Oceanographers have long known that the 20-year-old paradigm for describing the global ocean circulation– called the Great Ocean Conveyor – was an oversimplification. It's a useful depiction, but it's like describing Beethoven's Fifth Symphony as a catchy tune.
The conveyor belt paradigm says the Gulf Stream-warmed ocean releases heat to the atmosphere in the northern North Atlantic, leaving ocean water colder and denser as it moves north. The cold waters sink and flow southward along the "deep western boundary current" that hugs the continental slope from Canada to the equator. To replace the down-flowing water, warm surface waters from the tropics are pulled northward along the conveyor's upper limb.
But while the conveyor belt paradigm establishes the melody, the subtleties and intricacies of the symphony of global ocean circulation largely remain a puzzle.
Now, research led by oceanographers at Woods Hole Oceanographic Institution (WHOI) and Duke University have teased out a new piece of that puzzle, expanding our understanding of this circulation model. Using field observations and computer models, the study shows that much of the southward flow of cold water from the Labrador Sea moves not along the deep western boundary current, but along a previously unknown path in the interior of the North Atlantic.
The study by co-principal authors Amy Bower, a senior scientist in the WHOI Department of Physical Oceanography, and Susan Lozier, a professor of physical oceanography at Duke University's Nicholas School of the Environment, will be published in the May 14 issue of the research journal Nature.
... more @ eurekalert.org
(edited to add quotes & chose a less inflammatory title)Science Daily is reporting that just because they teach you something in graduate school doesn’t make it right. A 50 year old model of global thermohaline circulation that predicts a deep Atlantic counter current below the Gulf Stream is now formally called into question by an armada of subsurface RAFOS floats drifting 700 - 1500m deep. Nearly 80% of the RAFOS floats escaped the Deep Western Boundary Current (DWBC), drifting into the open ocean.
This confirms suspicions that have been around since the 1990’s, and likely plays havoc with global models of climate change. The findings by Drs. Amy Bower of Wood’s Hole and Susan Lozier of Duke University et al. are published in a forthcoming issue of Nature.
The implications would be for more cold, oxygenated water along the Mid-Atlantic Ridge, but I’m just making that last part up. Best to read for yourself. As I recall, the DWBC was notoriously slow. You have to wonder whether a big yellow float responds to these currents the same as suspended matter, like plankton and particulates. Either way, the research represents a major paradigm shift in ocean circulation theory.
- via "Deep Sea News"
