Understanding present and future dynamics of ENSO and the IOD
Project leaders: Drs Agus Santoso (CSIRO and UNSW) and Guojian Wang (CSIRO)
Staff: Drs Dave Bi and Benjamin Ng.
[Music plays and animation waves appear moving up from the bottom of the screen and text appears above: The Centre for Southern Hemisphere Oceans Research]
[Image shows animation waves moving up the screen and over the text and then the image changes to show Agus Santoso talking to the camera and text appears: Agus Santoso, CSHOR Project Leader, University of New South Wales]
Agus Santoso: The project I will be leading will be investigating the role of Southern Hemisphere oceans in the dynamics of El Nino and Indian Ocean Dipole.
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Southern Ocean is a big question mark, so by understanding the role of southern oceans, then we will be able to improve things like prediction of El Nino Southern Oscillation and of course eventually it will benefit many people.
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This work is important because tropical climate variability like El Nino and Indian Ocean Dipole impact on climate around the world such as countries like Australia.
[Image changes to show Ming Feng and Larry Marshall clapping as a plaque is unveiled and then shaking hands and then the image changes to show Agus talking to the camera]
CSHOR will benefit people in how we can manage resources and how we can manage doing flood management better in terms of anticipating all these impactful climate events in present day and in the future.
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The El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) affect millions of human lives in the tropical belt and beyond. The likelihood of extreme weather events such as drought, heatwaves, floods, and cyclones is elevated during such events, particularly extreme ENSO and extreme positive IOD. Understanding their dynamics is of utmost importance as to enhance our capacity to predict their occurrences, especially their trends in a climate that is undergoing change.
Present outstanding issues on this topics are many, and these include: generation mechanism of ENSO diversity (mechanism of extreme El Niño and weak El Niño) and the associated diversity in ENSO teleconnections; uncertainty in projected change in future ENSO and the IOD; and the role of the Southern Hemisphere oceans, in the ENSO and the IOD life cycle.
The objectives of the project are to:
- understand how ENSO and IOD events are generated, in particular, how they attain extreme amplitude, how they interact with each other and with the Southern Hemisphere oceans
- examine the causes for decadal modulation of ENSO and IOD characteristics, and the potential role of Southern Hemisphere oceans
- project changes in ENSO and the IOD under greenhouse warming, as well as their interactions and teleconnection, and assess uncertainty in the projected change.
Predicting Tropical Pacific decadal climate variability and change
1 October 2021
Tropical Pacific decadal climate variability and change (TPDV) affects the global climate system, extreme weather events, agricultural production, streamflow, marine and terrestrial ecosystems, and biodiversity. Although major international efforts are underway to provide decadal climate predictions, there is still a great deal of uncertainty. A review article by Power et al. (Including Cai, W., Zhang, X., and Wang, G.) (2021), published in Science, critically synthesises what is known and not known about the characteristics and causes of TPDV, and the accuracy to which it can be simulated and predicted. The article concludes with recommendations to improve our understanding of and ability to predict TPDV.
Read the review article at this link.
Enhanced North Pacific impact on ENSO under greenhouse warming
20 September, 2021
A majority of El Niño Southern Oscillation (ENSO) events are preceded by the North Pacific Meridional Mode (NPMM), a dominant coupled ocean–atmospheric mode of variability. How the precursory NPMM forcing on ENSO responds to greenhouse warming remains unknown. Using climate model ensembles under high-emissions warming scenarios, the authors of a study recently published in Nature Climate Change (Jia et al., 2021), find an enhanced future impact on ENSO by the NPMM. This is manifested by increased sensitivity of boreal-winter equatorial Pacific winds and sea surface temperature (SST) anomalies to the NPMM three seasons before.
Go to the Nature Climate Change publication via this link.
Changing El Niño–Southern Oscillation in a warming climate
18 August, 2021
A review article by Cai et al. (2021), published in Nature Reviews Earth & Environment, synthesises advances in observed and projected changes of multiple aspects of El Niño–Southern Oscillation (ENSO), including the processes behind such changes. The review finds that models which best capture key ENSO dynamics also tend to project an increase in future ENSO sea surface temperature (SST) variability and, thereby, ENSO magnitude under greenhouse warming, as well as an eastward shift and intensification of ENSO-related atmospheric teleconnections. Read the CSHOR post here.
Dr Guojian Wang’s science journey
14 April 2021
Dr Guojian Wang from the CSHOR team has shared a story on his science journey with the CSIRO blog. Read more about Guojian’s research into El Nino Southern Oscillation and the Indian Ocean Dipole, and what inspired him into a science carer, at this link.
