Uncertainty in Reconstructing Paleo‐Elevation of the Antarctic Ice Sheet From Temperature‐Sensitive Ice Core Records

Paleotemperature reconstructions from ice cores are mixed signals of changes in climate and ice‐surface elevation. A common, temperature‐based paleoaltimetry method suggests these signals can be disentangled by comparing two proxy locations with similar climates. The difference between the records is assumed to be due to elevation, which is estimated by scaling the temperature difference by a lapse rate. We investigate the uncertainty associated with this approach using a case study of the Antarctic Ice Sheet during the Last Glacial Maximum. From an ensemble of climate simulations, we extract modeled temperatures at locations of real ice cores. We find uncertainty on the order of hundreds of meters that results from spatial heterogeneity in non‐adiabatic temperature change, which itself stems in part from elevation‐induced atmospheric circulation change. Our findings suggest that caution is needed when interpreting temperature‐based paleoaltimetry results for ice sheets. Plain Language Summary Ice cores, cylinders of ice extracted from glaciers or ice sheets, such as the Antarctic Ice Sheet, are important tools for studying Earth's past climate. The temperature information preserved in ice cores is a result of both changes in the climate and changes in the ice sheet. In general, the taller the ice sheet, the colder its surface. By knowing how much of the temperature information in ice cores is a result of climate and how much is a result of elevation, we can better understand how ice sheets shrank and grew as climate changed in the past. Previous efforts to answer this question have relied on a simple relationship between elevation and air temperature: with few exceptions, air in the troposphere (the lowest part of the atmosphere) gets predictably colder as it moves up in the atmosphere and warmer as it moves down. Using a computer to approximate the climate over the Antarctic Ice Sheet, we find that this elevation‐temperature relationship explains part of the temperature information stored in ice cores. We also find that the climate factors cannot be ignored as we seek to advance our understanding of how ice sheets evolved as climate changed in the past. Key Points A widely‐used, temperature‐based paleoaltimetry method is derived from the first law of thermodynamics Estimates of relative elevation change between Antarctic ice core sites yield large uncertainties and low signal‐to‐noise ratios Uncertainty arises from spatial variability in the diabatic temp