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1 ttp://news.discovery.com/earth/iceland-volcano-aurora.html

2 Outline Role of volcanism on the climate system Distribution of Arctic volcanoes Types of eruptions Frequency of Arctic eruptions Influence on Arctic climate Observed impacts Little Ice Age (LIA) Projected impacts

3 Role of volcanism on the climate system Erupt gases and solid particles into troposphere and lower stratosphere CO 2 SO 2 Water vapor Tephra

4 Sulfuric acid (H 2 SO 4 ) aerosols Forms naturally via atmospheric oxidation of SO 2 in the presence of water Creates atmospheric cooling as aerosols in the stratosphere scatter and absorb incoming solar radiation increasing opacity of the atmosphere Aerosol particles also serve as surfaces for heterogeneous chemical reactions that liberate chlorine to destroy ozone Can have a large regional effect on radiative balance and climate

5 Figure from (Robock, 2003)

6 Geographic Distribution of Active Volcanos

7 Alaska and Iceland Volcanoes formed by the subduction of the Pacific Plate under the North American Plate. Volcanism due to hotspot created by the divergence of the North American and Eurasian plates along the Mid-Atlantic Ridge.

8 Types of Eruptions Explosive >95% of erupted magma is tephra Effusive (Flood Basalt) >95% of erupted magma is lava Mt. St. Helens issues/stater0004/ F_MtStHelens.html Fissure vent eruption on Eyjafjallajokull in Iceland utm_source=sbhomepage&utm_medium=link&utm_content=channellink

9 Explosive Eruptions Occur in both Alaska and Iceland Short explosive events (hours to days) Instantaneous atmospheric loading of SO 2 into the stratosphere (Thordarson et al., 2003) Can have episodic eruption periods

10 Effusive Eruptions Flood basalt eruptions linked to mass extinction events in geologic past (Wignall, 2001) Most significant eruptions over last 1130 years in Iceland in terms of climate and environmental impacts (Thordarson and Larsen, 2005) Sequential eruptive episodes result from the periodic injection of fresh magma allowing eruptions to last from months to >100 years (Thordarson et al, 2003)

11 Mass of sulfur released by Holocene flood lava eruptions in VGK Icelandic volcanic system (Thordarson et al., 2003) Mt of SO 2 released into the atmosphere in largest events (Self et al., 2005)

12 Frequency of Icelandic eruptions over the last 1100 years 205 identified eruptive events 124 explosive, 14 effusive, 21 mixed (Thordarson and Larsen, 2007)

13 Observed Impacts Laki: Fissure eruption in Iceland year reduction in average surface temperature of >1.3 C across Europe and North America Stable anti-cyclonic air masses drew aerosols and gases down creating a dry acidic fog across Europe Shorter cooler summers that followed the eruption hindered crop germination Massive plant damage and soil acidification from acid rain suggesting the ph of the aerosol <2.0 Increased mortality rates in England and France for 1783 No summer in 1783 in Alaska (Grattan, 2005)

14 Temperature Anomalies following Laki Eruption Mean winter temperatures in England Anomalously cold winters for 2 years following the eruption Mean summer temperatures in England Anomalously hot summer in 1783 suggested to be due to greenhouse warming from high concentrations of SO 2 in the troposphere (Rampino et al., 1995)

15 Volcanism as a Trigger for the LIA Extensive debate regarding cause of LIA Miller et al. (2011) used precisely dated ice-cap growth records from Arctic Canada and Iceland Onset between 1275 and 1300 AD Substantial intensification of summer cold and ice growth AD with maximum ice dimensions reached about 1850 AD Intervals of sudden and sustained ice growth coincide with two of the most volcanically perturbed half centuries in the last millennium

16 Solitary eruptions offer short lived negative radiative forcing while decadally paced eruptions may produce greater cooling than large single eruptions as the recurrence interval is shorter than upper ocean temperature relaxation times (in order of decades) (Zhong et al., 2010) LIA Triggered by repeated episodes of explosive volcanism Sustained by sea ice/ocean feedback during a summer insolation minimum (Miller et al., 2011) Ice cap on Baffin Island, Canada (Credit: Gifford Miller, University of Colorado at Boulder) Polar/presentations/2010/zhong.pdf

17 Little Ice Age Hypothesis Supported by Community Climate System Model 3 Decadally paced explosive volcanism can produce persistent regional summer cooling that is maintained by sea-ice/ocean feedbacks long after volcanic aerosols are removed Model resulted in rapid and sustained expansion of Arctic sea ice when given favorable initial state (Miller et al., 2011)

18 Projected Global Impacts Few studies have been done to project the effects of large high latitude eruptions Stratospheric version of GISS ModelE GCM used to model eruptions of Katmai 1912 and Laki 1783 Show high latitude eruptions remain in hemisphere where they erupted unlike tropical eruptions Significant aerosol perturbation in Northern Hemisphere Significant cooling over southern Asia during boreal winter due to reduction in strength of the monsoon Warm temperatures and decreased cloud cover over India (Oman et al., 2005; Oman et al., 2006)

19 Relationship with Future Climate Volcanic gases could considerably enhance the anthropogenic air pollution already concentrated in major population centers Significant ozone loss via heterogeneous reactions Large eruptions and/or prolonged eruptive periods can contribute to short term regional and/or hemispheric climate change Extensive environmental impacts