Rapid evaluation framework for the CMIP7 assessment fast track

As Earth system models (ESMs) grow in complexity and in volumes of output data, there is an increasing need for rapid, comprehensive evaluation of their scientific performance. The upcoming Assessment Fast Track for the Seventh Phase of the Coupled Model Intercomparison Project (CMIP7) will require expeditious response for model analyses designed to inform and drive integrated Earth system assessments. To meet this challenge, the Rapid Evaluation Framework (REF), a community-driven platform for benchmarking and performance assessment of ESMs, was designed and developed. The initial implementation of the REF, constructed to meet the near-term needs of the CMIP7 Assessment Fast Track, builds upon community evaluation and benchmarking tools. The REF runs within a containerized workflow for portability and reproducibility and is aimed at generating and organizing diagnostics covering a variety of model variables. The REF leverages best-available observational datasets to provide assessments of model fidelity across a collection of diagnostics. All diagnostics were identified and finally selected with community involvement and consultation. Operational integration with the Earth System Grid Federation (ESGF) will permit automated execution of the REF for specific diagnostics as soon as model data are published on ESGF by the originating modelling centres. The REF is designed to be portable across a range of current computational platforms to facilitate use by modelling centres for assessing the evolution of model versions or gauging the relative performance of CMIP simulations before being published on ESGF. When integrated into production simulation workflows, results from the REF provide immediate quantitative feedback that allows model developers and scientists to quickly identify model biases and performance issues. After the REF is released to the community, its subsequent development and support will be prioritized by an international consortium of scientists and engineers, enabling a broader impact across Earth science disciplines. For instance, the REF will facilitate improvements to models and reductions in uncertainties for projections since ESMs are the main tool for studying the global Earth system. Production of reproducible diagnostics and community-based assessments are the key features of the REF that help to inform mitigation and adaptation policies

Biological production in the Indian Ocean upwelling zones – Part 1: refined estimation via the use of a variable compensation depth in ocean carbon models

Biological modelling approach adopted by the Ocean Carbon-Cycle Model Intercomparison Project (OCMIP-II) provided amazingly simple but surprisingly accurate rendition of the annual mean carbon cycle for the global ocean. Nonetheless, OCMIP models are known to have seasonal biases which are typically attributed to their bulk parameterisation of compensation depth. Utilising the criteria of surface Chl a-based attenuation of solar radiation and the minimum solar radiation required for production, we have proposed a new parameterisation for a spatially and temporally varying compensation depth which captures the seasonality in the production zone reasonably well. This new parameterisation is shown to improve the seasonality of CO2 fluxes, surface ocean pCO2, biological export and new production in the major upwelling zones of the Indian Ocean. The seasonally varying compensation depth enriches the nutrient concentration in the upper ocean yielding more faithful biological exports which in turn leads to accurate seasonality in the carbon cycle. The export production strengthens by  ∼ 70 % over the western Arabian Sea during the monsoon period and achieves a good balance between export and new production in the model. This underscores the importance of having a seasonal balance in the model export and new productions for a better representation of the seasonality of the carbon cycle over upwelling regions. The study also implies that both the biological and solubility pumps play an important role in the Indian Ocean upwelling zones

Understanding the Seasonality, Trends, and Controlling Factors of Indian Ocean Acidification Over Distinctive Bio-Provinces

The Indian Ocean (IO) is witnessing acidification as a direct consequence of the continuous rising of atmospheric CO2 concentration and indirectly due to rapid ocean warming, which disrupts the pH of the surface waters. This study investigates the pH seasonality and trends over various bio-provinces of the IO and regionally assesses the contribution of each of its controlling factors. Simulations from a global and a regional ocean model coupled with biogeochemical modules were validated with pH measurements over the basin and used to discern the regional response of pH seasonality (1990–2010) and trend (1961–2010) to changes in Sea Surface Temperature (SST), Dissolved Inorganic Carbon (DIC), Total Alkalinity (ALK), and Salinity (S). DIC and SST are significant contributors to the seasonal variability of pH in almost all bio-provinces. Total acidification in the IO basin was 0.0675 units from 1961 to 2010, with 69.3% contribution from DIC followed by 13.8% contribution from SST. For most of the bio-provinces, DIC remains a dominant contributor to changing trends in pH except for the Northern Bay of Bengal and Around India (NBoB-AI) region, wherein the pH trend is dominated by ALK (55.6%) and SST (16.8%). Interdependence of SST and S over ALK is significant in modifying the carbonate chemistry and biogeochemical dynamics of NBoB-AI and a part of tropical, subtropical IO bio-provinces. A strong correlation between SST and pH trends infers an increasing risk of acidification in the bio-provinces with rising SST and points out the need for sustained monitoring of IO pH in such hotspots. © 2023. American Geophysical Union. All Rights Reserved.11Nsciescopu

