Modeling the mid-Piacenzian warm climate using the water isotope-enabled Community Earth System Model (iCESM1.2)

Author:

Sun Yong1,Ding Lin1,Su Baohuang2,Dowsett Harry3,Wu Haibin1,Ramstein Gilles4

Affiliation:

1. Chinese Academy of Sciences

2. Chinese Academy of Meteorological Sciences

3. U.S. Geological Survey, 926A National Center

4. LSCE/IPSL, CEA ‐ CNRS ‐ UVSQ, Université Paris‐Saclay

Abstract

Abstract The mid-Piacenzian warm period (MPWP, ~3.264–3.025 Ma, previously referred to as the mid-Pliocene warm period), is the most recent geological period with atmospheric CO2 concentrations (400ppmv) close to today, but global surface temperatures were higher than today and in equilibrium with the CO2 concentrations. Therefore, the mid-Piacenzian equilibrated climate is often compared to the modern transient climate. In this study, we conduct a water isotope-enabled Community Earth System Model (iCESM1.2) simulation to study the large-scale features of the MPWP following the protocols of Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). This MPWP simulation exhibits considerable warming in the high latitudes comparable to high-latitude MPWP surface warming evidenced in proxy records (i.e., polar amplification) that has been often underestimated in previous simulations. The improved performance of iCESM1.2over the PlioMIP2 models is due to a larger contribution of iCESM1.2-simulated downward clear-sky surface long wave radiation fluxes affecting polar amplification. Compared to the PI period, the total precipitation simulated by iCESM1.2 is generally wetter than the PlioMIP2 multi-model ensemble mean (MME) except for the opposite performance between iCESM1.2 and PlioMIP2 MME over the regions [~30S°–10N]. A heavier δ18Op during the MPWP mainly occurred in the tropical Indian ocean and surrounding Asian-African-Australian monsoon regions. There are contrasting changes in the tropical meridional and zonal atmospheric circulations (Hadley and Walker cells) during the MPWP. A weakened and expanded Hadley circulation (toward the poles) led to a reduction in tropical precipitation [~30S°–10N] and a poleward shift of the edge of the northern subtropical arid zone. In contrast, the tropical zonal atmospheric overturning circulation (Walker cell) and the global ocean meridional overturning circulation (MOC) are generally enhanced during the MPWP compared to the PI period.

Publisher

Research Square Platform LLC

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