If you are flying an airplane and detect an unusual odor in a confined space 5 miles up in the air, what can it be? Burritos for lunch?   

Not this time. The foul smell with traces of sulfur in the cockpit came from none other than the Grímsvötn volcano that was spewing gas and ash from southeast Iceland. Sulfur dioxide often indicates volcanic ash, and the presence of ash in the atmosphere can endanger jet engines. Once landed, Captain Klaus Sievers used data from the MetOp satellite via the Support to Aviation Control Service – SACS – to confirm that it was high-altitude sulfur dioxide.

Inhalation of sulfur dioxide, even at low concentrations, can affect people with respiratory problems. Flight crews are advised to use oxygen masks while the smell lingers.  When sulfur dioxide combines with water in the atmosphere, sulphuric acid is formed, which can damage aircraft windows, fade exterior paint and build up sulphate deposits in engines. This leads to higher maintenance costs. 

Sulfur dioxide from Grímsvötn volcano on 27 May 2011. Once landed, Captain Klaus Sievers used satellite data provided by the Support to Aviation Control Service (SACS) to confirm the presence of sulfur dioxide and, subsequently, the presence of some volcanic aerosol. This image is based on data from the GOME-2 instrument on the MetOp-A satellite.  Credits: DLR/BIRA-IASB/Eumetsat

“As I found out, the smell of Grímsvötn is not pleasant. For comfort and safety reasons, it would be good if it were possible to avoid such an experience for you and all people on the airplane,” said Sievers.

Volcanic ash and sulphur dioxide can spread rapidly in the atmosphere, affecting skies over a wide area.  The eruptions of Iceland’s Eyjafjallajökull in April 2010 and Grímsvötn in May 2011 caused air traffic to be temporarily suspended throughout Europe, affecting economic, political and social activities worldwide.

 Based on multi-satellite observations, SACS provides early warning ash and sulfur dioxide information about volcanic eruptions. When an eruption occurs, an alert is sent to interested users, most notably to Volcanic Ash Advisory Centres, and public maps are generated showing the extent and intensity of the volcanic plumes.