Monsoon approaches India (NASA)
Monsoon approaches India (NASA)

Indian Ocean Dipole rains on ENSO’s influence

03 August 2011

The Indian Ocean may play a major role in modulating the effect of the Pacific Ocean’s El Niño Southern Oscillation (ENSO) on the Indian monsoon, according to a new paper by CCRC researchers. 

The paper, Multi-Decadal modulation of El Niño-Indian monsoon relationship by Indian Ocean Variability, has highlighted how the Indian Ocean Dipole (IOD) appears to have a high level of influence over India’s monsoon season on decadal timescales.

It is well known that the Indian monsoon often fails during El Nino events, bringing drought to the region. Recent work has also shown that this failure does not happen if the Indian Ocean is in a certain state, called a ‘positive IOD’.  A new study by researchers at the CCRC has found that these relationships can be used to explain the reduction in droughts that has occurred in recent decades.

“What we have found is that this mechanism is not only at play during year-to-year variations in the Indian monsoon but it can also explain a weakening in the relationship between ENSO and the Indian monsoon during recent decades,” said lead author, Dr Ummenhofer.

 “This research indicates that we need a more nuanced view of the relationship between the Indian Ocean and the Pacific ENSO than previously believed.”

Dr Ummenhofer’s research looked at 130 years of data, showing the effect of the IOD over multi-decadal timescales.

Broadly, the data indicated that:

  • When an El Niño event occurred independently without a positive IOD, the monsoon season broke down and the rains failed.
  •  When a positive IOD occurred with an El Niño event, rainfall during the monsoon season was generally average.
  • When a positive IOD occurred without an El Niño event, rainfall was generally above average.

Based on these findings, the recent weakening of the El Niño effect on the Indian monsoon from 1975-2006 can be explained in large part by the fact that many El Niños during this period occurred along side a positive IOD.

The higher frequency of this combination appeared to support successful Indian monsoons. It also contributed to drier conditions across south-east Australia.

“This early research reinforces that we need to focus more resources on studying the Indian Ocean if we are to understand the climate patterns in Australia, India and South East Asia in the future,” Dr Ummenhofer said.

“We urgently need to determine how climate change is affecting the frequency and nature of the IOD and, if so, what this means for future rainfall patterns around agricultural regions in Australia and across Asia.

The project is part of new Australian Research Council funded research: The changing relationship between the South Asian and Australian Monsoon in a warming world.

The project was awarded to Alex Sen Gupta, Matthew England, Andrea Taschetto, Caroline Ummenhofer, together with three collaborators at the Indian Institute of Tropical Meteorology, Karumuri Ashok, Raghavan Krishnan and Sahai Atul.

The research is of great importance to Australia’s future as tropical monsoonal systems have enormous social, economic and environmental impact across the north of Australia and the wider South Asian region.

The success or failure of the Australian and South Asian Monsoons can mean the difference between prosperity and severe hardship in the affected regions.

This project will help to understand the causes of the monsoon variability, both natural and human-induced, and what the future might have in store.

This paper has just appeared as a research highlight in Nature Climate Change.


UNSW logo Indian Ocean causes Big Dry: drought cycles over the southeast linked to the Indian Ocean Dipole
05 February 2009
The causes of south-eastern Australia's longest, most severe and damaging droughts have been discovered, with the surprise finding that they originate far away in the Indian Ocean.


Latest news

Dr Michael Molitor Public lecture - De-carbonising for growth: why everyone is wrong about the costs of addressing climate change
20 April 2014
We will rapidly de-carbonize the global energy system not because we care sufficiently about the enormous risks flowing from a climate system profoundly modified by human activity but because, in the absence of this gigantic infrastructure investment opportunity, we will never generate sufficient economic growth between now and 2050. This inevitable outcome has dramatic implications for Australia's future energy supply and prosperity.

Plastic bottle caps found in the ocean (source: NOAA PIFSC) Ocean debris leads the way for castaway fisherman
05 February 2014
The fisherman who washed up on the Marshall Islands last weekend was very lucky to have stranded on a remote beach there. The currents in the Pacific Ocean would have inevitably taken him into the great garbage patch of the North Pacific, where he could then have been floating for centuries to come.

Man in heat wave Get used to heat waves: extreme El Niņo events to double
20 January 2014
Extreme weather events fuelled by unusually strong El Niņos, such as the 1983 heatwave that led to the Ash Wednesday bushfires in Australia, are likely to double in number as our planet warms.

More news...

Copenhagen Diagnosis logo

The Copenhagen Diagnosis

On 25th November 2009 members of The Climate Change Research Centre, as part of a group of 26 international climate scientists, were part of a major international release of a new report synthesizing the latest climate research to emerge since the last IPCC Assessment Report of 2007.


World map

There are no time-travelling climatologists: why we use climate models

In the absence of time-travelling climatologists, models are unrivalled tools for understanding our changing climate system. That is, climate models are scientific tools. We should recognise them as such and consider them with rigorous scientific, not political, scepticism.



The Big Engine 2: oceans and weather

Federation Fellow and 2008 Eureka Prize winner, Professor Matthew England of CCRC, on the latest research into the role oceans play on weather.


Smoke stack

The Science of Climate Change: Questions and Answers

Co-authored by Professor Steven Sherwood and Professor Matt England of CCRC, this Academy of Science report aims to summarise and clarify the current understanding of the science of climate change for non-specialist readers.


Ocean weather

The Big Engine 1: oceans and weather

Federation Fellow and 2008 Eureka Prize winner, Professor Matthew England of CCRC, on the latest research into the role oceans play on weather.


Tree rings

New insights into the climate of the past 2,000 years

A comprehensive new scientific study has revealed fresh insights into the climate of the past 2,000 years, providing further evidence that the 20th century warming was not a natural phenomenon. After 1900, increasing temperatures reversed a previous long-term cooling trend. This 20th Century warming has occurred simultaneously in all regions except Antarctica.



The dynamics of the global ocean circulation

The ocean is far from a stagnant body of water. Instead, it is constantly in motion, at speeds from a few centimetres per second to two metres per second in the most vigorous currents.


Plastic rubbish

Leave the ocean garbage alone: we need to stop polluting first

Recent plans to clean plastics from the five massive ocean garbage patches could do more damage to the environment than leaving the plastic right where it is.


Plastic rubbish

Charting the garbage patches of the sea

Just how much plastic is there floating around in our oceans? Dr Erik van Sebille from UNSW's Climate Change Research Centre has completed a study of ocean "garbage patches", and has found that in some regions the amount of plastic outweighs that of marine life.



UCC logo

Share | | RSS feed