Examples and corresponding options¶

This section gives a very brief overview of some coupling options. Please see sections referenced below for more information.

One way coupling to a climate model¶

One-way coupling of PISM to a climate model can be achieved by reading a NetCDF file with time- and space-dependent climate data produced by a climate model.

There are two cases:

coupling to a climate model that includes surface (firn, snow) processes
coupling to a climate model providing near-surface air temperature and precipitation

Reading ice surface temperature and mass balance¶

This is the simplest case. It is often the preferred case, for example when the climate model in use has high quality surface mass and energy sub-models which are then preferred to the highly simplified (e.g. temperature index) surface models in PISM.

Variables: climatic_mass_balance, ice_surface_temp
Options: -surface given -surface_given_file forcing.nc
See also: Reading top-surface boundary conditions from a file

Reading air temperature and precipitation¶

As mentioned above, if a climate model provides near-surface air temperature and precipitation, these data need to be converted into top-of-the-ice temperature and climatic mass balance.

One way to do that is by using a temperature index (PDD) model component included in PISM. This component has adjustable parameters; default values come from [148].

Variables: precipitation, air_temp
Options: -atmosphere given -atmosphere_given_file forcing.nc -surface pdd
See also: Boundary conditions read from a file, Temperature-index scheme

If melt is negligible -surface pdd should be replaced with -surface simple (see section The “invisible” model).

Using climate anomalies¶

Prognostic modeling experiments frequently use time- and space-dependent air temperature and precipitation anomalies.

Variables: precipitation, air_temp, precipitation_anomaly, air_temp_anomaly
Options: -atmosphere given,anomaly, -atmosphere_given_file forcing.nc, -atmosphere_anomaly_file anomalies.nc, -surface simple
See also: Boundary conditions read from a file, Using climate data anomalies, The “invisible” model

The simple surface model component re-interprets precipitation as climatic mass balance, which is useful in cases when there is no melt (Antarctic simulations is an example).

Simulations of the Greenland ice sheet typically use -surface pdd instead of -surface simple.

SeaRISE-Greenland¶

The SeaRISE-Greenland setup uses a parameterized near-surface air temperature [145] and a constant-in-time precipitation field read from an input (-i) file. A temperature-index (PDD) scheme is used to compute the climatic mass balance.

Variables: precipitation, lat, lon
Options: -atmosphere searise_greenland -surface pdd
See also: SeaRISE-Greenland, Temperature-index scheme

The air temperature parameterization is a function of latitude (lat), longitude (lon) and surface elevation (dynamically updated by PISM).

SeaRISE-Greenland paleo-climate run¶

The air temperature parameterization in the previous section is appropriate for present day modeling. PISM includes some mechanisms allowing for corrections taking into account differences between present and past climates. In particular, one can use ice-core derived scalar air temperature offsets [8], precipitation adjustments [31], and sea level offsets from SPECMAP [9].

Variables: precipitation, delta_T, delta_SL, lat, lon
Options: -atmosphere searise_greenland,delta_T -atmosphere_delta_T_file delta_T.nc -surface pdd -sea_level constant,delta_sl -ocean_delta_sl_file delta_SL.nc
See also: SeaRISE-Greenland, Scalar temperature offsets, Temperature-index scheme, Constant in time and space, Scalar sea level offsets

Note that the temperature offsets are applied to air temperatures at the atmosphere level. This ensures that \(\Delta T\) influences the PDD computation.

Antarctic paleo-climate runs¶

Variables: climatic_mass_balance, air_temp, delta_T, delta_SL
Options: -surface given,delta_T -surface_delta_T_file delta_T.nc -sea_level constant,delta_sl -ocean_delta_sl_file delta_SL.nc
See also: Reading top-surface boundary conditions from a file, Scalar temperature offsets, Constant in time and space, Scalar sea level offsets