Experiment 2
Experiment 2 is intended to act as a validation test where models can demonstrate their ability to both retreat and advance a circular calving front a given rate in a controlled, spatially symetrical fashion. We use the steady state solution obtained from Experiment 1 in the circular domain as the initial condition for this experiment, with the initial calving front position located a distance of 750 km from the centre of the domain. For the first half of the experiment the calving front will be made to retreat, before advancing during the second half of the experiment and reaching a final position that is the same as its initial position by the end of the simulation.
To achieve a particular rate of position change in the calving front we impose a calving rate suche that the difference between this imposed calving rate and the ice velocity at the calving front is equal to the desired rate of change in calving front position. For this experiment we seek to simulate a calving front thats rate of change of position varies in a sinusoidal fashion for the 1000 years of the simulation. For the first 500 years the calving front position retreats before advancing in the second 500 years of the simulation. The retreat rate reaches a maximum of 300 m/a after 250 years, is zero at 500 years and then reachs a maximum advance rate of 300 m/a after 750 years. The rate of calving position change (Wv) at a given year (t) is given by;
Wv = -300*sin(2
with Wv positive for an advancing calving front, negative for a retreating. The calving rate (Cr) required to achieve this value of Wv can be deterimed from the ice velocity at the calving front (Iv) such that
Cr = Iv-Wv
with the calving rate definied as positive in the direction towards the ground line (Cr = +100 m/a would imply that 100 horizontal metres of ice are calved per year)
This experiment has been deliberately chosen to test a number of aspects of implementing a calving front within one experiment where the simulated results can be easily compared to the expected result. This experiment will test models capabilities to not only retreat a calving front but also alow it to advance again. The calving rate has also been deliberately chosen to vary in time and thus not be a neat multiple of model grid resolution. This will require participating models to consider a method for tracking the position of the calving front at the sub grid scale to accurately track its position over time. The rate of advance has also been chosen to be less than the ice velocity at the calving front, as having the calving front advancing quicker than the ice at the calving front would be unphysical. By specifying a perfect circle that contracts and expands in time as the calving front boundary we also test model symetry when utilising discrete grids or meshes.
A snapshot of ice thickness, velocities and mask on the common results grid should be provided every 100 years of simulation time. The common results grid is a regular, uniform grid of 800 km by 800 km with a resolution of 5 km centered on the middle of the domain (0,0). This gives dimensions of 321 by 321, with X and Y values ranging from -800 km to 800 km. We also ask that participants provide a profile of results, sampled on the same order of resolution as the native model grid (albeit with some interpolation), on the eight experimental profiles originating from the domain center located at (0,0) every year of simulation time.
- Profile A (along the line x=0 in the positive y direction)
- Profile B (along the line y=x in the positive x and y direction)
- Profile C (along the line y=0 in the positive x direction)
- Profile D (along the line y=-x in the positive x and negative y direction)
- Profile E (along the line x=0 in the negative y direction)
- Profile F (along the line y=x in the negative x and y direction)
- Profile G (along the line y=0 in the negative x direction)
- Profile H (along the line y=-x in the negative x and positive y direction)
For example, the results from Kori uses the following points Circle_Profiles.csv
Ice thickness should be given in units of meters, whilst velocity should be seperated into an X and Y component alligend with the results grid in units of m/a. All results should be interpolated onto the results grid in a linear fashion. Ice mask should be equal to 1 for grounded ice, 2 for floating ice, and 3 for open ocean with no ice. Results should be interpolated onto the results grid using a nearest neighbour method, such that its values are whole integers. Values of ice velocity and thickness that are in the open ocean should be set to NaN values, regardless of whether individual models utilising some manner of minimum ice thickness to represent open ocean or similar.
