First direct evidence of ocean mixing across the gulf stream

University of Maryland researcher discovers important ocean blender effect that may influence climate and fisheries from Florida to Newfoundland

University of Maryland

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IMAGE: The “Triaxus ” towing platform breaks through the choppy surface of the ocean during a storm. By towing such a platform with monitoring instruments through the water, changing its depth in… view more  Credit: Photo credit Craig M. Lee, UW APL

New research provides the first direct evidence for the Gulf Stream blender effect, identifying a new mechanism of mixing water across the swift-moving current. The results have important implications for weather, climate and fisheries because ocean mixing plays a critical role in these processes. The Gulf Stream is one of the largest drivers of climate and biological productivity from Florida to Newfoundland and along the western coast of Europe.

The multi-institutional study led by a University of Maryland researcher revealed that churning along the edges of the Gulf Stream across areas as small as a kilometer could be a leading source of ocean mixing between the waters on either side of the current. The study was published in the Proceedings of the National Academy of Sciences on July 6, 2020.

“This long-standing debate about whether the Gulf Stream acts as a blender or a barrier to ocean mixing has mainly considered big ocean eddies, tens of kilometers to a hundred kilometers across,” said Jacob Wenegrat, an assistant professor in UMD’s Department of Atmospheric and Oceanic Science and the lead author of the study. “What we’re adding to this debate is this new evidence that variability at the kilometer scale seems to be doing a lot of mixing. And those scales are really hard to monitor and model.”

As the Gulf Stream courses its way up the east coast of the U.S. and Canada, it brings warm salty water from the tropics into the north Atlantic. But the current also creates an invisible wall of water that divides two distinct ocean regions: the colder, fresher waters along the northern edge of the Gulf Stream that swirl in a counterclockwise direction, and the warmer, saltier waters on the southern edge of the current that circulate in a clockwise direction.

How much ocean mixing occurs across the Gulf Stream has been a matter of scientific debate. As a result, ocean models that predict climate, weather and biological productivity have not fully accounted for the contribution of mixing between the two very different types of water on either side of the current.

To conduct the study, the researchers had to take their instruments to the source: the edge of the Gulf Stream. Two teams of scientists aboard two global-class research vessels braved winter storms on the Atlantic Ocean to release a fluorescent dye along the northern front of the Gulf Stream and trace its path over the following days.

The first team released the dye along with a float containing an acoustic beacon. Downstream, the second team tracked the float and monitored the concentration of dye along with water temperature, salinity, chemistry and other features.

Back on shore, Wenegrat and his coauthors developed high-resolution simulations of the physical processes that could cause the dye to disperse through the water in the manner the field teams recorded. Their results showed that turbulence across areas as small as a kilometer exerted an important influence on the dye’s path and resulted in significant mixing of water properties such as salinity and temperature.

“These results emphasize the role of variability at very small scales that are currently hard to observe using standard methods, such as satellite observations,” Wenegrat said. “Variability at this scale is not currently resolved in global climate models and won’t be for decades to come, so it leads us to wonder, what have we been missing?”

By showing that small-scale mixing across the Gulf Stream may have a significant impact, the new study reveals an important, under-recognized contributor to ocean circulation, biology and potentially climate.

For example, the Gulf Stream plays an important role in what’s known as the ocean biological pump–a system that traps excess carbon dioxide, buffering the planet from global warming. In the surface waters of the Gulf Stream region, ocean mixing influences the growth of phytoplankton–the base of the ocean food web. These phytoplankton absorb carbon dioxide near the surface and later sink to the bottom, taking carbon with them and trapping it in the deep ocean. Current models of the ocean biological pump don’t account for the large effect small-scale mixing across the Gulf Stream could have on phytoplankton growth.

“To make progress on this we need to find ways to quantify these processes on a finer scale using theory, state-of-the-art numerical models and new observational techniques,” Wenegrat said. “We need to be able to understand their impact on large-scale circulation and biogeochemistry of the ocean.”

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The field research was conducted from the University-National Oceanographic Laboratory System vessels R/V Knorr and R/V Atlantis and was supported by the Scalable Lateral Mixing and Coherent Turbulence Departmental Research Initiative of the Office of Naval Research. The content of this article does not necessarily reflect the views of these organizations.

