Antarctic surface mass balance trends over the 20th century in reconstructed reanalyses and CMIP5 climate models

Over the Antarctic Ice Sheet (AIS), changes in precipitation, the dominant component of its surface mass balance (SMB) and the largest source of mass input, will significantly impact sea level rise. Some studies have assessed the various abilities of climate models in capturing the mean of modern-day precipitation through comparison with atmospheric reanalysis fields and found increasing precipitation leading to increasing SMB over Antarctica. However, it is well known that the reanalysis precipitation fields exhibit large biases over the AIS. To address this issue, we use long-term reconstructed versions of ERA-Interim, CFSR, and MERRA-2 to evaluate precipitation change rather than mean value. These reconstructions are based on ice cores sampled across the continent, providing an AIS-wide look at snow accumulation and its uncertainties. Comparing the Coupled Model Intercomparison Project version 5 (CMIP5) to the reconstructions offers insight into the ability of these climate models to capture precipitation changes over the 20^th century. The reconstructions reproduce the overall increasing SMB trend and in particular, show an increasing SMB trend on the Antarctic Peninsula and a strong decreasing SMB trend over the Ross Sea sector of West Antarctica. We find that while some models are capable of capturing the spatially-averaged SMB trend over time, none capture the spatial trends that occur in the reconstructions.