When climate scientists look to the future to determine what the effects of climate change may be, they use computer models to simulate potential outcomes such as how precipitation will change in a warming world.Examining samples from corals in the Great Barrier Reef, the researchers discovered between 1750 and present day, as the global climate warmed, wet-season rainfall in that part of the world increased by about 10%, and the rate of extreme rain events more than doubled.
As the corals are bathed in this freshwater outflow, they pick up geochemical signals from the river and record them into their carbonate skeletons. The core samples of the corals display faint bands of lighter and darker material. These bands reflect each rainy and dry season the coral lived through. The bands also hold information about the climate in each season, just as trees' rings record climate patterns during the years it grows.
The coral core was taken from a remote region off northeastern Queensland by the Australian Institute of Marine Science. The land surrounding the river watershed is also in a protected area, meaning that nutrients and sediment flushed into the river by rains are unlikely to be generated by human activity.
The researchers also measured how much of the element barium is contained in each of the bands. The coral skeleton is composed of calcium, but when barium is deposited onto the skeleton, it can replace calcium. The more barium detected in the band, the more river discharge was flowing over the coral.
Because the coral record is located off northeastern Australia, the researchers wanted to understand if the whole of Australia experienced similar rainfall. Looking at instrumental rainfall records across Australia, the researchers found that the increased rainfall patterns did not occur evenly across Australia.
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Fonte: physorg_com - 🏆 388. / 55 Leggi di più »