Ocean biogeochemical modelling

Fennel, Katja; Mattern, Jann Paul; Doney, Scott C.; Bopp, Laurent; Moore, Andrew M.; Wang, Bin; Yu, Liuqian

doi:10.1038/s43586-022-00154-2

“…GOBMs require higher resolution to ensure that they are correctly capturing all the relevant scales of climate‐driven variability. Given the need to also lengthen the spinup phase of these models to reach preindustrial equilibrium, achieving a higher resolution may require substantial technological or methodological innovations. Data assimilation models provide a potential avenue for alleviating some of the structural errors and biases in ocean biogeochemical models (e.g., Fennel et al., 2022). They also have the ability to integrate multiple data sources, which together can provide stronger constraints on global carbon cycling than those derived from a single data source such as the purely pCO 2 ‐based or DIC‐based products.…”

Section: Discussionmentioning

confidence: 99%

Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

DeVries,

Yamamoto,

Wanninkhof

et al. 2023

Global Biogeochemical Cycles

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This contribution to the RECCAP2 (REgional Carbon Cycle Assessment and Processes) assessment analyzes the processes that determine the global ocean carbon sink, and its trends and variability over the period 1985‐2018, using a combination of models and observation‐based products. The mean sea‐air CO2 flux from 1985‐2018 is ‐1.6±0.2 PgC yr‐1 based on an ensemble of reconstructions of the history of sea surface pCO2 (pCO2 products). Models indicate that the dominant component of this flux is the net oceanic uptake of anthropogenic CO2, which is estimated at ‐2.1±0.3 PgC yr‐1 by an ensemble of ocean biogeochemical models, and ‐2.4±0.1 PgC yr‐1 by two ocean circulation inverse models. The ocean also degasses about 0.65±0.3 PgC yr‐1 of terrestrially‐derived CO2, but this process is not fully resolved by any of the models used here. From 2001‐2018, the pCO2 products reconstruct a trend in the ocean carbon sink of ‐0.61±0.12 PgC yr‐1 decade‐1, while biogeochemical models and inverse models diagnose an anthropogenic CO2‐driven trend of ‐0.34±0.06 and ‐0.41±0.03 PgC yr‐1 decade‐1, respectively. This implies a climate‐forced acceleration of the ocean carbon sink in recent decades, but there are still large uncertainties on the magnitude and cause of this trend. The interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate‐driven variability exceeding the CO2‐forced variability by 2‐3 times. These results suggest that anthropogenic CO2 dominates the ocean CO2 sink, while climate‐driven variability is potentially large but highly uncertain and not consistently captured across different methods.

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“…They simulate the normalCO2 flux at the air–sea interface and the exchange of carbon between the surface and the deep ocean, with all their seasonal, interannual and longer time-scale variations. They further include a low- to intermediately complex representation of the biological carbon cycle [8]. They are closely tied to recent climate change and variability as they are forced with atmospheric reanalysis fields, such as the Japanese 55-year atmospheric reanalysis (JRA55-do) [9].…”

Section: Introductionmentioning

confidence: 99%

Sparse observations induce large biases in estimates of the global ocean CO ₂ sink: an ocean model subsampling experiment

Hauck

¹

,

Nissen

²

,

Landschützer

³

et al. 2023

Phil. Trans. R. Soc. A.

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Estimates of ocean CO 2 uptake from global ocean biogeochemistry models and p CO 2 -based data products differ substantially, especially in high latitudes and in the trend of the CO 2 uptake since 2000. Here, we assess the effect of data sparsity on two p CO 2 -based estimates by subsampling output from a global ocean biogeochemistry model. The estimates of the ocean CO 2 uptake are improved from a sampling scheme that mimics present-day sampling to an ideal sampling scheme with 1000 evenly distributed sites. In particular, insufficient sampling has given rise to strong biases in the trend of the ocean carbon sink in the p CO 2 products. The overestimation of the CO 2 flux trend by 20–35% globally and 50–130% in the Southern Ocean with the present-day sampling is reduced to less than 15 % with the ideal sampling scheme. A substantial overestimation of the decadal variability of the Southern Ocean carbon sink occurs in one product and appears related to a skewed data distribution in p CO 2 space. With the ideal sampling, the bias in the mean CO 2 flux is reduced from 9–12% to 2–9% globally and from 14–26% to 5–17% in the Southern Ocean. On top of that, discrepancies of about 0.4 PgC yr − 1 (15%) persist due to uncertainties in the gas-exchange calculation. This article is part of a discussion meeting issue ‘Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities’.

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“…As a result, an excellent agreement between model and observation does not guarantee that the model's representation of unobserved properties is correct (Fennel et al, 2022). In our results, the optimized model output matched relatively well the observations provided (Fig.…”

Section: In Situ Production Of Cdom and Synchronization With Phytopla...mentioning

confidence: 59%

Chromophoric dissolved organic matter dynamics revealed through the optimization of an optical-biogeochemical model in the NW Mediterranean Sea

Alvarez

¹

,

Cossarini

²

,

Teruzzi

³

et al. 2023

Preprint

0

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Abstract. Chromophoric dissolved organic matter (CDOM) significantly contributes to the non-water absorption budget in the Mediterranean Sea. The absorption coefficient of CDOM, αCDOM(λ), is measurable in situ and remotely from different platforms and can be used as an indicator of the concentration of other relevant biogeochemical variables, e.g., dissolved organic carbon. However, our ability to model the biogeochemical processes that determine CDOM concentrations is still limited. Here we propose a novel parametrisation of the CDOM cycle that accounts for the interplay between the light- and nutrient-dependent dynamics of local CDOM production and degradation, as well as its vertical transport. The parameterization is included in a one-dimensional (1D) configuration of the Biogeochemical Flux Model (BFM), which is here coupled to the General Ocean Turbulence Model (GOTM) through the Framework for Aquatic Biogeochemical Models (FABM). Here BFM is augmented with a bio-optical component that revolves spectrally the underwater light transmission. We did run this new GOTM-FABM-BFM configuration to simulate the seasonal αCDOM(λ) cycle at the deep-water site of the BOUSSOLE project in the North-Western Mediterranean Sea. Our results show that accounting for both nutrient and light dependence of CDOM production improves the simulation of the seasonal and vertical dynamics of αCDOM(λ), including a subsurface maximum that forms in spring and progressively intensifies in summer. Furthermore, the model consistently reproduces the higher-than-average concentrations of CDOM per unit chlorophyll concentration observed at BOUSSOLE. The configuration, outputs and sensitivity analyses from this 1D model application will be instrumental for future applications of BFM to the entire Mediterranean Sea in a 3D configuration.

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Ocean biogeochemical modelling

Cited by 42 publications

References 186 publications

Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Sparse observations induce large biases in estimates of the global ocean CO ₂ sink: an ocean model subsampling experiment

Chromophoric dissolved organic matter dynamics revealed through the optimization of an optical-biogeochemical model in the NW Mediterranean Sea

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Ocean biogeochemical modelling

Cited by 42 publications

References 186 publications

Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Sparse observations induce large biases in estimates of the global ocean CO 2 sink: an ocean model subsampling experiment

Chromophoric dissolved organic matter dynamics revealed through the optimization of an optical-biogeochemical model in the NW Mediterranean Sea

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Sparse observations induce large biases in estimates of the global ocean CO ₂ sink: an ocean model subsampling experiment