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Mysterious ocean currents

  1. Apr 16, 2008 #1

    wolram

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    From EurekAlert, 16 April.

    Mysterious striped currents in our oceans
    IT’S amazing that nobody has spotted it before. Superimposed on every ocean on the planet there is a striped pattern of currents. Yet what causes them is a mystery.

    Between 1992 and 2003, Peter Niiler of the Scripps Institution of Oceanography in San Diego, California, and colleagues collected data from more than 10,000 drifting ocean buoys, which they tracked with satellites. As expected, the buoys’ movements were influenced mainly by known global currents, which are driven by wind and by differences in the temperature and salinity of seawater.

    But when the team analysed the data, it emerged that something else had been subtly influencing the buoys’ paths. It turned out that there were alternating strips of water running eastward or westward, a bit like parallel moving sidewalks. Niiler recalls his reaction: “My God, we’ve never seen these before.”

    Satellite measurements showed that the interfaces between adjacent currents were alternately associated with slight peaks and troughs in sea level. When the team looked at this variation globally, they found that the 150-kilometre-wide bands covered pretty much every ocean (see Map).

    To confirm that the currents were real, the team set out to measure them directly in two regions in the eastern Pacific. “Their existence is so surprising that we had to prove first that they are not an artefact of satellite data,” says Nikolai Maximenko of the University of Hawaii. Sure enough, they recorded currents flowing in opposite directions at around 40 metres per hour (Geophysical Research Letters, DOI: 10.1029/2008GL033267). This is slower than most previously known ocean currents, which may explain why the striped flows have remained undiscovered until now. “Only a very lazy canoeist would notice the effect,” says Maximenko.

    The flows extend right down to the ocean floor, and the boundaries between currents are alternately associated with peaks and troughs in temperature as well as sea level. This suggests that they influence processes such as nutrient and energy flow around the oceans, but this has yet to be proven, says Niiler.

    What causes the striped flows remains a puzzle. “They are a fascinating new aspect to the ocean’s circulation, but the jury is still out on the mechanisms leading to their formation,” says Geoff Vallis of the Geophysical Fluid Dynamics Laboratory at Princeton University.

    He points out that similar patterns exist in atmospheric flows on other planets, for example, Jupiter. Whether similar effects are at play here is unclear, he says.
     
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  3. Apr 16, 2008 #2

    DaveC426913

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  4. Apr 16, 2008 #3

    wolram

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  5. Apr 17, 2008 #4

    matthyaouw

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    Interesting find! thanks for posting it.
     
  6. Apr 21, 2008 #5

    AHJ

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    Niiler Striations and Global CO2 Models

    Niiler has been busting his buns getting these physical measurements accomplished over twenty years using drifter buoys largely designed by himself. There are hundreds of his buoys all over the oceans. The hard data from his drifters is the only source of the primary data behind these conclusions, although they have been enhanced with larger resolution satellite-derived data points; and he deserves great credit for this. Without these measurements this pattern of striated currents would never have been deduced. And they could completely shift our understanding of the planet's fluid dynamics.

    For one thing the Niiler striations demonstrate that none of our models of ocean circulation are sufficiently accurate, as none of them predicted the Niiler striations even though all the major ones (a dozen or more) agree on accurately modeling temperature and salinity observations. The measurements Niiler brought in, integrated with satellite observation values, have produced previously invisible phenomena that have important implications for our understanding of the whole atmospheric/oceanic fluid system. Previous models --because of this-- have been revealed as wanting in some important way.

    But it is on these inaccurate models that most of our intricate analyses of global warming and CO2 build up are built. It is possible that the ocean currents he has dexcribed have very different effects in their scrubbing of CO2 than previously estimated. The Niiler striation patterns run deep, and the up-welling and down-welling in these bands may have important effects on the CO2 cycle.

    I believe when the full impact of Niiler's long, underappreciated efforts on physical measurement of these currents is seen clearly, it may be colossal. In any case it should be appreciated as the important contirbution it is.
     
  7. Apr 21, 2008 #6

    wolram

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    Thank you AHJ, your post is much appreciated.
     
  8. Apr 22, 2008 #7

    wolram

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    I have been around the net looking for more info on this with no luck
    Any body know what over all effect this could have?

    For one thing the Niiler striations demonstrate that none of our models of ocean circulation are sufficiently accurate, as none of them predicted the Niiler striations even though all the major ones (a dozen or more) agree on accurately modeling temperature and salinity observations. The measurements Niiler brought in, integrated with satellite observation values, have produced previously invisible phenomena that have important implications for our understanding of the whole atmospheric/oceanic fluid system. Previous models --because of this-- have been revealed as wanting in some important way.
     
