antarctica¶

The landice/antarctica test group includes a test case for creating a mesh for Antarctica.

config options¶

The test group uses the following default config options. At this point only the mesh generation options are adjusted through the config file.

# config options for antarctica test cases
[mesh]

# number of levels in the mesh
levels = 5

# Bounds of Antarctic mesh
x_min = -3333500.
x_max = 3330500.
y_min = -3333500.
y_max = 3330500.

# distance from ice margin to cull (km).
# Set to a value <= 0 if you do not want
# to cull based on distance from margin.
cull_distance = 50.0

# mesh density parameters
# minimum cell spacing (meters)
min_spac = 4.e3
# maximum cell spacing (meters)
max_spac = 2.e4
# log10 of max speed (m/yr) for cell spacing
high_log_speed = 2.5
# log10 of min speed (m/yr) for cell spacing
low_log_speed = 0.5
# distance to ice edge or grounding line at which cell spacing = max_spac (meters)
high_dist = 2.e5
# distance to ice edge or grounding line within which cell spacing = min_spac (meters)
low_dist = 4.e4

# These will not be applied unless use_bed = True.
# They are taken from the humboldt.mesh_gen test case
# and have not been evaluated for Antarctica.
# distance at which bed topography has no effect
high_dist_bed = 1.e5
# distance within which bed topography has maximum effect
low_dist_bed = 7.5e4
# Bed elev beneath which cell spacing is minimized
low_bed = 50.0
# Bed elev above which cell spacing is maximized
high_bed = 100.0

# mesh density functions
use_speed = True
use_dist_to_grounding_line = True
use_dist_to_edge = False
use_bed = False

[antarctica]
# path to directory containing BedMachine and Measures datasets
# (default value is for Perlmutter)
data_path = /global/cfs/cdirs/fanssie/standard_datasets/AIS_datasets

# filename of the BedMachine thickness and bedTopography dataset
# (default value is for Perlmutter)
bedmachine_filename = BedMachineAntarctica_2020-07-15_v02_edits_floodFill_extrap_fillVostok.nc

# filename of the MEASURES ice velocity dataset
# (default value is for Perlmutter)
measures_filename = antarctica_ice_velocity_450m_v2_edits_extrap.nc

# projection of the source datasets, according to the dictionary keys
# create_SCRIP_file_from_planar_rectangular_grid.py from MPAS_Tools
src_proj = ais-bedmap2

# number of processors to use for ESMF_RegridWeightGen
nProcs = 128

mesh_gen¶

landice/antarctica/mesh_gen creates a 4-20km variable resolution mesh with the mesh file name Antarctica.nc. In addition, two region masks are generated based on the IMBIE1 (http://imbie.org/imbie-2016/drainage-basins/) and ISMIP6 basins (defined in Jourdain et al. 2020).

The test case performs interpolation of observational data from gridded datasets to the Antarctic mesh. This takes care of the peculiarities of the current gridded compilation dataset (antarctica_8km_2020_10_20.nc), as well as using conservative remapping directly from the high-resolution BedMachineAntarctica and MeASUReS velocity datasets. There is a fairly heavy degree of pre-processing done to get the BedMachine and MeASUReS datasets ready to be used here. The pre-processing includes renaming variables, setting reasonable _FillValue and missing_value attributes, extrapolating fields to avoid interpolation ramps at ice margins, updating mask values, and raising the bed topography at Lake Vostok to ensure a flat ice surface there.

Those data files and processing scripts currently live here on Perlmutter: /global/cfs/cdirs/fanssie/standard_datasets/AIS_datasets. Eventually that pre-processing could be integrated into a new step in COMPASS, or the processed data files could be added to the server on Anvil and downloaded as needed. However, until then, this test case provides a reproducible workflow for setting up Antarctic meshes at varying resolutions

There is no model integration step.