As the world faces the imminent threat of a Super El Niño, NASA satellites have revealed the ominous patterns behind this building weather pattern.
During an El Niño year, the sea surface temperature in the equatorial Pacific Ocean soars, making the whole world warmer on average.
Using two decades of observations from space, scientists have now tracked how these warming waters have a massive impact on ocean life.
Warm ocean waters during an El Niño limit nutrient availability for marine organisms around the globe, threatening the stability of critical ecosystems.
Normally, tiny plant–like organisms called phytoplankton feed on the current of cold, nutrient–rich water welling up from the deep oceans.
However, warming oceans interfere with this stream of vital minerals, causing a condition called ‘nutrient stress’.
These conditions are even stronger during an El Niño year, stifling the critical flow of nutrients and undermining the basis of the entire marine ecosystem.
Laura Lorenzoni, program scientist for NASA’s Ocean Biology and Biogeochemistry Program at NASA Headquarters in Washington, says: ‘This is fundamental, as plankton communities are the base of the marine food web on which important economic activities rely.’
NASA satellite observations have revealed the ominous patterns leading to an El Niño year from space by tracking the levels of chlorophyll in ocean plankton (pictured)
Nutrient stress is caused when phytoplankton aren’t getting enough minerals, such as iron, phosphorus, and nitrogen.
Without these minerals, the plankton can’t grow and reproduce properly, which has a knock–on effect all the way up the food chain.
Scientists combined satellite observations and genetic testing of phytoplankton gathered from all around the world to see how nutrient stress is affected by ocean heat.
Using the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA’s Aqua satellite, the researchers were able to measure shifts in the ratio of carbon to chlorophyll in plankton seen from space.
When the amount of chlorophyll decreases relative to carbon, this is a sign that the plankton are under increasing stress.
To back up their observations, they also looked at subtle genetic markers in samples of Prochlorococcus, a tiny but abundant marine microbe that shows signs of nutrient stress in its DNA.
This revealed that the worst nutrient stress appears in the subtropical gyres, vast areas of relatively calm water in the Atlantic, Pacific, and Indian Oceans, where a layer of warm water forms at the surface.
Co–author Dr Adam Martiny, an oceanographer at the University of California, says: ‘When the surface of the ocean warms, it generates this very stable situation where a layer of low–density water sits on top of higher–density cold water.
The warming waters of an El Niño year trap nutrients below the surface, causing plankton to experience nutrient stress. Pictured: Red regions show the regions of highest nutrient–related stress
‘You’ve probably experienced that if you’ve ever been to a lake in the summertime—it’s super warm right on the surface, and very cold deeper down when you stick your legs in.’
That layer traps the nutrients below, preventing them from reaching the plankton living near the surface and causing increased nutrient stress.
In the South Pacific, one of the most nutrient–poor regions, a layer of warm surface water contributed to nitrogen and iron shortages, producing the most severe nutrient–related stress that the team discovered.
El Niño and La Niña years are part of a naturally occurring pattern called the El Niño–Southern Oscillation, which shifts between hot and cool phases every two to seven years.
During the hotter El Niño part of the cycle, warm waters that build up in the Pacific spread out and raise the Earth’s average surface temperature.
The researchers found that these warming events create thick layers of hot water that significantly reduce the amount of nutrients reaching the surface.
Between 2015 and 2016, the world was hit by one of the strongest El Niño events on record, which saw sea surface temperatures in critical regions climb 2.3°C (4.1°F).
Using their satellite data, the scientists could clearly see how this El Niño event smothered ocean upwelling in the equatorial Pacific and led to increased nutrient stress.
During the 2015 El Niño (bottom), there was a significant increase in nutrient stress around the Pacific compared to the cool La Niña event in 2011 (top)
This comes as scientists warn that the coming Super El Niño is likely to be the strongest event ever recorded
These findings come as experts warn that the world is rapidly approaching the start of a ‘Super El Niño’, expected to be the strongest ever recorded.
Recent research conducted by the European Centre for Medium–Range Weather Forecasts (ECMWF) shows that sea temperatures will be well above average later this year.
In almost every scenario, temperatures in the equatorial Pacific Ocean will climb 3°C (5.4°F) above average by December.
However, some worrying simulations show that the sea surface will be more than 4°C (7.2°F) warmer in these critical ocean regions.
Dr Theodore Keeping, an extreme weather expert from Imperial College London, told the Daily Mail: ‘If this forecast came true, it would be the strongest El Niño on record’.
Dr Keeping adds that this will have a ‘huge influence on the weather around the world’, changing the tracks of storms and driving heatwaves or droughts.
Similarly, this Super El Niño is expected to send global temperatures soaring and could make 2026 the hottest year on record.
That could mean beating the record set in 2024, when global warming exceeded 1.5°C (2.7°F) above the pre–industrial average for the first time.