CSHOR Session at AMOS 2021
CSHOR project leaders, Guojian Wang, Agus Santoso, Xuebin Zhang and Benjamin Ng are convening a session titled, ‘Southern hemisphere oceans and climate variability‘ at the AMOS 2021 Conference – online from 8 to 12 February 2021.
Abstract: The southern hemisphere oceans encompass many key elements of the Earth’s climate system, e.g., Indo-Pacific warm pool, Indonesian Throughflow, Super-gyre Circulation, and the vast Southern Ocean. Although more than 80% of the southern hemisphere is covered by ocean, the Amazonia, which has the largest rainforest in the world working as the lungs of the planet, and the Antarctic, which is covered by an average two-kilometre-thick ice sheet, can influence the Earth’s climate tremendously. All these components are influenced by climate variability in the region, including in the Indo-Pacific Oceans, such as the El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) which exert significant impact on weather patterns, rainfall, air-sea fluxes, sea level, ocean density and circulations, ecosystems, and many others. How these modes of variability teleconnect in the southern hemisphere, and how they change under global warming, continue to be areas of active research.
Abstracts close on 6 November 2020.
Visit the conference website at this link.
Opposite response of strong and moderate positive Indian Ocean Dipole to greenhouse warming
1 December 2020
A new study by Cai, Yang and Wu et al. published today in Nature Climate Change shows that climate extremes seen in 2019-20 are likely to occur more frequently under greenhouse warming. Faster warming in the equatorial northwestern Indian Ocean favours atmosphere convection in the region. Equatorial nonlinear positive feedbacks responsible for the strong cooling in the equatorial eastern Indian Ocean are strengthened. Low-tropospheric warming which is faster than the surface warming is inconducive to Ekman pumping that drives warm anomalies. For further detail and a link to the full article, go to the CSHOR post at this link.
Book Release – ENSO in a changing climate
Update – on 29 December 2020, the book, ‘El Niño Southern Oscillation in a Changing Climate’, launched in November 2020, was highlighted in a Sydney Morning Herald article explaining El Niño and La Niña events.
El Niño is an unusual warming of the tropical Pacific that wreaks havoc on weather systems around the globe. It happens every few years and, like its cold counterpart La Niña, has profound effects on society and the environment. The irregular cycle between warm El Niño and cold La Niña events, referred to as El Niño Southern Oscillation, or ENSO, is the focus of a new book, El Niño Southern Oscillation in a Changing Climate, published by Wiley as part of the centennial celebration of the American Geophysical Union. The book is the first comprehensive examination of how ENSO cycle dynamics and impacts may change under the influence of rising greenhouse gas concentrations in the atmosphere.
Michael McPhaden (U.S. National Oceanic and Atmospheric Administration (NOAA) and CSHOR Advisory Committee Member), Agus Santoso (University of New South Wales (UNSW) and CSHOR project leader), and Wenju Cai (CSIRO and CSHOR Director), served as editors of the book.
Read the Editors’ Vox on the Eos website at this link.
La Niña event expected in 2020/21
28 September 2020
Dr Agus Santoso was interviewed by Peter Hannam for the Sydney Morning Herald/The Age about an emerging La Niña in 2020. The article reports that the Bureau of Meteorology is expected to declare a La Niña event is under way in the Pacific, underscoring climate influences that point to a wetter than usual end to 2020 across northern and eastern Australia. The article is available here.
Butterfly effect and a self-modulating El Niño response to global warming
3 September 2020
In an article published online today in Nature we show that like a butterfly effect, an infinitesimal random perturbation to identical initial conditions induces vastly different initial ENSO variability, which systematically affects its response to greenhouse warming a century later. In experiments with higher initial variability, a greater cumulative oceanic heat loss from ENSO thermal damping reduces stratification of the upper equatorial Pacific Ocean, leading to a smaller increase in ENSO variability under subsquent greenhouse warming. This self-modulating mechanism operates in two large ensembles generated using two different models, each commencing from identical initial conditions but with a butterfly perturbation; it also operates in a large ensemble generated with another model commencing from different initial conditions and across climate models participating in the Coupled Model Intercomparison Project. Thus, if the greenhouse-warming-induced increase in ENSO variability is initially suppressed by internal variability, future ENSO variability is likely to be enhanced, and vice versa. This self-modulation linking ENSO variability across time presents a different perspective for understanding the dynamics of ENSO variability on multiple timescales in a changing climate. Go to the CSHOR post for a link to the article and to related news items.
Abellán, E., McGregor, S., England, M. H., & Santoso, A. (2017). Distinctive role of ocean advection anomalies in the development of the extreme 2015–16 El Niño. Climate Dynamics. https://doi.org/10.1007/s00382-017-4007-0.
