POLARiso

MARiso code is available here: **https://gitlab.com/Mar-Group/MARv3/-/tree/mariso**

The code is freely distributed, you just have to log to gitlab to access it.

1.1 Implementation of water stable isotopes without fractionation

Objectives:

Add water stable isotopes for each water component and check if the water is correctly tracked.

Add isotopes as standard outputs

Method:

• Water isotopes added for each water component (see last section).
• Mass transfers between water components applied similarly to the water isotopes without fractionation.
• Water isotopes advected as classical water components by the dynamical core of the model.
• Fixed isotopic values at the lateral boundaries and for model initialization.

1.2 Implementation of isotope forcing without fractionation

Objectives:

Implement the isotopic forcing (inputs) of the regional climate model without fractionation.

Method:

• Interpolation of the isotopic composition of water vapor modeled by LMDZiso for MAR forcing and initialization.
• Isotopic composition of clouds, precipitation and drifting snow (Table 1) initialized with water vapor ratios.
• Isotopic composition at the surface of the ocean: global seawater 18-O database (Schmidt et al., 1999)
• Isotopic composition of the snow: Antarctic snow isotopic composition database (Masson-Delmotte et al., 2008)

1.3 Implementation of fractionation coefficients

Objectives:

Implement fractionation for each phase change.

Method

• Fractionation equations following LMDZiso, with adapted equations for polar regions (Jouzel and Melivat, 1984).
• Use MAR specificities for improving the isotope fractionation: super-saturation, mixed-phase clouds, drifting snow.

Model set-up, forcing, existing parameterizations and future implementations

• Model set-up
• Forcings
• Water components included in MAR
• Water stable isotopes to be implemented in MAR