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Wednesday, July 2, 2008

Ocean Sucking Up More Ozone than First Thought


Ozone_hole_2 The day that someone finally manages to create a climate model that accurately predicts the full range of planetary weather systems, I think we will probably be a hundred years too late. It is such a tough challenge, attempting to pin together the whole range of influences that go in to making our planets weather what it is.

More proof of this difficulty is found in a recent discovery by researchers working off the west-African coast of Cape Verde. What the researchers found has totally shifted the thinking concerning two types of greenhouse gases: ozone and methane.


The group found that 50% more ozone is being destroyed above the Atlantic Ocean than was previously thought. As a result, through the release of halogens from the seawater, 12% more methane is being chewed up as well.

"At the moment this is a good news story: more ozone and methane being destroyed than we previously thought," says Alastair Lewis of the National Center for Atmospheric Science in Leeds, UK. "But the tropical Atlantic cannot be taken for granted as a permanent sink for ozone. The composition of the atmosphere is in fine balance here."

Methane and ozone number 2 and 3 on the list of most important anthropogenic greenhouse gases, those created by man. However, once again heralding back to the inability to clearly predict what is happening to our weather systems, ozone has commonly been very imprecisely measured in terms of where and in what quantities it is being produced and subsequently removed.

This is not a surprise, considering that ozone is often found to be removed above tropical oceans, where the data is rare. This is why an international team, including Lewis, headed to the Cape Verde Atmospheric Observatory, located at 16.848N, 24.871W (use Google Earth), to be the first to use the Observatory for this purpose.

Ozone is known to be broken down largely by sunlight and water vapor, through the production of hydroxyl radicals, which then in turn remove the methane from the atmosphere. Other things, like iodine and bromine, are also known to break down ozone, and when the researchers plugged these two values in to their climate model they were better able to predict the decay of ozone in the region. The results point to the creation of an ozone sink created by these chemicals.

"It has come as a surprise to find these chemicals, not only in coastal regions with lots of iodine rich seaweed, but also in the middle of the Atlantic ocean," says Lewis. "We have no reason to think that our study area is different from other tropical ocean regions, so similar ozone destruction could be happening on a huge global scale," he added.

However we need to be careful not to change the balance, as it is very fine. "It will only take a small increase in nitrogen oxides from fossil fuel combustion, carried here from Europe, West Africa or North America on the trade winds, to tip the balance from a sink to a source of ozone," explains Lewis.

Posted by Josh Hill.

Original here

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