The first synthesis relied on inferences from widespread airborne and satellite observations and numerical models, for which most of the underlying data sets have since been updated. Version 2 features a revised synthesis mask of the likely basal thermal state over the Greenland Ice Sheet based on four input sources:

-Basal temperature fields from ISMIP6 control runs of 10 ice sheet models (Goelzer et al., 2020)
-Gridded basal melt rate inferred from 1-D modeling of radiostratigraphy (MacGregor et al., 2016)
-Modeled ratio of surface speed to maximum deformation speed (Joughin et al., 2016)
-Basal water from radar soundings (Panton and Karlsson, 2015; Leysinger-Vieli et al., 2018; Jordan et al., 2018; Bowling et al., 2019)