Skip to Main content Skip to Navigation
Journal articles

Evidence for Interhemispheric Mercury Exchange in the Pacific Ocean Upper Troposphere

Abstract : Even though anthropogenic mercury (Hg) emissions to the atmosphere are ∼2.5 times higher in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH), atmospheric Hg concentrations in the NH are only ∼1.5 times higher than in the SH. Global Hg models attribute this apparent discrepancy to large SH oceanic Hg emissions or to interhemispheric exchange of Hg through the atmosphere. However, no observational data set exists to serve as a benchmark to validate whether these coarse-resolution models adequately represent the complex dynamics of interhemispheric Hg exchange. During the 2015-2016 El Niño, we observed at mount Chacaltaya in the tropical Andes a ∼50% increase in ambient Hg compared to the year before, coinciding with a shift in synoptic transport pathways. Using this event as a case study, we investigate the impact of interhemispheric exchange on atmospheric Hg in tropical South America. We use HYSPLIT to link Hg observations to long-range transport and find that the observed Hg increase relates strongly to air masses from the tropical Pacific upper troposphere (UT), a region directly impacted by interhemispheric exchange. Inclusion of the modeled seasonality of interhemispheric air mass exchange strengthens this relationship significantly. We estimate that interhemispheric exchange drives Hg seasonality in the SH tropical Pacific UT, with strongly enhanced Hg between July and October. We validate this seasonality with previously published aircraft Hg observations. Our results suggest that the transport of NH-influenced air masses to tropical South America via the Pacific UT occurs regularly but became more detectable at Chacaltaya in 2015-2016 because of a westward shift in air mass origin.
Document type :
Journal articles
Complete list of metadata

https://hal-insu.archives-ouvertes.fr/insu-03706371
Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Tuesday, June 28, 2022 - 3:47:55 PM
Last modification on : Monday, July 4, 2022 - 9:41:59 AM

File

JGR Atmospheres - 2022 - Koeni...
Publisher files allowed on an open archive

Licence


Distributed under a Creative Commons Attribution 4.0 International License

Identifiers

Collections

Citation

Alkuin M. Koenig, Jeroen E. Sonke, Olivier Magand, Marcos Andrade, Isabel Moreno, et al.. Evidence for Interhemispheric Mercury Exchange in the Pacific Ocean Upper Troposphere. Journal of Geophysical Research: Atmospheres, 2022, 127, ⟨10.1029/2021JD036283⟩. ⟨insu-03706371⟩

Share

Metrics

Record views

20

Files downloads

0