Results should be submitted as a NETcdf file, with naming convention of "CalvingMIP_EXPNUMBER_MODELNAME_INSTITUTION NAME.nc". For example, the results for Experiment 1 made using the Kori model by the group from Université libre de Bruxelles would be named "CalvingMIP_EXP1_Kori_ULB.nc". A list of the required data fields is below. To aid analysis of results, please make sure that variable names are an exact match A matlab script that correctly formats results into this format is available in the code section. An example of correctly formatted results are available from the PROTECT data servers, access available upon request.
Naming conventions have been chosen to, as far as possible, be compatible with the ISMIP6 naming conventions to allow for later comparison between projects.
Of particular note for CalvingMIP is the variable 'tendlicalvf', tendency of land ice mass due to calving. To avoid confusion, we define this variable to be the total, domain wide mass flux of ice at the calving front (Calving front ice velocity times calving front ice thickness times ice density) irrespective of whether the calving front is advancing, retreating or stationary.
| NetCDF Variable name | NetCDF Standard name | Description | Units |
|---|---|---|---|
| X | X coordinates of results grid | m | |
| Y | X coordinates of results grid | m | |
| Time1 | Simulation time of yearly line profiles and calving front results | a | |
| Time100 | Simulation time of 100 yearly 2d snapshot results | a | |
| xvelmean | land_ice_vertical_mean_x_velocity | X velocity | m a-1 |
| yvelmean | land_ice_vertical_mean_y_velocity | Y velocity | m a-1 |
| lithk | land_ice_thickness | Ice thickness | m |
| mask | Ice mask | grounded=1, floating=2, open ocean=3 | |
| topg | bedrock_altimetry | Bedrock height | m |
| iareafl | grounded_ice_sheet_area | Total area of grounded ice | m2 |
| iareagr | bedrock_altimetry | Total area of floating ice | m2 |
| lim | land_ice_mass | Total mass of ice in the domain | kg |
| limnsw | land_ice_mass_not_displacing_sea_water | Total mass of ice in the domain that does not disoalce seawater (grounded) | kg |
| tendlicalvf | tendency_of_land_ice_mass_due_to_calving | Total mass flux across the calving front | kg a-1 |
| tendligroundf | tendency_of_grounded_ice_mass | Total mass flux across the grounding line | kg a-1 |
| iareatotalNW | total_ice_area_NorthWest | Total area of grounded and floating ice in positive Y, negative X quadrant | m2 |
| iareatotalNE | total_ice_area_NorthEast | Total area of grounded and floating ice in positive Y, positive X quadrant | m2 |
| iareatotalSW | total_ice_area_SouthWest | Total area of grounded and floating ice in negative Y, negative X quadrant | m2 |
| iareatotalSE | total_ice_area_SouthEast | Total area of grounded and floating ice in negative Y, positive X quadrant | m2 |
| lithkA | land_ice_thickness_along_profile_A | Profile A ice thickness | m |
| sA | distance_along_profile_A | Distance from start of profile A | m |
| xvelmeanA | land_ice_vertical_mean_x_velocity_along_profile_A | Profile A X velocity | m a-1 |
| yvelmeanA | land_ice_vertical_mean_y_velocity_along_profile_A | Profile A Y velocity | m a-1 |
| maskA | Ice mask along profile A | grounded=1, floating=2, open ocean=3 | |
| xcfA | x_calving_front_on_profile_A | Profile A calving front X position | m |
| ycfA | y_calving_front_on_profile_A | Profile A calving front Y position | m |
