DOI: 10.5285/9b138820-eec3-43ae-a49b-068a9f5931a4
title: HadCM3 and HadGEM3 LIG model outputs: A sea ice-free Arctic

description: The HadGEM3 (HadGEM3-GC3.1 or HadGEM3-GC3.1-N96ORCA1) PI simulation was initialized using the standard CMIP6 protocol using constant 1850 GHGs, ozone, solar, tropospheric aerosol, stratospheric volcanic aerosol and land-use forcing. The PI spin-up was 700 model-years, which allowed the land and oceanic masses to attain approximate steady state. The HadGEM3 LIG (Last Interglacial) simulation was initialized from the end of the spin-up phase of the equivalent pre-industrial (PI) simulation. After initialization, the LIG was run for 350 model-years. This 350 LIG spin-up permits the model to reach atmospheric equilibrium and to achieve an upper-ocean equilibrium. The model was then run for a further 200 model-years of LIG production run. This has been demonstrated to be an adequate run length to appropriately capture the model internal variability. This dataset contains outputs from the 200 years of production run of the period. The HadCM3 PI simulation was run for a period of over 600 years. The HadCM3 LIG simulation was initialized from the end of a previous CMIP5 LIG simulation, which was of length 400 years and initiated from the end of the corresponding PI, and run for further 250 years. The total spin-up phase for the HadCM3 LIG simulation used in this study was thus 600 model-years, and the length of the production (at atmospheric and upper-oceanic equilibrium) LIG HadCM3 simulation is 50 model-years. This work was funded by NERC standard research grant nos. NE/P013279/1 and NE/P009271/1.
description: The simulations were carried out using the HadGEM3 and HadCM3 climate models. These model simulations were run on the ARCHER UK National Supercomputing Service (http://www.archer.ac.uk) and processed on the JASMIN data analysis platform (http://jasmin.ac.uk/). They are Tier 1 LIG simulations, on the basis of the standard CMIP6-PMIP4 LIG experimental protocol. The prescribed LIG (127,000 yr) protocol differs from the CMIP6 PI simulation protocol in astronomical parameters and the atmospheric trace GHG concentrations. LIG astronomical parameters are prescribed according to orbital constants43, and atmospheric trace GHG concentrations are based on ice-core measurements. other boundary conditions, including solar activity, ice sheets and aerosol emissions, are identical to the PI simulation. We run two LIG simulations, one using the UK CMIP6 HadGEM3 model and the other using the CMIP3 HadCM3 model. HadGEM3 is the lowest-resolution version of the UK CMIP6 physical climate model. It is a global coupled atmosphere-land-ocean-ice model that comprises the Unified Model atmosphere model, the JULES land surface model, the NEMO ocean model and the CICE sea-ice model.
description: HadGEM3 (HadGEM3-GC3.1 or HadGEM3-GC3.1-N96ORCA1). HadCM3. Simulations were run on the ARCHER UK National Supercomputing Service (http://www.archer.ac.uk) and processed on the JASMIN data analysis platform (http://jasmin.ac.uk/), between 2018 and 2020.
description: The Unified Model atmospheric component of HadGEM3 utilizes a horizontal grid spacing of approximately 135 km on a regular latitude-longitude grid. The NEMO ocean model of HadGEM3 employs an orthogonal curvilinear grid with a 1° resolution everywhere but near the equator, where it decreases to 0.33°. The atmosphere and ocean models use 85 and 75 vertical (pressure) levels, respectively. HadCM3 is the UK CMIP3 coupled atmosphere-ocean general circulation model30. Our version of HadCM3 includes the dynamic vegetation model TRIFFID (ref. 47) and the land surface model MOSES 2.1 (ref. 48). The horizontal resolution of the atmosphere model is 3.75° longitude by 2.5° latitude. The ocean model uses a resolution of 1.25° longitude by 1.25° latitude. The atmospheric and oceanic components use 19 and 20 vertical levels, respectively.