Analysis of temperature and salinity shakes view of global water flow.

[amyrose2712]

Ocean conveyor-belt model stirred up
Analysis of temperature and salinity shakes view of global water flow.
Adam Mann

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.

Snip

The idea of the seas moving as a smooth belt is being changed by the accessibility of satellite data, says oceanographer Joël Hirschi, also at the National Oceanography Centre and a co-author of the earlier study. The essential outline remains, he says, "but on top of that conveyor picture, there is a lot of variability going on".

Hirschi compares the variation in flow to daily weather patterns in Earth's atmosphere. Modelling the MOC is like knowing the average state of the atmosphere, he says. It can provide an overall description of the climate, but the detailed, local differences will still be hard to predict.

http://www.nature.com/news/2010/100912/full/news.2010.461.html?s=news_rss