But in the Atlantic “the heat is moving northward throughout the whole Atlantic Ocean,” says David Thornalley, a paleo-oceanographer at University College London and co-author of one of the new studies. In the Pacific Ocean equatorial heat is transported north and south toward both poles. It also helps draw carbon dioxide from the atmosphere into the sea. This cycle, called the Atlantic Meridional Overturning Circulation (AMOC), plays a key role in moving heat around the planet as well as nutrients throughout the ocean. As that segment of ocean flow, known as the Gulf Stream, pushes north, it cools and becomes denser and eventually sinks, forming the so-called deepwater that flows back southward along the ocean floor toward Antarctica. before darting toward northwestern Europe (giving the British Isles a climate far balmier than Newfoundland at a similar latitude). The warm, salty waters of the tropical Atlantic cruise northward along the eastern U.S. The Atlantic meridional overturning circulation (AMOC) and the subpolar gyre, where ocean waters cool when the AMOC weakens. If models are not sensitive enough to the changes going on in the North Atlantic, “that sort of puts the warning flag a little higher,” says Thomas Delworth, an ocean and climate modeler at the National Oceanic and Atmospheric Administration who was not involved in the research. Which pieces might be missing, though, could determine how worrying this trend is. The results imply climate models are missing key pieces of the puzzle, and that ill effects could be on their way. Rather, it is part of a longer-term decline that has put the circulation at its weakest state in centuries. But two new studies, published Wednesday in the journal Nature, suggest the recent weakening spotted by ocean sensors is not just a short-term blip, as some had thought. Such concerns had been quelled over the last decade as climate models suggested this branch of the ocean’s circulatory system was not likely to see a rapid slowdown, which would slow any consequences. east coast, key fisheries could be devastated by spiking water temperatures and weather patterns over Europe could be altered. Sea levels could ratchet upward along the U.S. Climate scientists have been concerned since the 1980s that rising global temperatures could throw a wrench in the conveyor belt–like system, with possibly stark climatic consequences. That northward flow is a key part of the larger circulation of water, heat and nutrients around the world’s oceans. If that languidness continues and deepens, it could usher in drastic changes in sea level and weather around the ocean basin. In recent years sensors stationed across the North Atlantic have picked up a potentially concerning signal: The grand northward progression of water along North America that moves heat from the tropics toward the Arctic has been sluggish.