Alkenone Paleotemperatures in the Eastern Tropical Pacific Since the LGM: Magnitude and Timing of Deglacial Warming

High productivity and relatively cool tropical temperatures in the upwelling environment of the eastern equatorial Pacific make alkenone paleothermometry an attractive method for reconstructing past sea surface temperatures. However, because of the complex temporal and spatial ocean dynamics in this region, interpretation of alkenone unsaturation data requires careful consideration of production and sedimentation processes affecting alkenone delivery and burial in seafloor sediments. Here we report new results from application of this method in four equatorial cores spanning the last 30,000 years. Results indicate a range of Last Glacial Maximum cooling between 1 and 3 ° C relative to present, while the timing of deglacial warming is generally in phase with planktonic δ ¹⁸O within the resolution of the records. A warming trend through the Holocene is evident in a site offshore Ecuador, which supports the idea of a cooler middle Holocene due to more persistent upwelling and weaker ENSO. Core-top alkenone SST values are in general warmer than annual mean modern temperatures, possibly indicating a seasonal production bias or lateral delivery of alkenones from warmer waters north of the equator. While attesting to the essential robustness of alkenone paleothermometry in this region, these results also underscore the need for more systematic study and evaluation of this method as a monitor of regional paleoceanographic change.