A new study published within Proceedings of the National Academy of Sciences (PNAS) has revealed that there exists the real possibility of a Gulf Stream tipping point. If crossed, then this major ocean current could halt. Because it greatly influences the climate of Northern Europe, this could result in a radical shift in the climate.
Clarity
Some stories have perhaps gone a bit over the top with their headlines. For example, Gozmodo ran the story under the headline “A Major Ocean Current May Be Hurtling Towards Collapse“. My quibble there is not the content of the story, just the clickbait headline. The actual text is fine.
What the study reveals is the possibility, they are not declaring that this is imminent.
Yes, this is the plot for the 2004 movie “The Day After Tomorrow“. Don’t freak out. While fun, the movie is scientifically silly.
Let’s dig into the details a bit to understand what the actual study reveals.
Paper: Risk of tipping the overturning circulation due to increasing rates of ice melt
Submitted in Aug 2020, and accepted for publication in Jan 2021, it documents a study conducted by researchers at the Niels Bohr Institute, University of Copenhagen.
The public use the term “Gulf Stream”, as I did above, but the paper references the more scientifically correct term of the Atlantic Meridional Overturning Circulation (AMOC). In the context of the global ocean currents, this is the specific flow of warm surface water north from the Gulf. That then returns to the south as a cold deep current
It is basically a huge circulation system. It transports heat from the tropics further north, hence it has a huge influence on the climate of Northern Europe. This vast system moves almost 20 million cubic meters of water per second – almost a hundred times the Amazon flow.
What the paper reveals is that there is a climate related tipping point. As we keep pumping out more and more CO2 and so warm the world, this results in a greatly increased flow of cold fresh water flowing into the North Atlantic from a melting Greenland. This has the potential to disrupt the AMOC and bring it to a halt …
Using a global ocean model subject to freshwater forcing, we show that a collapse of the Atlantic Meridional Overturning Circulation can indeed be induced even by small-amplitude changes in the forcing, if the rate of change is fast enough.
Comments by the Researchers
Johannes Lohmann, one of the authors of the study …
“The AMOC is at risk of collapsing when a certain level of freshwater flow into the North Atlantic from increasing ice melt in Greenland is reached. These tipping points have been shown previously in climate models, where meltwater is very slowly introduced into the ocean. In reality, increases in meltwater from Greenland are accelerating and cannot be considered slow.”
“the safe levels of global warming before such a collapse occurs may be smaller than previously thought, and may also be difficult to predict with certainty,”
To be wholly and completely clear. This is not a claim that this will happen, it simply brings to the table the distinct possibility.
The very existence of such a possible tipping point should greatly worry us. It is yet one more data point that confirms that when it comes to addressing climate change, doing nothing is really not a viable option if we wish to avoid catastrophic change.
AMOC (Gulf Stream) tipping points – tweets
It is all complicated and debated.