Could Antarctic ice trigger an Atlantic Meridional Overturning Circulation collapse?

Imagine your home's central heating system relies on a delicate balance of hot and cold water pressure to keep the rooms warm. If you dump a massive bucket of ice water directly into the return pipe, the whole pump grinds to a halt.

This is the scale of what is happening to our oceans. Scientists have long worried about an Atlantic Meridional Overturning Circulation collapse, the shutdown of a giant marine conveyor belt that carries warm water north. While most eyes are on Greenland's melting ice, new early-stage research suggests the real threat might come from the opposite end of the globe.

In a new preprint awaiting peer review, researchers simulated how varying levels of Antarctic meltwater affect global currents. They measured ocean density gradients and simulated different freshwater flows. The data show that while small amounts of southern meltwater actually strengthen the conveyor belt, massive discharges do the opposite. Large volumes of Antarctic freshwater alter seawater density, change the depth of the pycnocline, and eventually cause the system to collapse.

The mechanics of an Atlantic Meridional Overturning Circulation collapse

If these preliminary findings hold, climate models will need a major rewrite. The study suggests that confining meltwater to West Antarctica makes it easier for density changes to travel north. To accurately project future climate shifts, scientists must now model the combined effects of both polar ice sheets.

• Antarctic meltwater acts as a remote control for northern ocean currents.
• West Antarctic melting poses the greatest risk for density disruption.
• Current climate models may underestimate the speed of ocean circulation decay.