Changing climatic conditions are disrupting ocean currents faster than expected, raising concerns over its role as a global thermostat and the marine life it supports. A recent study has discovered that climate change disrupts ocean stability, which helps store away most of the world’s extra heat and a substantial amount of CO2.
Published in the journal Nature, the research analyzed 50 years of data about the way in which surface water “decouples” from the deeper ocean. Water on the surface is warmer and therefore less dense than deep seawater, a contrast that is further intensifying by climate change.
Rising temperatures are causing huge proportions of freshwater to flow into the seas from rapidly melting ice sheets and glaciers, lowering the salinity of the upper layer and further reducing its density. This increasing contrast between the densities of the oceanic layers makes mixing harder, which makes it less possible for the heat and carbon dioxide to enter the deep seas.
Climate change disrupts ocean stability that helps store away most of the world’s extra heat and a substantial amount of CO2 | Image: Pablo A. Cumillaf
According to lead author Jean-Baptiste Sallee of Sorbonne University and France’s CNRS national scientific research center,
Similar to a layer of water on top of oil, the surface waters in contact with the atmosphere mix less efficiently with the underlying ocean. We here show that this change has occurred at a rate much quicker than previously thought: more than six times quicker…But by stabilizing, the ocean’s role to buffer climate change is made harder as it is made more difficult for the ocean to absorb these vast amounts of heat and carbon.
The research studied global temperature and salinity obtained between 1970 and 2018 – including those from electronically tracked marine mammals with a focus on the warm months, which provide many pertinent data. The barrier layer dividing the ocean surface and the deep layers had intensified globally at a much larger rate than previously thought.
Researchers also found that airstreams had been increased by climate change had also acted to expand the ocean surface layer by five to 10 meters per decade over the last half-century. A substantial number of marine animals live in this surface layer, with a food network that is dependent on phytoplankton.
But with intensified winds, the phytoplankton is churned deeper, away from the light that helps them flourish, possibly disturbing the larger food network. According to the International Panel for Climate Change (IPCC), the oceans play a crucial role in reducing the effects of changing climate by soaking up nearly a quarter of man-made CO2 and over 90 percent of the heat generated by greenhouse gases.
A recent study has discovered that the Atlantic Ocean circulation system is at its weakest in the last 1000 years. This system is moving more slowly than ever in the last 1,600 years and those are ominous signs. Apparently, increased rainfall and melting of the Greenland ice sheet have increased the freshwater supply in the oceans, disturbed the normal cycle that circulates the water.