Eyjafjallajökull 2010: Ash and aerosol during and after the eruption

Transcription

1 Eyjafjallajökull 2010: Ash and aerosol during and after the eruption { Evgenia Ilyinskaya, Guðrún Nína Petersen, Sibylle von Löwis, Halldór Björnsson, Matthew J. Roberts, Steinunn S. Jakobsdóttir, Sigurlaug Hjaltadóttir, Þórður Arason, et al.

2 Overview of the talk Volcano monitoring systems in Iceland Course of Eyjafjallajökull eruption The volcanic plume and the atmosphere Aerosol and ash measurements during and after the eruption At the edge of the ash plume on April 17 (E. Ilyinskaya)

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4 Geophysical monitoring network 62 seismic stations ~70 GPS stations 6 strainmeter stations

5 Start of the summit eruption 5

6 Eruptions of Eyjafjallajökull after the settlement ~ Photo: B. Sveinsson

7 The 2010 eruption: unusual in many ways Explosive activity went on for a long time Unusually high proportion of fine ash April 17, photo: B. Palmason

8 Eyjafjallajökull eruption in 2010: Two distinct eruption phases 1. Flank eruption on Fimmvörðuháls March 20 April 12: - Lava fountaning and lava flows - Tourist attraction - Negligible ash Phase I 2. Summit crater eruption April 14 May 23: - With highly explosive phases - Tephra and ash production - Disruptions to air traffic - Significant local ash fall Phase II Photos: E. Ilyinskaya

9 Fimmvörðuháls

10 Highly ash-rich activity I (April 14 17) Plume height 9.5 km on the first day, then 5-7 km Intraglacial eruption: contact of magma and glacial meltwater - explosivity intensified (?) Ash output kg s -1 Significant local ash fall Fine grain size Summit crater on April 15, 17:18 UTC (radar image)

11 April 16, 18:00 April 17, 18:00 Photos: E. Ilyinskaya

12 Mildly explosive activity (April 18 30) Dry eruption. Commencement of lava flow. Plume height 3-5 km Decrease in ash output kg s -1 Coarser ash grain size Change in wind direction - airports in Iceland close for the first time April 24 Mixed eruptive phase: ash generation + lava flows

13 Highly ash-rich activity II (May 1 18) Plume height 6-7 km. Lava flow halts Further European airspace closures

14 Explosive phase II: SO 2 increase preceeds ash May 4 14:09 UTC : Low SO 2 output May 5 13:13 UTC: High SO 2 output May 5 20:27 UTC : Low ash output May 6 11:50 UTC: High ash output

15 Photo: Joe Palca, NPR Ash characteristics

16 Ash grain size distributions Red: Highly explosive activity (April 15-17) Poorly sorted 30 % of fallout < 18 µm Up to 7% < 1µm Green: Mildly explosive activity (April 18-30) Better sorted 2.5 % of fallout < 18 µm < 0.1 % < 1µm XRD analysis (Ilyinskaya et al. 2011, Atmospheric Environment, in press)

17 Ash morphology Highly explosive activity: fine, poorly sorted grains commonly as aggregated clusters Mildly explosive activity: coarser, better sorted grains, more fluid and vesiculated (SEM images: E. Ilyinskaya, PhD thesis)

18 Near-source aerosol optical thickness and size distributions Flank eruption (black) Dominated by µm particles. Highly explosive activity (red) Significant short-interval fluctuations in the N ratio of coarse/fine particles Mildly explosive activity (green) Strongly bimodal size distribution (<0.4 and >1µm) Retrievals of Sun photometry measurements on April 1, 17 and 23 (Ilyinskaya et al. 2011, Atmos. Env., in press)

19 Composition of soluble aerosol and gas: difference between explosive phases April 14 17: Intraglacial, highly explosive Gaseous emissions of SO 2, HCl and HF not detected (direct sampling and remote sensing) Suspended aerosol: water droplets, other species b.d.l. Ash-adsorbed aerosol: F:Cl ratio 0.3 April 18 30: Dry, mildly explosive eruption Detection of gaseous SO 2, HCl and HF Suspended aerosol: dominated by Cl - (> 1 µm) and SO 4 2- (< 0.4 µm) Drastic change in ash-adsorbed aerosol: F:Cl ratio ~10. Up to 1000 mg/kg ash of F -. Ash-adsorbed aerosol April Ash-adsorbed aerosol April 18-25

20 Eruption cessation (May 23?) May 18 onwards: decreased activity May 23: No juvenile material, but still some seismic unrest August Photo: K. Weber

21 March Photo: J. Sigurdsson

22 The aftermath: Resuspended ash Photo: S. Karlsdóttir Reykjavík, June

23 Visibility: Very good Air quality: Good

24 Visibility: >16 km Air quality: Acceptable

25 Visibility: 4 km Air quality: Bad

26 Visibility: 1.6 km Air quality: Very bad

27 Visibility: 1 km Air quality: Very bad

28 Visibility: < 400 m Air quality: Very bad

29 TPC [cm -3 ] Wind velocity [ms -1 ] Wind direction [ ] Resuspended ash in the atmosphere MODIS image Resuspended ash and dust spreads over a large area Several hundred kilometres away from source, the dust cloud is still visible TPCs correspond to wind speed dependent on wind direction Tindfjöll - Drangshlíðardalur max ~ 900 cm -3 < 2.5 µm µm : : : :00 Date / Time (UTC)

30 What now? New techniques deployed: Mobile radar (CPA, Italy) Lidar (NCAS) OPC instrument (UAS Dusseldorf) in the field ( µm) UV gas spectrometers (DOAS) in the field (Chalmers) Several instrument grant applications submitted Extensive report on Eyjafjallajökull eruption (ICAO) useful for future eruptions

31 Unanswered questions Quantification of produced ash Would the same amount of fine ash have been produced without magma-ice interaction? Unprecendented problem with resuspended ash: timescale? "Missing" gas emissions April Discrepancies between ground and satellite measurements in the later eruptive stages

32 Takk fyrir { Photo: Ó. Sigurjónsson