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

Nicholas Thomas Hitt1, Kim M Cobb1, Hussein R Sayani2, Pamela R Grothe3, Tianran Chen4, Hai Cheng5, R. Lawrence Edwards6, Yanbin Lu7, Daniel Deocampo8 and Kayla J Townsend4, (1)Georgia Institute of Technology, Earth and Atmospheric Sciences, Atlanta, GA, United States, (2)Georgia Institute of Technology, Earth and Atmospheric Sciences, Atlanta, United States, (3)University of Mary Washington, Earth and Environmental Sciences, Fredericksburg, United States, (4)Georgia Institute of Technology Main Campus, Earth and Atmospheric Sciences, Atlanta, GA, United States, (5)Xi'an Jiaotong University, Institute of Global Environmental Change, Xian, China, (6)University of Minnesota, Minneapolis, MN, United States, (7)University of Minnesota, Department of Earth Sciences, Minneapolis, MN, United States, (8)Georgia State University, Department of Geosciences, Atlanta, GA, United States
Abstract:
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 20th 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

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