| xvelmeancfA | land_ice_vertical_mean_x_velocity_at_calving_front_on_profile_A | Profile A Calving Front X velocity | m a-1 |
| yvelmeancfA | land_ice_vertical_mean_y_velocity_at_calving_front_on_profile_A | Profile A Calving Front Y velocity | m a-1 |
| lithkcfA | land_ice_thickness_at_calving_front_on_profile_A | Profile A Calving Front ice thickness | m |
| lithkB | land_ice_thickness_along_profile_B | Profile B ice thickness | m |
| sB | distance_along_profile_B | Distance from start of profile B | m |
| xvelmeanB | land_ice_vertical_mean_x_velocity_along_profile_B | Profile B X velocity | m a-1 |
| yvelmeanb | land_ice_vertical_mean_y_velocity_along_profile_B | Profile B Y velocity | m a-1 |
| maskB | Ice mask along profile B | grounded=1, floating=2, open ocean=3 | |
| xcfB | x_calving_front_on_profile_B | Profile B calving front X position | m |
| ycfB | y_calving_front_on_profile_B | Profile B calving front Y position | m |
| xvelmeancfB | land_ice_vertical_mean_x_velocity_at_calving_front_on_profile_B | Profile B Calving Front X velocity | m a-1 |
| yvelmeancfB | land_ice_vertical_mean_y_velocity_at_calving_front_on_profile_B | Profile B Calving Front Y velocity | m a-1 |
| lithkcfB | land_ice_thickness_at_calving_front_on_profile_B | Profile B Calving Front ice thickness | m |
| lithkC | land_ice_thickness_along_profile_C | Profile C ice thickness | m |
| sC | distance_along_profile_C | Distance from start of profile C | m |
| xvelmeanC | land_ice_vertical_mean_x_velocity_along_profile_C | Profile C X velocity | m a-1 |
| yvelmeanC | land_ice_vertical_mean_y_velocity_along_profile_C | Profile C Y velocity | m a-1 |
| maskC | Ice mask along profile C | grounded=1, floating=2, open ocean=3 | |
| xcfC | x_calving_front_on_profile_C | Profile C calving front X position | m |
| ycfC | y_calving_front_on_profile_C | Profile C calving front Y position | m |
| xvelmeancfC | land_ice_vertical_mean_x_velocity_at_calving_front_on_profile_C | Profile C Calving Front X velocity | m a-1 |
| yvelmeancfC | land_ice_vertical_mean_y_velocity_at_calving_front_on_profile_C | Profile C Calving Front Y velocity | m a-1 |
| lithkcfC | land_ice_thickness_at_calving_front_on_profile_C | Profile C Calving Front ice thickness | m |
| lithkD | land_ice_thickness_along_profile_D | Profile D ice thickness | m |
| sD | distance_along_profile_D | Distance from start of profile D | m |
| xvelmeanD | land_ice_vertical_mean_x_velocity_along_profile_D | Profile D X velocity | m a-1 |
| yvelmeanD | land_ice_vertical_mean_y_velocity_along_profile_D | Profile D Y velocity | m a-1 |
| maskD | Ice mask along profile D | grounded=1, floating=2, open ocean=3 | |
| xcfD | x_calving_front_on_profile_D | Profile D calving front X position | m |
| ycfD | y_calving_front_on_profile_D | Profile D calving front Y position | m |
| xvelmeancfD | land_ice_vertical_mean_x_velocity_at_calving_front_on_profile_D | Profile D Calving Front X velocity | m a-1 |
| yvelmeancfD | land_ice_vertical_mean_y_velocity_at_calving_front_on_profile_D | Profile D Calving Front Y velocity | m a-1 |
| lithkcfD | land_ice_thickness_at_calving_front_on_profile_D | Profile D Calving Front ice thickness | m |
| lithkE | land_ice_thickness_along_profile_E | Profile E ice thickness | m |
| sE | distance_along_profile_E | Distance from start of profile E | m |
| xvelmeanE | land_ice_vertical_mean_x_velocity_along_profile_E | Profile E X velocity | m a-1 |
| yvelmeanE | land_ice_vertical_mean_y_velocity_along_profile_E | Profile E Y velocity | m a-1 |