Optimization of Biological Production for Indian Ocean upwelling zones: Part – I: Improving Biological Parameterization via a variable Compensation Depth

Abstract. Biological modeling approach adopted by the Ocean Carbon Cycle Model Inter-comparison Project (OCMIP-II) provided amazingly simple but surprisingly accurate rendition of the annual mean carbon cycle for the global ocean. Nonetheless, OCMIP models are known to have seasonal biases which are typically attributed to their bulk parameterization of compensation depth. Utilizing the principle of minimum solar radiation for the production and its attenuation by the surface Chl-a, we have proposed a new parameterization for a spatially and temporally varying compensation depth which captures the seasonality in the production zone reasonably well. This new parameterization is shown to improve the seasonality of CO2 fluxes, surface ocean pCO2, biological export and new production in the major upwelling zones of the Indian Ocean. The seasonally varying compensation depth enriches the nutrient concentration in the upper ocean yielding more faithful biological exports which in turn leads to an accurate seasonality in carbon cycle. The export production strengthens by ~ 70 % over western Arabian sea during monsoon period and achieved a good balance between export and new production in the model. This underscores the importance of having a seasonal balance in model export and new production for a better representation of the seasonality of carbon cycle over upwelling regions The study also implies that both the biological and solubility pumps play an important role in the Indian Ocean upwelling zones. </jats:p

Quantification of Enhancement in Atmospheric CO2 Background Due to Indian Biospheric Fluxes and Fossil Fuel Emissions

© 2021. American Geophysical Union. All Rights Reserved.Regional carbon emissions impact global atmospheric carbon dioxide (CO2) background concentrations. This study quantified the enhancement in the atmospheric CO2 mole fractions due to biospheric and fossil fuel fluxes from India. Sensitivity experiments using model simulations were conducted, allowing CO2 enhancement due to biospheric and fossil fuel fluxes from India to diffuse into the global atmospheric background. The areal extent of column-averaged enhancement of 0.2 ppm and above due to Indian fluxes are spread over a larger area covering the Indian subcontinent, neighboring Asian regions, and the north Indian Ocean in all four seasons. The boundary layer CO2 enhancement due to biospheric fluxes (fossil fuel fluxes) have a maximum range of −2.6 to +1.4 ppm (1.8–2.0 ppm) most time of the year. At higher altitude, the amplitudes of enhancement are reduced from ±1.8 to ±0.6 ppm as we go up from 850 to 500 hPa due to diffusion by prevailing atmospheric dynamics and convection. With the information of the areal extent of >0.2 ppm CO2 enhancement due to Indian fluxes, we have evaluated the representativeness of satellite observations (GOSAT and OCO-2) in capturing those enhancements. Both the satellite coverage show a similar number of observations (0.1 per day) during all seasons except for June to August, wherein the cloud screening eliminates almost all the satellite data over the region. Within this areal extent, the satellite XCO2 shows average anomalies of nearly ±2.0 ppm; it is a valuable piece of information because it is well above the retrieval uncertainty, yet capturing the potential enhancement due to fluxes from India. The study implies that the regions of enhancement greater than 0.2 ppm can be considered locations for surface observations representing Indian fluxes. Similarly, the region with enhancement greater than one ppm could be covered by satellites/airborne observations to discern enhancement in the atmospheric CO2 mole fractions due to Indian fluxes.11Nsciescopu