Deep ocean warming as climate changes

Much of the “excess heat” stored in the subtropical North Atlantic is in the deep ocean (below 700 m), new research suggests.

The oceans have absorbed about 90% of human-caused warming. The study found that in the subtropical North Atlantic (25°N), 62% of the warming from 1850 to 2018 occurs in the deep ocean.

The researchers, from the University of Exeter and the University of Brest, estimate that the deep ocean will warm an additional 0.2°C over the next 50 years.

Warming oceans can have a variety of consequences, including sea level rise, altered ecosystems, currents and chemistry, and deoxygenation.

“As our planet warms, it is essential to understand how the excess heat absorbed by the ocean is redistributed within the ocean from the surface to the bottom, and it is important to take into account the deep ocean to assess the growth of Earth’s ‘energy imbalance’,” said Dr Marie-José Messias, from the University of Exeter.

“In addition to discovering that the deep ocean retains much of this excess heat, our research shows how ocean currents redistribute heat in different regions. We found that this redistribution was a key driver of warming in the Atlantic North.”

The researchers studied the system of currents known as the Atlantic Meridional Overturning Circulation (AMOC).

The AMOC works like a conveyor belt, carrying warm water from the tropics north, where cooler, denser water sinks into the deep ocean and slowly spreads south.

The results highlight the importance of warming transfer by the AMOC from one region to another.

Messias said excess heat from the Southern Hemisphere oceans was becoming significant in the North Atlantic, now accounting for about a quarter of the excess heat.

The study used temperature records and chemical “tracers” – compounds whose composition can be used to uncover past changes in the ocean.

– This press release was originally published on the University of Exeter website

Back To Top