Rapid melt from Antarctica could help preserve crucial ocean current

The melting of the Greenland ice sheet is expected to slow down or even slow down. destroy the Atlantic Ocean current that keeps Europe warmMeltwater from West Antarctica could preserve this vital flow.

But this will not be enough to prevent serious climate change. The Atlantic Meridional Overturning Circulation (AMOC) would still be reduced by 60 percent and would take 3,000 years to fully recover.

“I would say don’t be too quick to say AMOC will collapse,” says Sasha Sinet at Utrecht University in the Netherlands. “But what I show here doesn't change much about what will happen in the next century. You probably won't have time to tell whether the AIOC has been stabilized by West Antarctica or not.”

The AMOC is a system of currents that transports warm surface water from the tropics to northern Europe, where it cools and sinks before flowing south to Antarctica. The current carries 1.2 petawatts of heat – equivalent to the energy generated by 1 million power plants – making Europe much warmer than Labrador or Siberia at the same latitude. But light, fresh meltwater from the Greenland ice is expected to keep the AMOC's salty, dense water from sinking, slowing the flow.

If the AIOC collapses, winter temperatures could reach almost -50°С (-58°F) in Northern Europe. Iceland this week declared AMOC's closure an “existential” security threat. Sea levels will also be higher along the US east coast, and Africa could suffer more severe droughts.

Recent research concluded that even if we reach net zero by 2075 and then begin removing CO2 from the atmosphere, the risk of a possible AMOC collapse could still be 25 percent. One study predicted closure for decades, while another said Antarctic winds will keep the AMOC weakened.

Meanwhile, the melting of the West Antarctic ice sheet has accelerated in recent decades, with some studies suggesting that that it will most likely collapse completely. However, the impact this will have on AMOC is unclear.

According to modeling by Sinet and colleagues, the timing of melting is critical. If the centuries-long pulse of Antarctic meltwater comes at the same time as a massive meltwater melt from Greenland, it will only hasten the closure of the AIOC.

However, if Antarctic waters arrive about 1,000 years before the peak of the Greenland melt, the AIOC will weaken for a few hundred years, but then recover over the next 3,000 years. Although the AIOC eventually recovered in all scenarios, this early Antarctic melt prevented its complete collapse and accelerated its resurgence.

This may be because light, fresh meltwater collects around Greenland, the sinking of dense, salty AMOC water moves south, and the current later regains strength as the meltwater moves away from Antarctica.

While it's unlikely that West Antarctica will melt so early or Greenland will melt so late, these results show a greater connection between the AIOC and Antarctic melt, he says. Louise Sime at the British Antarctic Survey.

“I don't think we knew before this study that there was a possibility that changes in Antarctica could potentially change the effects of melting the Greenland ice sheet that much. [on the AMOC]”, she says.

However, the link now needs to be explored with more complex models because that study did not include possible feedback effects, such as changing wind patterns, that could expand Antarctic sea ice, she adds.

Even if the dramatic melting of West Antarctic ice prevents the AMOC from collapsing, it would still cause sea levels to rise by as much as 3 meters, flooding coastal cities.

“Unfortunately, it’s no consolation that one disaster can reduce the risk of another,” says Stefan Rahmstorf at the University of Potsdam, Germany.