Scientists continue to sound the alarm over the unpleasant consequences of global climate change, National Geographic states.
Climate change has brought about major changes in ocean stability faster than scientists predicted, according to a new study. The study looked at 50 years of data and tracked how surface water is “separated” from deeper layers of the ocean.
Climate change has disrupted vertical water exchange in the oceans, a process that helps trap much of the world’s excess heat and much of the CO₂.
Surface water is warmer and less dense than water at depth. Global warming is causing huge volumes of freshwater to enter the seas due to the melting of ice sheets and glaciers, which reduces the salinity of the upper layer and further reduces its density.
This increasing contrast between the density of the ocean layers makes it difficult to exchange water – heat, oxygen, and carbon are becoming increasingly difficult to penetrate deep into the ocean.
“Like a layer of water on top of oil, surface water in contact with the atmosphere mixes less efficiently with the ocean below,” – Jean-Baptiste Sallet, lead study author at the University of Sorbonne and CNRS, France’s national research center.
Scientists were aware of this process, but a new study found it was happening six times faster than past climate models predicted.
The report used observational data for global temperature and salinity from 1970 to 2018. Various marine mammals also helped in collecting the data, which were monitored using electronic GPS trackers.
The researchers also found that, contrary to their expectations, winds amplified by climate change have also contributed to the deepening of the ocean’s surface layer by 5-10 meters over a decade over the past half-century. This surface layer is home to a significant number of marine animals, whose food web depends on phytoplankton.
But as the wind intensifies, phytoplankton moves deeper and gets farther from the light, thanks to which it grows. This has the potential to disrupt food chains further.
“These are fundamental changes to the basic structure of our oceans. They are more pronounced than we have thought until now,” – Jean-Baptiste Sallet.
According to the Intergovernmental Panel on Climate Change (IPCC), the oceans play a critical role in mitigating climate change, absorbing about a quarter of anthropogenic CO₂ and absorbing more than 90% of the heat generated by greenhouse gases.
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