Weakening currents in the Atlantic may mean a wetter northern Australia and drier New Zealand

Europe is warmed by heat from ocean currents, which move water from the warm tropics to the colder North Atlantic. Once the warm, salty water from the tropics reach the polar region, they cool enough to sink to the depths and flow back towards the Southern Ocean.

This enormous system of currents is known as the Atlantic Meridional Overturning Circulation (AMOC). Climate scientists are increasingly worried about the AMOC, which appears to be slowing down.

While there’s still debate over whether the AMOC has weakened over the last decades, climate models consistently show the AMOC will significantly weaken over the coming century due to the increase in heat-trapping atmospheric greenhouse gases. As more heat stays in the system, the ocean heats up and ice melts, adding fresh water to polar oceans. The overall effect is to slow these currents. The AMOC could weaken 30% by 2060.

A weaker AMOC would mean big changes in Europe, which benefits directly from the warmer waters it brings. But it would also change the climate in the Southern Hemisphere. Our new research shows a weakening of the AMOC would lead to a large change in rainfall patterns, leading to wetter summers in northern Australia and a drier New Zealand year-round. Indonesia and northern Papua New Guinea would also become drier.