  9. Apr 24, 2008 #8

    AHJ

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    Official Scripps Release on Niiler Striations

    The official Scripps Istitute release can be found at scrippsnews.ucsd.edu/.

    Regards,

    AHJ
     
  10. Apr 24, 2008 #9

    LURCH

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    As these currents are in alternating bands in opposite directions, wuold they have any net effect on energy transportation on the large-scale?
     
  11. Apr 24, 2008 #10

    AHJ

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    An excerpt:

    "In portions of the Southern Ocean, these striations-also known as ocean fronts-produce alternating eastward and westward accelerations of circulation and portions of them nearly circumnavigate Antarctica. These striations also delineate the ocean regions where uptake of carbon dioxide is greatest. In the Atlantic Ocean, these flows bear a strong association to the Azores Current along which water flowing south from the North Atlantic circulation is being subducted. The spatial high-resolution view of the linkage between the striations and the larger scale patterns of currents could improve predictions of ocean temperatures and hurricane paths.

    In addition, the striations are connected to important ecosystems like the California and Peru-Chile current systems. Off California, the striations are linked to the steady east-west displacements, or meanders, of the California Current, a major flow that runs from the border of Washington and Oregon to the southern tip of Baja California. The striations run nearly perpendicular to the California Current and continue southwestward to the Hawaiian Islands.

    Niiler said there are a number of scientists who have theorized the existence of striations in the ocean. He was the first to formulate such a theory as a postdoctoral researcher at Harvard University in 1965. Niiler's theory today is that the steady-state striations in the eastern North Pacific are caused by the angular momentum of the swirling eddies within the California Current System. "

    It seems to me that we are looking at a larger net deployment of energy than we envisioned under the earlier model of coherent wide rivers of flow, especially because I believe these Niiler currents run deeper than previously imagined -- 2300 feet or more. That's a lot of tonnage, and making a SWAG, I would say a greater volume of ongoing displacement than was previously thought.

    A

    AHJ
     
  12. Jun 10, 2008 #11
    These ocean stripes could be caused by sea water being heated at the mid-ocean ridges which also have a stripey layout of alternating cracks and projections.
    -perhaps more heating where there are cracks and less where there are no cracks.
    The water would cool,roll down the ridge slopes and pick up speed eventually hitting the continental shelves and rising to the surface.In the atlantic ocean water moving east along the seafloor would surface and come back on the surface of the atlantic in a westerly direction.Water moving west along the seafloor would do the opposite.
     
  13. Jun 10, 2008 #12

    matthyaouw

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    Surely they'd coincide with the ocean ridges in some way if that were the case?
     
  14. Jun 12, 2008 #13
    They are parallel to the cracks in many of the ocean ridges - that's for sure.
     
  15. Jun 12, 2008 #14

    matthyaouw

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    Looking at the map here they seem to run east or west entirely independant of the direction the ridges run.
     
  16. Jun 12, 2008 #15
    As the earth rotates those stripes that aren't already in a west-east alignment will become east-west aligned because of the coriolis effect.
     
  17. Jun 12, 2008 #16
    As the earth rotates those stripes that aren't already in a west-east alignment will become east-west aligned because of the coriolis effect.The stripes move 30 - 40 times more slowly than large ocean currents and so a north or south moving stripe will turn east or west in a far smaller distance - hence stripes around antarctica are east-west close to antarctica.
     
    Last edited: Jun 12, 2008
  18. Jun 13, 2008 #17

    matthyaouw

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    Why do some run east and some west then?
     
  19. Jun 13, 2008 #18
    Stripes heading north will be deflected to the west and stripes heading south will be deflected to the east.This is what the coriolis effect does.Also you don't need a continental shelf for a warm current of sea water at the bottom of the ocean to bump into and rise up against to the surface - a wall of colder more dense water will give the same result and there is plenty of descending cold water ( part of the global conveyor) sinking off the antarctic coast to provide this wall.
     
  20. Jun 13, 2008 #19

    DaveC426913

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    I am not convinced it is this simple. It's not like the stripes are bodies of cohesively moving water such that they could be deflected. The stripes are abstractions that represent water with differing properties.
     
    Last edited: Jun 13, 2008
  21. Jun 13, 2008 #20
    The stripes are not abstractions because they have velocities of 1.5 cm per second.
    If you travelled on the gulf stream northwards you would find yourself drifting slowly east on an eastward moving stripe at 1.5 cm per second.The man who discovered the stripes himself invoked a concept that includes velocity -angular momentum -to explain the stripes.
     
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