An Unprecedented Set of High‐Resolution Earth System Simulations for Understanding Multiscale Interactions in Climate Variability and Change

Abstract

We present an unprecedented set of high-resolution climate simulations, consisting of a 500-year pre-industrial control simulation and a 250-year historical and future climate simulation from 1850 to 2100. A high-resolution configuration of the Community Earth System Model version 1.3 (CESM1.3) is used for the simulations with a nominal horizontal resolution of 0.25°for the atmosphere and land models and 0.1°for the ocean and sea-ice models. At these resolutions, the model permits tropical cyclones and ocean mesoscale eddies, allowing interactions between these synoptic and mesoscale phenomena with large-scale circulations. An overview of the results from these simulations is provided with a focus on model drift, mean climate, internal modes of variability, representation of the historical and future climates, and extreme events. Comparisons are made to solutions from an identical set of simulations using the standard resolution (nominal 1°) CESM1.3 and to available observations for the historical period to address some key scientific questions concerning the impact and benefit of increasing model horizontal resolution in climate simulations. An emerging prominent feature of the high-resolution pre-industrial simulation is the intermittent occurrence of polynyas in the Weddell Sea and its interaction with an Interdecadal Pacific Oscillation. Overall, high-resolution simulations show significant improvements in representing global mean temperature changes, seasonal cycle of sea-surface temperature and mixed layer depth, extreme events and in relationships between extreme events and climate modes. Plain Language Summary Although the current generation of climate models has demonstrated high fidelity in simulating and projecting global temperature change, these models show large uncertainties when it comes to questions concerning how rising global temperatures will impact local weather conditions. This is because the resolution (~100 km) at which the majority of climate models simulate the climate is not fine enough to resolve these small-scale regional features. Conducting long-term (multi-centuries) high-resolution (~10 km) climate simulations has been a great challenge for the research community due to the extremely high computational demands. Through international

Revisiting AMOC Transport Estimates From Observations and Models

“…This configuration uses the Community Earth System Model version 2 (CESM2; Danabasoglu et al., 2020) framework. The simulation is forced with the adjusted Japanese Reanalysis data sets (JRA55‐do; Tsujino et al., 2018) for the 1958–2018 period and has been performed by the International Laboratory for High‐Resolution Earth System Prediction (iHESP; Chang et al., 2020). The 1958–2018 forcing period is cyclically repeated multiple times to reduce model transients and drifts.…”

Effects of strongly eddying oceans on multidecadal climate variability in the Community Earth System Model

“…Models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5; Taylor et al, 2012) generally underestimate multidecadal climate variability (Cheung et al, 2017;Mann et al, 2020). The amplitudes of Pacific and Atlantic multidecadal variability, as measured by the AMV and PDO indices, are significantly lower than in observations.…”

An outsized role for the Labrador Sea in the multidecadal variability of the Atlantic overturning circulation

“…In this study, we examine an unprecedented high-resolution (HR; 0.1° ocean coupled to 0.25° atmosphere) preindustrial control simulation using the Community Earth System Model (CESM) version 1.3 ( 17 , 18 ) that offers a uniquely compelling portrait of the role of Labrador Sea processes in intrinsic LF AMOC variability. This mesoscale eddy-resolving simulation shows markedly improved SPNA realism compared to a low-resolution (LR; 1° ocean coupled to 1° atmosphere) counterpart in the magnitude and location of winter deep convection and density-space overturning.…”