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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 10 | Copyright
Clim. Past, 14, 1377-1390, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 01 Oct 2018

Research article | 01 Oct 2018

Inter-annual variability in the tropical Atlantic from the Last Glacial Maximum into future climate projections simulated by CMIP5/PMIP3

Chris Brierley1 and Ilana Wainer2 Chris Brierley and Ilana Wainer
  • 1Environmental Change Research Centre, Department of Geography, University College London, Gower St, London, WC1E 6BT, UK
  • 2Departamento de Oceanografia Física, Química e Geológica, Instituto Oceanográfico da Universidade de São Paulo, Praça do Oceanográfico, 05508-120, São Paulo, Brasil

Abstract. Tropical Atlantic variability (TAV) plays an important role in driving year-to-year changes in rainfall over Africa and South America. In this study, its response to global climate change is investigated through a series of multi-model experiments. We explore the leading modes of TAV during the historical, Last Glacial Maximum, mid-Holocene, and future simulations in the multi-model ensemble known as PMIP3/CMIP5. Despite their known sea surface temperature biases, most of the models are able to capture the tropical Atlantic's two leading modes of SST variability patterns – the Atlantic Meridional Mode (AMM) and the Atlantic zonal mode (also called the Atlantic Niño or ATL3). The ensemble suggests that AMM amplitude was less during the mid-Holocene and increased during the Last Glacial Maximum, but is equivocal about future changes. ATL3 appears stronger under both the Last Glacial Maximum and future climate changes, with no consistent message about the mid-Holocene. The patterns and the regions under the influence of the two modes alter a little under climate change in concert with changes in the mean climate state. In the future climate experiment, the equatorial mode weakens, and the whole Northern Hemisphere warms up, while the South Atlantic displays a hemisphere-wide weak oscillating pattern. For the LGM, the AMM projects onto a pattern that resembles the pan-Atlantic decadal oscillation. No robust relationships between the amplitude of the zonal and meridional temperature gradients and their respective variability was found.

Publications Copernicus
Short summary
Year-to-year changes in rainfall over Africa and South America are influenced by variations in the temperatures of tropical Atlantic variability. Here we investigate how these variations behave under climate change using a series of multi-model experiments. We look at how cold and warm climates of the past relate to future shifts in variability.
Year-to-year changes in rainfall over Africa and South America are influenced by variations in...