PlioVAR KM5c

PlioVAR KM5c SST Database

The map below shows the sites and data used in McClymont et al. 2020: (Climate of the Past) to synthesise ocean temperatures through a 20 kyr timeslice of KM5c (3.195-3.215 Ma) as part of the PlioVAR project. Clicking on sites in the map below will provide further information on data in the synthesis. A summary of all data in the database can be downloaded here.

Sites were included if they met a set of stratigraphic protocols agreed by the PAGES-PlioVAR working group (McClymont et al., 2015), having either a ≤10 kyr resolution benthic δ¹⁸O data which could be tied to the LR04 stack or the paleomagnetic tie-points for Mammoth top (3.22 Ma) and Mammoth bottom (3.33 Ma). For some sites revisions to the published age model were made, for example if the original data had been published prior to the LR04 stack (Lisiecki and Raymo, 2005) or prior to revisions to the paleomagnetic timescale (Gradstein et al. 2012). See the supplementary information of McClymont et al. 2020: (Climate of the Past) for further information.

Alkenone calibration

The majority of the alkenone-derived sea-surface temperature (SST) datasets included in the PlioVAR synthesis used the U^K₃₇’ index, and applied the core-top calibration (60°S-60°N) by “Müller et al. (1998)”. A subsequent expansion of the global core-top database (<70°N) and use of Bayesian statistical analysis to assess the relationship(s) between predicted and recorded ocean temperatures has results in a revised U^K₃₇’ calibration “BAYSPLINE” (Tierney and Tingley, 2018). The results of both calibrations are shown in the PlioVAR database.

Mg/Ca calibration

Many Mg/Ca-based paleotemperature calibrations have been developed and refined over the last two decades. The PlioVAR database contains both the “Original” temperature reconstructions using these calibrations as well as those obtained when using a Bayesian approach that incorporates laboratory culture and core top information to generate probabilistic estimates of past temperatures (“BAYMAG”) (Tierney et al., 2019).

Temperature anomalies

For all anomaly calculations we define the pre-industrial using the NOAA-ERSST5 dataset for years 1870-1899 CE (Huang et al., 2017). In addition to ERSST5, reconstructed temperatures for all calibrations are also compared to temperatures for the nearest core-top (U^K₃₇’) or forward modelled core-top (Mg/Ca) sample.