Dear CF community,
On behalf of ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6), I wanted to add a few names to our initial request (29th October 2015, see below), and ask if 3 names in our initial request could be slightly modified.
I look forward to any comments that you may have,
Kind regards and many thanks,
Sophie on behalf of ISMIP6
Note, in all cases where land_ice is used, we follow the CF definition of "Land ice" meaning glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves (the later is part of the ice sheet that flows over the ocean).
When ISMIP6 talks about ice sheet models, it generally includes both ice-sheets resting on bedrock and ice shelves, although some models may not include ice shelves. This is the reason that sometime "grounded" is used: to emphasis that when a model includes both ice sheet and ice shelf, we only want the grounded ice sheet part.
NEW STANDARD NAMES
Proposed standard name: land_ice_runoff_flux
Units: kg m-2 s-1
Long name: Land ice runoff flux
Definition: Runoff flux over land ice is the difference between any available liquid water in the snowpack less any refreezing. Computed as the sum of rainfall and melt of snow less any refreezing or water retained in the snowpack
Proposed standard name: magnitude_of_land_ice_basal_drag
Units: Pa
Long name: Magnitude of land ice basal drag
Definition: The magnitude of basal drag at land ice base
Proposed standard name: tendency_of_land_ice_mass_due_to_surface_mass_balance
Units: kg s-1
Long name: Total surface mass balance flux
Definition: The total surface mass balance flux over land ice is a spatial integration of the surface mass balance flux
Proposed standard name: tendency_of_land_ice_mass_due_to_basal_mass_balance
Units: kg s-1
Long name: Total basal mass balance flux
Definition: The total basal mass balance flux over land ice is a spatial integration of the basal mass balance flux
Proposed standard name tendency_of_land_ice_mass_due_to_calving
Units: kg s-1
Long name: Total calving flux
Definition: The total calving flux over land ice is a spatial integration of the calving flux
Martin Juckes also suggested that ISMIP6 request for three new Area Types need to be added to the ?Area Type Table?. (
http://cfconventions.org/Data/area-type-table/4/build/area-type-table.html ). These are needed when a variable such as ?land_ice_basal_temperature? is a result of two different models (depending whether the land ice rests on the bedrock, or floats over the ocean). The ISMIP6 data request for the CMIP6 effort would then ask for 2 variables, using the same standard name but different cell methods and long names.
For example: with standard name: ?land_ice_basal_temperature?
On the side where land ice rest on bedrock:
short name: litempotl
standard name: land_ice_basal_temperature
long name: Basal temperature of grounded land ice
cell_methods:are: mean where grounded_ice_sheet
While on the side where land ice floats on sea water:
short name: litempoto
standard name: land_ice_basal_temperature
long name: Basal temperature of floating ice shelf
cell_methods:are: mean where floating_ice_shelf
A1) Proposed standard term to be added to the CF Area Type Table: ice_sheet
Definition: ice sheet indicates where ice sheet are present. It includes both grounded ice sheet resting over bedrock and ice shelves flowing over the ocean, but excludes ice-caps and glaciers (in contrast to land_ice, which includes all components).
A2) Proposed standard term to be added to the CF Area Type Table: floating_ice_shelf
Definition: floating ice shelf indicates where ice shelf are present. Ice shelf are the component of ice sheets that flows over the ocean.
A3) Proposed standard term to be added to the CF Area Type Table: grounded_ice_sheet
Definition: grounded ice sheet indicates where the ice sheet rest over bedrock and is thus grounded.
MODIFICATION FROM 29th October 2015 email. Note that the names that were submitted have not yet been approved, hence why we suggest the modifications based on feedback that we have received from our community:
Proposed standard name: snow_land_ice_interface_temperature
Units: K
Long name: Temperature at the interface between land ice and snow
Definition: Surface Temperature that is used to force ice sheet models. It is the temperature at the base of the snowpack models, and does not vary with seasons. Report surface temperature of ice sheet where snow thickness is zero
WAS INITIALLY PROPOSED AS: temperature_at_ground_level_in_snow_or_firn
MOTIVATION FOR CHANGE: initial name led to confusions (in particular the use of firn).
