Giant clams tell the story of past typhoons
A highly precise method to determine past typhoon occurrences from giant clam shells has been developed, with the hope of using this method to predict future cyclone activity.
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The whole Tridacna maxima valve. The shell was cut in two sections along the maximum growth axis [Credit: Komagoe T. et al., 2018] |
With the global warming of the climate, scientists are concerned that major tropical cyclones such as typhoons and hurricanes will increase. To better predict the frequency of these weather patterns, understanding typhoons in the past warmer periods of Earth's history is particularly important.
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Enlarged image of the shell edge showing a stripe pattern of growth increments. Geochemical analysis of increments reveals the clam's paleoenvironment [Credit: Komagoe T. et al., 2018] |
Live specimens were sampled from the waters surrounding Okinotori Island, which lies in the middle of a common path taken by typhoons before making landfall in Japan and other parts of Asia. The team analyzed the shell growth increment of each year, measuring its thickness, stable isotope ratio, and the barium/calcium ratio. They then compared the data with the past environmental records such as typhoons and water temperatures.
"Since microstructural and geochemical features are well preserved in giant clam fossils, it may now be possible to reconstruct the timing and occurrence of past typhoons to a level of accuracy that was previously impossible," says Tsuyoshi Watanabe of Hokkaido University.
The findings are published in the Journal of Geophysical Research: Biogeosciences.
Source: Hokkaido University [May 24, 2018]
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