| maskE | Ice mask along profile E | grounded=1, floating=2, open ocean=3 | |
| xcfE | x_calving_front_on_profile_E | Profile E calving front X position | m |
| ycfE | y_calving_front_on_profile_E | Profile E calving front Y position | m |
| xvelmeancfE | land_ice_vertical_mean_x_velocity_at_calving_front_on_profile_E | Profile E Calving Front X velocity | m a-1 |
| yvelmeancfE | land_ice_vertical_mean_y_velocity_at_calving_front_on_profile_E | Profile E Calving Front Y velocity | m a-1 |
| lithkcfE | land_ice_thickness_at_calving_front_on_profile_E | Profile E Calving Front ice thickness | m |
| lithkF | land_ice_thickness_along_profile_F | Profile F ice thickness | m |
| sF | distance_along_profile_F | Distance from start of profile F | m |
| xvelmeanF | land_ice_vertical_mean_x_velocity_along_profile_F | Profile F X velocity | m a-1 |
| yvelmeanF | land_ice_vertical_mean_y_velocity_along_profile_F | Profile F Y velocity | m a-1 |
| maskF | Ice mask along profile F | grounded=1, floating=2, open ocean=3 | |
| xcfF | x_calving_front_on_profile_F | Profile F calving front X position | m |
| ycfF | y_calving_front_on_profile_F | Profile F calving front Y position | m |
| xvelmeancfF | land_ice_vertical_mean_x_velocity_at_calving_front_on_profile_F | Profile F Calving Front X velocity | m a-1 |
| yvelmeancfF | land_ice_vertical_mean_y_velocity_at_calving_front_on_profile_F | Profile F Calving Front Y velocity | m a-1 |
| lithkcfF | land_ice_thickness_at_calving_front_on_profile_F | Profile F Calving Front ice thickness | m |
| lithkG | land_ice_thickness_along_profile_G | Profile G ice thickness | m |
| sG | distance_along_profile_G | Distance from start of profile G | m |
| xvelmeanG | land_ice_vertical_mean_x_velocity_along_profile_G | Profile G X velocity | m a-1 |
| yvelmeanG | land_ice_vertical_mean_y_velocity_along_profile_G | Profile G Y velocity | m a-1 |
| maskG | Ice mask along profile G | grounded=1, floating=2, open ocean=3 | |
| xcfG | x_calving_front_on_profile_G | Profile G calving front X position | m |
| ycfG | y_calving_front_on_profile_G | Profile G calving front Y position | m |
| xvelmeancfG | land_ice_vertical_mean_x_velocity_at_calving_front_on_profile_G | Profile G Calving Front X velocity | m a-1 |
| yvelmeancfG | land_ice_vertical_mean_y_velocity_at_calving_front_on_profile_G | Profile G Calving Front Y velocity | m a-1 |
| lithkcfG | land_ice_thickness_at_calving_front_on_profile_G | Profile G Calving Front ice thickness | m |
| lithkH | land_ice_thickness_along_profile_H | Profile H ice thickness | m |
| sH | distance_along_profile_H | Distance from start of profile H | m |
| xvelmeanH | land_ice_vertical_mean_x_velocity_along_profile_H | Profile H X velocity | m a-1 |
| yvelmeanH | land_ice_vertical_mean_y_velocity_along_profile_H | Profile H Y velocity | m a-1 |
| maskH | Ice mask along profile H | grounded=1, floating=2, open ocean=3 | |
| xcfH | x_calving_front_on_profile_H | Profile H calving front X position | m |
| ycfH | y_calving_front_on_profile_H | Profile H calving front Y position | m |
| xvelmeancfH | land_ice_vertical_mean_x_velocity_at_calving_front_on_profile_H | Profile H Calving Front X velocity | m a-1 |
| yvelmeancfH | land_ice_vertical_mean_y_velocity_at_calving_front_on_profile_H | Profile H Calving Front Y velocity | m a-1 |
| lithkcfH | land_ice_thickness_at_calving_front_on_profile_H | Profile H Calving Front ice thickness | m |
Example results for this experiment using the Kori model are shown below.
