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Man-made climate change has increased surface temperatures across the globe, leading to atmospheric instability and amplifying extreme weather events such as storms.
In this file photo taken on August 28, 2019, a wave crashes off Teahupoo, Tahiti. Image: AFP
PARIS – Global warming is making the oceans more stable, increasing surface temperatures and reducing the carbon they can absorb, according to research published Monday by climate scientists who warned the findings have “profound and troubling” implications.
Man-made climate change has increased surface temperatures across the globe, leading to atmospheric instability and amplifying extreme weather events such as storms.
But in the oceans, higher temperatures have a different effect, slowing down the mixing between the warming surface and the cooler, oxygen-rich waters below, the researchers said.
This “stratification” of the ocean means that there is less deep water rising to the surface carrying oxygen and nutrients, while the water at the surface absorbs less atmospheric carbon dioxide to bury it deep.
In a report published in the magazine Nature Climate Change, the international team of climate scientists said they found that stratification globally had increased by a “substantial” 5.3% between 1960 and 2018.
Most of this stabilization occurred towards the surface and was largely attributed to increases in temperature.
They said this process is also exacerbated by the melting of sea ice, which means that more fresh water, which is lighter than salt water, also accumulates on the ocean surface.
Study co-author Michael Mann, a professor of climate science at Pennsylvania State University, said in a comment posted on Newsweek that the “apparently technical finding has profound and troubling implications.”
These include potentially driving more “intense and destructive hurricanes” as the ocean surface warms.
Mann also noted a reduction in the amount of CO2 absorbed, which could mean that carbon pollution builds up faster than expected in the atmosphere.
He cautioned that sophisticated climate models often underestimate the stratification of the oceans and may also be underestimating its impact.
Since warmer upper waters receive less oxygen, there are implications for marine life as well.
By absorbing a quarter of man-made CO2 and absorbing more than 90 percent of the heat generated by greenhouse gases, the oceans keep people alive, but at a terrible cost, according to the Intergovernmental Panel on Climate Change. (IPCC).
The seas have become acidic, potentially undermining their ability to reduce CO2. Warmer surface water has expanded the strength and range of deadly tropical storms. Marine heat waves are wiping out coral reefs and accelerating the melting of glaciers and ice sheets that drive sea level rise.
Last year, research published in the Proceedings of the US National Academy of Sciences calculated that climate change would empty the ocean of nearly a fifth of all living creatures, measured en masse, by the end of the century.
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