Merging late Holocene molecular organic and foraminiferal‐based geochemical records of sea surface temperature in the Gulf of Mexico

A molecular organic geochemical proxy (TEX 86 ) for sea surface temperature (SST) is compared with a foraminifera‐based SST proxy (Mg/Ca) in a decadal‐resolution marine sedimentary record spanning the last 1000 years from the Gulf of Mexico. We assess the relative strengths of the organic and inorganic paleoceanographic techniques for reconstructing high‐resolution SST variability during recent climate events, including the Little Ice Age (LIA) and the Medieval Warm Period (MWP). SST estimates based on the molecular organic proxy TEX 86 show a similar magnitude and pattern of SST variability to foraminiferal Mg/Ca‐SST estimates but with some important differences. For instance, both proxies show a cooling (1°C–2°C) of Gulf of Mexico SSTs during the LIA. During the MWP, however, Mg/Ca‐SSTs are similar to near‐modern SSTs, while TEX 86 indicates SSTs that were cooler than modern. Using the respective SST calibrations for each proxy results in TEX 86 ‐SST estimates that are 2°C–4°C warmer than Mg/Ca‐SST throughout the 1000 year record. We interpret the TEX 86 ‐SST as a summer‐weighted SST signal from the upper mixed layer, whereas the Mg/Ca‐SST better reflects the mean annual SST. Downcore differences in the SST estimates between the two proxies (ΔT = TEX 86 − Mg/Ca) are interpreted in the context of varying seasonality and/or changing water column temperature gradients.