These included identifying tiny fragments of rock that Antarctic glaciers picked up as they scraped seaward over the continent’s surface. The scientists used multiple techniques to reconstruct past conditions. (Pierre Dutrieux/Lamont-Doherty Earth Observatory) Icebergs broken off and drifting far from the coast of Antarctica are key to the initiation of ice ages, says a new study. This causes the ocean to pull increased amounts of carbon dioxide from the atmosphere, reducing the so-called greenhouse effect, and pushing Earth into ice-age conditions. Then, as the Southern Ocean gets saltier and the North Atlantic gets fresher, global ocean circulation patterns change dramatically. This, in turn, shifts huge volumes of freshwater away from the Southern Ocean and into the Atlantic. In the new study, scientists from more than a dozen institutions propose that when Earth’s orbit is just right, icebergs broken off from the coasts of Antarctica drift further and further away from the continent before ultimately melting. However, the changes are relatively small, so it has been a mystery how they bring such dramatic shifts in climate. These cycles increase or decrease the amount of solar radiation that reaches the planet’s surface. Scientists have long agreed that repeated ice ages over millions of years have been paced by cyclic changes in Earth’s orbit around the sun. The findings were published this week in the journal Nature. According to the study, the icebergs introduced freshwater into certain areas of the ocean that triggered a series of chain reactions, culminating with Earth plunging into prolonged periods of cold. Large numbers of icebergs drifting unusually far from Antarctica before melting into ocean waters have been key to initiating ice ages of the past, says a new study.
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