Proposed standard name: grounded_ice_sheet_area
Units: m2
Long name: Area covered by grounded ice sheet
Definition: Total area of the grounded ice sheet, where grounded indicates that the ice rests on bedrock, and therefore excludes ice shelves.
WAS INITIALLY PROPOSED AS: grounded_land_ice_area
MOTIVATION FOR CHANGE: more consistent with another proposed standard name (grounded_ice_sheet_area_fraction, entry 20 in email of 29th October 2016)
Proposed standard name: floating_ice_shelf_area_fraction
Units: 1
Long name: Floating Ice Shelf Area Fraction
Definition: Fraction of grid cell covered by ice sheet flowing over seawater (also called ice shelf).
WAS INITIALLY PROPOSED AS: floating_ice_sheet_area_fraction, (see entry 21)
MOTIVATION FOR CHANGE: the modification would allow for more symmetry with proposed name floating_ice_shelf_area (entry 19)
Begin forwarded message:
From: sophie <sophie.nowicki at nasa.gov<mailto:sophie.nowicki at nasa.gov>>
Subject: standard name proposal for ISMIP6
Date: October 29, 2015 at 4:09:09 PM EDT
To: <cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu>>
Dear CF community,
On behalf of ISMIP6 (The Ice Sheet Model Intercomparison Project for CMIP6), please find below a request for new standard names that are needed for ISMIP6. We thank Alison Pamment and Martin Juckes for their initial review of this proposed list.
Kind regards,
Sophie, on behalf of ISMIP6
Note, in all cases where land_ice is used, we follow the CF definition of "Land ice" meaning glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves (the later is part of the ice sheet that flows over the ocean).
When ISMIP6 talks about ice sheet models, it generally includes both ice-sheets resting on bedrock and ice shelves, although some models may not include ice shelves. This is the reason that sometime "grounded" is used: to emphasis that when a model includes both ice sheet and ice shelf, we only want the ice sheet part.
Proposed standard name 1: temperature_at_ground_level_in_snow_or_firn
Units: K
Long name: Temperature at the interface between land ice and snow or firn
Definition: Surface Temperature that is used to force ice sheet models. It does not vary with seasons. In some models it is the temperature at the base of the snow, and in other at the base of firn (firn is a type of snow that has been left over from past seasons, and is therefore ice that is at an intermediate stage between snow and glacial ice). Report surface temperature of ice sheet where snow or firn thickness is zero
Proposed standard name 2: land_ice_basal_temperature
Units: K
Long name: Temperature at the basal interface of the land ice.
Definition: Basal temperature that is used to force the ice sheet models. Report temperature AT interface. Beneath ice shelves it is the temperature AT ice ocean interface. Beneath grounded ice, it is the temperature AT ice bedrock interface.
Proposed standard name 3: land_ice_surface_melt_flux
Units: kg m-2 s-1
Long name: Surface ice melt flux
Definition: Loss of ice mass resulting from surface melting. Computed as the total surface melt water on the land ice portion of the grid cell divided by land ice area in the grid cell.
Proposed standard name 4: land_ice_basal_specific_mass_balance_flux
Units: kg m-2 s-1
Long name: Land ice basal mass balance flux
Definition: Specific mass balance means the net rate at which ice is added per unit area at the land ice base. Computed as the total basal mass balance on the land ice portion of the grid cell divided by land ice area in the grid cell. A negative value means loss of ice.
Proposed standard name 5: land_ice_specific_mass_flux_due_to_calving
Units: kg m-2 s-1
Long name: Land ice calving flux
Definition: Loss of ice mass resulting from iceberg calving. Computed as the rate of mass loss by the ice shelf (in kg s-1) divided by the horizontal area of the ice sheet (m2) in the grid box.
Proposed standard name 6: land_ice_specific_mass_flux_due_to_calving_and_ice_front_melting
Units: kg m-2 s-1
Long name: kg m-2 s-1
Definition: Total mass balance at the ice front (or vertical margin). It includes both iceberg calving and melt on vertical ice front.
