The Ocean Carbon States Database: a proof-of-concept application of cluster analysis in the ocean carbon cycle

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We present results from the NASA GISS ModelE2.1-G-CC Earth System Model with coupled climate-carbon cycle simulations that were submitted to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) Coupled Climate-Carbon Cycle MIP (C4MIP). Atmospheric CO 2 concentration and carbon budgets for the land and ocean in the historical simulations were generally consistent with observations. Low simulated atmospheric CO 2 concentrations during 1850-1950 were due to excess uptake from prescribed land cover change, which erroneously replaced arid shrublands with higher biomass crops, and assumed high 2004 LAI values in vegetated lands throughout the historical simulation. At the end of the historical period, slightly higher simulated CO 2 than observed resulted from the land being an insufficient net carbon sink, despite the net effect of CO 2 fertilization and warming-induced increases to leaf photosynthetic capacity. The global ocean carbon uptake agreed well with the observations with the largest discrepancies in the low latitudes. Future climate projection at 2091-2100 agreed with CMIP5 models in the northward shift, of temperate deciduous forest climate and expansion across Eurasia along 60°N latitude, and dramatic regional biome shifts from drying and warming in continental Europe. Carbon feedback parameters were largely similar to the CMIP5 model ensemble. 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 more negative ocean carbon-climate feedback is due to the large slowdown of the Atlantic overturning circulation. Plain Language Summary The Earth's global carbon cycle traces surface-atmosphere exchanges of CO 2 by the ocean and the land, including both natural processes (photosynthesis, respiration, ecological dynamics, gas exchange, and atmospheric transport) and anthropogenic activities (fossil fuel emissions and land use change). Scientists synthesize current understanding of carbon cycle science in Earth System Models (ESMs), to simulate the most significant processes in a highly complex system and to quantify how the land and ocean carbon sources and sinks of atmospheric CO 2 behave and how they will change in the future. The NASA GISS ModelE2.1-G-CC ESM couples the NASA Ocean Biogeochemistry Model (NOBM) in the ocean, the Ent Terrestrial Biosphere Model (Ent TBM) on land, and CO 2 transport through the atmosphere and interactions with Earth's radiation. Here we describe experiments that were contributed to the Coupled Model Intercomparison Project 6 (CMIP6). Results indicate that GISS ModelE2.1 reproduces the large-scale properties of the carbon cycle generally consistently with measured data. In future warmer climates, major regional biome changes will occur in temperate to subarctic climates. The land and the ocean become net sinks, but they will have reduced ability to take up additional CO 2 and thereby ameliorate climate warming.

Section: Journal Of Advances In Modeling Earth Systemsmentioning

confidence: 84%

Global Carbon Cycle and Climate Feedbacks in the NASA GISS ModelE2.1

Ito

Romanou

Kiang

et al. 2020

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“…There is parallel development of ModelE coupled to HYCOM (Sun & Bleck, 2006), where 'R' and 'G' are replaced by 'H'. The suffix 'CC' refers to an interactive carbon cycle (Romanou et al, 2013(Romanou et al, , 2014Latto & Romanou, 2018;Ito et al, 2020;Lerner et al, 2020). The domain of GISS-E2.2 extends into the mesosphere and has a better stratospheric circulation (Rind et al, 2020;Orbe et al, 2020), while GISS-E3 incorporates a new cubed-sphere grid and improved model physics.…”

Section: Models and Experimentsmentioning

confidence: 99%

CMIP6 Historical Simulations (1850–2014) With GISS‐E2.1

Miller

Schmidt

Nazarenko

et al. 2021

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“…The dominant drivers of the seasonal cycle of pCO 2, sw are those associated with the largest right‐hand side terms. Similar methods based on Taylor series expansions have been used to assess drivers in the variability of pCO 2, sw and the CO 2 flux (Doney et al., 2009; Latto & Romanou, 2018; Lovenduski et al., 2007; Mogollón & Calil, 2018). Offline calculations of pCO 2, sw are performed using the OMIP‐BGC carbonate chemistry protocols, which estimate pCO 2, sw from

{normalC normalO}_{2}^{*}

(the sum of carbonic acid and dissolved CO 2 ) and the solubility of CO 2 by (i) calculating the solubility of CO 2 as a function of temperature and salinity (as for the CO 2 flux), and (ii) calculating

{normalC normalO}_{2}^{*}

from pH and DIC, where pH is obtained by solving the pH‐alkalinity equation with the SolveSaphe algorithm (Munhoven, 2013; Orr et al., 2017).…”

Section: Resultsmentioning

confidence: 99%

“…The dominant drivers of the seasonal LERNER ET AL. (Doney et al, 2009;Latto & Romanou, 2018;Lovenduski et al, 2007;Mogollón & Calil, 2018 CO from pH and DIC, where pH is obtained by solving the pH-alkalinity equation with the SolveSaphe algorithm (Munhoven, 2013;Orr et al, 2017).…”

Section: Drivers Of Seasonal Pcomentioning

confidence: 99%

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Drivers of Air‐Sea CO₂ Flux Seasonality and its Long‐Term Changes in the NASA‐GISS Model CMIP6 Submission

Lerner

Romanou

Kelley

et al. 2021

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Climate change will affect both the mean state and seasonality of marine physical and biogeochemical properties, with important implications for the oceanic sink of atmospheric CO2. Here, we investigate the seasonal cycle of the air‐sea exchange of CO2 and pCO2,sw (surface seawater pCO2) and their long term changes using the CMIP6 submission of the NASA‐GISS modelE (GISS‐E2.1‐G). In comparison to the CMIP5 submission (GISS‐E2‐R), we find that on the global scale, the seasonal cycles of the CO2 flux and NPP have improved, while the seasonal cycles of dissolved inorganic carbon (DIC), alkalinity, and macronutrients have deteriorated. Moreover, for all ocean biogeochemistry fields, changes in skill between E2.1‐G and E2‐R display large regional variability. For E2.1‐G, we find similar modeled and observed CO2 flux seasonal cycles in the subtropical gyres, where seasonal anomalies of pCO2,sw and the flux are temperature‐driven, and the Southern Ocean, where anomalies are DIC‐driven. Biases in these seasonal cycles are largest in the subpolar and equatorial regions, driven by a combination of biases in temperature, DIC, alkalinity, and wind speed. When comparing the historical simulation to a simulation with an idealized increase in atmospheric pCO2, we find that the seasonal amplitudes of the CO2 flux and pCO2,sw generally increase. These changes are produced by increases in the sensitivity of pCO2,sw to its respective drivers. These findings are consistent with the notion that the seasonality of pCO2,sw is expected to increase due to the increase of atmospheric pCO2, with changes in the seasonality of temperature, DIC, and alkalinity having secondary influences.