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The rising importance of pan-tropical interactions

Did you know that the El Niño Southern Oscillation is a phenomenon involving two-way interactions among the tropical basins? Noel Keenlyside writes about a recent study he has contributed to.

feedback_loops_pacific_atlantic_indian_oceans
Schematic summarizing the feedback loops within the Pacific and to the tropical Atlantic and Indian Oceans that underlie the El Niño Southern Oscillation is a phenomenon. Figure from Cai et al. 2019.
Photo:
Cai et al. 2019

Written by Noel Keenlyside, Professor at the Bjerknes Centre and the Geophysical Institute at the University of Bergen.

Research during the last decade has shown just that the traditional view of El Niño as a one-way driver of global weather patterns – teleconnections – is inaccurate. While climate variability in the tropical Atlantic and Indian Ocean is largely forced by El Niño variability, they both feedback on to El Niño. These two-way interactions are integral to the dynamics of El Niño and impacts its properties and predictability.

 

feedback_loops_pacific_atlantic_indian_oceans

Schematic summarizing the feedback loops within the Pacific and to the tropical Atlantic and Indian Oceans that underlie the El Niño Southern Oscillation is a phenomenon. Figure from Cai et al. 2019.

Photo:
Cai et al. 2019

 

The strength of these interactions varies in time and they became stronger after the 70’s, coinciding with a strengthening of El Niño variability and an increase in its predictability. The warming of the Atlantic has likely played an important role in these changes, but the mechanisms remain to be properly established.

The importance of pan-tropical connections on the timescales of decades has also become recently appreciated. The role of the Atlantic has also become stronger during the recent decades. In particular, the recent warming of the Atlantic drove a strengthening of the trade winds and cooling over the Pacific and contributed greatly to the global warming hiatus. Again, the mechanisms behind the strengthening of this relation remain to be established.

There is a growing scientific consensus on the importance of pan-tropical teleconnections. This is reflected by the recent publication of a review paperin Science. The international research activity funded and stimulated EU-PREFACE project lead by UiB contributed to reaching this scientific milestone. The Bjerknes Climate Prediction Unit through new initiatives such as the EU-TRIATLAS project will continue research in this important and exciting area.

References

Cai, W., L. Wu, M. Lengaigne, T. Li, S. McGregor, J.-S. Kug, J.-Y. Yu, M. F. Stuecker, A. Santoso, X. Li, Y.-G. Ham, Y. Chikamoto, B. Ng, M. J. McPhaden, Y. Du, D. Dommenget, F. Jia, J. B. Kajtar, N. Keenlyside, X. Lin, J.-J. Luo, M. Martín-Rey, Y. Ruprich-Robert, G. Wang, S.-P. Xie, Y. Yang, S. M. Kang, J.-Y. Choi, B. Gan, G.-I. Kim, C.-E. Kim, S. Kim, J.-H. Kim, and P. Chang, 2019: Pantropical climate interactions. Science, 363.

This is also publised at the web-pages of The Bjerknes Centre for climate research.