Ice age ocean current disruptions linked with greenhouse gas changes
Scientists say they’ve discovered another huge climate warning sign in the Arctic. Past increases in CO2 levels in the air drove ocean currents to a tipping point had a big impact on hemispheric weather patterns.
Within the span of just a few decades, rising CO2 concentrations drove temperatures in Greenland up by 10 degrees Celsius, according to a new study led by researchers with the Alfred Wegener Institute and the University of Cardiff.
The study, published in the journal Nature Geoscience, confirms that, in the past, gradually rising CO2 concentrations have set off abrupt changes in ocean circulation. These sudden changes, referred to as Dansgaard-Oeschger events, have been observed in ice cores collected in Greenland.
The events marked abrupt climate changes in the far North, but the causes remain unclear.
“With this study, we’ve managed to show for the first time how gradual increases of CO2 triggered rapid warming,” said lead author Xu Zhang.
The study hows how the climate system is globally connected. Increased CO2 intensifies the trade winds over Central America, as the eastern Pacific is warmed more than the western Atlantic. This is turn produces increased moisture transport from the Atlantic, and with it, an increase in the salinity and density of the surface water. T
hese changes lead to an abrupt amplification of the large-scale overturning circulation in the Atlantic.
“Our simulations indicate that even small changes in the CO2 concentration suffice to change the circulation pattern, which can end in sudden temperature increases,” said Zhang.
According to the study, rising CO2 levels are the dominant cause of changed ocean currents during the transitions between glacial and interglacial periods.
“We can’t say for certain whether rising CO2 levels will produce similar effects in the future, because the framework conditions today differ from those in a glacial period,” said AWI researcher Gerrit Lohmann.
“That being said, we’ve now confirmed that there have definitely been abrupt climate changes in the Earth’s past that were the result of continually rising CO2 concentrations.”