Scientists have used many years of data to show that the average air and ocean temperatures of Earth are steadily increasing because of human-caused emissions of greenhouse gases like carbon dioxide or methane. A new study has determined that there are two bands of warming water in the world's oceans. One of these bands is in the southern hemisphere, while the other is in the northern hemisphere, but both are around 40 degrees latitude and stretch around the planet.
The southern band is warming at a faster pace, and the warmest areas can be found near the Atlantic Ocean east of Argentina, and around New Zealand and Tasmania. Meanwhile in the upper band, the most significant warming is seen in the Atlantic east of the US and east of Japan in the Pacific. The findings have been reported in the Journal of Climate.
"This is very striking. It's unusual to discover such a distinctive pattern jumping out from climate data," noted senior study author Dr. Kevin Trenberth of the University of Auckland and the National Center of Atmospheric Research in Colorado.
While ocean water may seem to be getting only slightly warmer, these changes can have huge impacts on marine habitats and ecosystems, with far-reaching effects on interconnected systems. Warming oceans can also fill the atmosphere with water vapor, which can power stronger rain storms and more extreme weather events.
The researchers relied on vast amounts of data to analyze the ocean by one latitude degree increments, to a depth of 2,000 meters, from the years 2003 to 2023. The changes were compared to similar data from 2000 to 2004, which was the baseline.
These bands have been forming since 2005, according to the study, as the jet stream has shifted. The jet stream refers to very strong winds in the upper atmosphere that blow from west to east, and move weather systems along. Ocean currents have also changed, helping to generate these warmer bands.
There were also significant heat increases in regions from ten degrees north to twenty degrees south. But variations introduced by the El Niño-Southern Oscillation climate pattern dampened the effect, added Trenberth.
"What is unusual is the absence of warming in the subtropics, near twenty degrees latitude, in both hemispheres. The climate is changing because of the build-up of greenhouse gases, and most of the extra heat ends up in the ocean," sid Trenberth. "However, the results are by no means uniform, as this research shows. Natural variability is likely also at play."
Sources: University of Auckland, Journal of Climate