Quantifying polar wander and its impact on reconstructions of past climates

Paleogeographic reconstructions are essential for studying the evolution of Earth’s surface, climate, and life. The main quantitative tool to reconstruct the past position of continental landmasses is paleomagnetism, with apparent polar wander paths (APWPs) providing direct estimates of their paleolatitude through geological time. Traditionally, APWPs have been calculated from study-mean paleomagnetic poles, which are assigned equal weight regardless of their uncertainties and the amount of data used to calculate them. Here, we introduce the next generation of APWPs that are calculated from site-level paleomagnetic data instead of from study-mean poles. This alternative approach assigns larger weight to larger data sets and incorporates both spatial and temporal uncertainties. We demonstrate the advantages of this new method using a recently published global APWP based on site-level data (Vaes et al., 2023). This APWP yields improved estimates of the rate and magnitude of both apparent and true polar wander, providing a more robust paleomagnetic reference frame for paleogeographic reconstructions. We then assess the impact of paleogeography and polar wander on simulations of global climate, with a focus on the greenhouse climates of the early Cenozoic. We find that the choice of absolute reference frame can significantly alter global ocean circulation as well as regional temperature and precipitation patterns. Moreover, we find that shifts in the reconstructed locations of temperature proxy sites can lead to changes in model-data mismatches by up to 5°C. This has important implications for integrating model predictions with proxy data, for instance in reconstructing key climate characteristics such as latitudinal temperature gradients. These findings underscore the importance of using an appropriate and accurate reference frame for paleoclimate simulations and their integration with proxy data.