Nothing lasts forever, not even the ocean and its currents …
Intense climate change in the future may affect the world in a very different way than current models predict. If the concentration of carbon dioxide in the atmosphere doubles, the important ocean current that affects climate and weather around the world will disappear. And then the weather model of the future will be very different from modern forecasts.
The meridional thermohaline circulation of the Atlantic Ocean has been described as a huge oceanic conveyor belt. It is a system of water currents that carries warm water from the Atlantic to the Arctic, creating mild climates in Western Europe.
In the north Atlantic Ocean, surface water cools and sinks to the ocean floor, while another current carries this cold water south again. This process is part of a large system of thermohaline currents that circulate around the world from pole to pole. But some scientists believe that the Atlantic Ocean's meridional thermohaline circulation is not accurately represented in current climate models. They argue that many models describe the flow as more stable than it actually is.
The latest study suggests that circulation is weakening and this is affecting climate predictions. Wei Liu from Yale University and his colleagues from the University of California at San Diego and the University of Wisconsin at Madison took a generally accepted climate model and "weakened" the meridional thermohaline circulation in the Atlantic Ocean. Next, the researchers ran an experiment to see how the fix would affect the projections for future climate change. They immediately doubled the carbon dioxide concentration relative to current levels in the corrected and uncorrected models, and then allowed both models to evolve for hundreds of simulated years.
The difference was striking. In the uncorrected climate model, the meridional thermohaline circulation of the Atlantic Ocean weakens for a short time, but is eventually restored. In the revised model, circulation weakens and disappears after 300 years. The climatic implications in the revised model are also staggering. Without the usual transportation of warm water to the Arctic, the North Atlantic, including the UK, Iceland and northwest Europe, faces a cold snap. Sea ice will begin to grow in the Arctic.
Since the Atlantic Ocean's meridional thermohaline circulation is part of a large global conveyor system that includes warm and cold currents between the equator and both poles, the model predicts severe climatic changes in other parts of the world. Without the reverse movement of cold water in the south, it will become much warmer. The result will be a polarization of precipitation over the Americas. It will rain more in northeastern Brazil and less in Central America. The model also predicts strong sea ice loss in Antarctica.
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Thermohaline circulation is a large-scale oceanic circulation created by the difference in water density resulting from the inhomogeneous distribution of temperature and salinity in the ocean. The adjective thermohaline consists of two parts: "thermo" - temperature, "khalin" - salinity.