CrevProp: A crevasse propagation model

crevprop documentation

Description

A thermo-visco-elastic modoel for hydraulically driven crevasse propagation through cold ice. This model was originally created by Kristin Poinar (Poinar et al., 2017), written in MatLab. The Python implementation was initially created by jzmejia Aug 2021. This repo contains the python implementaion of crevprop which includes added functionality, project restructuring, and additional/expanded equations.

Usage

import pandas as pd
from crevprop.iceblock import IceBlock 

# initialize model geometry for a domain with an ice thickness
# of 1000 m and vertical resolution (dz spacing) of 1 m.
df = pd.read_csv('temperature_profile.csv')
creep_df = pd.read_csv('creep_deformation_file_name.csv', 
                        names=['t','z'])  

ib=IceBlock(1000,
            1, 
            dt=1, 
            years_to_run=2,
            thermal_freq=10,
            crev_spacing=30,
            u_surf=200,
            T_profile=df,
            sigmaT0=120e3,
            creep_table=creep_df,
            include_creep=True,
            Qin_annual=5000,
            shear_modulus=0.1e9
           )

Important

This model is currently under development and is not ready for public use. Module is currently unstable and we can not guarantee the validity of results or functionality until version 1 release.

Model Overview

iceblock.py - main container user interfaces with to run model, spin up domain, and evolve through time.
temperature_field.py - Thermal model for iceblock, manages and calculates changing ice temperatures, crevasse refreezing.
crevassefield.py - Main container managing crevasse field geometry and crevasse instances for each crevasse in domain.
crevasse.py - Crevasse object implementing crevasse evolution and fracture mechanics to evolve crevasses through time.
fracture.py - Individual functions for linear elastic fracture mechanics. Called by Crevasse. Stand alone use.
physical_constants.py - Utilities, called by other files.

Model Parameters

Note: This content will be moved to the documentation and removed from the README.md.

Model parameters to navigate the equations used in crevasse_propagation within relevant literature (e.g., Poinar et al., 2017; Van der Veen 2007; Weertman 1964, 1983, 1996).

parameter		module	units
Ice thickness	H	ice_thickness	m
Crevase spacing	R	crev_spacing	m
Water depth in crevasse	w	water_depth	m
Longitudinal stress	$\sigma _{y}$	sigmaT0	kPa
Shear modulus	$\mu$	shear_modulus,mu	0.07-3.9 GPa
Water flux	Q	Qin	m $^{2}$ per timestep
Water flux initialization		Qin_annual	m $^{2}$ a $^{-1}$
Fracture toughness of ice	$K_{IC}$	fracture_toughness	Pa m $^{0.5}$

Comparison with notation used in the literature

Comparison between Weertman (1964, 1983, 1996), van der veen 2007, and Poinar 2017.

parameter	1964	1983	1996	van der veen	poinar
ice thickness				H	H
variable depth			y	b	z
crevasse depth		L	L	d	d
depth to water surface			- $y_o$	a	w
height of water column				d-a
average tensile stress		T	$\sigma _A$	$R_{xx}$	$\sigma$
tensile stress $^1$	$\tau (x)$	$\sigma _{xx}(y)$	$\sigma _T$	$\sigma_{xx}$	$\sigma'_y$
compressive hydrostatic stress			$\sigma_C$	$L$
shear modulus		$\mu$	G		$\mu$
constant	$\alpha$		$\alpha _i$
stress intensity factor			$K$
K at crack tip			$K_I$
critical K for ice			$K_{gc}$		KIC
net Burgers vector			$b_T$
crevasse opening displacement			$D(y)$		e(d,z)
crevasse width					W(z)

$^1$ deviatoric stress in the crevasse opening direction (first principal stress)