Bordbar, M. H., M. H. England, A. Sen Gupta, A. Santoso, A. S. Taschetto, T. Martin, W. Park, M. Latif (2019). Uncertainty in near-term global surface warming linked to tropical Pacific climate variability. Nature Communications, 10:1990. https://doi.org/10.1038/s41467-019-09761-2.
Cai, W., McPhaden, M. J., Grimm, A. M., Rodrigues, R. R., Taschetto, A. S., Garreaud, R. D., . . . Vera, C. (2020). Climate impacts of the El Niño–Southern Oscillation on South America. Nature Reviews Earth & Environment, 1(4), 215-231. https://doi.org/10.1038/s43017-020-0040-3.
Cai, W., Ng, B., Geng, T. Wu, L., Santoso, A., McPhaden, M. J. (2020). Butterfly effect and a self-modulating El Niño response to global warming. Nature, 585, 68–73. https://doi.org/10.1038/s41586-020-2641-x.
Cai, W., Santoso, A., Collins, M. et al. (Including Wang, G. and Ng, B.) (2021). Changing El Niño–Southern Oscillation in a warming climate. Nature Reviews Earth and Environment. https://doi.org/10.1038/s43017-021-00199-z.
Cai, W., A. Santoso, G. Wang, L. Wu, M. Collins, M. Lengaigne, S. Power, and A. Timmermann (2020). Chapter 13: ENSO Response to Greenhouse Forcing. AGU Monograph: ENSO in a Changing Climate. McPhaden, M., A. Santoso, W. Cai (Eds.), Wiley. https://doi.org/10.1002/9781119548164.ch13.
Cai, W., G. Wang, B. Dewitte, L. Wu, A. Santoso, K. Takahashi, Y. Yang, A. Carreric, and M. J. McPhaden (2018b). Increased variability of Eastern Pacific El Niño under greenhouse warming. Nature, 564, 201-206. https://doi.org/10.1038/s41586-018-0776-9.
Cai, W., Wang, G., Gan, B., Wu, L., Santoso, A., Lin, X., Chen, Z., Jia, F., & Yamagata, T. (2018). Stabilised frequency of extreme positive Indian Ocean Dipole under 1.5 °C warming. Nature Communications, 9(1), 1419. https://www.nature.com/articles/s41467-018-03789-6.
Cai, W., Wang, G., Santoso, A., Lin, X., & Wu, L. (2017). Definition of Extreme El Niño and Its Impact on Projected Increase in Extreme El Niño Frequency. Geophysical Research Letters, 44(21), 11,184-111,190. http://dx.doi.org/10.1002/2017GL075635.
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Holmes, R. M., McGregor, S., Santoso, A., & England, M. H. (2018). Contribution of Tropical Instability Waves to ENSO Irregularity. Climate Dynamics. https://doi.org/10.1007/s00382-018-4217-0.
Hu, S., Sprintall, J., Guan, C., McPhaden, M. J., Wang, F., Hu, D., & Cai, W. (2020). Deep-reaching acceleration of global mean ocean circulation over the past two decades. Science Advances, 6(6), eaax7727. https://doi.org/10.1126/sciadv.aax7727.
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Karamperidou, C., M. F. Stuecker, A. Timmermann, K.-S. Yun, S.-S. Lee, F.-F. Jin, A. Santoso, M. J. McPhaden, and W. Cai (2020). Chapter 21: ENSO in a Changing Climate: Challenges, Paleo-Perspectives, and Outlook. AGU Monograph: ENSO in a Changing Climate. McPhaden, M., A. Santoso, W. Cai (Eds.), Wiley. https://doi.org/10.1002/9781119548164.ch21.
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Makarim, S., J. Sprintall, Z. Liu, W. Yu, A. Santoso, X.-H. Yan, R. D. Susanto (2019). Previously unidentified Indonesian Throughflow pathways and freshening in the Indian Ocean during recent decades. Scientific Reports, 9:7364. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6517581/.
McKenna, S., A. Santoso, A. Sen Gupta, A. Taschetto, W. Cai (2020). Indian Ocean Dipole in CMIP5 and CMIP6: Characteristics, biases, and links to ENSO. Scientific Reports 10(1), 11500. https://doi.org/10.1038/s41598-020-68268-9.
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Wang, G., Cai, W., & Santoso, A. (2021). Simulated thermocline tilt over the tropical Indian Ocean and its influence on future sea surface temperature variability. Geophysical Research Letters, 48, e2020GL091902. https://doi.org/10.1029/2020GL091902.
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