Ocean regions show simultaneous changes in temperature salinity oxygen and acidity
Lead author Dr Zhetao Tan reported that 30 to 40 percent of upper ocean layers already show clear changes in at least two of these properties compared to sixty years ago. Some ocean regions display simultaneous alterations in temperature salinity and oxygen with up to a quarter of waters affected in certain areas.
The team pinpointed the tropical and subtropical Atlantic North Pacific Arabian Sea and Mediterranean Sea as regions most impacted by these compound changes. Researchers warn that simultaneous shifts in multiple variables could force marine ecosystems beyond their capacity to adapt. Prof Lijing Cheng stated the ocean's condition is shifting in multiple ways at once including in deeper layers once viewed as stable.
The study's analysis distinguishes long term climate signals from shorter term variability allowing researchers to track comprehensive ocean transitions and measure how far changes reach below the surface.
Prof Sabrina Speich emphasized the urgent need for sustained ocean monitoring. She said "Our findings are based on direct physical and biogeochemical observations. They underscore the urgent need for sustained high quality ocean monitoring to inform global climate action."
The presence of multiple stressors is disrupting marine species migration and population stability according to Dr Laurent Bopp who noted "Marine species face heightened stress when exposed to multiple stressors simultaneously forcing migration or decline. This disruption can destabilize global fisheries compromise food security and jeopardize livelihoods."
The researchers warned these changes risk reducing the ocean's absorption of carbon and heat limiting its function as a climate regulator.
Dr Karina von Schuckmann said "This framework provides a scientific foundation for assessing climate risks and supporting policies such as the expansion of marine protected areas under the UN's High Seas Treaty."
Research Report:Observed large scale and deep reaching compound ocean state changes over the past 60 years
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