Teilprojekt C5 - Matthew Toohey (1) and Doreen Metzner (2)
(1) How does the impact of tropical volcanic eruptions depend on eruption season?
(2) Simulations of the climate response to major volcanic eruptions using
different complexities of earth system climate models
(1) Major volcanic eruptions in the tropics have particularly strong climate impacts, since the circulation pattern of the stratosphere, or Brewer-Dobson circulation, leads to long lifetimes and near-global coverage for volcanic aerosols introduced into the tropical stratosphere. The Brewer-Dobson circulation is strongly hemispherically and seasonally dependent, with poleward meridional transport and mixing occurring most strongly in the winter hemisphere.
Using simulations with the MAECHAM5-HAM general circulation model including detailed aerosol microphysics, and the MPI Earth System Model, we examine how the transport of volcanic aerosols, and the resulting climate impact of major tropical eruptions depends on the
season of eruption. A number of paleo-eruptions in the Central American Volcanic Arc (CAVA) are simulated, with different SO2 emission strengths estimated from field measurements. We examine how the magnitude and season of eruption affect the hemispheric asymmetry of both stratospheric aerosol optical depth (AOD) and sulphur deposition over the poles. Large
hemispheric asymmetries in stratospheric aerosol distribution may affect how the global mean temperature is perturbed by a given volcanic eruption. This work could be useful in better interpreting volcanic signals in paleo-ice core data and improving the accuracy of estimated AOD data sets used in the model simulation of past climate.
(2) One of the most important natural causes of climate change are major volcanic eruptions as they have an significant impact on the Earth’s global climate system. To evaluate the climate response to major volcanic eruptions we use the Earth System Model of Intermediate Complexity (EMIC) CLIMBER by forcing it with a new radiative forcing
data set comprising large Plinian eruptions from volcanoes at the Central American Volcanic Arc (CAVA) over the last 200 ka. This specifically created radiative forcing data set is based on the "petrological method" and use information about strength and height of the volcanic sulphur injection (Kutterolf et al. 2008a,b). Our first evaluation involves simulations forced with the assessed radiative forcing of the largest CAVA eruption (650 Mt SO2) Los Chocoyos (84 ka). By comparing these runs with simulations of the best observed large volcanic eruption, the one of Mt Pinatubo in June 1991 (17 Mt SO2), we analyse similarities and differences, which may be generated by complex relationships between the radiative forcing and the climate system. The same set of forcing is also used for simulations with the complex Earth System Model (ESM) from MPI. Similarities and differences between the two different model runs will be used for a better understanding of the complex climate
interactions after major volcanic eruptions. We consider global atmospheric effects as well as possible changes in the ocean circulation, the carbon cycle and vegetation.
SFB Seminarraum Gebäude 8A IFM-GEOMAR, Ostufer
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