Global warming may be accelerated by an ocean tipping point

The oceans play a fundamental role in limiting global warming by absorbing carbon dioxide emissions from the atmosphere. However, according to a new study led by the University of Texas at Austin, intense warming in the future will likely lessen this crucial ability, leading to even more severe climate change.

By using a climate simulation configured to a worst-case emissions scenario, the experts found that the oceans’ ability to soak up CO2 would peak by the end of the century, becoming only half as efficient at absorbing this hazardous gas by 2300. 

This phenomenon will be caused by the emergence of a low-alkalinity water that will hinder the capacity of the oceans to absorb CO2. Although the emissions scenario employed in this study is unlikely due to current efforts to limit greenhouse gas emissions, these findings reveal a previously unknown tipping point which, if activated, will irreversibly exacerbate global warming.

“We need to think about these worst-case scenarios to understand how our CO2 emissions might affect the oceans not just this century, but next century and the following century,” said lead author Megumi Chikamoto, a geophysicist at the University of Utah who conducted this study during a fellowship at UT Texas.

Currently, the world’s oceans soak up nearly a third of human-generated CO2 emissions. However, when exposed to extreme climate change that supercharges rainfall and slows ocean currents, the surface of the oceans becomes covered in a warm layer of fresh water which cannot mix easily with the cooler, more alkaline waters below it. As this surface layer becomes increasingly saturated with CO2, its alkalinity declines, along with its ability to absorb more CO2, eventually turning it into a barrier for CO2 absorption, and thus leaving more of the gas in the atmosphere, and consequently accelerating warming.

This finding is a powerful reminder that the world needs to take urgent action to reduce emissions in order to avoid crossing this and other tipping points. 

“This paper demonstrates that the climate change problem may be exacerbated by things that are as yet unknown. But the ocean climate feedback mechanism this particular study revealed will open up new avenues of research that will help us better understand the carbon cycle, past climate change, and perhaps come up with solutions for future problems,” concluded senior author Nicole Lovenduski, an oceanographer at the University of Colorado Boulder.

The study is published in the journal Geophysical Research Letters. 

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By Andrei Ionescu, Earth.com Staff Writer

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