Climate Research: Sulphur

Sulphur isotopes prove past volcanic eruptions

Climatologists may now be one step further in dating volcanic eruptions of the past and estimating their extent and consequences for the Earth's climate: conclusions can be drawn about correspondingly large eruptions and their atmospheric how climatic consequences.

The researchers led by Mélanie Baroni from the Joseph Fourier University in St. Martin d`Hères, France, compared the known sulfur isotope ratios that were found after the major eruptions of Mount Agung on Bali in 1963 and Mount Pinatubo on the Philippines were deposited in Antarctica in 1991, with correspondingly older samples from their ice core. Typically, after the events, larger amounts of sulfur-33 than sulfur-34 appeared in the deposits: The powerful eruptions blew high concentrations of sulfur dioxide into the stratosphere, where it was photochemically oxidized to form sulfuric acid with enhanced levels of ³³S - a unique chemical signature. In the months that followed, the conditions in the ice shifted in the direction of ³⁴S, since the ^{33S continued to decrease.}

Sulphur from organic compounds, which did not rise to the stratosphere and therefore ^{33S is completely absent, usually dominates in the deposits. The scientists now want to use the characteristic isotope distributions to break down the climate history of the past even more precisely. Volcanic eruptions like that of Pinatubo emit enormous amounts of aerosol and sulfuric acid, which wrap around the globe like an atmospheric veil, cooling it.}