age_flow_line

A numerical age model along a flow line of an ice sheet

What this manual is and is not?

This manual is a documentation on how to use the age_flow_line software.
It is not a description of the age_flow_line principles and assumptions. Please read to the scientific articles describing age_flow_line for that purpose:
Parrenin, F., Bazin, L., Capron, E., Landais, A., Lemieux-Dudon, B. and Masson-Delmotte, V.: IceChrono1: a probabilistic model to compute a common and optimal chronology for several ice cores, Geosci. Model Dev., 8(5), 1473–1492, doi:10.5194/gmd-8-1473-2015, 2015.
It is not an operating system or python documentation. Please use your operating system or python documentation instead.

Where can I get help on age_flow_line?

You can also directly email to Frédéric Parrenin: [email protected]

How to download age_flow_line?

Go here:
https://github.com/parrenin/age_flow_line/
and click on the donwload button.
In the downloaded folder, you will find the following files:

• README.md : is the current documentation of age_flow_line.
• LICENCE : is the age_flow_line licence file.
• age_flow_line.py : is the main program that you will run.
• Clean.py : is a python script to clean a model experiment directory
• DC-BELDC : is an example experiment directory: it contains all the necessary numerical settings and input files for the flow line between Dome C and Little Dome C.

What do I need to run age_flow_line?

age_flow_line is a scientific python3 software, therefore you need a scipy distribution.
age_flow_line is developed and tested using the anaconda distribution, therefore we recommend it.
Anaconda can be downloaded here (use the python3 version):
https://www.anaconda.com/download

Paleochrono probably works on other scipy distributions, provided they contain the following python modules:

• sys
• os
• time
• math
• numpy
• matplotlib
• scipy
• resource
• yaml

How to run age_flow_line?

Assuming you use anaconda, you can go in the spyder shell and type the following commands in the ipython interpreter:

cd path-to-age_flow_line
run age_flow_line.py exp_directory/

where path-to-age_flow_line is the directory containing age_flow_line and exp_directory is the name of your experiment directory. The DC-LDC experiment directory is provided for you convenience. It takes a few seconds to run on a recent computer.

What is the structure of an experiment direcotry?

You can have a look at the provided DC-LDC directory.

You have one parameter file parameters.yml which contains general parameters for the experiment.

Then you have several input file in .txt format:

• accumulation.txt: the surface accumulation along the flow line
• melting.txt: the basal melting along the flow line
• thickness.txt: the thickness along the flow line
• surface.txt: the surface elevation along the flow line
• tube_width.txt: the flow tube width along the flow line
• sliding.txt: the basal sliding along the flow line
• p_Lliboutry.txt: the p exponent of the Lliboutry velocity profile along the flow line
• relative_density.txt: a depth vs relative density profile
• temporal_factor.txt: the accumulation/melting relative temporal variations

What are the outputs of a run?

If the run went correctly, it has created output files for the whole flow line:

• flow_line_output.txt: is the output for the whole flow line
• age_pi_theta.pdf: is the figure for the age field in the (pi,theta) coordinate system
• age_x_z.pdf: is the same using the (x,z) coordinate system
• age_x_depth.pdf: is the same using the (x,depth) coordinate system
• boundary_conditions_x.pdf: is the figure with the boundary conditions as a function of x
• calculated_quantities_x.pdf: is the figure with some 1D quantities along the flow line
• iso-omega_lines_x_z.pdf: are the iso-omega lines in (x,z)
• iso-omega_lines_x_depth.pdf: same using the depth
• mesh_pi_theta.pdf: is the mesh in (pi,theta)
• mesh_x_z.pdf: is the mesh in (x,z)
• mesh_x_depth.pdf: is the mesh in (x,depth)
• R_temporal_factor.pdf: is the figure with the accu/melting temporal factor
• stream_lines_x_z.pdf: are the stream lines / trajectories in (x,z)
• stream_lines_x_depth.pdf: same using (x,depth)
• thinning_analytical_x_z.pdf: is the thinning function calculated analytically in (x,z)
• thinning_analytical_x_depth.pdf: same in (x,depth)
• thinning_x_z.pdf: is the thinning function calculated by finite difference in (x,z) coordinate system

If you have defined virtual ice cores, it has also created some output files:

• IC_ice_core_output.txt: is the output for the IC ice core
• IC_ice_core_vs_depth.pdf: figure with a few quantities as a function of the depth in the IC ice core
• IC_ice_core_vs_age.pdf: figure with a few quantities as a function of the age in the IC ice core

What to do if something goes wrong?

Some errors can be eliminated by restarting the kernel in spyder (under "Console">"Restart kernel").
If the problem persist, please post an email to the author or on the mailing list with the error message appearing on the command line.