FVCOM_Petermann_Discharge_Input_Files

Overview

This repository contains all the input files that are required to run the subglacial discharge experiments for the Petermann ice shelf-fjord system using the Finite Volume Community Ocean Model (FVCOM). A manuscript investigating the mechanisms behind subglacial discharge-driven increase in melt and their evolution with increasing discharge in a warmer future climate is presently under consideration for peer-review and publication in a suitable scientific journal. The metadata provided here will be updated accordingly. 

Pre-requisites

The open source code Finite Volume Community Ocean Model version 4.0 (FVCOM v4.0) augmented by an ice shelf (Zhou and Hattermann, 2020) and sea ice module (Prakash et al., 2022) is required to conduct the numerical experiments, and is made publicly available at https://github.com/abhay26992/FVCOM_Petermann_Code. A detailed description of our high-resolution (200 m) unstructured grid 3-D regional model setup centered on the Petermann ice shelf and fjord is available from Prakash et al. (2022) and Prakash et al. (2023).

File description

The model input files can be classified under 2 broad categories, namely 

static, and 

time-varying.

Static : These include the following files

zisf.dat (realistic Petermann ice shelf draft derived from BedMachine v3 (Morlighem et al., 2017)), 

dep.dat (smoothed bathymetry, which has been modified to provide an improved (with respect to BedMachine v3 (Morlighem et al., 2017)) representation of the sub-ice shelf topography), 

cor.dat (Coriolis),

sigma.dat (terrain-following vertical coordinate system),

grd.dat (FVCOM Petermann Fjord regional model grid)

Time-varying: These include the following files

(a) Atmospheric Forcing

ocnice_YYYY_wnd.nc (wind forcing), 

ocnice_YYYY_fwf.nc (freshwater flux), and

ocnice_YYYY_hf.nc (heat flux), 

where YYYY represents the forcing year, e.g. 2014.

(b) Sea ice forcing

ocnice_YYYY_icenudge.nc (includes sea ice concentration and thickness, bulk ice salinity, and sea ice velocities),

where YYYY represents the forcing year, e.g. 2014.

(c) Ocean boundary conditions

pf_l_bcorr_climaYY.nc (bias-corrected lateral ocean boundary conditions which includes temperature, salinity, ocean velocities, and sea surface elevation)

where YY represents the forcing year, e.g. 14 (for 2014).

In addition to these two broad categories, a restart file (*_restart_*.nc) is included in each run directory, which is used to provide "realistic" (a.k.a. "hotstart") initial ocean conditions. The restart file in the directory control_run_2014 includes a "realistic" initial (July 01, 2014 00:00:00 UTC) ocean condition derived from a 4-km pan-Arctic (A4) ROMS model (Hattermann et al., 2016). Thereafter, the FVCOM model solution on January 01, 2015 00:00:00 UTC is used to "hotstart" the 2015 calendar year. Lastly, the stable FVCOM model solution from January 01, 2016 00:00:00 UTC is used to "hotstart" the 2016 calendar year, as well as the discharge experiments. Note that the discharge experiments depart from the control experiment (control_run_2016) by introducing subglacial discharge of varying magnitudes. All other conditions are kept the same, in order to isolate and investigate the impact of subglacial discharge on the basal melting of the Petermann ice shelf. The namelist file (*.nml) for each run is also included in the corresponding directory.

To minimize storage space, each run directory is populated with only the input files that are unique to that run. For e.g., control_run_2015/2016 and the discharge_experiments do not include the static files from control_run_2014, however, they are required to conduct each of these runs. Likewise, discharge_experiments do not include the time-varying forcing files, since they are identical to the ones contained in control_run_2016. The discharge_experiments do however include the discharge forcings for the present, RCP 8.5, and median(present,RCP 8.5) scenarios. These are the riverdata (riverdata.nc (present), riverdata_expC.nc (median), and riverdata_expD.nc (RCP 8.5)) and the corresponding rivernamelist (riverNamelist.nml, riverNamelist_expC.nml, riverNamelist_expD.nml) files. Note that a rivernamelist is different from a namelist file, in that it only contains information about the subglacial discharge.

Development of the smoothed model topography datasets for our unstructured grid (horizontal resolutions of 200 m, 2km, and 4km) regional model domain, including localized improvements made within the Petermann Fjord; the ocean nesting and surface forcing methodologies (models used, downscaling procedure etc.); bias-correction, among other technical details, are detailed in Prakash et al. (2022) and Prakash et al. (2023).