Climate change has made major changes to ocean sustainability faster than previously expected, according to a study published Wednesday, raising warnings over its role as a global thermostat and the marine life it supports .
The research published in the journal Nature they looked at 50 years of data and followed the way surface water separates from the deepest ocean.
Climate change has disturbed ocean mixing, a process that helps store most of the world’s excess heat and a significant proportion of CO2.
Water on the surface is warmer – and therefore denser – than the water below, a contrast strengthened by climate change.
Global warming is also causing large amounts of freshwater into the oceans from melting ice sheets and glaciers, reducing the salinity of the high level and further reducing the density.
This difference between the densities of ocean layers makes mixing harder, so oxygen, heat and carbon are less able to penetrate the deep oceans.
“Like a layer of surface oil, the surface waters in contact with the atmosphere mix as efficiently as the underground ocean,” said lead author Jean-Baptiste Sallee of Sorbonne University and research center French national scientific journal CNRS.
He said that while scientists were aware that this process had begun, “we are here to show that this change has taken place at a much faster rate than previously thought: more than six times more. soon. “
The report used observations of global temperature and salinity obtained between 1970 and 2018 – including those from electronically detected marine mammals – with a focus on the summer months, which have more data.
He said the level of barrier separating the ocean surface and the deep layers had strengthened worldwide – measured by the difference in density – at a much larger level than previously thought. seo.
Researchers also found that, contrary to their expectations, climates strengthened by climate change had also deepened ocean surface coverage by five to 10 meters per decade over the last half century.
This surface layer is home to a large number of cetaceans, with a phytoplankton-dependent food web.
But as the winds rise, the phytoplankton mash deeper, away from the light that helps them grow, disturbing the wider food web.
These are “not small changes that only some experts care about,” Sallee told AFP.
“They represent a fundamental change in the basic structure of our oceans. A clearer path than we thought so far.”
Trouble and trouble
The oceans play a vital role in mitigating the effects of climate change by absorbing around a quarter of man-made CO2 and emitting over 90 per cent of the heat from greenhouse gases, according to the Intergovernmental Panel on Climate Change (IPCC).
“But with stabilization, the ocean’s role in protecting against climate change has been made more difficult by making it more difficult for the ocean to absorb large amounts of heat and carbon,” said Sallee.
Scientists are increasingly warning about the potential effects of warming on our oceans.
In 2019, a study was published in the US Proceedings of the National Academy of Sciences calculate that climate change would be evacuating an ocean of nearly one-fifth of the living creatures, measured by mass, by the end of the century.
Climate scientist Michael Mann warned in September that the results of a study he co-authored Climate Change Nature – which suggested that global ocean flow had increased 5.3 percent from 1960 to 2018 – had “deep and difficult” effects.
These included potentially more intense hurricanes driven by ocean warming.
And in February, do some research in Geology of nature found that the northerly expansion of the Gulf Stream – the major ocean heatwave affecting weather in Europe and U.S. sea levels – is the weakest in more than a thousand years , probably due to climate change.
They said more water and melting of Greenland’s ice sheet has increased the freshwater of the high seas, disrupting the normal cycle that carries warm, salt water north of the zone. and pouring deep salt water back to the south.
© Agence France-Presse