Global warming is making the oceans more stable, raising surface temperatures and reducing the carbon they can absorb, according to a study published Monday by climate scientists, who warned that the findings had “profound and disturbing” consequences.
Man-made climate change has raised surface temperatures across the planet, leading to atmospheric instability and intensifying extreme weather events such as storms.
But in the oceans, higher temperatures have different effects, slowing mixing between warming surfaces and cooler, oxygen-rich waters below, researchers say.
This oceanic “stratification” means that less deep water rises to the surface, carrying oxygen and nutrients, while surface water absorbs less atmospheric carbon dioxide to be buried at depth.
In a report published in the journal Climate change in nature, an international team of climate scientists said it found that global stratification increased by a “significant”
Most of this stabilization occurs at the surface and is mainly due to rising temperatures.
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.
The study’s co-author Michael Mann, a professor of climate science at Pennsylvania State University, said in a commentary published in Newsweek that “the seemingly technical finding has profound and disturbing consequences.”
These include potentially driving more intense, destructive hurricanes as ocean surfaces warm.
Mann also pointed to a reduction in the amount of CO2 absorbed, which could mean that carbon pollution accumulates faster than expected in the atmosphere.
He warned that complex climate models often underestimate ocean stratification and may also underestimate its impact.
With warmer upper waters, which receive less oxygen, there are also consequences for marine life.
By absorbing a quarter of man-made CO2 and absorbing more than 90 percent of the heat generated by greenhouse gases, the oceans keep the population 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 waters have expanded the strength and range of deadly tropical storms.
Sea heat waves destroy coral reefs and accelerate the melting of glaciers and ice sheets, leading to rising sea levels.
Last year, a study published in American Proceedings of the National Academy of Sciences estimates that climate change will empty the ocean of nearly one-fifth of all living things, measured in mass, by the end of the century.
© Agence France-Presse