AGU: Geophysical Research Letters

 

Editors' Highlight

Sea surface temperatures through time: A new sampling method for analyzing corals

Coral skeletons have tremendous potential as high-resolution archives of past ocean conditions, but interpretations of skeletal chemistry in terms of ocean temperature are complicated by physiological "vital effects" and complex growth strategies. As a result, different corals growing in the same location can yield a broad range of reconstructed temperatures. Cohen and Thorrold (2007) developed a new, potentially more accurate way to extract temperature data from corals. The authors noted that growth involves an initial extension (upward growth) of skeletal elements, followed by their subsequent thickening (outward growth). Upward growth is fast but thickening is slow, often taking many months to a year. They realized that current sampling methods that combine the initial and thickening growth result in highly variable chemical signatures among different corals. The authors analyzed two species of Atlantic corals, selectively targeting the fast growing region at the centers of the skeletal elements. This method yielded similar temperature records from different colonies and different species. Using this approach, corals dating back to the late eighteenth century around Bermuda revealed SSTs about 1°C cooler than today.

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