Figure 2. Observed and simulated CO2 plumes from Katla volcano on 18 and 20 October 2016 and 4 October 2017. The panels show the wind direction and speed measured during each flight and along-track points of CO2 and CH4 concentrations. (a) Observed CO2 peak on 20 Oct 2016 (flight B989). (b) The best-fit simulated sources for the CO2 peak observed on 20 Oct 2016: rivers Fremri Emstruá and Krossá, ice cauldron cluster A, and Goðabunda rise. The figure shows simulation of 5 kt/d of CO2, but good agreement was also reached with 10 kt/d. (c) Two observed CO2 peaks on 4 Oct 2017 (flight C060), to the northwest (NW) and southeast (SE) of the caldera. (d) The best-fit simulated sources for the CO2 peaks observed on 4 Oct 2017: river Fremri Emstruá and ice cauldron clusters E, F and G. The figure shows simulation of 5 kt/d of CO2, but good agreement was also reached with 10 kt/d. (e) Two observed CO2 peaks on 18 Oct 2016 (flight B987), to the west and east of the caldera. (f) The best-fit simulated sources for the CO2 peaks observed on 18 Oct 2016—rivers Fremri Emstruá and Krossá and ice cauldron cluster G. Both of the observed CO2 peaks can be traced to Katla when CO2 is simulated as a dense gas with emission rate of 15 kt/d.
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