Observations

Focus Group Statement (Task J):

An unexpected outcome of ISMIP6 was the difficulty of ice sheet models in reproducing changes observed over the Greenland and Antarctic ice sheets over the last couple of decades (Aschwanden et al., 2021; Slater et al., 2020). One target for ISMIP7 is thus to improve simulations over the contemporary period (the last 40 years during which satellite observations are available) and evaluate models based on their skill in reproducing recent changes. Methods such as Bayesian calibration have the potential to reduce the uncertainty in sea level projections. Consensus estimates of ice sheet mass changes, against which ice sheet simulations can be compared, are available via the ESA-NASA Ice sheet Mass Balance Inter-comparison Exercise (IMBIE), which reconciles satellite measurements of ice sheet mass balance from three different geodetic techniques (Shepherd et al. 2012, Otosaka et al. 2023). Similarly, there are new observational datasets becoming available that could be used in the initialization of ice sheet models. However these data are not always appropriate for comparison with ice sheet models due to different spatial or temporal data reporting standards, nor is it clear how to best carry out model-observation intercomparisons.

As part of ISMIP7, we will support the ice sheet modeling community efforts by providing and recommending observational datasets for the initialisation, calibration, and validation of ice sheet model outputs. . We will produce a data package,  MIPkit, consisting of a series of observations that can be used in the initialization of ice sheet models, including ice velocities, surface elevation and its change, geothermal heat flux maps, ice mask, calving fronts and grounding lines etc. This data package will be in a model friendly format with a consistent regular grid and regular time stamps on netCDF format. It will also include guidance regarding best practices and information on the limitations of the different datasets. Our experience with previous community efforts such as SeaRISE (Bindschadler et al., 2013, Nowicki et al., 2013a, 2013b) is that community datasets encourage consistency among data from different sources and ensure observational datasets and model output cover the same spatial extent or ice sheet boundaries. Finally, we will work closely with IMBIE to validate ISMIP7 model outputs at both the ice sheet wide and drainage basin scales in order to better understand to what extent ice sheet models can reproduce observed mass changes.