the eruption of the Grímsvötn volcano in Iceland on the evening of 21 May 2011, two separate plumes of ejected sulphur dioxide (SO₂) and volcanic ash have been observed by EUMETSAT's geostationary and polar orbiting instruments.

Volcanic activity in central Iceland, during 21 May, was observed via the High Resolution Visible (HRV) channel of MSG, at the three to five kilometre resolution (see image and animations below). Due to extended low cloud coverage, the exact start of the eruption was not visible on satellite images; the first clear appearance on the Meteosat-8 rapid scan images was at 19:05 UTC. According to the Icelandic Met Office, at 21:00 UTC the eruption plume had risen to an altitude of over 65,000ft (~20km).

On 22 May the Meteosat-9 HRV images showed that multiple volcanic eruption clouds were still reaching significant vertical heights, with much of this high-altitude material drifting northward. Another lower-altitude hazy volcanic ash cloud could also be seen spreading out just off the southern coast of Iceland.

This Meteosat-8 visible channel animation shows the volcanic eruption cloud emanating from the Grímsvötn volcano in Iceland on 21 May 2011.

Figure 1: Meteosat-8 visible, 21 May

Figure 2: Meteosat-9 HRV, 21 May 2011, 19:15 UTC

Large Area (source: D. Santek)
Animation (18:30–21:15 UTC, animated source: D. Santek)
Animation Met-8 Rapid Scan (18:45–22:00 UTC)
Animation 22 May (04:00–23:45 UTC)
Animation 22 May (06:00–21:45 UTC)

The volcanic eruption cloud was even apparent on the very edge of GOES-13 (GOES-East) imagery, as can be seen in an animation of visible channel images (below). The oblique viewing angle from this satellite helped to emphasize the large vertical extent of the eruption cloud.

Grimsvötn volcanic ash and SO2 plumes — Figure 3: GOES-13 Visible, 21 May 2011, 19:45 UTC. Large Area. Animation (18:45–22:15 UTC)

Volcanic plumes are seen to follow different routes, possibly due to different eruption heights of the SO₂ and the ash. Shortly after the eruption the majority of the SO₂ drifted north-westward and north-eastward (two branches were observed), whereas the volcanic ash quickly dispersed. Two days later, on 23 May, a significant fraction of the emitted volcanic ash has been transported southwards (Figure 4 & 5).

Approximate distribution of ash and SO2 ejected by... — Figure 4: Meteosat-9 Dust RGB, 23 May 2011 08:45 UTC

Figure 5: Meteosat-9 24-hour Microphysics RGB, 23 May 2011, 18:00 UTC

The animation below shows the Grímsvötn volcanic ash cloud drifting south east. Clouds contaminated with volcanic ash are highlighted by the pink hues in order to separate them from non-contaminated cloud decks.

Figure 6: Meteosat-9 ACMP, 23 May 12:00 UTC–24 May 07:00 UTC

Three days later, on 26 May, parts of the SO₂ plume that had drifted north-westward towards Canada (outside the view of MSG) could again be observed on MSG (Figure 7), when it drifted back with the westerly flow (see green SO₂ plumes).

Figure 7: Meteosat-9 ACMP, 26 May 11:00 UTC–28 May 11:00 UTC

The high-resolution Infrared Atmospheric Sounding Interferometer (IASI) on EUMETSAT's Metop-A polar-orbiting satellite also observed the SO₂ as it spread out over Greenland, Canada, the polar regions and towards Siberia. Some of the SO₂ reached the stratosphere, leading to relatively long persistence at higher altitudes. The large area covered by the plume can be seen in the image and animation shown below. SO₂ observations with the IASI instrument are defined by the variation of IASI brightness temperature measurements in the IR window region around 8.5 microns.

Figure 8: Metop-A IASI SO2, 24 May 2011, afternoon composite

Animation (21–24 May 2011)

On 26 May sulphur dioxide (SO2) clouds from Grimsvötn were still visible on the edge of Airmass RGB imagery.

Sulphur Dioxide clouds from Grimsvötn — Figure 9: Meteosat-9 Airmass RGB, 26 May 2011 06:00 UTC

2004

In the early morning of Monday 1 November 2004, after a run of seismic activity that started in mid-2003, there was an earthquake beneath Grímsvötn, Iceland (see map). On the same day, an eruption warning was sent to the Civil Defence shortly before tremors indicated that the eruption of Grimsvötn had started (at 21:50 UTC). The eruption plume was first detected by weather radar around midnight. It reached an altitude of 13km. However, as reported by the Nordic Volcanological Institute, there were eruptions pulsed resulting in a changing eruption column height from 8–9km up to 13–14km.

On 3 November 2004, the ash plume reached Norway, Finland and Sweden (see chart showing significant weather) causing the diversion of transtlantic flights to the south of Iceland to avoid the ash cloud, and the cancellation of domestic flights to the northeast of Iceland. The Dutch airline KLM had to cancel 59 flights, stranding hundreds of passengers at Amsterdam's Schiphol Airport because of the cloud of ash 'hanging above Europe' (suspended ash particles can cause abrasion inside the engine that can result in stalling and shutdown). From 3 to 5 November 2004, the intensity of the eruption decreased substantially. Finally, as reported by the Institute of Earth Sciences at the University of Iceland, the eruption of Grimsvötn volcano ended on 6 November 2004.

Looking at the Meteosat-8 images below, the volcanic cloud is best visible in the high-resolution visible (HRV) channel, which shows a highly-reflective cloud stationary over the Grimsvötn area. At 09:30 UTC, with the Sun shining at low elevation angle from the south-east, the volcanic cloud produces a distinct shadow on the lower-level clouds that surround the volcano. From the length of that shadow and the Sun zenith angle, one could calculate the height of the volcanic cloud above the low-level clouds.

According to observations (see also the pictures of the eruption), the volcanic plume was mainly formed of steam and ash, but it also contained sulphur dioxide. The existence of sulphur dioxide within the plume is confirmed by the WV7.3–IR13.4 and the IR10.8–IR8.7 brightness temperature difference images at 14:00 UTC that clearly show the volcanic plume. The IR10.8–IR8.7 difference shows values of about -5K, which indicates that the plume at this time reached the lower stratosphere (about 13–14km) where the temperature increases with height. Earlier, at 11:00 UTC, the volcanic plume is also well visible in the difference images, but the difference IR10.8–IR8.7 is positive (about + 6K), indicating that the volcanic plume was below the tropopause (about 8–9km) where the temperature decreases with height.

Animation of the IR10.8 channel data confirms the pulsating character of the Grimsvötn eruption on 2 November 2004: between 12:00 and 13:30 UTC the top of the volcanic plume cooled down from about -20°C to -55°C. Also the HRV channel shows that between 12:00 and 13:30 UTC an intensive eruption took place that resulted in an increase of the height of the volcanic cloud.

As regards the ash, from the IR10.8–IR12.0 difference images it is difficult to confirm the presence of ash within the volcanic plume. Normally, this difference should be negative for ash clouds. An explanation could be that there was too much water vapour in the volcanic cloud and/or that the ash particles were too big/heavy so that most of them dropped down in the vicinity of the volcano. The latter is confirmed by the fact that the ash fall deposit was limited to the areas close to the volcano (see MODIS image).