HR: 13:55h
AN: V13G-02    [Abstracts]
TI: Direct Sampling of a 35 Hour Old Volcanic Cloud From Hekla Volcano (Iceland)
AU: * Rose, W I
EM: raman@mtu.edu
AF: Geological Eng & Sciences, Michigan Technological University, Houghton, MI 49931 United States
AU: Hunton, D
EM: Donald.Hunton@hanscom.af.mil
AF: Air Force Research Laboratory, Space Vehicles Directorate, Hanscomb AFB, MA 01731 United States
AU: Anderson, B
EM: b.e.anderson@larc.nasa.gov
AF: NASA, Langley Research Center, Hampton, VA 23681 United States
AU: Oppenheimer, C
EM: co200@cam.ac.uk
AF: Cambridge University, CAM, Cambridge, CB2 3EQ United Kingdom
AU: Mather, T
EM: tam21@hermes.cam.ac.uk
AF: Cambridge University, CAM, Cambridge, CB2 3EQ United Kingdom
AU: Millard, G
EM: Genevieve.Millard@atm.ch.cam.ac.uk
AF: Cambridge University, CAM, Cambridge, CB2 3EQ United Kingdom
AU: Thornton, B
EM: Brett.Thornton@Colorado.EDU
AF: University of Colorado, UCB, Boulder, CO 80309 United States
AU: Gerlach, T
EM: tgerlach@usgs.gov
AF: USGS, Cascade Volcano Observatory, Vancouver, WA 98683 United States
AB: Thirty-five hours after the eruption and stratospheric emplacement of the volcanic cloud, at 0508-0518 UT (for a distance of about 100 km) on 28 Feb 2000 an instrumented atmospheric research DC-8 aircraft from NASA Dryden intersected the volcanic cloud at an altitude of 10.4 km at 76.4-75.7 N Lat and 9.0 to 4.4 W Long. The aircraft was instrumented to study polar stratospheric clouds as part of the SAGE III Ozone Loss and Validation Experiment, and most of the atmospheric instruments were collecting data during the encounter. Overall this data set offers much that is new about stratospheric volcanic clouds, especially the point that they may be ice-dominated during their first few days. It is the first time that many gas species have been detected in situ within such a cloud, and the chance to get a systematic measurement set involving many measurements spatially associated-a kind of snapshot of a cloud cross section-- allows us to think about processes, reactions and interrelationships between species.The 35 hr old Hekla volcanic cloud at 10.4 km altitude was sharply deliniated by three gaseous volcanogenic species, SO2, HCl and HF, and a much higher number and mass loading of suspended particles.Whereas scrubbing of haloid gases from volcanic plumes by liquid water has been thought to be important in "wet" atmospheric conditions, this scrubbing was not substantially effective in the Hekla case, and haloid gases reached the stratosphere in high proportions. Reflected by its HOx, the volcanic cloud had an oxidizing reactive character which caused some original volcanic gas components (H2S, H2, CO and perhaps CH4) to be completely or partly oxidized after 35 hours. HNO3 and NOy (which cannot consist only of HNO3) were also conspicuous volcanic cloud components, supporting observations in ground based passive volcanic degassing. Observations of elevated OH and HO2 in the Hekla volcanic cloud validate suggestions that they might be generated in eruption plumes. These elevated levels also are apparently preserved for more than a day, and survive long polar nights. Ozone is dramatically destroyed inside the volcanic cloud, most probably by active Cl (+Br?) species which form from heterogeneous reactions involving cloud particles, perhaps sulfates especially. Particles of three types are important to consider for heterogeneous reactions: Ice larger than 1 micron, sulfate smaller than 1 micron and volcanic ash. While dominant soon after eruption, ice was apparently decreasing rapidly in the 35 hr period. Sulfate particles occur in highest abundance where ozone is most depleted. The 1-2 hr long Hekla explosive phase consisted of a tiny fraction of the magma erupted in the 11 hrs, but perhaps the majority of the volcanic gas.
DE: 0370 Volcanic effects (8409)
DE: 3311 Clouds and aerosols
DE: 8408 Volcano/climate interactions (1605, 3309)
DE: 8409 Atmospheric effects (0370)
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005