The nightmare scenario of Atlantic Ocean currents collapsing, with weather running amok and putting Europe in a deep freeze, looks unlikely this century, a new study concludes.In recent years, studies haveraised the alarmabout the slowing and potential abrupt shutdown of theAtlantic end of the ocean conveyor belt system. It transports rising warm water north and sinking cool water south and is a key factor in global weather systems. A possibleclimate change-triggered shutdown of whats called the Atlantic Meridional Overturning Circulation or AMOC could play havoc with global rain patterns, dramatically cool Europe while warming the rest of the world and goose sea levels on Americas East Coast, scientists predict.Its the scenario behind the 2004fictionalized disastermovie The Day After Tomorrow, which portrays a world where climate change sparks massive storms, flooding, and an ice age.Scientists at the United Kingdoms Met Office and the University of Exeter used simulations from 34 different computer models of extreme climate change scenarios to see if the AMOC would collapse this century, according to a study in Wednesdays journal Nature. No simulation showed a total shutdown before 2100, said lead author Jonathan Baker, an oceanographer at the Met Office.It could happen later, though, he said. The currents have collapsed in the distant past.Still, the computer simulations should be reassuring to people, Baker said.But this is no greenlight for complacency, Baker warned. The AMOC is very likely to weaken this century and that brings its own major climate impacts.The Atlantic current flows because warm water cools as it reaches the Arctic, forming sea ice. That leaves salt behind, causing the remaining water to become more dense, sinking and pulled southward. But as climate change warms the world and more fresh water flows into the Arctic from the melting Greenland ice sheet, the Arctic engine behind the ocean conveyor belt slows down. Previous studies predict it stopping altogether with one of them sayingit could happen within a few decades.But Baker said the computer models and basic physics predict that a second motor kicks in along the Southern Ocean that surrounds Antarctica. The winds there pull the water back up to the surface, called upwelling, where it warms, Baker said. Its not as strong, but it will likely keep the current system alive, but weakened, through the year 2100, he said.Bakers focus on the pulling up of water from the deep instead of just concentrating on the sinking is new and makes sense, providing a counterpoint to the studies saying collapse is imminent, said Oregon State University climate scientist Andreas Schmittner, who wasnt part of the research.Those Southern Ocean winds pulling the deep water up act like a powerful pump keeps the AMOC running even in the extreme climate change scenarios, Baker said.As the AMOC weakens, a weak Pacific version of it will likely develop to compensate a bit, the computer models predicted.If the AMOC weakens but not fully collapses, many of the same impactsincluding crop losses and changes in fish stocklikely will still happen, but not the big headline one of Europe going into a deep freeze, Baker said.Scientists measure the AMOC strength in a unit called Sverdrups. The AMOC is now around 17 Sverdrups, down two from about 2004 with a trend of about 0.8 decline per decade, scientists said.One of the debates in the scientific world is the definition of an AMOC shutdown. Baker uses zero, but other scientists who have been warning about the shutdown implications, use about 5 Sverdrups. Three of Bakers 34 computer models went below 5 Sverdrups, but not to zero.Thats why Levke Caesar and Stefan Rahmstorf, physicists at the Potsdam Institute for Climate Research and authors ofan alarming 2018 studyabout potential shutdown, said this new work doesnt contradict theirs. Its more a matter of definitions.An AMOC collapse does not have to mean 0 (Sverdrups) overturning and even if you would want to follow that definition one has to say that such a strong AMOC weakening comes with a lot (of) impacts, Caesar wrote in an email. The models show a severe AMOC weakening that would come with severe consequences.The Associated Press climate and environmental coverage receives financial support from multiple private foundations. AP is solely responsible for all content. Find APs standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org.Seth Borenstein, AP science writer