Triggers for the Late Ordovician Ice Age: Volcanic Aerosols vs. CO 2 Konrad Cunningham UG Eric Santiago HSS Linda Sohl PI Mark Chandler PI

Ordovician Period  Started about 500 million years ago.  Hardly any plants or animals lived on the land; most were in the sea.  Compared to today’s Sun, the Sun of the Ordovician was 4% dim.  Most land masses were in the Southern Hemisphere.

The Ice Age of the Ordovician  Lasted ~0.5 to ~1.5 million years.  Some researchers think that there was a high level of atmospheric CO 2  Our hypothesis: the sharp decrease in temperature could have been caused by a combination of low CO 2 and high SO 2 related to volcanic activity in the atmosphere.

Paleogeography

Volcano locations in the late Ordovician  The volcanoes were part of an island arc between Laurentia and Baltica.  These volcanoes were active and created 5,000 times the volume of ash than Mt. St. Helens’ eruption in  The eruptions were 3 of the 20 largest events in the last 600 million years.

Anomaly Plots for SurfAirTemp CO2=1000 ppm, Solar=96% CO2=500 ppm, Solar=96% CO2=3000 ppm, Solar=96% CO2=1000ppm; Solar=94%

Conclusion  Ord_testrun3 shows that a ice age is highly improbable with high atmospheric CO 2, no matter what the level of solar luminosity.  Ord_testrun8 gives us the most probable conditions on Earth that would help create an ice age.  Future simulations will explore the effects of both high SO 2 and low CO 2 on Ordovician climate.

References  Alaska Volcano Observatory  ATMOSPHERIC TRANSMISSION OF DIRECT SOLAR RADIATION AT MAUNA LOA, HAWAII   Global Volcanism Program  Volcanic SO2 Archive Service  Mount Pinatubo Eruption  Ordovician  Impacts of Volcanic Gases  Ancient Oceans Separate the Continents  The Geology of Ohio—The Ordovician  The size and frequency of the largest explosive eruptions on Earth  Nature and Origin of Life on Planetary Bodies