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Greenland Ice Core Evidence of the 79 AD Vesuvius Eruption Open Access Geoscientific Geoscientific Open Access 1,2,* 2,* 3 4 4 1 4 C EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Open Access Biogeosciences Biogeosciences Discussions Open Access Open Access Clim. Past, 9, 1221–1232, 2013 Climate www.clim-past.net/9/1221/2013/ Climate doi:10.5194/cp-9-1221-2013 of the Past of the Past © Author(s) 2013. CC Attribution 3.0 License. Discussions Open Access Open Access Earth System Earth System Dynamics Dynamics Discussions Greenland ice core evidence of the 79 AD Vesuvius eruption Open Access Geoscientific Geoscientific Open Access 1,2,* 2,* 3 4 4 1 4 C. Barbante , N. M. Kehrwald , P. Marianelli , B. M. Vinther , J. P. Steffensen ,Instrumentation G. Cozzi , C. U. Hammer , Instrumentation H. B. Clausen4, and M.-L. Siggaard-Andersen4 Methods and Methods and 1Institute for the Dynamics of the Environmental Processes, CNR, University of Venice, 30123 Venice, Italy 2Department of Environmental Sciences, Informatics and Statistics, University of Venice, Ca’Data Foscari, Systems 30123 Venice, Italy Data Systems 3Department of Earth Sciences, University of Pisa, 56126 Pisa, Italy Discussions Open Access 4 Open Access Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark Geoscientific *These authors contributed equally to this work. Geoscientific Model Development Model Development Correspondence to: C. Barbante ([email protected]) Discussions Received: 2 October 2012 – Published in Clim. Past Discuss.: 7 November 2012 Open Access Open Access Revised: 9 April 2013 – Accepted: 7 May 2013 – Published: 13 June 2013 Hydrology and Hydrology and Earth System Earth System Abstract. Volcanic tephra are independent age horizons and graphic site of the eruption. MajorSciences low-latitude explosive vol- Sciences can synchronize strata of various paleoclimate records in- canoes that inject H2SO4 into the stratosphere are capable of cluding ice and sediment cores. The Holocene section of cooling the global climate for several years (Kelly et al., 1996 Discussions Open Access the Greenland Ice Core Project (GRIP) ice core is dated by and references within). The most recent extremeOpen Access examples multi-parameter annual layer counting, and contains peaks in of such global cooling include the eruption of Tambora, In- 2− Ocean Science acidity, SO4 and microparticle concentrations at a depth of donesia, resulting in theOcean “year without Science a summer” (Stothers, 429.1 to 429.3 m, which have not previously been definitively 1984; Briffa et al., 1998) or Pinatubo, Philippines, which Discussions ascribed to a volcanic eruption. Here, we identify tephra par- masked global warming trends during the 1990s (Soden et ticles and determine that volcanic shards extracted from a al., 2002). Knowledge of past volcanic activity, especially Open Access depth of 429.3 m in the GRIP ice core are likely due to the eruptions which have sufficiently polluted theOpen Access stratosphere 79 AD Vesuvius eruption. The chemical composition of the to influence the climate over several years, is essential to Solid Earth tephra particles is consistent with the K-phonolitic compo- interpreting past climatic trends.Solid Earth Discussions sition of the Vesuvius juvenile ejecta and differs from the Ice cores from polar ice sheets offer quantitative and well- chemical composition of other major eruptions (≥ VEI 4) dated records of past volcanic activity reaching back several between 50–100 AD. millennia (Davies et al., 2010; Lowe, 2011; Zielinski et al., Open Access Open Access 1996). The volcanic signals observed in ice cores include in- creased concentrations of sulfuric acid and/or sulfates. Vol- The Cryosphere canos release SO2 intoThe the atmosphereCryosphere which oxidizes in the 1 Introduction Discussions eruption plume to form H2SO4 (Rampino and Self, 1982; Langway et al., 1988; Bluth et al., 1993). The conversion of Major volcanic eruptions are phenomena which have dra- SO2 into H2SO4 facilitates transport of volcanic emissions to matic consequences for climate and human lives. Volcanic the polar regions as H SO is able to reach the stratosphere. tephra can blanket landscapes thousands of kilometers from 2 4 This atmospheric height means that even H2SO4 that forms the eruptive site (Davies et al., 2005) thereby destroying un- in low-latitude volcanic clouds can eventually reach the polar derlying vegetation and property. In many cases vast amounts regions (Rampino and Self, 1982; Langway et al., 1988). Vol- of sulfuric acid (H2SO4) and associated aerosols pollute the canically produced acids including H2SO4 are scavenged by stratosphere for several years. This stratospheric veil reduces precipitation and are deposited by snow onto the Greenland the solar radiation reaching earth’s surface and causes a gen- ice sheet (Clausen and Hammer, 1988; Langway et al., 1988; eral cooling for months to decades (Briffa et al., 1998). Clausen et al., 1997; Zielinski and Germani, 1998). During The climatic impact of volcanos depends on the volume of years without major eruptions the snow falling onto the ice aerosols injected into the stratosphere as well as the geo- Published by Copernicus Publications on behalf of the European Geosciences Union. 