DOI: 10.5061/dryad.4b8gthtsv
title: Data from: Using Antarctic subglacial relic landscapes to inform past ice sheet retreat in the warm Pliocene

description: We use high-resolution ice sheet model simulations to better understand if
 the preservation of a relic landscape precludes significant glacial
 retreat into the Aurora Subglacial Basin sector of East Antarctica in at
 least the past 3 million years. Transient ice sheet model (ISM)
 simulations were performed through selected glacial-interglacial cycles of
 the mid-Piacenzian warm period (mPWP). We use the PSU-ISM, a 3-D
 thermomechanical ice sheet-shelf model, with climatic forcing applied
 using the multi-dimensional matrix method. To ensure stability of the
 high-resolution runs, a sequence of simulations at increasing spatial and
 temporal resolution was required. To explore the relationship between
 retreat in this sector and the preserved landscape, an ensemble of
 simulations was created by invoking the Marine Ice Cliff Instability
 (MICI) process at a range of levels. Continental scale simulations at 40
 km resolution were run for 500 kyrs (3.4–2.9 Ma) to identify time periods
 of greatest retreat for each calving parameter set. We focused on four
 interglacial periods for the highest resolution (5 km) simulations, which
 relate to the Marine Isotope Stages (MIS): MG1, KM5, K1, G17. To
 understand controls on the preservation of the Highland A relic landscape,
 we present key model variables relating to the basal thermal regime and
 erosional potential.
description: # Data from: Using Antarctic subglacial relic landscapes to inform past
 ice sheet retreat in the warm Pliocene Dataset DOI:
 [10.5061/dryad.4b8gthtsv](https://doi.org/10.5061/dryad.4b8gthtsv) ##
 Description of the data and file structure This dataset contains
 time-evolving Antarctic ice sheet model (ISM) output relating to multiple
 de-glaciation cycles within the Pliocene. To conduct these transient
 simulations, we use the PSU-ISM. ### Files and variables #### File:
 ISM_Output_Timeseries_Rae.zip **Description:** Tabular data (can be opened
 with any text editor) relating to the continental-scale model simulations
 ('Rae' forcing), performed at 40 km grid resolution. Model
 history writes occur every 1000 years (from 3.4 - 2.9 Ma). Five simulation
 files relate to different levels of Marine Ice Cliff Instability (MICI),
 which is parameterised in the model. The levels are: Off, Low, MedLo,
 MedHi, and Max.  Key tabular fields include: * 'esl': ice sheet
 configuration converted to sea level equivalent (m) * 'esle':
 ice sheet configuration converted to sea level equivalent for East
 Antarctica only (m)  - Time and run identifiers * time – Model time (years
 relative to present; negative values indicate years before present). -
 weirun – Model run identifier or weighting factor (constant in this
 output). * Orbital and astronomical parameters - ro18 – δ¹⁸O reference
 value or isotopic forcing parameter. * sealev – Global mean sea level
 relative to present (m). - ecc – Orbital eccentricity. * obl – Orbital
 obliquity (tilt; degrees). - prec – Climatic precession parameter. *
 dtanta – Antarctic temperature anomaly (°C). - dtants – Antarctic summer
 temperature anomaly (°C). * dtantj – Antarctic winter temperature anomaly
 (°C). - dtseas – Seasonal temperature anomaly (°C). * rco2 – Atmospheric
 CO₂ concentration or radiative forcing related to CO₂. - facice –
 Ice-related forcing factor. * facorb – Orbital forcing factor. - facco2 –
 CO₂ forcing factor. * Ice volume (km³) - toti – Total ice volume. * totig
 – Grounded ice volume. - totif – Floating ice volume. * Ice area (km²) -
 tota – Total ice area. * totag – Grounded ice area. - totaf – Floating ice
 area. * Sea-level and height contributions (m) - h – Mean ice thickness or
 equivalent height. * eofe – East Antarctic ice contribution to sea level.
 - eofw – West Antarctic ice contribution to sea level. * eof – Total
 Antarctic ice contribution to sea level. - esle – East Antarctic sea-level
 equivalent. * eslw – West Antarctic sea-level equivalent. - esl – Total
 sea-level equivalent from ice. * odtsurf – Ocean surface temperature
 anomaly (°C). - odt400 – Ocean temperature anomaly at 400 m depth (°C).
 #### File: ISM_Output_Rae_All.zip **Description:**  NetCDF files (.nc)
 from each simulation ('Rae' forcing) were produced for the
 Aurora Subglacial Basin domain over 4 interglacial periods, which related
 to the Marine Isotope Stages (MIS): MG1, KM5, K1, G17. These simulations
 have a duration of 25 kyr with model history writes every 100 years. The
 spatial resolution is 5 km. As above, there are different simulations for
 the five levels of Marine Ice Cliff Instability (MICI): Off, Low, MedLo,
 MedHi, and Max. 20 files in total cover 4 MIS for 5 MICI levels. Key 3D
 model output fields include: * 'h': ice thickness (m) *
 'maskwater': 0 if bare ground or grounded ice; 1 if ocean (with
 or without ice shelf) * 'budgall': annual overall local ice
 budget (m y^-1^ ice equiv.) * 'fract': basal non-frozen fraction
 * 'heatb': heating due to basal shear stress (J m^-2^ y^-1^) *
 'ua' & 'va': vertical-mean horizontal ice
 velocities (m y^-1^) * 'ubot' & 'vbot': basal ice
 horizontal velocities (m y^-1^) ## Code/software #### File: Code.zip
 **Results_Metrics.py:** This Python script file conducts the majority of
 analyses used in the manuscript, and can be used with
 the ISM_Output_Rae_All.zip data files.
 **Plotting_model_output_timeseries.py** This Python script file can be
 used to analyse the tabular output from the continental-scale model
 simulations contained in the ISM_Output_Timeseries_Rae.zip folder. For
 both scripts,  the user will need to install the Python libraries listed
 at the top of the file and set up the directories ('dir_path')
 to reference the location where the data (already unzipped) has been
 downloaded to.