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  • Pat Neuman
    This image shows the oceans and continents that surround Antarctica. The tip of South America is on the upper left, the tip of Africa is at the upper right and
    Message 1 of 1 , Dec 5, 2006
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      This image shows the oceans and continents that surround Antarctica.
      The tip of South America is on the upper left, the tip of Africa is at
      the upper right and Australia is at the bottom right. The ocean colors
      indicate temperature, with the darkest blue indicating the coldest
      water. The black arrows show the direction the Southern Hemisphere
      westerly winds and the Antarctic Circumpolar Current take as they
      swirl around the southernmost continent. Copyright 2006 Paul J.
      Goodman, The University of Arizona.
      Southern Ocean Could Slow Global Warming
      by Staff Writers
      Tuscon AZ (SPX) Dec 06, 2006
      The Southern Ocean may slow the rate of global warming by absorbing
      significantly more heat and carbon dioxide than previously thought,
      according to new research.
      The Southern Hemisphere westerly winds have moved southward in the
      last 30 years. A new climate model predicts that as the winds shift
      south, they can do a better job of transferring heat and carbon
      dioxide from the surface waters surrounding Antarctica into the
      deeper, colder waters.

      The new finding surprised the scientists, said lead researcher Joellen
      L. Russell. "We think it will slow global warming. It won't reverse or
      stop it, but it will slow the rate of increase."

      The new model Russell and her colleagues developed provides a
      realistic simulation of the Southern Hemisphere westerlies and
      Southern Ocean circulation.

      Previous climate models did not have the winds properly located. In
      simulations of present-day climate, those models distorted the ocean's
      response to future increases in greenhouse gases.

      "Because these winds have moved poleward, the Southern Ocean around
      Antarctica is likely to take up 20 percent more carbon dioxide than in
      a model where the winds are poorly located," said Russell, an
      assistant professor of geosciences at The University of Arizona in Tucson.

      "More heat stored in the ocean means less heat stored in the
      atmosphere. That's also true for carbon dioxide, the major greenhouse

      "But there are consequences," Russell said. "This isn't an unqualified
      good, even if more carbon dioxide and heat goes into the ocean."

      As the atmosphere warms, storing more heat in the ocean will cause sea
      levels to rise even faster as the warmed water expands, she said.
      Adding more CO2 to the oceans will change their chemistry, making the
      water more acidic and less habitable for some marine organisms.

      Russell and her colleagues conducted the study while she was a
      researcher at Princeton University and the National Oceanic and
      Atmospheric Administration's Geophysical Fluid Dynamics Laboratory in
      Princeton, N.J.

      Her co-authors on the article, "The Southern Hemisphere Westerlies in
      a Warming World: Propping open the Door to the Deep Ocean," are GFDL
      researchers Keith W. Dixon, Anand Gnanadesikan, Ronald J. Stouffer and
      J.R. Toggweiler. The article will be published in the December 15
      issue of the Journal of Climate. NOAA funded the work.

      The researchers characterize the Southern Ocean as "the crossroads of
      the global ocean's water masses, connecting the Atlantic, Pacific and
      Indian Oceans as well as connecting the deep ocean to the surface."

      The current set of computer models that scientists use to predict
      future climate differ in the degree to which heat is sequestered by
      the Southern Ocean. The models vary in how they represent the behavior
      of the Southern Hemisphere Westerlies and the Antarctic Circumpolar
      Current, the largest current on the planet.

      The team's model does a better job of depicting the location and
      observed southward shift of the Southern Hemisphere atmospheric winds
      than do previous global climate circulation models. The new model
      developed at GFDL shows that the poleward shift of the westerlies
      intensifies the strength of the winds as they whip past the tip of
      South America and circumnavigate Antarctica.

      "It's like a huge blender," Russell said as she held up a globe and
      demonstrated how the winds whirl around the southernmost continent.
      Those winds, she said, propel the Antarctic Circumpolar Current. The
      current drives the upwelling of cold water from more than two miles
      deep. The heavy, cold water comes to the surface and then sinks back
      down, carrying the carbon dioxide and heat with it.

      The new model forecasts this shift in the winds will continue into the
      future as greenhouse gases increase.

      Stouffer said, "The poleward intensification of the westerlies will
      allow the ocean to remove additional heat and anthropogenic carbon
      dioxide from the atmosphere. Thus, the deep ocean has the potential to
      slow the atmospheric warming through the increased storage of heat and

      The team's next step will be figuring out how warming, ice-melt and
      ongoing shifts in the Southern Hemisphere westerlies will affect the
      biogeochemistry of the Southern Ocean and the global budgets for heat
      and carbon dioxide.

      Related Links
      University of Arizona
      Geophysical Fluid Dynamics Laboratory
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