Perspectives on mapping the MARGO reconstructions by variogram analysis/kriging and objective analysis

Paleo-data are not always useful in their original scattered distribution: For many numerical modeling issues and for display and comparison, gridded versions that provide meaningful estimates for under-sampled regions are a must. We constructed a test data set with a spatial resolution identical to the Multi-proxy Approach for the Reconstruction of the Glacial Ocean (MARGO) samples from the World Ocean Atlas temperatures and assess the performance of (i) variogram estimation and kriging and (ii) the Levitus objective analysis in reconstructing the original data. The two methods complement each other with respect to the facility of application and the quality of the results. Kriging requires a careful parameter adjustment but delivers the smallest deviation from the original data (1.22 °C in the global average), whereas the Levitus analysis provides a fast and efficient tool for checking the samples from different proxy data against each other during the compilation of the final MARGO database, at the expense of a slightly higher error (1.56 °C).