Ocean Sciences Research Spotlight

Notorious Ocean Current Is Far Stronger Than Previously Thought

The Antarctic Circumpolar Current is the only ocean current to circle the planet and the largest wind-driven current on Earth. It's also 30% more powerful than scientists realized.

Source: Geophysical Research Letters

By Emily Underwood

Notorious among sailors for its strength and the rough seas it creates, the Antarctic Circumpolar Current (ACC) is the largest wind-driven current on Earth and the only ocean current to travel all the way around the planet. Now, researchers have found that the current transports 30% more water than previously thought. The revised estimate is an important update for scientists studying how the world’s oceans will respond to a warming climate.

The ACC transports massive amounts of water between the Atlantic, Indian, and Pacific oceans in an eastward loop. Just how much water has long been uncertain, however, because of the difficulty and expense of accurately measuring its flow.

Researchers measure the strength of the Antarctic Circumpolar Current
A working day aboard research vessel and ice breaker N. B. Palmer. All hands concentrate as a current- and pressure-recording inverted echo sounder (CPIES) is deployed off the working deck into the Antarctic Circumpolar Current to begin its 4-year measurement mission at the seafloor in Drake Passage. Credit: T. Chereskin

For the new study, Donohue et al. installed gauges along the bottom of Drake Passage, spanning an 800-kilometer passage between Cape Horn and the South Shetland Islands of Antarctica. Housed in glass spheres and spaced between 30 and 60 kilometers apart along a line near the seafloor, the gauges included pressure sensors, floating current meters attached by 50-meter tethers, and instruments that measure acoustic travel time from the seafloor to the sea surface.

The classic estimate used for the ACC’s transport is 134 sverdrups (Sv). One sverdrup is equivalent to 1 million cubic meters per second. Using 4 years of data collection from 2007 to 2011, the researchers found that the transport rate was 30% higher than historical estimates, around 173.3 Sv. Although it’s possible that stronger winds in the Southern Ocean over the past few decades may have caused the increase, satellite-based studies showing that transport has remained fairly steady during this time suggest that improved measurement tools, not increased wind, are responsible for the discrepancy. (Geophysical Research Letters, doi:10.1002/2016GL070319, 2016)

—Emily Underwood, Freelance Writer

Citation: Underwood, E. (2016), Notorious ocean current is far stronger than previously thought, Eos, 97, https://doi.org/10.1029/2016EO064319. Published on 27 December 2016.
© 2016. The authors. CC BY-NC-ND 3.0
  • Gord Marsden

    And all the oil in the world is 169 m3 /sec . Or one millionth the circulation of this current. Going to be difficult to heat up even with a burner

    • Pierre Martin-Cocher

      Even if the burner is the sun? think harder.

      • Gord Marsden

        Burn all the oil reserves in the world in an instant in an imaginary burner on the bottom of the Pacific Ocean and you can’t raise the temp by 0.5 degree. If you think the CO2 effect Is more than the direct energy released think harder. At cretateous times CO2 was 30000ppm .it’s 400 now.

        • Pierre Martin-Cocher

          You ought to communicate your findings in a paper, so as to educate the rest of us poor morons…

          • Pierre Martin-Cocher

            seriously, what are your sources? 30,000 ppm? that is just ludicrous.

        • mark conley

          good thinking Gord,
          just as well all the life forms extant today weren’t around 65,000,000 years ago then

          • Gord Marsden

            But life can survive. My sources are test amber air bubbles. CO2 at the Devonian was 70000 ppm also very life sustainable.

    • Its not the heat from the oil or the coal but the CO2 that it produces which traps the suns heat. But I expect you know that.

      • Gord Marsden

        I do. But you can do the experiment . Burn a bit of any hydrocarbon in a sealed vessel in the sun. The same vessel with hydrocarbon unburnt beside it.also in the sun what they call the base line . The burn causes way more heat than the sunshine.
        About 100 times more +/-. Therefore. If you can heat it with direct energy you can’t heat it with greenhouse effect. But you figured that out yourself I know

        • pgardner

          What you are saying makes no sense.
          You burn the fuel and the heat is gone within minutes but the CO2 and its warming effect linger in the atmosphere for decades. Ironically, before emission controls on cars and factories, the warming effect of CO2 was largely masked by the cooling effect of soot. Of course, the soot was killing people so we sensibly got rid of it. Now we are left with the CO2 problem.

          • Gord Marsden

            Decades. Nay nay. Plants and algae eat it .soon as it drifts by. And it’s 400 ppm up from 300 ppm. It was 30000 at the time of mammals. It’s been dropping since. And the heat doesn’t last seconds. You need to check your heat Flux equations

  • Markon

    Emily, would the information gained not help understand how the oceans would respond to a cooling climate as well, or is your bias showing?