1222 C. Barbante et al.: Greenland ice core evidence of the 79 AD Vesuvius eruption sheet only contains background amounts of H2SO4. This al- historical data and volcanological literature suggests that the ternation ultimately creates ice layers with varying acid con- eruption occurred between 24–25 August, 79 AD (Stothers centrations. The volcanic H2SO4 preserved in ice cores can and Rampino, 1983). The Vesuvius eruption may be the old- be detected as acidity peaks determined from electrical con- est eruption that can be dated to an exact year (Zielinski and ductivity measurements (ECM) values and/or as increased Germani, 1998) and is therefore an important horizon for 2− concentrations in sulfate ions (SO4 ) (Clausen et al., 1997; synchronizing chronologies. Bigler et al., 2007; Davies et al., 2010). Volcanos also eject The famous observations of Pliny the Younger form the HCl and HF into their plume which may work to enhance the bulk of the historical record of the 79 AD Vesuvius eruption, ECM signals (Langway et al., 1988; Clausen et al., 1997). and the term “plinean” is applied to eruptions characterized The intensity of the volcanic signal recorded in polar ice by a basal gas thrust and an upper steady sustained convective cores depends to some extent on the eruption site, where column (Cioni et al., 2000). The deposits of the 79 AD erup- neighboring volcanoes have a greater impact than low- tion record a complex eruptive sequence, with a thick blan- latitude eruptions. Greenland ice cores mainly record North- ket of pyroclastic fall and flow products covering the volcano ern Hemisphere volcanic activity (e.g., Clausen and Ham- and a wide surrounding area. During the plinian phase a mix- mer, 1988; Langway et al., 1988; Clausen et al., 1997) al- ture of gas and tephra particles were injected into the atmo- though it has been speculated that a few Southern Hemi- sphere which returned to the surface primarily by dry depo- sphere eruptions such as 186 AD Taupo, New Zealand, may sition (Carey and Sigurdsson, 1987; Cioni et al., 1992, 2000; have reached sufficient stratospheric heights (55 km) that Sigurdsson et al., 1990). The plinian phase created two com- they were deposited on the the Greenland ice sheet (Hammer, posite eruption units formed by a sequence of white and grey 1984; Zielinski et al., 1994). When a volcanic signal is faint pumice intercalated by ash flow. Deposits are composition- in the ice core stratigraphy additional information is gener- ally zoned from early phonolitic white pumice to late phono- ally required in order to identify the eruption. Acidity peaks tephritic grey pumice. In both the white and grey pumice the are not always indicative of volcanic eruptions (Davies et al., main phenocrysts are sanidine and clinopyroxene (Cioni et 2010) and additional information may be necessary to de- al., 1995). However, the groundmass of the white and grey velop more robust conclusions to determine if an ice layer in- pumice varies where the white pumice is characterized by dicates a past eruption. Often only the chemical signature or colorless glass while the grey matrix contains a greater per- presence of micrometer size tephra particles in the ice helps centage of brown glass microliths. The white pumice forms a to “fingerprint” the acidity signal to a specific eruption site. SSE dispersal fan and deposits record a progressive increase Volcanoes eject silicate particles with distinct chemical of magma discharge rate (up to 8 × 107 kg s−1) resulting in compositions and these airborne glass particles are deposited the continuous rise of a convective column up to 26 km. The on ice sheets. Due to their size and insolubility in the at- grey pumice has a SE dispersal, with a slight counterclock- mosphere, these particles are often deposited as dry depo- wise rotation with respect to the white pumice axis. Follow- sition on glacier surfaces before the other byproducts such ing the shift in magma composition a new, rapid increase of 8 −1 as H2SO4 arrive (Hammer et al., 2003; Vinther et al., 2006; magma discharge rate (up to 1.5 × 10 kg s ) occurred with Davies et al., 2010). This difference in depositional tim- the growth of a column up to 32 km (Carey and Sigurds- ing sometimes leads to tephra horizons in ice cores located son, 1987; Sigurdsson et al., 1990). The final phreatomag- stratigraphically below H2SO4 peaks. Individual glass shards matic phase caused pyroclastic flows and surges following can be extracted from the ice layers and can be matched to the caldera collapse (Carey and Sigurdsson, 1987; Cioni et the the chemical composition of tephra from known erup- al., 1992, 2000).
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