GFDL’s ESM2 Global Coupled Climate–Carbon Earth System Models. Part I: Physical Formulation and Baseline Simulation Characteristics

Abstract

The physical climate formulation and simulation characteristics of two new global coupled carbon–climate Earth System Models, ESM2M and ESM2G, are described. These models demonstrate similar climate fidelity as the Geophysical Fluid Dynamics Laboratory’s previous Climate Model version 2.1 (CM2.1) while incorporating explicit and consistent carbon dynamics. The two models differ exclusively in the physical ocean component; ESM2M uses Modular Ocean Model version 4p1 with vertical pressure layers while ESM2G uses Generalized Ocean Layer Dynamics with a bulk mixed layer and interior isopycnal layers. Differences in the ocean mean state include the thermocline depth being relatively deep in ESM2M and relatively shallow in ESM2G compared to observations. The crucial role of ocean dynamics on climate variability is highlighted in El Niño–Southern Oscillation being overly strong in ESM2M and overly weak in ESM2G relative to observations. Thus, while ESM2G might better represent climate changes relating to total heat content variability given its lack of long-term drift, gyre circulation, and ventilation in the North Pacific, tropical Atlantic, and Indian Oceans, and depth structure in the overturning and abyssal flows, ESM2M might better represent climate changes relating to surface circulation given its superior surface temperature, salinity, and height patterns, tropical Pacific circulation and variability, and Southern Ocean dynamics. The overall assessment is that neither model is fundamentally superior to the other, and that both models achieve sufficient fidelity to allow meaningful climate and earth system modeling applications. This affords the ability to assess the role of ocean configuration on earth system interactions in the context of two state-of-the-art coupled carbon–climate models.

Reproducibility of precipitation distribution over the tropical oceans in CMIP5 multi-climate models compared to CMIP3

“…3 (see Chikira and Sugiyama 2010 for detail). The convective schemes in CSIRO-Mk3-6-0 (Rotstayn et al 2012), CNRM-CM5 (Voldoire et al 2013), and GFDL-ESM2 (Dunne et al 2012) are not modified from their older versions, but the DI of CNRM-CM5 and GFDL-ESM2G is improved whereas that of CSIRO-Mk3-6-0 and GFDL-ESM2M is degraded. These results suggest some other factors influencing the double ITCZ bias.…”

Northern-hemispheric differential warming is the key to understanding the discrepancies in the projected Sahel rainfall

“…These two models originate from 'gfdl_cm2_1' and 'miroc3_2_medres' in CMIP3, which also predicted extreme drying and wetting, respectively. The two versions of models developed from the same modelling group are basically the same except for incorporating carbon dynamics and some minor tuning in physical models 37,38 . The future scenario chosen for the present study is the Representative Concentration Pathways 4.5 (RCP4.5), a mid-range mitigation scenario.…”

Capturing interactions between nitrogen and hydrological cycles under historical climate and land use: Susquehanna watershed analysis with the GFDL land model LM3-TAN

“…LM3-TAN was expanded to include vegetation-and soil-N dynamics from LM3V-N (Gerber et al, 2010), new soil physics and hydrology from LM3 (Milly et al, 2014), and N cycling processes described here. LM3 was used as a component of the GFDL Earth System Models (Dunne et al, 2012) and included several enhancements, such as vertically resolved soil physics and hydrology and explicit river dynamics and physics. LM3-TAN includes soil denitrification and transport and chemistry of N cycle in rivers.…”