Archive | February, 2014

Small volcanic eruptions and the global warming ‘pause’

25 Feb
Wellcome Library, London  Mount Vesuvius emitting a column of smoke after its eruption on 8 August 1779. Coloured etching by Pietro Fabris, 1779.

Wellcome Library, London
A small eruption of Mount Vesuvius on 8 August 1779, part of a sequence that culminated in a moderate eruption. Coloured etching by Pietro Fabris, 1779. Copyrighted work available under Creative Commons Attribution only licence CC BY 2.0

A new paper in Nature Geoscience by Santer and colleagues revisits the volcanic scenarios used in modern climate model simulations. The authors consider the effects of including a ‘more realistic’ model for the influence of small volcanic eruptions on the climate system over the past two decades. Of course, more realistic means more difficult.. and one of the long-standing and unresolved problems with small volcanic eruptions is that not only are they small, but their consequences are unpredictable. These complications arise, in part, from the fact that the part of the volcanic system that is responsible for the climate impact are the emitted gases (notably, sulphur dioxide or SO2), and not the volcanic ash. In real volcanoes, these two parameters don’t seem to be very well correlated – and it has been well known for some time that small but explosive eruptions of sulphur-rich magmas might well have a disproportionate effect on the climate system (see, for example, Rampino and Self, 1984; Miles et al., 2004). For this reason, models of volcano-climate impact that only use information on eruption size (as measured by the Volcanic Explosivity Index) will usually only be a poor approximation to reality. A better representation might instead be a volcanic sulphur dioxide climatology, building on the extensive work of the volcanic emissions satellite-remote sensing community since the first volcanic plume satellite measurements in 1979. The currently most up to date compilations of volcanic SO2 emissions since 1996 can be found in Carn et al., (2003) and McCormick et al., (2013).

Reading between the lines, it looks as though Santer and colleagues have come to a similar conclusion – finding that their model simulations get a little closer to observations of tropospheric temperature trends when they introduce a ‘realistic’ volcanic scenario to simulate the past 25 years of eruptions. What a pity that the volcanic dataset they relied on to line up particular eruptions with aerosol optical depth perturbations was patched together from secondary sources.  Clearly, as they suggest, more work is needed – but why not start by bringing the  climate modeling community and volcanologists together to find out what we each think that we know ?

Further reading.

Carn SA et al. 2003 Volcanic eruption detection by the Total Ozone Mapping Spectrometer (TOMS) instruments: a 22-year record of sulphur dioxide and ash emissions, In: Oppenheimer et al. (eds), Volcanic Degassing, Geological Society, London, Special Publications 213, 177-202.

McCormick BT et al. 2013 Volcano monitoring applications of the Ozone Monitoring Instrument, In: Pyle DM et al. (eds), Remote Sensing of Volcanoes and Volcanic ProcessesGeological Society, London, Special Publications 280, 1259-291.

Miles GM, Grainger RG and Highwood EJ 2004 The significance of volcanic eruption strength and frequency for climate Q. J. R. Met. Soc. 130 2361–76

Rampino MR and Self S 1984 Sulphur-rich volcanic eruptions and stratospheric aerosols, Nature 310, 677 – 679

Santer B et al, 2014, Volcanic contribution to decadal changes in tropospheric temperature Nature Geoscience (2014) doi:10.1038/ngeo2098

Related posts.

For more information on William Hamilton and Vesuvius, try this delightful blog post by Karen Meyer-Roux.

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Update on the eruption of Gunung Kelud

19 Feb
Area – thickness plot for Kelut fall deposits.  1990 data from Bourdier et al., 1997 (not all proximal data are plotted).

Preliminary ash thickness – isopach area plot for the February 2014 Kelut eruption. 1990 data from Bourdier et al., 1997 (not all proximal data are plotted).

The dramatic eruption of Gunung Kelud, or Kelut, led to a flurry of images of ash appearing on many social media platforms, including Flickr, Instagram and Twitter. As an experiment in a volcanology class, we sought out images that we could locate on a map, and by classifying the ash deposits as ‘light’, ‘moderate’ or ‘heavy’, generated a very rough contour map of the ash fallout from the eruption. The data show, very crudely, an exponential decay of ash thickness away from the volcano, and allows us to estimate the amount of ash deposited across Java during the eruption. Our current estimate is that the eruption may have deposited the equivalent of 0.2 – 0.3 cubic km of magma across the region. There are considerable uncertainties in this value, but it does confirm that the 2014 eruption was indeed substantial, rating as a Magnitude 4 (VEI 4) event.

Fuller details can be found in a preliminary report: Ash fallout from the 2014 Kelut eruption.

The eruption of Kelut, Java, February 2014

16 Feb
Image of the ash plume from Kelut, drifting across the Indian Ocean on 14th Feb, 2014. NASA Earth Observatory image by Jesse Allen, using data from the Land Atmosphere Near real-time Capability for EOS (LANCE).

Image of the ash plume from Kelut, drifting across the Indian Ocean on 14th Feb, 2014.
NASA Earth Observatory image by Jesse Allen, using data from the Land Atmosphere Near real-time Capability for EOS (LANCE).

I have used storify.com to put together a synopsis of the February eruption of Kelut, Java, Indonesia. There are some additional links to more detailed posts and related information below.

Related posts

Collections on Storify

Links for further information on activity and monitoring

The Kameni islands, Santorini, Greece

14 Feb

A glimpse of the spectacular Kameni or ‘burnt’ islands of Santorini, Greece from the air reveals in intricate detail the overlapping lava flows, explosion craters and fields of volcanic ash from which the islands have been built in successive eruptions over the past 2000 years, and more.

Air photo mosaic of the Kameni island of Santorini, based on images taken during a 2004 NERC Airborne Research and Survey Facility campaign

Air photo mosaic of the Kameni island of Santorini, based on images taken during a NERC Airborne Research and Survey Facility campaign in 2004, and published later in an open access paper (Pyle and Elliott, 2006). A high resolution (340 Mb) version of this image is now available from figshare.

Of course, what we can see from the air is just the literal ‘tip’ of the present-day volcano which has grown up within the flooded caldera of Santorini since the last major explosive eruption, the Minoan eruption of ca. 1600 BC. Historical records and accounts from as far back as the Greek geographer Strabo, suggest that there have been at least ten eruptions in and around the Kameni islands since 197 BC. It is quite likely that there have been more that either weren’t noticed (because they were underwater), or that have been forgotten about with the passage of time. The present day the Kameni islands have a volume of about 3 cubic kilometres (of lava), measured from the sea-floor, and must have grown up at an average rate of about 1 million cubic metres per year since the Minoan eruption.

Data sources.

The high resolution version of the composite aerial photograph of the Kameni islands is available to download from figshare,
http://dx.doi.org/10.6084/m9.figshare.928563

Link to the original paper: DM Pyle and  JR Elliott, 2006, Quantitative morphology, recent evolution and future activity of the Kameni islands volcano, Santorini, Greece, Geosphere 2 (5), 253-268  [Open Access]

Related web pages and posts.

A blog post from August 2013 – ‘Santorini: a volcano in remission

Some web pages introducing the volcanic history of the Kameni islands.