Dust dumped on ocean floor impacts global climate

February 29th, 2008 - 6:30 pm ICT by admin  

Washington, Feb 29 (IANS) Nine hundred million tonnes of dust from deserts and land that is dumped into the ocean every year impacts global climate, but exactly how was for long a mystery. Researchers now claim to have found at least part of the answer. The quantity of dust entering equatorial Pacific peaked sharply during repeated ice ages and then declined when the climate warmed. Researchers have found that at the height of each of the five known ice ages, accumulation of the isotope thorium 232, a tracer for land dust, shot up 2.5 times over the level of warmer interglacial times, Sciencedaily.com reported.

These peaks appear about every 100,000 years, with the last one 20,000 years ago, culminating in the last glacial age. Through other isotopes, the scientists traced the dust on the western side to Asia and that on the eastern side to South America.

Now that all the records have been shown to coincide, “it suggests that the whole world hydrologic cycle varies in unison, on a pretty rapid time scale”, said Gisela Winckler, geochemist at Columbia University and co-author of the paper.

The dust probably helped make the climate even colder for a while, and this has implications for the current day, said Robert F. Anderson, another co-author.

Many types of dust transported at high altitudes tend to reflect sunlight, lowering the energy reaching earth, said Anderson. And, when it settles into the ocean, there could be an intriguing further effect.

Rich in the plant nutrient iron, the dust could have fertilised near-surface plankton on a massive scale.

A dozen early experiments in different regions have shown that plankton growth increases when iron is artificially added, but scientists have yet to show that this could lock significant amounts of carbon dioxide into the ocean.

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