Aerosols from the June 2011 eruption of Nabro volcano in Eritrea in northeast Africa breached the stratosphere layer. This discovery was reported in the July 6 issue of Science by researchers led by Adam Bourassa of the University of Saskatchewan (U of S) Institute of Space and Atmospheric Studies.
The stratosphere is the layer next to the turbulent troposphere that is nearest the Earth’s surface. It has an altitude of 10 km from the poles and 17 km at the equator.
Initially, it was believed that storms cannot breach this layer. However, recent data showed volcanic gas and aerosols from the eruption of Nabro volcano met the path of the annual Asian summer monsoons and were transported to this layer.
Bourassa said aerosols in the lower atmosphere are affected by weather conditions and return to earth with precipitation. However, once they breach the stable stratosphere layer, they can persist for years and scatter incoming sunlight that can result to lowering of the earth’s surface temperature.
A similar phenomenon occurred in 1991 when Mt. Pinatubo in the Philippines erupted. The resulting massive volcanic ash dropped worldwide temperatures by one and a half degrees Celsius. Although this change was temporary since the ash were localized in the lower atmosphere and dissipated with rain.
The Nabro eruption caused the first detection of volcanic aerosol in the stratosphere and the highest atmospheric aerosol load ever measured by the OSIRIS. The OSIRIS is an instrument built by the Canadian Space Agency to study the upper atmospheres. It was launched in 2001 aboard the Swedish satellite Odin.
Bourassa said the OSIRIS has been gathering data for over a decade and has proven to be invaluable in studying climate and weather conditions. It circles the earth from pole to pole every one and a half hours collecting data and sending it to the U of S Analysis Centre.
It is hoped these recent findings will shed more light in understanding climate weather and change. This is especially vital for modelling studies as we continue to struggle with the effects of global warming.