For this reason, it's an excellent idea to see "who" is being referenced--and what degree of reliability they carry for the information you've decided will back up or challenge your reason for including it in a paper. Let's look at a sample from an article on changing conditions in the salinity (salt level) of today's oceans--and notice "WHO" said so. I've placed the specific sources and their employment in highlight format:
A climate surprise may be brewing in the North AtlanticBy Charles W. Petit
Straight west from Paris, the City of Light, is the raw, sub-Arctic town of Gander in Newfoundland, whose tourist board boasts of icebergs and caribou herds. Parisian winters run nearly 20 degrees Fahrenheit warmer than Gander's, at the same latitude. The reason is 2,500 churning, intervening miles of radiator called the Atlantic Ocean, its warmth carried to Europe by prevailing winds. But an unsettling change reported at a recent oceanography meeting could mean a shorter sidewalk cafe season on the Champs-Elysees.
Nearly the whole North Atlantic from Canada to Scandinavia and the British Isles, to depths of more than a mile, has received a vast influx of fresh water since the 1960s, perhaps from rivers, rain, or melting ice. Some experts say the influx could disrupt ocean currents vital not only to Europe's relatively mild weather, but also to world climate patterns. And while gradual global warming may be what has unleashed the burst of fresh water, its effects could come suddenly--in decades--and chill Europe while most of the world keeps warming.
Debate is already underway about whether the finding is bad news, good news, or merely fascinating. But one thing seems clear. "It is the biggest oceanographic change ever seen, anywhere, in the modern instrumental era," says the oceanographer who led the analysis, Robert Dickson, who works at a British government lab in Lowestoft, England.
The shift in salt content--well under a part per thousand--may seem at first blush an arcane item only of academic interest. The water wouldn't taste different. But researchers worry that it takes little to alter the forces that drive ocean currents.
The North Atlantic is the headwaters of an interlinked system of currents sometimes called the oceanic conveyor belt, which ferries vast quantities of heat from the tropics to the poles. In the Atlantic, the Gulf Stream and other warm currents at the surface carry a volume of 75 Amazon rivers northward. Meandering near Greenland, these currents shed heat at a rate of half a million nuclear reactors. The waters are already unusually salty, which makes them dense, and the heat loss makes them denser still--so dense that they sink and flow back south along the ocean bottom, drawing additional southerly waters north at the surface. This powerful "overturning" feeds energy into other currents that lace the Pacific, Indian, and polar oceans and help determine the locations of deserts, rainy regions, and typical storm tracks around the world. As fresh water dilutes the salt in the North Atlantic, the water becomes less dense. And if the water arriving from the south can't sink even after it cools off, it won't make room for the next batch. By putting the brakes on this circulation, "fresher water in the North Atlantic could be real trouble," says Dan Seidov of Pennsylvania State University.
Dickson and colleagues from Britain, Canada, and Germany broke the news at a mid-February ocean science conference in Honolulu, citing data from scientists who have been dropping instruments into the North Atlantic for decades. "This is the first time it's all been put together," notes Terrence Joyce of the Woods Hole Oceanographic Institution. "It is amazing and, in terms of oceanography, exciting."
Igor Yashayaev, a Canada-based researcher working with Dickson, figures the lowered salinity is equivalent to adding a layer of fresh water 12 feet deep to the North Atlantic. Experts are unsure whether it is coming from heavier rain and river runoff or melting of Arctic glaciers and sea ice. Nor do they know whether the cause is a natural climate cycle, global warming due to human activity, or some mix of the two. And they don't know exactly how much additional fresh water it would take to push the Atlantic over the edge and cause its circulation to collapse.
Still, "the density is already very close to the critical point," says Andrew Weaver of the University of Victoria in British Columbia, Canada. If the oceanic conveyor belt does shut down, impacts could come fast. "It's like a light switch, not a dimmer," says Arnold Gordon of Columbia University's Lamont-Doherty Earth Observatory. The world has gone through at least two dozen drastic climate shifts in the past 100,000 years, when regional temperatures dropped or soared 10 degrees or more in a matter of decades. Ominously, a shutdown or start-up of the North Atlantic circulation was a key factor in most of them. The latest, the so-called Younger Dryas 13,000 years ago, struck as the world was slowly emerging from the last ice age, and abruptly plunged Europe and parts of North America back into glacial conditions.
No one expects an oceanic shutdown to bring the ice age back to London and Paris. But there are already hints that the North Atlantic's heat pump is faltering, while most of the rest of the planet warms. "It's curious that the only place in the world where temperate glaciers are advancing is in Scandinavia," says Weaver. In another sign of trouble in the deep, some of the bottom currents carrying cold water back south seem to have weakened by 20 percent in recent years.
It's not just the North Atlantic. "There are large-scale changes going on in all the world's oceans," says Tim Barnett of the Scripps Institution of Oceanography near San Diego. He and other scientists reported last year that nearly all the world's oceans are warming, with human-caused global warming the most likely culprit.
The change in the Atlantic, if it comes, might not be all bad. "It might be good for Europe," says Gordon. "The rest of the Earth is going to undergo significant warming, except perhaps there." But no one wants to be taken by surprise. Great Britain intends to spend $30 million over the next six years to monitor the Atlantic for any shifts in warm surface water going north and cold bottom water returning south.
Meanwhile, says Joyce, "I'm in the dark on how close to an edge or transition to a new ocean and climate regime we might be. But I know which way we are walking. We are walking toward the cliff."