In addition to Wenegrat, co-authors of the study included researchers from Stanford University, University of Massachusetts, Dartmouth, University of Cambridge, University of Washington, University of Victoria and Oregon State University.

The research paper, “Enhanced mixing across the gyre boundary at the Gulf Stream front,” Jacob O. Wenegrat, Leif N. Thomas, Miles A. Sundermeyer, John R. Taylor, Eric A. D’Asaro, Jody M. Klymak, R. Kipp Shearman, and Craig M. Lee, was published in the July 6, 2020 issue of the Proceedings of the National Academy of Sciences.

From EurekAlert!

29 thoughts on “First direct evidence of ocean mixing across the gulf stream

  1. The Gulf Stream is one of the largest drivers of climate and biological productivity from Florida to Newfoundland and along the western coast of Europe.

    Concerning climate, it’s not just the west coast of Europe, the effect goes far inland from there.

  2. Is it possible these days to read a scientific article WITHOUT CO2 getting popped into verbiage somewhere?

  3. Key phrase..
    ““What we’re adding to this debate is this new evidence that variability at the kilometer scale seems to be doing a lot of mixing. And those scales are really hard to monitor and model.”

    More problems for getting a model to capture the massive complexity of the climate system. Like the clouds.
    Mixing of two liquid streams, with flow gradients, temperature and salinity gradients, all subject to turbulence makes computation difficult if not impossible.

    And yet based on these models, we should destroy our energy infrastructure and hobble the economy? Sorry, not reliable enough, the models are just tools to enforce a socialist agenda.

    • The instrument/dye “platform” was towed, “changing its depth in a ‘yo-yo’ pattern as it traveled”.

      This makes me wonder how much such churning effected the mixing they were trying to study.
      As has been realized many times, it is impossible to observe or measure something without changing it.

      • The churning they were measuring was 100’s of meters to several kilometers across. The sled in the picture looks to be a meter or two across.

      • AndyHce – July 7, 2020 at 1:11 pm

        This makes me wonder how much such churning effected the mixing they were trying to study.

        Andy, I really don’t think that “churning” of the water affected their testing one iota, but winter storms would severely have. To wit:

        Two teams of scientists ….. braved winter storms on the (northern edge of the Gulf Stream) Atlantic Ocean ……. to release a fluorescent dye along the northern front of the Gulf Stream and trace its path over the following days.

        • This was my thought. It is a very interesting experiment and likely providing useful new insights. That said, the winter storm conditions may be yielding very different measurements than if they did this during calmer, warmer weather. More refined laminar flow versus turbulent flow might well be partly weather dependent.

  4. “The gulfstream…buffering the planet against global warming.” Enough already, we are freezing in Argentina and Chile, snowpack already twice normal, can’t play golf, and corona virus pandemic/panic enjoying the weather. Stop the Gulfstream before it is too late! Sorry England. This study is about funding the obvious. Try something hard.

  5. Having been in the ocean in such turmoil handling mechanical stuff, even at night, I wondered how much the Triaxus affects eddy diffusion?

  6. They actually measured something.
    I trust they will all be immediately drummed out of the Cult of Calamitous Climate.
    Measurements?
    How dare you!
    Now if these researchers practice the scientific method,we all stand to learn more about this planet ,but of the Climatology dominates their careers we will see them suffer,cause the “Science is settled” even though it is apparent we do not know so much of what we need to.

    I wonder if the same information is available from those fishing the area?
    The same effects should effect the fishery in notable ways.
    Which might allow one to judge if the claimed effect is real or illusionary.

    Given the current state of affairs,I next expect a “It’s worse than we ever knew” Ozone Hole type fiasco.
    Has Climatology made me too cynical?

  7. Isn’t this study just stating the obvious? The boundaries of the Gulf Stream have to be mixing with waters not in the stream.

  8. For those going fishing in the Gulf Stream off Hatteras or Morehead City, North Carolina the transition of crossing from the inshore waters to the Gulf Stream waters is stark, especially in the fall and winter months. You go from greenish to greenish-blue waters into tropical waters in a matter of a couple of hundred feet and the air temperature can go up 25 degrees F.

