NOAA/WDS Paleoclimatology - Global Alkenone UK37 Surface Sediment Database

The alkenone‐based UK'37 proxy is a cornerstone of paleoclimatology, providing insight into the temperature history of the Earth's surface ocean. Although the relationship between UK'37 and sea surface temperatures (SSTs) is robust and well supported by experimental data, there remain outstanding issues regarding the seasonality of production of alkenones and the response of UK'37 at very warm and cold SSTs. Using a data set of over 1,300 core‐top UK'37 measurements, we find compelling evidence of seasonal production in the North Atlantic, North Pacific, and Mediterranean Oceans. We also find significant attenuation of the UK'37 response to SST at warm temperatures (>24C), with the slope reduced by nearly 50% as UK'37 approaches unity. To account for these observations in a calibration, we develop a new Bayesian B‐spline regression model, BAYSPLINE, for theUK'37 paleothermometer. BAYSPLINE produces similar estimates as previous calibrations below ~24 degrees, but above this point it predicts larger SST changes, in accordance with the attenuation of the UK'37 response. Example applications of BAYSPLINE demonstrate that its treatment of seasonality and slope attenuation improves paleoclimatic interpretations, with important consequences for the inference of SSTs in the tropical oceans. BAYSPLINE facilitates a probabilistic approach to paleoclimate, building upon growing efforts to develop more formalized statistical frameworks for paleoceanographic reconstruction.