Proposed standard name 7: water_flux_into_sea_water_from_land_ice
Units: kg m-2 s-1
Long name: Water flux into Sea Water from Land Ice
Definition: Computed as the water flux into the ocean due to land ice (runoff water from surface and base of land ice or melt from base of ice shelf or vertical ice front) into the ocean divided by the area ocean portion of the grid cell.
Proposed standard name 8: land_ice_surface_x_velocity
Units: m s-1
Long name: X-component of land ice surface velocity
Definition: u-velocity at land ice surface
Proposed standard name 9: land_ice_surface_y_velocity
Units: m s-1
Long name: Y-component of land ice surface velocity
Definition: v-velocity at land ice surface
Proposed standard name 10: land_ice_surface_upward_velocity
Units: m s-1
Long name: Upward component of land ice surface velocity
Definition: Upward velocity at land ice surface
Proposed standard name 11: land_ice_basal_upward_velocity
Units: m s-1
Long name: Upward component of land ice basal velocity
Definition: Upward velocity at land ice base
Proposed standard name 12: magnitude_of_shear_stress_at_land_ice_base
Units: Pa
Long name: Magnitude of land ice basal shear stress
Definition: The magnitude of the shear stress at land ice base
Proposed standard name 13: magnitude_of_normal_stress_at_land_ice_base
Units: Pa
Long name: Magnitude of land ice basal normal stress
Definition: The magnitude of the normal stress at land ice base
Proposed standard name 14: magnitude_of_longitudinal_stress_at_land_ice_base
Units: Pa
Long name: Magnitude of land ice basal longitudinal stress
Definition: The magnitude of the longitudinal stress at land ice base
Proposed standard name 15: upward_geothermal_heat_flux_at_ground_level
Units: W m-2
Long name: Geothermal Heat flux beneath land ice
Definition: The geothermal heat flux beneath land ice is the geothermal heat flux at the ice-bedrock interface, where ground level means under the ice, in regions covered by land ice
Proposed standard name 16: land_ice_mass
Units: kg
Long name: Land ice mass
Definition: The mass of land ice (glaciers, ice caps, ice sheet and ice shelves), computed as the ice volume times density.
Proposed standard name 17: land_ice_mass_not_displacing_sea_water
Units: kg
Long name: Land ice mass that does not displace sea water
Definition: The mass of land ice that does not displace sea water if removed, computed as the ice volume times density. It excludes ice shelves, and components of the grounded ice sheet that would not displace sea level (for example, in regions where the ice rests on a bedrock that sits below sea level)
Proposed standard name 18: grounded_land_ice_area
Units: m2
Long name: Area covered by grounded ice sheet
Definition: Total area of the grounded land ice, where grounded indicates that the ice rests on bedrock, and therefore excludes ice shelves.
Proposed standard name 19: floating_ice_shelf_area
Units: m2
Long name: Area covered by floating ice shelves.
Definition: Total area of the floating ice shelves, which is the land ice component that flows over sea water.
EXISTING standard name: land_ice_area_fraction
Units: 1
Long name: Land Ice Area Fraction
Definition from cfconventions.org<
http://cfconventions.org/>: "X_area_fraction" means the fraction of horizontal area occupied by X. "Land ice" means glaciers, ice-caps and ice-sheets resting on bedrock and also includes ice-shelves.
Proposed standard name 20: grounded_ice_sheet_area_fraction
Units: 1
Long name: Grounded Ice Sheet Area Fraction
Definition: Fraction of grid cell covered by grounded ice sheet, where grounded indicates that the quantity correspond to the ice sheet that flows over bedrock.
Proposed standard name 21: floating_ice_sheet_area_fraction
Units: 1
Long name: Floating Ice Sheet Area Fraction
Definition: Fraction of grid cell covered by ice sheet flowing over seawater (also called ice shelf).
Note land_ice_area_fraction already exist, hence the suggestion to add grounded_ice_sheet_area_fraction and floating_ice_sheet_area_fraction: These could also use instead the existing name "area_fraction", with a coordinate variable or scalar coordinate variable of "area_type" and add new entries to the area_type table (
http://cfconventions.org/Data/area-type-table/current/build/area-type-table.html). Alison suggested that this is discussed on list.
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