Temperature reconstructions of euphotic oceans via coccolith clumped isotopes

• Main Authors: Mejía, Luz María, Taylor, Victoria Emma, Meckler, Anna Nele, Stoll, Heather, Bernasconi, Stefano, Fernández, Álvaro, Zhang, Hongrui, Guitián, José, Sadatzki, Henrik, Hernández-Almeida, Iván, Pälike, Heiko
• Other Authors: Consejo Superior de Investigaciones Científicas https://ror.org/02gfc7t72
• Format: Still Image
• Language: unknown
• Published: European Geosciences Union 2024
• Subjects: Iceland; North Atlantic
• Online Access: http://hdl.handle.net/10261/365914; https://doi.org/10.5194/egusphere-egu24-12593

Póster presentado en EGU General Assembly (2024), Vienna, Austria & Online | 14–19 April 2024 Clumped isotope thermometry applied to carbonate fossils is a promising technique to derive independent and accurate reconstructions of absolute ocean temperatures, a key parameter in understanding past Earth Climate Sensitivity. Other more commonly used temperature proxies have several disadvantages, including requiring assumptions of seawater chemistry compositions (e.g. foraminifera Mg/Ca and δ18O), or being based on empirical correlations without a complete understanding of its controlling mechanisms (e.g. TEX86 and Uk'37). Conversely, clumped isotope thermometry is based on thermodynamics, and is independent from seawater chemistry. Here we present clumped isotopes (Δ47) in coccolith separations from globally distributed Holocene core tops, a monospecific Coccolithus pelagicus sediment trap in the Iceland Sea, downcore sediments from the North Atlantic during the last 16 Ma, and downcore sediments from tropical (Equatorial Pacific) and high latitudes (South Tasman Rise) spanning the Cenozoic. Calcification temperatures of the sediment trap agree with satellite derived temperatures, further supporting a lack of or small vital effects in coccolith clumped isotopes. Temperatures derived from Δ47 of tropical Holocene coccoliths are colder than modern Sea Surface Temperatures (SSTs). This suggests that coccolithophores may inhabit deeper than surface waters in these areas, which if proven to be true, would have implications for how other proxies, such as Uk'37, are calibrated to SSTs. At higher latitudes, calcification temperatures from Holocene coccolith separations are more similar to SSTs, and we suggest they are indicators of mixed layer depth temperatures in these regions. Pure coccoliths from the North Atlantic during the last 16 Ma show Δ47-derived temperatures that are 10 °C colder than those derived with alkenones from the same samples. This suggests a modest, rather than an extreme polar amplification, ...