Because few ice core records from the Himalayas exist, understanding of the onset and timing of the human impact on the atmosphere of the “roof of the world” remains poorly constrained. We report a continuous 500-y trace metal ice core record from the Dasuopu glacier (7,200 m, central Himalayas), the highest drilling site on Earth. We show that an early contamination from toxic trace metals, particularly Cd, Cr, Mo, Ni, Sb, and Zn, emerged at high elevation in the Himalayas at the onset of the European Industrial Revolution (∼1780 AD). This was amplified by the intensification of the snow accumulation (+50% at Dasuopu) likely linked to the meridional displacement of the winter westerlies from 1810 until 1880 AD. During this period, the flux and crustal enrichment factors of the toxic trace metals were augmented by factors of 2 to 4 and 2 to 6, respectively. We suggest this contamination was the consequence of the long-range transport and wet deposition of fly ash from the combustion of coal (likely from Western Europe where it was almost entirely produced and used during the 19th century) with a possible contribution from the synchronous increase in biomass burning emissions from deforestation in the Northern Hemisphere. The snow accumulation decreased and dry winters were reestablished in Dasuopu after 1880 AD when lower than expected toxic metal levels were recorded. This indicates that contamination on the top of the Himalayas depended primarily on multidecadal changes in atmospheric circulation and secondarily on variations in emission sources during the last 200 y.
|Original language||English (US)|
|Number of pages||7|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Feb 25 2020|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS. This work was funded by the NSF Atmospheric Chemistry Program (Award 1149239), the NSF–Earth System History Program, The Ohio State University, the Ohio State Committee of Science and Technology, and the National Natural Science Foundation of China. The mass spectrometer (ICP-SFMS) at the BPCRC was funded by NSF–Major Research Instrumentation Award 0820779 and by the Climate Water Carbon Program of The Ohio State University. We thank the many scientists, engineers, technicians, and graduate students from the BPCRC and the Lanzhou Institute of Glaciology and Geocryology (China). We also thank Jacopo Gabrieli and Carlo Barbante at the University of Venice for providing the lathe that allowed us to process the firn sections. We are also grateful to Julien Nicolas for performing the graphic display of the back trajectories and Susan Kaspari for providing trace metal data from the Mount Everest ice core. Finally, we thank two anonymous reviewers for providing constructive comments that allowed us to remarkably improve the initial manuscript. This is BPCRC Contribution No. C-1591.
- Ice cores
- North Atlantic Oscillation
- Trace metals
PubMed: MeSH publication types
- Historical Article
- Journal Article
- Research Support, Non-U.S. Gov't
- Research Support, U.S. Gov't, Non-P.H.S.