Nasa recruits seal to dive deep into the science of warming oceans

Sarah Knapton
Nasa tagged a southern elephant seal and followed it through its 3,000 mile three month journey  -  Sorbonne University/Etienne Pauthenet

Oceans may not absorb as much heat from climate change as expected, Nasa has discovered, after recruiting a seal to monitor how currents move warm water.

Experts at the US Space Agency’s Jet Propulsion Laboratory in Pasadena, California, tagged a southern elephant seal and monitored temperature changes as it swam more than 3,000 miles in the Antarctic Ocean.

Previously scientists believed that heat from global warming was being sucked down from the surface into the deep ocean, and feared that temperatures could rise substantially when the process became exhausted.

But the results showed that there are other currents that move the warm water back up again, from where it can evaporate.

The seal made around 80 dives at depths of up to 545 fathoms during its three month journey, collecting a continuous stream of data of how heat moves vertically between different layers of the ocean.

Scientists then compared the results with satellite data showing where swirling eddies existed within the current.

Analysis showed that these eddies act like ducts that carry heat from the ocean interior back to the surface. 

“Most current modeling studies indicate that the heat would move from the surface to the ocean interior in these cases, but with the new observational data provided by the seal, we found that that's not the case,” said lead author Lia Siegelman.

The seal data was compared with satellites showing where eddies were in the current  Credit: Nasa

Current climate modelsdo not factor in the effects which could be skewing projections, the researchers say.

“Inaccurate representation of these small-scale fronts could considerably underestimate the amount of heat transferred from the ocean interior back to the surface and, as a consequence, potentially overestimate the amount of heat the ocean can absorb,” added Miss Siegelman. 

“This could be an important implication for our climate and the ocean's role in offsetting the effects of global warming by absorbing most of the heat.”

The scientists say the phenomenon is also likely present in other turbulent areas of the ocean where eddies are common, including the Gulf Stream in the Atlantic Ocean and the Kuroshio Extension in the North Pacific Ocean.

The authors called for more research to quantify the long-term impact the heat channels may have on the global ocean and our climate system. 

And although observations were made in the late spring and early summer, the results may be more pronounced during winter months, they warn.

The new research was published in the journal Nature Geoscience.