Ocean conveyor-belt model stirred up
The accepted picture of how a massive oceanic conveyor belt of water turns has been complicated by findings published today in Nature Geoscience1. The results could help to boost the precision of climate-change models.
As tropical water from the Equator flows north in the Atlantic Ocean, it becomes cooler and denser. Evaporation along the way makes it saltier and further increases its density. In the frigid Arctic, the water sinks into the depths and then moves southward; returning to the surface once it has warmed up again.
But this simplified picture of what is known as meridional overturning circulation (MOC) has been brought into question by a paper suggesting that, in the past 50 years, ocean circulation closer to the Equator has grown weaker, whereas the northern waters have flowed more strongly.
“The more we look, the more complicated the ocean is,” says Susan Lozier, an oceanographer at Duke University in Durham, North Carolina, and lead author of the study.
When the conveyor-belt model was conceptualized in the 1980s, researchers understood only a rough outline of overall marine currents, she says. Because it is difficult to take measurements in the depths of the ocean, MOC models couldn’t reflect the intricacy of all the factors involved.