A new study shows that the impact of the El Niño weather phenomenon could have a “double whammy” effect, causing extreme weather to worsen and accelerating sea level rise..
Stronger “El Niño” events due to global warming could accelerate the irreversible melting of Antarctica’s ice sheet and ice shelves and sea level rise, according to research by the Antarctic government’s lead science agency, the Antarctic Australia.
Previous studies have found that increasing concentrations of greenhouse gases in the atmosphere are expected to increase the magnitude of the El Niño Southern Oscillation (ENSO), the planet’s largest annual climate fluctuation and a major driver of extreme droughts and floods. Extremely hot El Niño and cold La Niña events are expected to become more frequent as the planet warms.
Relatively little is known about the impact of Enso changes on Antarctica. A new study published this week in the journal Nature Climate Change, led by CSIRO researchers, found that the strongest El Niño events are likely to have divergent impacts on the ocean around the southern continent.
El Niño and warming ocean waters
The examination of 31 climate models found that a stronger El Niño can accelerate the warming of deeper ocean waters, while slowing the rate of warming at the surface, as westerly winds on the continental shelf become less intense. .
CSIRO’s principal research scientist and lead author of the study, Dr. Wenju Cai said the former would lead to faster melting of the ice sheet and ice shelves. The study did not look at how much faster melting can occur.
The Antarctic ice sheet is estimated to contain around 30 million cubic kilometers of ice, enough to raise global sea levels by 70 meters over centuries if it melted completely. A separate recent study estimated that global temperatures 1°C above pre-industrial levels, a point already passed, would be enough to gradually collapse the West Antarctic ice sheet, causing a four meter rise in sea level.
“This new research shows that a stronger El Niño can accelerate the warming of deep waters on the Antarctic shelf, causing ice shelves and ice sheets to melt more quickly.Cai said. “Our model also revealed that heating at the edges of floating sea ice slows down during this process, slowing the melting of sea ice near the surface.“.
The “double whammy”
Cai said the results suggest a stronger El Niño could have a “double whammy” effect as it would lead to worsening extreme weather – risk of heat, drought and bushfires in eastern Australia and flooding in California, Peru and Chile. ) and would accelerate sea level rise, causing more extreme coastal flooding.
Ariaan Purich, of Monash University’s School of the Earth’s Environment and Atmosphere and co-author of the report, said the results could have broad implications for the global climate system.
“Continuing to understand how Enso will respond to climate change is a critical area of climate research.“, he said. ′′ There’s still a lot more we need to understand about the processes that influence shelf temperatures, and the discovery is an important piece of the puzzle “.
Director of the Australian Center of Excellence in Antarctic Science, Professor Matt King, said it was a “serious and worrying work” made by renowned scientists, and much more “bad news” about Antarctica’s potential contribution to sea level rise.
“There are many uncertainties about Enso’s future and this is another cause for concern,” he said.
Strong events earlier than expected
A modeling study last year suggested that the strongest El Niño and La Niña events due to global warming could be detected in the eastern Pacific Ocean by 2030, decades earlier than expected.
Sea ice around Antarctica has reached a record low this year, and scientists report that they have “never seen such an extreme situation before”. Changes in melting sea ice do not directly affect sea levels, but scientists say its loss exposes ice sheets and glaciers to waves, accelerating their disintegration.
