Northern Australians won't want to hear it this summer, when massive rainfall caused widespread flooding, but there seems to be a message coming from the massive mounds of Porites coral that scientists have been studying along the Great Barrier Reef. The message is: Get used to it.
A high-resolution reconstruction of rainfall patterns going back to the middle of the 17th Century shows that extreme rain events are becoming more frequent, according to climate scientist Janice Lough at the Australian Institute of Marine Science in Townsville, Queensland.
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Summers of heavy rainfall flush more material over near-shore corals that absorb more humid acid, a compound that causes their skeletons to more brightly luminesce under ultraviolet light, leaving a visible signal of heavy rains in their annual growth rings.
"These coral samples, which date from 1639 to 1981, suggest that the summer of 1973-74 was the wettest in 300 years," Lough said in a statement released by the American Geophysical Union, which will publish her study in an upcoming issue of the journal Paleoceanography. "This summer is now being compared with that record-settling one," she said. The current La Niña is the strongest it has been since 1974.
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Lough's reconstructed rainfall record, which dates back further than monitoring records for La Niña, shows that from about 1685 to 1784, wet years occurred on average every 12 years, and very dry years every nine. From 1785 to 1884, the frequency fell: very wet years occurred about every 25 years, and very dry years every 14. Between 1885 and 1981, however, the frequency of extremes increased dramatically, with very dry years taking place every 7.5 years, on average, and very wet years about once every three years.
IMAGE: A diver coring large Porites coral, Rowley Shoals, Western Australia. Credit: Eric Matson, Australian Institute of Marine Science
Tags: Climate Change, Corals, Floods, Meteorology, Oceanography
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