Marine biogeochemical cycling and climate-carbon cycle feedback simulated by the NUIST Earth System Model: NESM-2.0.1

Abstract. In this study, we evaluate the performance of Nanjing University of Information Science & Technology Earth System Model, version 2.0.1 (hereafter NESM-2.0.1). We focus on model simulated historical and future oceanic CO₂ uptake, and analyze the effect of global warming on model-simulated oceanic CO₂ uptake. Compared with available observations and data-based estimates, NESM-2.0.1 reproduces reasonably well large-scale ocean carbon-related fields, including nutrients (phosphate, nitrite and silicate), chlorophyll, and net primary production. However, some noticeable discrepancies between model simulations and observations are found in the deep ocean and coastal regions. Model-simulated current-day oceanic CO₂ uptake compares well with data-based estimate. From pre-industrial time to 2011, modeled cumulative CO₂ uptake is 144 PgC, compared with data-based estimates of 155 ± 30 PgC. Diagnosed from the end of the benchmark 1 % per year CO₂ increase simulations, carbon-climate feedback parameter, which represents the sensitivity of ocean CO₂ uptake to climate change, is −7.1 PgC/K; Carbon-concentration feedback parameter, which represents the sensitivity of ocean CO₂ uptake to increase in atmospheric CO₂ is 0.81 PgC/ppm. These two feedback parameters diagnosed from model simulations are consistent with the mean value diagnosed from the CMIP5 (Coupled Model Intercomparison Project phase 5) model simulations under the same 1 % per year CO₂ simulations (−7.8 PgC/K and 0.80 PgC/ppm, respectively). Our results demonstrate that NESM-2.0.1 can be used as a useful tool in the investigation of feedback interactions between the ocean carbon cycle, atmospheric CO₂, and climate change.