The frequency of flooding increased in South America: what can happen with the arrival of El Niño?

The frequency of flooding increased in South America: what can happen with the arrival of El Niño?

The seas and atmosphere of planet Earth “dialogue” with each other. As a result of that interaction, natural phenomena such as El Niño/Southern Oscillation, which increases temperatures in the central and eastern part of the Equatorial Pacific Ocean, and then there are changes in the atmosphere.

At this time, there is 96% chance to develop El Niño over the coming months and next year, according to the World Meteorological Organization and the meteorological and climate services of the United States and Argentina.

The Child may imply that a increased rainfall and storms in parts of southern South America, especially in Paraguay, Argentina, Brazil and Uruguay. In some previous episodes such as 1997-1998 and 2015-2016, more rains and storms have been associated with flooding.

Could those disasters happen again?

In dialogue with Infobae, the doctor Carolina Vera, professor emeritus at the University of Buenos Aires, researcher at the Conicet and former Vice-Chair of Working Group I of the Intergovernmental Panel on Climate Change (IPCC), explained the complexity of the El Niño/Southern Oscillation (which they call ENSO) phenomenon.

“It’s a large-scale weather pattern. Sometimes it gives rise to the La Niña phase. In others, when the temperatures of the waters of the Equatorial Pacific Ocean The phase of the El Niño phenomenon increases, and the conditions of atmospheric circulation, such as pressure and winds, are altered, and that may favor more rainfall in South America,” Vera said.

However, the scientist clarified, “El Niño is not the only large-scale weather pattern that can act. There are two other independent factors that can reinforce or interfere with the El Niño signal. Those factors can cause it to rain more or rain less in South America.”

If in the austral spring El Niño occurs simultaneously with another phenomenon called “Indian Ocean Dipole (IOD), there may be more rainfall in the region. For now, forecasts indicate that the Dipole is positive this spring of 2023. Therefore, if there is a moderate El Niño combined with the Dipole, there could be more rainfall than normal. That is, it would be different from when El Niño occurs alone,” he said.

But everything is more complex. There is another factor that is known as “Southern Annular Mode” or also “Antarctic Oscillation“. The Southern Annular Mode is a pattern consisting of pressure anomalies of different signs between the south pole and mid-latitudes.

“We have discovered through research that if the El Niño phenomenon occurs during a negative phase of the southern annular mode, it can rain more than normal in the spring or summer. On the other hand, if El Niño occurs during a positive phase of the southern annular mode, it does not rain as much,” explained the researcher.

For example in 2015 and 2016 there was a strong El Niño phenomenon. The pattern of the southern annular mode in positive phase canceled its influence in summer. On the other hand, in the autumn it did rain and floods occurred. The study was published in the journal International Journal of Climatology.

So what can happen in 2023 and 2024? “El Niño and the Indian Ocean Dipole can be forecast several months in advance. In contrast, the Southern Annular Mode pattern can only be predicted only a few weeks in advance. Therefore Keep in mind that the atmosphere, which is chaotic, can give us surprises. It is monitored week by week,” he replied.

“Also, while El Niño may cause more rain, you have to consider the water content that may already be in the soil today. During the last three years there were droughts. Then Soil conditions can also influence whether or not floods develop.” he said. The researcher recommended that the population remain attentive to the information communicated by the meteorological services of each country.

With regard to soil conditions, a recent study that was published in the journal Scienceand it also added a new understanding of flooding in South America. The work was led by Stephen Jobbágy, Senior Researcher of the Conicet in the Environmental Studies Group of the National University of San Luis. Scientists from the Lancaster University UK.

They showed that there was an increase in flooding associated with the expansion of agriculture in the Argentina and part of Paraguay. They did this by combining data obtained by remote sensing and groundwater monitoring stations. Over the past 20 years, agricultural areas were more prone to flooding as groundwater transitioned from a deep state to a shallow state, more sensitive to heavy rainfall.

“Our study showed that less rain is now needed to flood the region. In a year with the El Niño phenomenon, even after such a tremendous drought, flooding can occur more easily than before.”, said Jobbágy, when asked by Infobae.

But the scientist clarified: “It is unlikely that in 2023 and 2024 we will see major flooding in the region. But if this year is wet, it can leave us ready for a flood in the next. Therefore, monitoring water table levels is key to anticipating. Some provinces are already on that path and are setting up more intense monitoring networks, such as the province of Córdoba.”

Last April a team of researchers from China had predicted a strong El Niño event by the end of 2023. However, there is still uncertainty.

Days ago, it was done in the Women’s Hall of the Bicentennial of the Casa Rosada in Buenos Aires, a training day on the impact of El Niño in Argentina. There Maria of Miracles Skansi, Central Director of Climate Monitoring of the National Weather Service said it is very likely that El Niño will develop, but still now in August It is not clear whether its intensity will be moderate or strong.

Since 1961, there were 21 El Niño events. For the quarter of October, November and December 2023, there is a greater chance of rainfall above normal values in the northeast and in the central east of Argentina and that would be in line with the El Niño signal, according to Skansi.

Michael Martin, former coordinator of the Scientific and Technological Network for Disaster Risk Management (GIRCYT Network), considered -when consulted by Infobae that every community should consider that disasters are not natural.

If you take into account that there are people exposed to potential risks of a disaster, the approach is different, since it favors more work on local risk prevention.

Since 2014 they are in force Different information management protocols that specify the steps to be followed by different public institutions for emergency preparedness such as a flood.


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