ISMIP6 Standalone Ice Sheet Experiments
initMIP: Focus on initialization
Earlier large-scale Greenland ice sheet (GrIS) experiments e.g. those run during ice2sea and SeaRISE initiatives have shown that ice sheet initialisation can have a large effect on sea-level projections and gives rise to important uncertainties. Improving initialisation techniques is currently a field of active research, which makes it difficult to prescribe one technique as the method of choice for ISMIP6. Instead, we first propose a “Come as you are”- approach, which allows participants to contribute with their currently used model setup and initialisation technique for intercomparison (initMIP). This, we hope, allows getting modellers involved early in the ISMIP6 process and keeps the workload for participants as low as possible. Furthermore, the proposed schematic experiments may facilitate to document on-going model development. Starting early in the CMIP6 process implies relying on schematic forcing for the initiation experiments that is independent from CMIP6 AOGCM output, which will only become available later on. The initMIP is the first in a series of ISMIP6 ice sheet model intercomparison activities. More information on initMIP can be found on the initMIP page.
Planning Future ISMIP6 Standalone Experiment: Current thoughts
As described in the main ISMIP6 page,the primary goal of ISMIP6 is to improve projections of sea level rise via projections of the evolution of the Greenland and Antarctic ice sheets under a changing climate, along with a quantification of associated uncertainties (associated with both uncertainty in climate forcing and in the response of the ice sheets).
The standalone ISMIP6 ice sheet experiments are therefore tightly linked with the CMIP6 past and future climate simulation from any AOGCM, and meant to complement the coupled ice sheet-climate simulation. The ISMIP6 flow is shown in the diagram below:
Ways of Providing Atmospheric Forcing
The table below illustrates the many possible ways that Atmospheric Forcings can be provided to an ice sheet model.
Please fill free to indicate other methods!
|1.||Coupled to a Regional Climate Model.||Full coupling.||
||Find out how groups anticipate doing this.|
|2.||SMB provided by a Regional Climate Model.||High resolution atmosphere.||
||What RCMs would be available and how many AOGCM-forced experiments would be practical?|
|3.||SMB calculated by ice-sheet model’s energy-balance scheme.||Fast allowing many experiments.||Not many groups would have this available.||
|4.||SMB calculated by ice-sheet model’s degree-day scheme.||
||Crude but degree-day factors could be determined from RCMs.||
||Use MAR/RACMO to determine how much DDF varies and if there is a parameterization for this.|
|5.||Interpolation of SMB directly from AOGCM.||Very fast.||AOGCMs would need to have appropriate physics and output these quantities; resolution issues at margins etc.||SMB terms.|
|6.||Adding SMB anomaly from AOGCM to best present day condition.||Very fast.||Present day conditions would come from observation/RCM. This is what SeaRISE did. Still need to decide how to correct for elevation feedback.||SMB terms.|
Ways of Providing Oceanic Forcing
The table below illustrates the many possible ways that Oceanic Forcings can be provided to an ice sheet model.
Please fill free to indicate new methods!
|1.||Coupled to a Regional Ocean Model.||Full coupling.||
||Lateral boundary conditions for RCM.||Find out how groups anticipate doing this.|
|2.||Melt rate + temp provided by a sub ice shelf cavity model.||High resolution ocean.||
||Lateral boundary conditions for RCM.||What RCMs would be available and how many AOGCM-forced experiments would be practical?|
|3.||Melt rate and heat flux parameterization from box model.||Fast.||Lateral boundary conditions.|
|4.||Use anomalies in surface temp to obtain melt rate (Rignot and Jacob).||
||Crude. Cte melt rate for whole ice shelf (but could perhaps combine with Sato and Greve 2012 to get varied sub-melt rate).||Sea surface temperature.|
|5.||Apply anomalies from AOGCM to best present day condition (observed or computed melt rates).||Very fast.||What to do when grounding line retreats? etc.|