In about 20 years, the Earth may experience a significant drop in estimated average temperatures, coupled with giant tsunamis, resembling disaster films.
A new study by a University of Southampton researcher named Sybren Drijfhout delved into the effects of Atlantic Meridional Overturning Circulation (AMOC), which is a major Atlantic current that involves a northward flow of warm water into the ocean surface and a downward flow of cool water deep into the ocean.
Collapse of the AMOC may result in cooling all around the world via rapid feedbacks that heighten the response in the Northern Hemisphere. The manner with which such rise in temperatures battle it out with global warming has garnered numerous associated assumptions but was never tackled using a climate model.
Extended climate change can be represented by a forced response, which can be identified using a box model containing two layers. Response and forcing are two different variables that are believed to have an imbalance. The said imbalance equates to the level of heat that is sent down deep into the ocean.
AMOC is considered to be one of the primary factors affecting the unforced alterations in ocean heat uptake, or the rate at which global ocean heat stores rises as the global mean surface temperature increases. Heat uptake is transported downward mostly due to diffusion. To keep a vertical temperature angle, the heat must be discharged from the deep to the upper part of the ocean.
The vigor of the heat pump is majorly determined by the AMOC. Sudden falter of the AMOC may lead to convective heat transport, while the diffusion downward stays the same, developing a net ocean heat uptake. The effects of AMOC weakening may have significant effects on climate, one of which is the apparent cooling in the North Atlantic and lesser warming in the Southern Hemisphere.
In the Drijfhout's study, he studied the effects of AMOC collapse in an experiment that combines continuous drenching and increasing carbon dioxide forcing, giving emphasis on how it changes the ocean heat uptake and top of atmosphere (TOA) radiation disequilibrium. The manner with which these alterations are converted into diverse warming indicators in the surface were also observed.
As per the study results, Drijfhout said that if the planet persists to warm, ocean currents such as AMOC may weaken, creating giant tsunamis. In 20 years, if AMOC and global warming happens simultaneously, the planet would begin to cool rather than warm. As per estimates, a drop of about 1.3 degrees Fahrenheit or -17 degrees Celsius would transpire, after which, the recovery phase would start.
"When a similar cooling or reduced heating is caused by volcanic eruptions or decreasing greenhouse emissions, the heat flow is reversed, from the ocean into the atmosphere." explained Drijfhout. He added that an almost same opposite action also happens at the TOA.
The solution for such flaws warrant further studies, as well as better satellite data of the planet's energy disequilibrium and enhanced information about the heat content of the oceans.
The study was published in the journal Nature Scientific Reports on Oct. 6
Photo: James Loesch | Flickr
