Warming winters are transforming the composition of the Black Sea

According to a new study published by the American Geophysical Union, warmer winters are changing the composition of the Black Sea. The research has implications for how future climate change will alter the structure of the world’s oceans. 

From 2005 to 2019, hotter winter weather has warmed the cold intermediate layer of the Black Sea by 1.26 degrees Fahrenheit. This is much more extreme than the fluctuations that typically occur in this middle layer of water.

The researchers discovered that the cold intermediate layer has now started to mix with the oxygen-free bottom layer and the oxygenated top layer of water. The phenomenon could potentially allow the water masses from the deeper layers of the sea to infiltrate the top layer, which would have unknown impacts on marine life.

The research indicates that climate change is causing the intermediate layer to warm and change, but natural fluctuations could also be playing a role. By analyzing smaller water bodies like the Black Sea, scientists can predict how climate change will affect larger water bodies. 

“We want to at least know what could happen under different global climate change scenarios,” said study lead author Emil Stanev, who is a physical oceanographer at Helmholtz-Zentrum Geesthacht Center for Materials and Coastal Research.

Each of the water layers in the Black Sea hosts specific organisms that are suited to its conditions. The water masses have distinct temperatures, salinities, and densities, and the cold layer separates the surface water that has low salinity from the deep water that is high in salinity. 

The scientists mapped the evolution of the Black Sea’s cold intermediate water mass for 14 years. They found that winter weather fluctuations changed the temperature and salinity of the middle layer, but the density of the water mass remained almost the same. 

As the Black Sea’s cold intermediate layer warms up, it has started to blend with the top and bottom layers of the sea along its edges. If this trend continues, the restructuring of the layers could bring corrosive and noxious chemicals at the bottom of the sea up to the surface.

The study is published in the journal JGR Oceans.

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By Chrissy Sexton, Earth.com Staff Writer

Paid for by Earth.com

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