Oceanic circulation has always been of concern to climatologists, and for decades (so we are told) the great oceanic conveyor was thought to be well understood. It now appears that the science of oceanic circulation is not exactly settled, and that the complexity of earth's thermodynamics might be generating a few more chapters in academia's halls.
In our limited experience, scientific method is portrayed as a rigorous and unbiased process of observation, questioning, hypothesis, experimentation, and subsequent data analysis, followed by acceptance or rejection of said hypothesis as a valid answer to the question. Having access to the remarkable power of the computer, we can now make predictive “models”. Assuming that all the inputs are known and correctly interpreted, we can then replicate the hypothesis for testing by someone else who desires verification of our conclusions. But does the computer facilitate this process or does it warp it by making extrapolation and assumption so easy as to make great leaps where the investigator ought to still be walking on the earth?
We opine that earth's thermodynamics are a bit more complex than most predictive models, and the introduction of as yet unknown variables can and do throw former hypotheses off the table with some regularity.
We point to the variation of opinion as to the actual method by which thermohaline circulation (THC) is reckoned and the effect thereof cataloged. If the authors of the articles cited below are to be believed, circulation models decades old may now be in need of revision. We note this apparent flux of understanding not to impugn scientists, but to remind the reader that investigators may or may not have access to all necessary information as they step forth to assert new truths they may claim to have discovered.
The operation of oceanic circulation is of profound importance to understanding terrestrial climate both present and future. We assert with great confidence that even though ours is a age of magnificent effort and unprecedented discovery, there are yet many mysteries to be unraveled and we ought to take that into account as we contemplate results of the latest university study. Science is never really “settled”.
Why climate changed is more difficult to answer. Unfortunately, the resolution and dating of paleoclimate records are sometimes insufficient for examining leads and lags in the climate system. Also, scientists are able to reconstruct only certain climate variables at certain locations, which give an incomplete picture of past events. To test ideas about causation, scientists have turned to computer climate models.
From nearly a decade ago
"It's difficult to predict what will happen," cautions Donald Cavalieri, a senior scientist at NASA's Goddard Space Flight Center, "because the Arctic and North Atlantic are very complex systems with many interactions between the land, the sea, and the atmosphere. But the facts do suggest that the changes we're seeing in the Arctic could potentially affect currents that warm Western Europe, and that's gotten a lot of people concerned." (editor's note: perhaps we should add the sun to the list of things that potentially affect the oceans)
For decades, a “conveyor belt” model, developed by paleoclimatologist Wallace Broecker, has served as a simple cartoon of ocean circulation. The diagram depicts warm water moving northward, plunging deep into the North Atlantic; then coursing south as cold water toward Antarctica; then back north again, where waters rise and warm in the North Pacific.
However, evidence has shown that waters rise to the surface not so much in the North Pacific, but in the Southern Ocean — a distinction that Marshall and Speer illustrate in their updated diagram.
Changes in ocean circulation are bound to cause further changes in global climate. Scientists are certain that Arctic water is becoming fresher. This can only mean that freshwater is building up in the Arctic Ocean, and indeed this has been measured in a portion of the ocean called the Beaufort Sea. One day, perhaps from something as simple as a change in wind direction, that accumulated freshwater will likely flow into the northern North Atlantic. No one knows what that might do to the ocean conveyor system. Says Haine, “It’s a fascinating time to study the changing Arctic Ocean.