This work confirms the presence of iodine in the stratosphere, corroborating previous hypothesis presented by IQFR scientists.

IQFR has taken part in an international study confirming that significant levels of iodine can reach the stratosphere, the region of the atmosphere between 10 and 40 kilometres high. Iodine can then affect the evolution of the ozone layer. The obtained results, which confirm modelling studies conducted by an IQFR research team, conclude that iodine levels measured in the lower stratosphere of mid-latitudes would be responsible for up to 32% of the halogen-mediated ozone loss, exceeding the relative contribution of chlorine (28%) and almost reaching the contribution of bromine (40%). The work has been published in the Proceedings of the National Academy of Sciences (PNAS).

Previous research on halogen chemistry in the stratosphere has focused on the ability of chlorine and bromine species to destroy stratospheric ozone. These substances, whose lifetimes are long enough to be transported to the stratosphere, are actively involved in the destruction of ozone. However, this new work confirms that iodine species can also reach the stratosphere and affect the ozone layer, despite their shorter lifetimes. These results show the importance of considering iodine chemistry both in the troposphere and in the stratosphere in climate models, since the natural emission of iodine species into the atmosphere is highly dependent on the evolution of climate. It is also expected that the relative impact of these iodine species will increase in the future with respect to that of chlorine and bromine.

For more than a decade, the IQFR group of atmospheric chemistry and climate (AC2) has studied the contribution of natural sources of short-lived halogens such as iodine to the oxidative capacity of the atmosphere and climate. This time, the group has collaborated with an USA team to obtain quantitative measurements of iodine in the stratosphere. The measurements of iodine both in the gas phase and in the aerosol phase have been performed by means of a laboratory installed in the Gulfstream-V aircraft of the NCAR (National Center for Atmospheric Research), including state of the art technology and instrumentation for high-atmosphere analysis.

Theodore K. Koenig, Sunil Baidar, Pedro Campuzano-Jost, Carlos A. Cuevas, Barbara Dix, Rafael P. Fernandez, Hongyu Guo, Samuel R. Hall, Douglas Kinnison, Benjamin A. Nault, Kirk Ullmann, Jose L. Jimenez, Alfonso Saiz-Lopez y Rainer Volkamer. Quantitative Detection of Iodine in the Stratosphere. Proceedings of the National Academy of Sciences (PNAS). DOI: 10.1073/pnas.1916828117