Corals Indicate Warming Pattern




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RWTH researcher Miriam Pfeiffer publishes research in Scientific Reports.

"Over the course of the 20th century, the western Indian Ocean has warmed faster than any of the other tropical oceans. This immensely contributes to the global rise of the sea temperature," says Dr. Miriam Pfeiffer from the RWTH Aachen Institute of Geology. In her work she focuses on man-induced global warming of the 20th century.

"However the temporal pattern of this warming is not well documented. It depends a great deal on the respective historical temperature reconstruction," explains the scientist. All of the data up until now has derived from the International Ocean-Atmosphere Dataset. It is the only archive with instrumental measurements of sea temperatures based in large part on ship data. The temperature of the oceans along commercial ship routes has been measured in different ways since the 1850s. "It is not easy to determine which data reflect the temperature change the best. Different measurement methods, such as with special buckets or thermometers installed in the engine coolant influx of the engine room, cause slightly deviating results. These must be elaborately corrected. Thus, we need independent data, which can be obtained from corals, among other sources," says Pfeiffer.

Ten Years of Research

For ten years the 45-year-old has researched tropical corals to learn about climate change. She has already recorded numerous measurements, where she independently drilled out coral cores during dives. A very gentle method was specifically developed to achieve this without damaging the coral colonies. Miriam Pfeiffer conducted the current measurements on the drilled cores of living astroides from the porites genus, which she obtained on the Seychelles and Chagos Archipelago. Using the cores she created a new, independent reconstruction of the temperature for the western Indian Ocean. To achieve this she used the geochemical composition of the coral skeleton, which clearly prove temperature fluctuations over many decades.

The results show that systematic measurement errors during World War II caused the differences in the temperature reconstructions. "This affects the calculated warming trend of the Indian Ocean and the global mean temperatures during the 20th century," says Pfeiffer. At the same time this is a strong signal, as it answers the question to an important climate process: how has the atmosphere reacted to the increase in seawater temperature? "My measured data contributes to our ability to use and evalute the correct temperature product, which can then be used for further model simulations of the future climate. The results also show that some areas of the tropics, such as the Seychelles and Chagos Archipelago, are particularly suited for investigating global warming."

Source: Press and Public Relations

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