Title: Atmospheric Sulfur Sources and Chemistry from Preindustrial to Present
Abstract: Aerosols are particles in the atmosphere that have a net cooling effect on global climate. Aerosols from human activities partially offset warming from greenhouse gases, but represent the largest uncertainty in estimating human influence on climate from 1850-2019. Sulfate aerosols have the largest cooling effect of any aerosol and also represent the largest uncertainty. Here we measure sulfur isotopes of sulfate in Greenland ice cores using isotope ratio mass spectrometry to determine how sulfate aerosol sources and oxidation chemistry have changed from over the industrial era. We report two major findings. First, passive volcanic degassing is an underestimated source of atmospheric sulfur due to the underestimated contribution of hydrogen sulfide emissions from quiescent volcanoes. Second, we find that pollution drives an industrial-era decline in ice core methanesulfonic acid, which was previously interpreted as a sign of collapsing phytoplankton populations. These findings have changed our understanding of sulfate aerosol sources and chemistry, with implications for estimating the influence of sulfate aerosols on global climate.
Bio: Ursula Jongebloed is an atmospheric chemist interested in aerosols and their role in Earth’s climate. Ursula’s research synthesizes atmospheric chemistry, isotope geochemistry, isotope ratio mass spectrometry, and climate science. Ursula measures stable isotopes in ice cores and aerosol samples and uses global models of atmospheric composition to determine aerosol sources and chemistry. Ursula’s work on sulfate sources and chemistry has been recognized with the 2nd place Wagner Award in Atmospheric Sciences and with an early-career grant from the Center for Oldest Ice Exploration. She also received the Certificate of Distinguished Service from the University of Washington Atmospheric and Climate Sciences Department for outstanding service, outreach, and leadership activities. Prior to PhD studies in Atmospheric and Climate Science at the University of Washington, Ursula received her B.A. from Dartmouth College with a double major in Chemistry and Earth Sciences.
Host: Tim Bertram