Indian Ocean warming modulates global atmospheric circulation trends
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Indian Ocean warming modulates global atmospheric circulation trends Shreya Dhame1 · Andréa S. Taschetto1 · Agus Santoso1,2 · Katrin J. Meissner1 Received: 11 November 2019 / Accepted: 9 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The Indian Ocean has warmed rapidly and notably at a faster rate than the other tropical ocean basins in the latter half of the twentieth century. We conduct sensitivity experiments using an atmospheric general circulation model to determine the impact of Indian Ocean surface warming on large-scale global atmospheric circulation trends and rainfall distribution, in terms of its pattern and magnitude. Indian Ocean warming drives changes in the local Indian Ocean Walker cell that leads to anomalous easterlies over the Pacific Ocean and strengthens the Pacific Walker Circulation. The anomalous Indian Ocean Walker cell results in anomalous subsidence over Central Africa and the tropical Atlantic, where it is associated with a precipitation decrease over the equator. During austral summer, Indian Ocean warming is associated with the intensification of the northern hemisphere Hadley cell and strengthening of the extratropical atmospheric circulation resembling a positive North Atlantic Oscillation. During austral winter, it is associated with weakening of the southern hemisphere Hadley cell and strengthening of a positive Southern Annular Mode pattern. More intensive warming in the western region of the Indian Ocean basin compared to the east has a significant impact on rainfall trends in the basin, easterly wind trend in the western Pacific and intensity of Hadley circulation changes. It is, however, the Indian Ocean warming across the entire basin that dominates the drying of the tropical Atlantic and the trends in extratropical modes of variability. This study suggests the Indian Ocean warming could have potentially influenced global atmospheric circulation trends observed in the recent decades. Keywords Indian Ocean warming · Walker and Hadley circulation · Inter-basin interaction · Atmospheric teleconnections
1 Introduction Since the mid-twentieth century, the Earth’s oceans have been warming with rising greenhouse gas emissions. The Indian Ocean and the western Pacific Ocean have been identified as the most sensitive ocean basins to anthropogenic greenhouse gas forcing (Deser et al. 2010; Knutson et al. 2006; Zhang et al. 2018a). This sensitivity is due to the mean sea surface temperature (SST) of the Indian Ocean being Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00382-020-05369-1) contains supplementary material, which is available to authorized users. * Shreya Dhame [email protected] 1
Climate Change Research Centre and ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, Australia
Centre for Southern Hemisphere Oceans Research (CSHOR), CSIRO Oceans and Atmosphere, Hobart 7004, Australia
2
uniformly warm across the equatorial region. In contrast,
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