Oh, Snap! OSNAP Study Shaking Up Understanding Of Ocean Conveyer Current
It may be the biggest wild card in the climate system. Scientists have long feared that the so-called “overturning” circulation in the Atlantic Ocean could slow down or even halt due to climate change — a change that would have enormous planetary consequences. But at the same time, researchers have a limited understanding of how the circulation actually works, since taking measurements of its vast and remote currents is exceedingly difficult. And now, a major new research endeavor aimed at doing just that has suggested a dramatic revision of our understanding of the circulation itself.
A new 21-month series of observations in the frigid waters off Greenland has led to the discovery that most of the overturning — in which water not only sinks but returns southward again in the ocean depths — occurs to the east, rather than to the west, of the enormous ice island. If that’s correct, then climate models that suggest the circulation will slow as the climate warms may have to be revised to take this into account
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The new results come from the $ 32 million OSNAP, or “Overturning in the Subpolar North Atlantic,” program, the first attempt to comprehensively measure the circulation in the exceedingly remote regions in question. These icy seas, it is believed, are where cold, salty waters — which are extremely dense — sink below the sea surface into the depths, and then travel back southward again all the way to the Southern Hemisphere.
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The OSNAP array is perhaps best thought of as a scientific line running across the North Atlantic Ocean from Canada to Scotland, touching the southern tip of Greenland along the way. In these waters, researchers have deployed 53 ocean moorings, each of which contains multiple instruments. The moorings take an array of measurements — ocean temperature, salinity, and other readings — at different depths across the entirety of the Atlantic. And that’s how they can get the pulse, so to speak, of the overturning circulation. A similar cross-Atlantic measuring system already exists much farther south, around the latitude of Florida — but scientists feel that measuring the circulation in the far less hospitable waters of the north, where sinking actually occurs, is essential to understand how it works.
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https://www.washingtonpost.com/climate-environment/2019/01/31/surprising-new-picture-ocean-circulation-could-have-major-consequences-climate-science/?noredirect=on&utm_term=.09a5418e907b