Carbon Uptake in the NASA GISS Global Carbon Cycle Model submitted to CMIP6
Abstract
We discuss key results and differences in simulations of the global carbon cycle with the NASA Goddard Institute for Space Studies (GISS) climate model (modelE2.1) with prescribed and interactive atmospheric CO2. These simulations have been submitted to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) Coupled Climate-Carbon Cycle MIP (C4MIP). In these Earth System type simulations, the land model consisted of a demographic dynamic global vegetation model (dDGVM), in which land ecosystem carbon dynamics prognostically simulated soil carbon and plant labile carbon from biophysics with prescribed natural vegetation cover and canopy structure from Moderate Resolution Imaging Spectroradiometer (MODIS) and the Ice, Cloud, and land Elevation Satellite Geoscience Laser Altimeter System (ICESat/GLAS); historical crop and pasture cover was prescribed annually from Pongratz et al. (2008) and the Land Use Harmonization (LUH) data set of Hurtt et al. (2006) ; the ocean model was fully interactive with the rest of the Earth System, and it included explicit autotrophic and heterotrophic functional types, nutrient distributions, particulate matter, carbon in dissolved organic and inorganic as well as particulate forms and alkalinity. Although atmospheric CO2 concentration and carbon budgets for the land and ocean in the historical simulations were generally consistent with observations, at the end of the historical period, slightly higher simulated CO2 than observed resulted from the land being an insufficient net carbon sink. The global ocean carbon uptake agreed well with the observations with the largest discrepancies in the low latitudes. Future climate projections reproduced changes to surface temperature and precipitation that would be consistent with a northward shift of deciduous forests, and of regional biomes in continental Europe, as previously seen in CMIP5 models. Carbon feedback parameters were largely similar to the CMIP5 model ensemble and to what other CMIP6 models reproduce. For our model, the variation of land feedback parameters within the uncertainty arises from the fertilization feedback being less sensitive due to lack of increased vegetation growth, and the comparably significantly more negative ocean carbon-climate feedback is due to the swift and dramatic slowdown of the Atlantic overturning circulation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA039.0010R
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 3360 Remote sensing;
- ATMOSPHERIC PROCESSES