An ensemble approach to reconstructing mid-20th century climate using young fossil corals: pitfalls and opportunities

The tropical Pacific is characterized by a rich spectrum of interannual to decadal-scale climate variability, and has played a key role in shaping the response of global surface temperature to greenhouse forcing, especially evident in the last decade [e.g. Kosaka and Xie, 2013]. However, instrumental records of tropical Pacific temperature and precipitation are sparse prior to the satellite era that began in the late 1970’s. Here we investigate the potential of using an “ensemble” of fossil Porites coral samples with U/Th dates that fall in the mid 20^th century to constrain temperature and hydrological conditions during this time. By comparing our ensemble of fossil coral d¹⁸O and Sr/Ca records to instrumental records of temperature, precipitation, and salinity over the study interval, as well as to long, continuous modern coral d¹⁸O and Sr/Ca records, we quantify the uncertainties of the fossil coral “ensemble” approach. Our findings illustrate that the fossil coral “ensemble” approach holds promise for compiling similar reconstructions during periods in the distant past, when direct observations of tropical Pacific climate are extremely scarce. Collectively, our new dataset will provide a useful benchmark for such reconstructions, including much-improved estimates of the uncertainties associated with fossil-coral based reconstructions of mean tropical Pacific climate.

References:

Kosaka, Yu & Xie, Shang-Ping (2013) Nature 10.1038/nature12534