ALBERT

Description: Composite core images for Ocean Drilling Program (ODP) Hole 1088B were generated by cutting individual core sections from core table photos (downloaded from JANUS: http://www-odp.tamu.edu/database/). Each section image was then compiled and scaled to the shipboard meters composite depth (mcd) using the Includes_Core_Table_Photos functions within Code for Ocean Drilling Data (CODD v1; www.codd-home.net; Wilkens et al. (2017)). To account for the single point lighting source used in core table photos, a lighting correction was also applied. As shipboard color reflectance data was not collected at Site 1088, core color information (hue, saturation, lightness, red, green, blue) was extracted every mm from the composite core images using the CODD “CreateHoleCoreImageProfiles” function. The extracted lightness (L) showed the clearest variability and was chosen to approximate Lstar data. The top 4 cm of each section was excluded from the L profile to remove a lighting artefact at section ends. To account for core heterogeneity, the L data was then despiked using the CODD “Median_DeSpike” function (despiked data over 2 s.d. from the median within a 400 point/0.4 m window) and then smoothed using an 11-point binomial smoothing. All extracted data is provided in supplementary table 1. The composite core images from Hole 1088B show clear evidence for core disturbance at the top of most cores (supplementary table 2). These intervals were excluded from the extracted lightness and shipboard magnetic susceptibility records. The shipboard magnetic susceptibility (MS) data was also despiked using the “Median_DeSpike” function (despiked data over 2 s.d. from the median within a 40 point/0.4 m window; supplementary tables 3). An astrochronology for Hole 1088B was generated between 4.2 and 7.9Ma (38-90 mcd), using 24 minimal tie points between L maxima and ~110 kyr eccentricity maxima (Ecc; Laskar et al. (2004). These additional age points are provided in supplementary table 4.

Description: During the Paleocene-Eocene Thermal Maximum (PETM), rapid release of isotopically light C to the ocean-atmosphere system elevated the greenhouse effect and warmed temperatures by 5-7 °C for 105 yr. The response of the planktic ecosystems and productivity to the dramatic climate changes of the PETM may represent a significant feedback to the carbon cycle changes, but has been difficult to document. We examine Sr/Ca ratios in calcareous nannofossils in sediments spanning the PETM in three open ocean sites as a new approach to examine productivity and ecological shifts in calcifying plankton. The large heterogeneity in Sr/Ca among different nannofossil genera indicates that nannofossil Sr/Ca reflects primary productivity-driven geochemical signals and not diagenetic overprinting. Elevated Sr/Ca ratios in several genera and constant ratios in other genera suggest increased overall productivity in the Atlantic sector of the Southern Ocean during the PETM. Dominant nannofossil genera in tropical Atlantic and Pacific sites show Sr/Ca variations during the PETM which are comparable to background variability prior to the PETM. Despite acidification of the ocean there was not a productivity crisis among calcifying phytoplankton. We use the Pandora ocean box model to explore possible mechanisms for PETM productivity change. If independent proxy evidence for more stratified conditions in the Southern Ocean during the PETM is robust, then maintenance of stable or increased productivity there likely reflects increased nutrient inventories of the ocean. Increased nutrient inventories could have resulted from climatically enhanced weathering and would have important implications for burial rates of organic carbon and stabilization of climate and the carbon cycle.