iPOGS: A 10-member ensemble of CESM HR RCP 6.0 (2006-2100) simulations

Current predictions and projections of future sea-level changes are based on Coupled Model Intercomparison Project (CMIP) class climate model simulations. Although this class of models is capable of simulating global sea-level rise and its basic spatial patterns, they are unable to robustly and accurately predict or project future regional and local sea-level changes because of their limitations in representing complex coastline and bathymetry features and regional ocean circulations with their coarse (approximately 100 km) horizontal resolutions. More specifically, sea-level changes within the Gulf of Mexico are closely linked to changes in the Loop Current and its eddies, which cannot be resolved by these CMIP-class models.

To address this fundamental issue, we have completed a 10-member ensemble of simulations with the Community Earth System Model (CESM) at a Tropical Cyclone-permitting and ocean-mesoscale-eddy-rich horizontal resolution (hereafter simply referred to as CESM-HR). The CESM-HR configuration is based on an earlier CESM version, CESM1.3, with many additional modifications and improvements. CESM-HR uses a 0.25 degree grid in the atmosphere and land components and a 0.1 degree grid in the ocean and sea-ice components. The primary reason for using an older model version, instead of the latest CESM2, is that CESM2 does not support a high-resolution version per the decision by the CESM Scientific Steering Committee. The component models within CESM1.3 are the Community Atmosphere Model version 5 (CAM5; Neale et al., 2012), the Parallel Ocean Program version 2 (POP2; Danabasoglu et al., 2012; Smith et al., 2010), the Community Ice Code version 4 (CICE4; Hunke and Lipscomb, 2008), and the Community Land Model version 4 (CLM4; Lawrence et al., 2011).

Following the protocol for the CMIP phase 5 (CMIP5) experiments, the representative concentration pathway 6.0 (RCP 6.0) was used to force the model from 2006 to 2100. RCP 6.0 represents a stabilization scenario, where the greenhouse gas emission rate is high initially, but total radiative forcing is stabilized after 2100 through the use of various technologies and strategies for reducing emissions. In this scenario, the specified amount of carbon concentration results in an average global radiative forcing increase of 6.0 W/m^2 by 2100. This CESM-HR ensemble was completed as part of our National Academy of Sciences (NAS) funded project entitled "Improving Prediction and Projection of Gulf of Mexico Sea-Level Changes Using Eddy-Resolving Earth System Models (iPOGS)". This effort is complementary to the 10-member ensemble of CESM-HR historical and future (with RCP 8.5 forcing) climate simulations produced by our National Science Foundation (NSF) funded project entitled "Understanding the role of mesoscale atmosphere-ocean interactions in seasonal-to-decadal climate prediction (MESACLIP)". Each RCP 6.0 simulation starts at the end of the corresponding historical simulation from MESACLIP, enabling the exploration of future projections associated with varying levels of mitigation and future greenhouse gas emissions. For example, Figure 1 [https://rda.ucar.edu/OS/web/datasets/d651008/docs/Figure1_RDA_d651008.png] shows the global-mean dynamical sea level (DSL) from simulations under different forcings. The stronger warming associated with the RCP 8.5 forcing results in an additional 10 cm rise in global-mean DSL by 2100 compared to that of the RCP 6.0 ensemble.

Citation: The two papers linked below are the most appropriate references for the CESM-HR ensemble. To cite the dataset, use Chang et al. (2025). We ask that you also cite the dataset itself using the reference Castruccio et al [https://rda.ucar.edu/datasets/d651008/citation/]. (2024) in any documents or publications using these data. Chang et al. (2020) describes the initial CESM-HR simulations, including the 500-year pre- industrial control simulation and the first 250-year historical and future climate simulation from 1850 to 2100. We would also appreciate receiving a copy of the relevant publications. This will help us to justify keeping the data freely available online in the future. Thank you!