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Influence of African dust on ocean–atmosphere variability in the tropical Atlantic

Nature Geoscience volume 4, pages 762–765 (2011)Cite this article

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Abstract

The dominant source of coupled ocean–atmosphere variability in the tropical Atlantic is the so-called Atlantic Meridional Mode1,2,3. This mode of variability is characterized by an interhemispheric gradient in sea surface temperatures and by oscillations in the strength of surface winds that cross the Equator, thereby reinforcing sea surface temperature anomalies1,2,3,4. The Atlantic Meridional Mode is thermodynamically damped and must receive external forcing to persist as observed3. However, it is not known which external forcing factors have excited the Atlantic Meridional Mode in the historical record. Here we present simulations with an ocean general circulation model that is forced by a record of surface radiation from anomalous dust concentrations in the atmosphere, reconstructed from a coral proxy and satellite retrievals. We show that the Atlantic Meridional Mode is excited by variability in African dust outbreaks on interannual to decadal timescales. Our analysis indicates that sea surface temperature anomalies resulting from the aerosol direct effect persist in time through the positive ocean–atmosphere feedback5 that defines the Atlantic Meridional Mode. We conclude that on interannual to decadal timescales, the state of the tropical Atlantic ocean is directly tied to dust emissions over West Africa, which in turn are linked to land-use change6,7,8.

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Figure 1: Historical DAOD and the structure of the AMM and the SST response to dust variability.
Figure 2: Monthly mean output from idealized coupled model experiments.
Figure 3: Observed and dust-forced component of the AMM time series.

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Acknowledgements

Financial support for this work was provided by NOAA/CLIVAR grants NA10OAR4310136 and NA10OAR4310207.

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Authors and Affiliations

  1. Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904, USA

    Amato T. Evan

  2. Atlantic Oceanographic and Meteorological Laboratory (NOAA/AOML), Miami, Florida 33149, USA

    Gregory R. Foltz

  3. JISAO/University of Washington and Pacific Marine Environmental Laboratory (NOAA/PMEL), Seattle, Washington 98115, USA

    Dongxiao Zhang

  4. Department of Atmospheric and Oceanic Sciences, University of Wisconsin at Madison, Madison, Wisconsin 53706, USA

    Daniel J. Vimont

Authors
  1. Amato T. Evan
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  2. Gregory R. Foltz
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  3. Dongxiao Zhang
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  4. Daniel J. Vimont
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Contributions

A.T.E. and D.J.V. designed and carried out the model experiments; A.T.E., G.R.F., D.J.V. and D.Z. analysed and interpreted the model output and co-wrote the paper.

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Correspondence to Amato T. Evan.

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The authors declare no competing financial interests.

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Evan, A., Foltz, G., Zhang, D. et al. Influence of African dust on ocean–atmosphere variability in the tropical Atlantic. Nature Geosci 4, 762–765 (2011). https://doi.org/10.1038/ngeo1276

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