    The fish also changes from colder water to tropical fish. You can fish for tuna and mackerel on one side and blue marlin or Mahi Mahi on the other. The warm water of the GS is fairly deep at this point and it is moving at a really good clip. The wave action if the wind is blowing into the current can be really tough to navigate through. The mixing of the two isn’t that obvious just looking from your boat crossing the boundary. At times it looks almost like a wall between the cold and the warm water. I would say the authors of the paper have brought some good information to us.

    • “You go from greenish to greenish-blue waters into tropical waters in a matter of a couple of hundred feet and the air temperature can go up 25 degrees F.”

      Europeans imagine they are too warm due to global warming, why not divert some of this warm water to New York State- they would probably enjoy it in the winter.

    • “The wave action if the wind is blowing into the current can be really tough to navigate through.” Boy… I’ll say. Several years ago a friend in a 33′ Nonsuch followed me across the Stream in a Northeast fresh breeze. He took a picture of my 44ft Cutter sitting perfectly level on top of one of those 8ft square waves with prop and rudder hanging off one side and the bow hanging off the other. You’re right, navigating the Stream with an opposing wind can get interesting.

  9. A little robot called the Wave Glider by Liquid Robotics could possibly collect the data much cheaper….but why? Why keep spending on models? Why not spend a few dollars on whether CO2 made by man is really a villain? Oh, that might end the climate model gravy train?

  10. I didn’t read anything about the depth that they studied/modeled. Perhaps I missed it.

  11. I think this is important work, but not because of Gulfstream mixing per se. Because it is yet another demonstration of the importance of small scales in fluid dynamics. Like Eschenbach’s TStorms thermoregulatory hypothesis here, or Lindzen’s adaptive infrared iris.

    As guest commented before, the CFL constraint computational intractability of these important small scales means climate models MUST be parameterized cor stuff like Gulf Stream mixing. That requires parameter tuning and back validation via hindcasting, and that drags in the Natural/anthropogenic attribution problem.

    So the resulting models forecast junk as illustrated by the modeled but observationally missing tropical hot spot.

  12. More playtime for the daydreamers.

    “Back on shore, Wenegrat and his coauthors developed high-resolution simulations of the physical processes that could cause the dye to disperse through the water in the manner the field teams recorded. …

    By showing that small-scale mixing across the Gulf Stream may have a significant impact”

    From some “recordings” through simulations, small Gulf Stream mixings are ???
    Yeah, right.

  13. “Current models of the ocean biological pump don’t account for the large effect small-scale mixing across the Gulf Stream could have on phytoplankton growth.”

    Well if the models are wrong, they obviously need to correct the data. Duh.
    That’s Climate Dowsing 101 level stuff.

  14. Hey cool, someone decided to go in 2 boats (very expensive), drop some measuring tools and observe the results!

    YEA SCIENCE!

    “running high resolution simulations”, why not run high resolution charts of your results? What nobody can figure out how to run a simply matplot?

    I’m not going into the entirety of the oversimplification of currents nor of plankton the author in this article makes–I just can’t….because the ocean is not simple. And the author totally forgot about the other currents in the N. Atlantic that contribute to the climate as well….classifying them as all “running clockwise”…um no. ..lots more to that bud.

  15. From the article: “By showing that small-scale mixing across the Gulf Stream may have a significant impact, the new study reveals an important, under-recognized contributor to ocean circulation, biology and potentially climate.”

    “May have”

    And of course, they had to get in the Human-caused climate change link to get paid/published.

    This study tells us more about what we don’t know than what we do know.

    As they say in the study: ““Variability at this scale is not currently resolved in global climate models and won’t be for decades to come, so it leads us to wonder, what have we been missing?”

    I would say they have been missing a lot of things. And probably will for sometime to come.

  16. Progress in climate especially ocean mixing will begin when the dominance of nonlinear chaotic dynamics are appreciated. After all the alternatives are exhausted, of course. This study is a step in the right direction.

  17. I wonder where Ben Franklin’s temperature data is that he was “recording” when he was studying the Gulf Stream?

    It would be interesting to compare Ben’s GS water temperatures ….. with 21st Century GS water temperatures.

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