West Antarctic meltwater could stabilise Atlantic Ocean Circulation
Dampening effect between different climate systems
Researchers at Utrecht University have shown that, under certain conditions, melting from the West Antarctic Ice Sheet can stabilise the Atlantic Meridional Overturning Circulation (AMOC). The study, published on 14 November in Science Advances, demonstrates how freshwater from the south can slow down the weakening of this crucial ocean current.
The Atlantic Meridional Overturning Circulation, the AMOC, has long been seen as a ticking time bomb. As the planet warms and meltwater from Greenland flows into the ocean, this oceanic engine could weaken, or even collapse, bringing major consequences for Europe’s climate.
New research by Sacha Sinet, a postdoctoral researcher at the Institute for Marine and Atmospheric Research Utrecht, and co-writers Anna von der Heydt and Henk Dijkstra, shows that changes in one part of the climate system can sometimes counteract, rather than reinforce, changes in another.
A stabilizing effect
The study shows that meltwater from the south can make the AMOC more resilient to disturbances from the north. “In my model experiments, when meltwater is released near West Antarctica, the ocean circulation can handle more Greenland melt,” says Sinet. “This is what we call a stabilizing interaction.”
The fact that West Antarctic meltwater can stabilise the AMOC does not mean it’s good news
Tipping climate systems
Both the AMOC and the ice sheets of Greenland and West Antarctica are among the climate system’s key ‘tipping elements’: components that can abruptly shift once a critical threshold is crossed. Tipping points can also influence one another: the collapse of one system may trigger a domino effect across others.
Research on tipping points often focuses on reinforcing interactions that can accelerate such domino effects. Sinet’s study shows that stabilising interactions are just as important, helping a system resist change instead of speeding it up.
From conceptual to complex models
The idea that southern meltwater can dampen or enhance ocean circulation had previously been demonstrated in simplified conceptual climate models. “Think of an ocean represented as a few interconnected boxes of water,” explains Sinet. “These models help us understand the underlying mechanisms, but they only capture part of the real physics of the climate.”
His new study takes the next step, using a climate model of intermediate complexity that more realistically simulates ocean and atmosphere. “We had good theoretical reasons to expect this, but seeing it materialize in the simulations was still surprising,” Sinet says. “It’s remarkable to see your expectations actually confirmed in a climate model that’s closer to reality.”
No reason for complacency
Still, the researcher warns for overly optimistic interpretations. The fact that West Antarctic meltwater can stabilise the AMOC does not mean it’s good news. “We’re talking about a scenario where an entire ice sheet disappears, causing meters of sea-level rise,” Sinet emphasises. “On its own, that would be catastrophic. My study mainly shows that we also need to understand stabilising interactions, because they determine how the climate system’s future may unfold, too.”