Is The North Atlantic Current Weakening?
Do you know what the North Atlantic Current is, and do you care? It might be a really good idea to find out and start caring.
I was on my way to bed when I decided to check Drudge and found this:
Road closures extend overnight; county schools cancel classes
A rare winter storm swept through Southern Nevada Wednesday, dumping the most snow on the valley in nearly three decades, grounding flights at the airport, forcing the closure of major highways and closing schools for today.
“This is the most snow we’ve had in Las Vegas in almost 30 years,” said Chris Stachelski, a meteorologist with the National Weather Service. “It’s a significant historical event.”
The heaviest snowfall occurred in the southeast valley, where about 3 inches of snow had accumulated by 7:45 p.m., with unconfirmed reports of as much as 6 inches in Henderson, he said.
Between 6 to 10 inches could fall in that area by the time the storm tapers off Thursday morning, and the northern and western parts of the valley could receive up to 4 inches of snowfall, he said.
So what does the above story have to do with the North Atlantic Current you may ask?
A video of “The Day After Tomorrow” about the complete screeching halt of the North Atlantic Current due to a massive influx of freshwater from the polar ice shelves melting.
Remember the flooding in LA last week? The icestorm in the Northeast? The unusual tornadoes during the spring and summer? The increased number and intensity of hurricanes that keep hitting the Gulf Coast? Is the picture starting to come into focus? Is the North Atlantic Current weakening?
I decided to do some digging and this is what I found, (and check the date):
Sirpa Hakkinen, lead author and researcher at NASA’s Goddard Space Flight Center, Greenbelt, Md. and co-author Peter Rhines, an oceanographer at the University of Washington, Seattle, believe slowing of this ocean current is an indication of dramatic changes in the North Atlantic Ocean climate. The study’s results about the system that moves water in a counterclockwise pattern from Ireland to Labrador were published on the Internet by the journal Science on the Science Express Web site at:
The current, known as the sub polar gyre, has weakened in the past in connection with certain phases of a large-scale atmospheric pressure system known as the North Atlantic Oscillation (NAO). But the NAO has switched phases twice in the 1990s, while the subpolar gyre current has continued to weaken. Whether the trend is part of a natural cycle or the result of other factors related to global warming is unknown.
“It is a signal of large climate variability in the high latitudes,” Hakkinen said. “If this trend continues, it could indicate reorganization of the ocean climate system, perhaps with changes in the whole climate system, but we need another good five to 10 years to say something like that is happening.” Rhines said, “The subpolar zone of the Earth is a key site for studying the climate. It’s like Grand Central Station there, as many of the major ocean water masses pass through from the Arctic and from warmer latitudes. They are modified in this basin. Computer models have shown the slowing and speeding up of the subpolar gyre can influence the entire ocean circulation system.”
The North Atlantic Current (North Atlantic Drift and the North Atlantic Sea Movement) is a powerful warm ocean current that continues the Gulf Stream northeast. West of Ireland it splits in two. One branch (the Canary Current) goes south while the other continues north along the coast of northwestern Europe where it has a considerable warming influence on the climate. Other branches include the Irminger Current and the Norwegian Current. Driven by the global thermohaline circulation (THC), the North Atlantic Current is also often considered part of the wind-driven Gulf Stream which goes further east and north from the North American coast, across the Atlantic and into the Arctic Ocean.
It is suspected that global warming might have a significant effect on the current; see Shutdown of thermohaline circulation for details.
Are you paying attention now?
THE GLOBAL OCEAN CONVEYOR—The global ocean circulation system, often called the Ocean Conveyor, transports heat throughout the planet. White sections represent warm surface currents. Purple sections represent deep cold currents. (Illustration by Jayne Doucette, WHOI)
DRAMATIC CHANGES IN THE NORTH ATLANTIC—Subpolar seas bordering the North Atlantic have become noticeably less salty since the mid-1960s, especially in the last decade. This is the largest and most dramatic oceanic change ever measured in the era of modern instruments. This has resulted in a freshening of the deep ocean in the North Atlantic, which in the past disrupted the Ocean Conveyor and caused abrupt climate changes. (B. Dickson, et. al., in Nature, April 2002)
If the climate system’s Achilles’ heel is the Conveyor, the Conveyor’s Achilles’ heel is the North Atlantic. An influx of fresh water into the North Atlantic’s surface could create a lid of more buoyant fresh water, lying atop denser, saltier water. This fresh water would effectively cap and insulate the surface of the North Atlantic, curtailing the ocean’s transfer of heat to the atmosphere.
An influx of fresh water would also dilute the North Atlantic’s salinity. At a critical but unknown threshold, when North Atlantic waters are no longer sufficiently salty and dense, they may stop sinking. An important force driving the Conveyor could quickly diminish, with climate impacts resulting within a decade.
In an important paper published in 2002 in Nature, oceanographers monitoring and analyzing conditions in the North Atlantic concluded that the North Atlantic has been freshening dramatically—continuously for the past 40 years but especially in the past decade.4 The new data show that since the mid-1960s, the subpolar seas feeding the North Atlantic have steadily and noticeably become less salty to depths of 1,000 to 4,000 meters. This is the largest and most dramatic oceanic change ever measured in the era of modern instruments.
At present the influx of fresher water has been distributed throughout the water column. But at some point, fresh water may begin to pile up at the surface of the North Atlantic. When that occurs, the Conveyor could slow down or cease operating.
Signs of a possible slowdown already exist. A 2001 report in Nature indicates that the flow of cold, dense water from the Norwegian and Greenland Seas into the North Atlantic has diminished by at least 20 percent since 1950.
What future climate scenarios should we consider?
The debate on global change has largely failed to factor in the inherently chaotic, sensitively balanced, and threshold-laden nature of Earth’s climate system and the increased likelihood of abrupt climate change. Our current speculations about future climate and its impacts have focused on the Intergovernmental Panel on Climate Change, which has forecast gradual global warming of 1.4° to 5.8° Celsius over the next century.
It is prudent to superimpose on this forecast the potential for abrupt climate change induced by thermohaline shutdown. Such a change could cool down selective areas of the globe by 3° to 5° Celsius, while simultaneously causing drought in many parts of the world. These climate changes would occur quickly, even as other regions continue to warm slowly. It is critical to consider the economic and political ramifications of this geographically selective climate change. Specifically, the region most affected by a shutdown—the countries bordering the North Atlantic—is also one of the world’s most developed.
The key component of this analysis is when a shutdown of the Conveyor occurs. Two scenarios are useful to contemplate:
Scenario 1: Conveyor slows down within next two decades.
Such a scenario could quickly and markedly cool the North Atlantic region, causing disruptions in global economic activity. These disruptions may be exacerbated because the climate changes occur in a direction opposite to what is commonly expected, and they occur at a pace that makes adaptation difficult.
Scenario 2: Conveyor slows down a century from now.
In such a scenario, cooling of the North Atlantic region may partially or totally offset the major effects of global warming in this region. Thus, the climate of the North Atlantic region may rapidly return to one that more resembles today’s—even as other parts of the world, particularly less-developed regions, experience the unmitigated brunt of global warming. If the Conveyor subsequently turns on again, the “deferred” warming may be delivered in a decade.
2008 just keeps getting better and better…..