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Modified k1 value and some of the doc #574

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2 changes: 1 addition & 1 deletion cicecore/cicedynB/general/ice_init.F90
Original file line number Diff line number Diff line change
Expand Up @@ -331,7 +331,7 @@ subroutine input_data
close_boundaries = .false. ! true = set land on edges of grid
seabed_stress= .false. ! if true, seabed stress for landfast is on
seabed_stress_method = 'LKD' ! LKD = Lemieux et al 2015, probabilistic = Dupont et al. in prep
k1 = 8.0_dbl_kind ! 1st free parameter for landfast parameterization
k1 = 7.5_dbl_kind ! 1st free parameter for landfast parameterization
k2 = 15.0_dbl_kind ! 2nd free parameter (N/m^3) for landfast parametrization
alphab = 20.0_dbl_kind ! alphab=Cb factor in Lemieux et al 2015
threshold_hw = 30.0_dbl_kind ! max water depth for grounding
Expand Down
2 changes: 1 addition & 1 deletion configuration/scripts/ice_in
Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,7 @@
e_ratio = 2.
seabed_stress = .false.
seabed_stress_method = 'LKD'
k1 = 8.
k1 = 7.5
k2 = 15.
alphab = 20.
threshold_hw = 30.
Expand Down
21 changes: 10 additions & 11 deletions doc/source/science_guide/sg_dynamics.rst
Original file line number Diff line number Diff line change
Expand Up @@ -240,9 +240,7 @@ CICE includes two options for calculating the seabed stress,
i.e. the term in the momentum equation that represents the interaction
between grounded ice keels and the seabed. The seabed stress can be
activated by setting ``seabed_stress`` to true in the namelist. The seabed stress (or basal
stress) parameterization of :cite:`Lemieux16` is chosen if ``seabed_stress_method``
= ``LKD`` while the new probabilistic approach is used if ``seabed_stress_method``
= ``probabilistic``.
stress) parameterization of :cite:`Lemieux16` is chosen if ``seabed_stress_method`` = ``LKD`` while the approach based on the probability of contact between the ice and he seabed is used if ``seabed_stress_method`` = ``probabilistic``.

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For both parameterizations, the components of the seabed
stress are expressed as :math:`\tau_{bx}=C_bu` and
Expand Down Expand Up @@ -301,7 +299,7 @@ keels in the Arctic Ocean :cite:`Amundrud04`.
Seabed stress based on probabilistic approach
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This new and more sophisticated grounding parameterization computes the seabed stress based
This more sophisticated grounding parameterization computes the seabed stress based
on the probability of contact between the ice thickness distribution
(ITD) and the seabed. Multi-thickness category models such as CICE typically use a
few thickness categories (5-10). This crude representation of the ITD
Expand Down Expand Up @@ -335,8 +333,7 @@ ITD and the seabed is given by
y)g(x)b(y) dy dx, \\
:label: Tbt

and then obtains :math:`T_{bt}` by multiplying :math:`T_{bt}^*` by :math:`e^{-\alpha_b * (1 - a_i)}` (similar to what is done for
``kseabed`` = 1).
and then obtains :math:`T_{bt}` by multiplying :math:`T_{bt}^*` by :math:`e^{-\alpha_b * (1 - a_i)}` (similar to what is done for ``seabed_stress_method`` = ``LKD``).

To calculate :math:`T_{bt}^*` in equation :eq:`Tbt`, :math:`f(x)` and :math:`b(y)` are discretized using many small categories (100). :math:`f(x)` is discretized between 0 and 50 m while :math:`b(y)` is truncated at plus and minus three :math:`\sigma_b`. :math:`f(x)` is also modified by setting it to zero after a certain percentile of the log-normal distribution. This percentile, which is currently set to 99.7%, notably affects the simulation of landfast ice and is used as a tuning parameter. Its impact is similar to the one of the parameter :math:`k_1` for the LKD method.

Expand All @@ -346,7 +343,7 @@ To calculate :math:`T_{bt}^*` in equation :eq:`Tbt`, :math:`f(x)` and :math:`b(y
T_b=\max[T_{bt}(i,j),T_{bt}(i+1,j),T_{bt}(i,j+1),T_{bt}(i+1,j+1)]. \\
:label: Tb

Following again the approach of ``kseabed`` = 1, the seabed stress coefficients are finally expressed as
Following again the LKD method, the seabed stress coefficients are finally expressed as

.. math::
C_b= T_b (\sqrt{u^2+v^2}+u_0)^{-1}, \\
Expand Down Expand Up @@ -385,7 +382,11 @@ is therefore simply equal to :math:`-\sigma_1/2`.
Following the approach of :cite:`Konig10` (see also :cite:`Lemieux16`), the
elliptical yield curve can be modified such that the ice has isotropic tensile strength.
The tensile strength :math:`T_p` is expressed as a fraction of the ice strength :math:`P`, that is :math:`T_p=k_t P`
where :math:`k_t` should be set to a value between 0 and 1 (this can be changed at runtime with the namelist parameter ``Ktens``).
where :math:`k_t` should be set to a value between 0 and 1 (this can
be changed at runtime with the namelist parameter ``Ktens``). The ice
strength :math:`P` is a function of the ice thickness distribution as
described in the `Icepack
Documentation<https://cice-consortium-icepack.readthedocs.io/en/master/science_guide/index.html>`_.

.. _stress-vp:

Expand Down Expand Up @@ -416,9 +417,7 @@ and :math:`P_R` is a “replacement pressure” (see :cite:`Geiger98`, for
example), which serves to prevent residual ice motion due to spatial
variations of :math:`P` when the rates of strain are exactly zero.

The ice strength :math:`P`
is a function of the ice thickness and concentration
as described in the `Icepack Documentation <https://cice-consortium-icepack.readthedocs.io/en/master/science_guide/index.html>`_. The parameter :math:`e` is the ratio of the major and minor axes of the elliptical yield curve, also called the ellipse aspect ratio. It can be changed using the namelist parameter ``e_ratio``.
The parameter :math:`e` is the ratio of the major and minor axes of the elliptical yield curve, also called the ellipse aspect ratio. It can be changed using the namelist parameter ``e_ratio``.

.. _stress-evp:

Expand Down