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Abstract. We present a global atlas of downcore foraminiferal oxygen and carbon isotope ratios available at https://doi.org/10.1594/PANGAEA.936747(Mulitza et al., 2021a). The database contains 2106 published and previously unpublished stable isotope downcore records with 361 949 stable isotopevalues of various planktic and benthic species of Foraminifera from 1265 sediment cores. Age constraints are provided by 6153 uncalibratedradiocarbon ages from 598 (47 %) of the cores. Each stable isotope and radiocarbon series is provided in a separate netCDF file containingfundamental metadata as attributes. The data set can be managed and explored with the free software tool PaleoDataView. The atlas will provideimportant data for paleoceanographic analyses and compilations, site surveys, or for teaching marine stratigraphy. The database can be updated withnew records as they are generated, providing a live ongoing resource into the future. 

The atlas contains a collection of 2,106 published and previously unpublished downcore stable isotope records of various planktonic and benthic species of foraminifera from 1,265 globally distributed sediment cores. Uncalibrated radiocarbon dates are provided for 598 cores in the collection. Each stable isotope and radiocarbon series is stored in a separate netCDF file containing fundamental meta data as attributes. The data set can be further explored and analyzed with the free software tool PaleoDataView (Langner, M. and Mulitza, S.: Clim. Past, 15, 2067–2072, https://doi.org/10.5194/cp-15-2067-2019). WA_Foraminiferal_Isotopes_2022.zip contains 2006 stable isotope records (in netCDF format) and 598 radiocarbon records (in netCDF format). The folder structure in the file should be preserved and is required to use the collection with the software PaleoDataView. 

Establishing tropical sea surface temperature (SST) during the Last Glacial Maximum (LGM) is important for constraining equilibrium climate sensitivity to radiative forcing. Until now, there has been little data from the central equatorial Pacific in global compilations, with foraminiferal assemblage‐based estimates suggesting the region was within 1°C of modern temperatures during the LGM. This is in stark contrast to multi‐proxy evidence from the eastern and western Pacific and model simulations which support larger cooling. Here we present the first estimates of glacial SST in the central equatorial Pacific from Mg/Ca inGlobigerinoides ruber. Our results show that the central Pacific cooled by about 2.0°C during the LGM, in contrast with previous global compilations but in agreement with models. Our data support a larger magnitude of tropical LGM cooling, and thus a larger equilibrium climate sensitivity, than previous studies which relied on foraminiferal assemblages in the central tropical Pacific.

 

Coral oxygen isotopes (δ¹⁸O) from the central equatorial Pacific provide monthly resolved records of El Niño‐Southern Oscillation activity over past centuries to millennia. However, calibration studies usingin situdata to assess the relative contributions of warming and freshening to coral δ¹⁸O records are exceedingly rare. Furthermore, the fidelity of coral δ¹⁸O records under the most severe thermal stress events is difficult to assess. Here, we present six coral δ¹⁸O records andin situtemperature, salinity, and seawater δ¹⁸O data from Kiritimati Island (2°N, 157°W) spanning the very strong 2015/16 El Niño event. Local sea surface temperature (SST) anomalies of +2.4 ± 0.4°C and seawater δ¹⁸O anomalies of −0.19 ± 0.02‰ contribute to the observed coral δ¹⁸O anomalies of −0.58 ± 0.05‰, consistent with a ∼70% contribution from SST and ∼30% from seawater δ¹⁸O. Our results demonstrate that Kiritimati coral δ¹⁸O records can provide reliable reconstructions even during the largest class of El Niño events.

 

The El Niño–Southern Oscillation (ENSO) represents the largest source of year‐to‐year global climate variability. While Earth system models suggest a range of possible shifts in ENSO properties under continued greenhouse gas forcing, many centuries of preindustrial climate data are required to detect a potential shift in the properties of recent ENSO extremes. Here we reconstruct the strength of ENSO variations over the last 7,000 years with a new ensemble of fossil coral oxygen isotope records from the Line Islands, located in the central equatorial Pacific. The corals document a significant decrease in ENSO variance of ~20% from 3,000 to 5,000 years ago, coinciding with changes in spring/fall precessional insolation. We find that ENSO variability over the last five decades is ~25% stronger than during the preindustrial. Our results provide empirical support for recent climate model projections showing an intensification of ENSO extremes under greenhouse forcing.