A small area in the southwest Pacific Ocean, located near New Zealand and Australia, can trigger temperature changes that affect the entire southern hemisphere. These changes have been informally called the “new El Niño”.
The “New El Niño”, discovered south of the Equator
The new climate pattern, which shares some characteristics with the El Niño phenomenon, has been named the Southern Hemisphere Circumpolar Wavenumber-4 Pattern.
Unlike El Niño, which starts in the tropics, this new pattern starts in the mid-latitudes. The study, published this month in the Journal of Geophysical Research: Oceans, underscores how important the interaction between the ocean and the atmosphere is to our climate, writes Phys.org.
Balaji Senapati, lead author of the study from the University of Reading, said: “This discovery is like finding a new change in the Earth’s climate. It shows that a relatively small area of the ocean can have far-reaching effects on global weather and climate.
Understanding this new weather system could greatly improve weather forecasting and climate forecasting, particularly in the Southern Hemisphere. It could help explain previously mysterious climate changes and improve our ability to predict extreme weather and climate events.”
Hidden in plain sight
The researchers used sophisticated climate models to simulate 300 years of climate conditions. This model combines atmospheric, oceanic, and sea ice components to create a comprehensive representation of Earth’s climate system. By analyzing this simulated data, the team identified a recurring pattern of sea surface temperature variations surrounding the Southern Hemisphere.
The weather pattern works as a global chain reaction. This pattern creates four alternating warm and cold zones in the oceans, forming a complete circle in the Southern Hemisphere. It starts near the ocean of New Zealand and Australia. When the ocean temperature changes in this small area, it triggers a ripple effect in the atmosphere. This creates a wave-like pattern that travels around the entire southern hemisphere, carried by strong westerly winds.
As this atmospheric wave moves, it affects the temperature of the ocean, creating the four warm and cold zones.
The ocean plays an important role in this process. When the atmospheric tide changes wind patterns, it affects how heat moves between the ocean and the air. This changes the depth of the ocean’s upper layer of warmer water, which can make temperature changes stronger or weaker.
This new pattern occurs independently of other weather systems known from the tropics, such as the El Niño warming pattern of currents and trade winds, or its opposite, the cooling phase, La Niña. This suggests that it has always been a part of Earth’s climate, but has barely been noticed.
