Oceans could be helping clean the atmosphere

Discussion in 'Earth Science' started by kmguru, Aug 16, 2002.

  1. kmguru Staff Member

    Oceans could be helping clean the atmosphere

    WASHINGTON (AP) — That refreshing breath of sea air may do more than raise the spirits. The world's oceans could be helping to clean the atmosphere, according to a study that says salty sea spray encourages rain that washes out dust and other pollutants.

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    Clouds form in pollution haze over the Indian Ocean

    "We have discovered a process by which nature apparently cleanses the ... air pollution quite effectively when it spills from land over to the oceans," said Daniel Rosenfeld of Hebrew University in Jerusalem.

    Practically all the pollutants are removed at the lower layer of the atmosphere, Rosenfeld said. That's one reason why the air in Hawaii is always so pristine, except during volcanic eruptions.

    It's the salt that does the trick, he added: "The conclusion stands that the air that we breathe near the surface remains clean because of the fact that the oceans are salty."

    Rosenfeld and his colleagues used satellite data to study the air over the Indian Ocean, where massive amounts of particles from burning, urban air pollution and desert dust are blown from southern Asia. Information on the haze particles, known as "aerosols," was collected by the U.S. National Oceanic and Atmospheric Administration research ship Ron Brown during a 1999 Indian Ocean research cruise.

    Rosenfeld stressed that effects seen over the Indian Ocean "are not unique to that part of the world."

    Nearly three-fourths of the Earth's surface is covered by water and the winds are constantly moving air from land onto the oceans and from the oceans onto land worldwide.

    Related items

    In other papers published by the American Association for the Advancement of Science this week:

    A team of British scientists reports finding a source of methyl and ethyl nitrates in the Atlantic Ocean. These compounds play an important role in regulating the amount of ozone in the atmosphere. It's not clear how the compounds were produced, but it's the first indication of an oceanic source for them, said team leader Adele L. Chuck of the University of East Anglia.

    Ariel D. Anbar and colleagues at the University of Rochester, N.Y., report that during the Proterozoic eon, 2.5 billion to 543 million years ago, the oceans were oxygenated only near the surface and contained sulfides in the deeper waters. They say that means primitive forms of cellular life probably could have lived only near shore where trace metals needed for nutrition were available.

    Rosenfeld's findings are reported in Friday's issue of Science Express, the Web edition of the Amereican Association for the Advancement of Science journal Science.

    "The paper presents an interesting point, which has not been discussed for some time," commented John N. Porter of the Hawaii Institute for Geophysics and Planetology.

    Porter said the idea of coarse sea salt initiating rainfall was proposed as early as the 1950s, but studies in the 1970s seemed to show it was not an important factor. Rosenfeld's work seems to support the earlier research, he said.

    Porter, who was not on Rosenfeld's team, said his own research indicated salt helped to increase rainfall in relatively clean air but was less effective in more polluted conditions.

    In his paper, Rosenfeld explained that tiny specks of air pollution can suppress rain by serving as nuclei on which moisture can condense. They form such tiny droplets that they can remain suspended in the air without falling. Slow upward movements of the air hold up tiny particles, which is why clouds float in the sky. Rain or snow fall when cloud drops or ice crystals grow big enough to fall though the rising air.

    When a cloud is made of many tiny drops, they might not grow large enough to begin falling.

    But the salt particles thrown into the air by sea spray are larger than the pollution particles. They attract water that forms into larger droplets. As these larger drops fall, they merge with the tiny ones, washing the pollutants out of the air.

    Rosenfeld said the research by him and three colleagues at Hebrew University began when Veerabhadran Ramanathan, one of the chief scientists of a U.N. study of Asia's "brown cloud" pollution "asked me what I think happens to the particles of the 'brown cloud' when it flows over the ocean."

    (Related story:Asian brown cloud may be changing weather.)

    When Rosenfeld looked at the clouds that formed in the polluted air over the ocean, they "to my surprise found out that these clouds readily precipitated ... in contrast to similar polluted clouds over land."

    Graham Feingold of the National Oceanic and Atmospheric Administration's Environmental Technology Laboratory in Boulder, Colo., was cautious about the the report.

    "We must bear in mind that only about one in every 100,000 particles is a giant particle capable of forming a small raindrop. Our current methods for measuring these particles, as well as other important parameters that determine precipitation formation, will have to be improved significantly before we can quantify the role of giant salt particles," Feingold said.

    If salty spray does help create rainfall over the ocean, could it also be used to increase rain in the desert, Rosenfeld was asked.

    "There is no reason why we can't do artificially over land what happens naturally over oceans. In fact, we have started in Israel an experiment of cloud seeding" using brine from the Dead Sea, he said in an interview via e-mail.

    However, Rosenfeld added, "Most deserts exist because of lack of clouds and moisture in the air. Where there are no suitable clouds, of course such methods are not going to help."

    Contributing: Jack Williams, USATODAY.com
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  3. Gifted World Wanderer Registered Senior Member

    Did you know the oceans also absorb CFCs? Let me explain.

    Water becomes saturated with CFCs at a very low concentration, so you might think that this wouldn't work. But, there is a lot of water in the oceans, and they can actually absorb quite a bit. enough in fact, to count.
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  5. kmguru Staff Member

    And you forgot to mention that CFCs are heavier than air - in case people think CFCs are like Helium.....

    We paid about $200 million to several Russian companies to stop producing CFCs so that they can license the newer FCs. I always thought that Fluorine is more reactive than Chlorine...what gives?
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  7. Thor "Pfft, Rebel scum!" Valued Senior Member

    Now this I understand. Seems like the ocean is the solution to all our problems, except drowning
  8. kmguru Staff Member

    even ocean is used for freedom....(boat people).....

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