Aerosol forcing of the position of the intertropical convergence zone since ad 1550

Ridley, Harriet E., Asmerom, Yemane, Baldini, James U. L., Breitenbach, Sebastian, Aquino, Valorie V., Prufer, Keith M., Culleton, Brendan J., Polyak, Victor, Lechleitner, Franziska A., Kennett, Douglas J., Zhang, Minghua, Marwan, Norbert, Macpherson, Colin G., Baldini, Lisa M., Xiao, Tingyin, Peterkin, Joanne L., Awe, Jaime and Haug, Gerald H. (2015) Aerosol forcing of the position of the intertropical convergence zone since ad 1550. Nature Geoscience, 8 (3). pp. 195-200. ISSN 1752-0894

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Official URL: https:/doi.org/10.1038/NGEO2353

Abstract

The position of the intertropical convergence zone is an important control on the distribution of low-latitude precipitation. Its position is largely controlled by hemisphere temperature contrasts1,2. The release of aerosols by human activities may have resulted in a southward shift of the intertropical convergence zone since the early 1900s (refs 1,3–6) by muting the warming of the Northern Hemisphere relative to the Southern Hemisphere over this interval1,7,8, but this proposed shift remains equivocal. Herewe reconstruct monthly rainfall over Belize for the past 456 years from variations in the carbon isotope composition of a well-dated, monthly resolved speleothem. We identify an unprecedented drying trend since AD 1850 that indicates a southward displacement of the intertropical convergence zone. This drying coincides with increasing aerosol emissions in the Northern Hemisphere and also marks a breakdown in the relationship between Northern Hemisphere temperatures and the position of the intertropical convergence zone observed earlier in the record. We also
identify nine short-lived drying events since AD 1550 each following a large volcanic eruption in the Northern Hemisphere. We conclude that anthropogenic aerosol emissions have led to a reduction of rainfall in the northern tropics during the twentieth century, and suggest that geographic changes in aerosol emissions should be considered when assessing potential future rainfall shifts in the tropics.

Item Type: Article
Subjects: F600 Geology
F700 Ocean Sciences
F800 Physical and Terrestrial Geographical and Environmental Sciences
F900 Others in Physical Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Rachel Branson
Date Deposited: 19 Feb 2020 09:23
Last Modified: 19 Feb 2020 10:04
URI: http://nrl.northumbria.ac.uk/id/eprint/42125

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