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Abstract. Projection of the contribution of ice sheets to sea level change as part ofthe Coupled Model Intercomparison Project Phase 6 (CMIP6) takes the formof simulations from coupled ice sheet–climate models and stand-alone icesheet models, overseen by the Ice Sheet Model Intercomparison Project forCMIP6 (ISMIP6). This paper describes the experimental setup forprocess-based sea level change projections to be performed with stand-aloneGreenland and Antarctic ice sheet models in the context of ISMIP6. TheISMIP6 protocol relies on a suite of polar atmospheric and oceanicCMIP-based forcing for ice sheet models, in order to explore the uncertaintyin projected sea level change due to future emissions scenarios, CMIPmodels, ice sheet models, and parameterizations for ice–ocean interactions.We describe here the approach taken for defining the suite of ISMIP6stand-alone ice sheet simulations, document the experimental framework andimplementation, and present an overview of the ISMIP6 forcing to beused by participating ice sheet modeling groups. 

Abstract. Here we present Antarctic snow accumulation variability at the regional scale over the past 1000 years. A total of 79 ice core snow accumulation records were gathered and assigned to seven geographical regions, separating the high-accumulation coastal zones below 2000 m of elevation from the dry central Antarctic Plateau. The regional composites of annual snow accumulation were evaluated against modelled surface mass balance (SMB) from RACMO2.3p2 and precipitation from ERA-Interim reanalysis. With the exception of the Weddell Sea coast, the low-elevation composites capture the regional precipitation and SMB variability as defined by the models. The central Antarctic sites lack coherency and either do not represent regional precipitation or indicate the model inability to capture relevant precipitation processes in the cold, dry central plateau. Our results show that SMB for the total Antarctic Ice Sheet (including ice shelves) has increased at a rate of 7 ± 0.13 Gt decade−1 since 1800 AD, representing a net reduction in sea level of ∼ 0.02 mm decade−1 since 1800 and ∼ 0.04 mm decade−1 since 1900 AD. The largest contribution is from the Antarctic Peninsula (∼ 75 %) where the annual average SMB during the most recent decade (2001–2010) is 123 ± 44 Gt yr−1 higher than the annual average during the first decade of the 19th century. Only four ice core records cover the full 1000 years, and they suggest a decrease in snow accumulation during this period. However, our study emphasizes the importance of low-elevation coastal zones, which have been under-represented in previous investigations of temporal snow accumulation.