Al Gore Says Our Children Will Never See Snow Again
Body of water circulation
2006: Freshwater flowing into the North Atlantic could shut downwards the sea conveyor chugalug that shuttles warm water toward Western Europe.
2016: The ocean conveyor belt may already be slowing, just information technology's not much of a conveyor belt at that.
Concluding twelvemonth may have been Globe's hottest on record (SN: 2/twenty/16, p. xiii). But for 1 small corner of the globe, 2015 was one of the coldest. Surface temperatures in the subpolar North Atlantic have chilled in recent years and, oddly enough, some research suggests global warming is partly responsible.
An influx of freshwater from melting glaciers and increasing rainfall can slow — and perchance even shut down — the sea currents that ferry warm water from the torrid zone to the North Atlantic. Nearly 10 years agone, scientists warned of a possible precipitous shutdown of this "ocean conveyor belt." Later years of closely monitoring Earth'southward flowing oceans, researchers say a sudden slowdown isn't in the cards. Some researchers report that they may now be seeing a more gradual slowing of the ocean currents. Others, meanwhile, have discovered that Earth's ocean conveyor belt may exist less of a bounding main superhighway and more than of a twisted network of side roads.
The consequences of a sea current slowdown won't be anywhere near every bit catastrophic as the over-the-top atmospheric condition disasters envisioned in the 2004 motion picture The Solar day Later Tomorrow, says Stephen Griffies, a physical oceanographer at NOAA'south Geophysical Fluid Dynamics Laboratory. "The doomsday scenario is overblown, only the possibility of a slowing down of the apportionment is real and will have important impacts on Atlantic climates," Griffies says.
EVERY WHICH WAY Tracking the motility of floating markers dropped into the northwest Atlantic (white-rimmed circles), researchers found that the thought of an ocean conveyor belt is overly simplistic. The markers apace separate, catastrophe upwards in many different destinations (solid circles).Amy Due south. Bower et al/Nature 2009
The Atlantic mixing that feeds the currents is powered past differences in the density of seawater. In the simple ocean conveyor-belt model, warm, less-dense surface h2o flows northward into the North Atlantic. Off Greenland, cold, denser water sinks into the deep bounding main and flows southward. This heat exchange, known as the Atlantic overturning apportionment, helps go along European cities warmer than their counterparts elsewhere in the globe.
Ten years ago, scientists knew from past changes in Earth's climate that temperature shifts can disrupt this density balance. Freshwater from the shrinking Greenland water ice canvass and increased rainfall make the Due north Atlantic waters less dense and therefore less likely to sink. Investigations into Earth'southward ancient climates show that the overturning circulation weakened around 12,800 years agone, probably causing cooling in Europe and ocean level ascent along North America's East Declension, equally piled-up water in the due north sloshed s.
Tracking ocean surface temperatures, researchers reported last year that the Atlantic overturning circulation significantly slowed during the 20th century, particularly later 1970. Comparing the recent slowdown with by events, the researchers reported in March in Nature Climate Change that the rapid weakening of the circulation is unprecedented in the last one,000 years.
That effect isn't the final word, though, says Duke Academy physical oceanographer Susan Lozier. Scientists take direct measured the speed of the ocean circulation just since the deployment of a network of ocean sensors in 2004. Earlier Atlantic circulation speed changes take to be gleaned from less reliable indirect sources such as sea surface temperature changes. "If you look at the most recent results, there's a reject, yes," she says. "Just nosotros can't say that's role of a long-term trend right now." And effects on Europe'due south climate could exist masked by other factors.
Another challenge is that over the last 10 years, "the sea conveyor-belt model broke," Lozier said in February at the American Geophysical Union's Ocean Sciences Coming together in New Orleans. From 2003 through 2005, she and colleagues tracked the movements of 76 floating markers dropped into the N Atlantic and pulled effectually by ocean waters. If the model was right, these markers should take traveled along the southward-flowing part of the conveyor chugalug. Instead, the markers moved every which way, the researchers reported in 2009 in Nature.
"We went from this uncomplicated ribbon of a conveyor belt to a complex catamenia field with multiple pathways," Lozier says. Determining past and possible future effects of climate change on ocean currents will require more measurements and a ameliorate understanding of how the bounding main truly flows, she says.
Fifty-fifty if the overturning apportionment cuts out completely, the resulting cooling event will probably exist short-lived, Griffies says. "At some point, fifty-fifty if the apportionment collapses, information technology would just be 10 or twenty years earlier the global warming signal would overwhelm that cooling" in Europe, he says. "This is not going to save us from a warmer planet."
Source: https://www.sciencenews.org/article/changing-climate-10-years-after-inconvenient-truth
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