scholarly journals Coastal-ocean uptake of anthropogenic carbon

2016 ◽  
Author(s):  
Timothée Bourgeois ◽  
James C. Orr ◽  
Laure Resplandy ◽  
Christian Ethé ◽  
Marion Gehlen ◽  
...  
Keyword(s):  
Coastal Ocean ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Temporal Data ◽  
Anthropogenic Carbon ◽  
Ocean Biogeochemical Model ◽  
Data Coverage ◽  
The Mean ◽  
Global Inventory ◽  
Offshore Transport

Abstract. Anthropogenic changes in atmosphere-ocean and atmosphere-land CO2 fluxes have been quantified extensively, but few studies have addressed the connection between land and ocean. In this transition zone, the coastal ocean, spatial and temporal data coverage is inadequate to assess its global budget. Thus we use a global ocean biogeochemical model to assess the coastal ocean's global inventory of anthropogenic CO2 and its spatial variability. We used an intermediate resolution, eddying version of the NEMO-PISCES model (ORCA05), varying from 20 to 50 km horizontally, i.e., coarse enough to allow multiple century-scale simulations but finer than coarse resolution models (~ 200 km), to begin to better resolve coastal bathymetry. Simulated results indicated that the global ocean absorbed 2.3 Pg C yr−1 of anthropogenic carbon during 1993–2012, consistent with previous estimates. Yet only 4.5 % of that (0.10 Pg C yr−1) is absorbed by the global coastal ocean, i.e., less than its 7.5 % proportion of the global ocean surface area. Coastal uptake is weakened due to a bottleneck in offshore transport, which is inadequate to reduce the mean anthropogenic carbon concentration of coastal waters to the mean level found in the open-ocean mixed layer.

scholarly journals Coastal-ocean uptake of anthropogenic carbon

2016 ◽  
Vol 13 (14) ◽  
pp. 4167-4185 ◽  
Author(s):  
Timothée Bourgeois ◽  
James C. Orr ◽  
Laure Resplandy ◽  
Jens Terhaar ◽  
Christian Ethé ◽  
...  
Keyword(s):  
Coastal Ocean ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Shelf Area ◽  
Surface Areas ◽  
Anthropogenic Carbon ◽  
The Mean ◽  
Continental Shelf Area ◽  
Global Inventory ◽  
Offshore Transport

Abstract. Anthropogenic changes in atmosphere–ocean and atmosphere–land CO2 fluxes have been quantified extensively, but few studies have addressed the connection between land and ocean. In this transition zone, the coastal ocean, spatial and temporal data coverage is inadequate to assess its global budget. Thus we use a global ocean biogeochemical model to assess the coastal ocean's global inventory of anthropogenic CO2 and its spatial variability. We used an intermediate resolution, eddying version of the NEMO-PISCES model (ORCA05), varying from 20 to 50 km horizontally, i.e. coarse enough to allow multiple century-scale simulations but finer than coarse-resolution models (∼  200 km) to better resolve coastal bathymetry and complex coastal currents. Here we define the coastal zone as the continental shelf area, excluding the proximal zone. Evaluation of the simulated air–sea fluxes of total CO2 for 45 coastal regions gave a correlation coefficient R of 0.8 when compared to observation-based estimates. Simulated global uptake of anthropogenic carbon results averaged 2.3 Pg C yr−1 during the years 1993–2012, consistent with previous estimates. Yet only 0.1 Pg C yr−1 of that is absorbed by the global coastal ocean. That represents 4.5 % of the anthropogenic carbon uptake of the global ocean, less than the 7.5 % proportion of coastal-to-global-ocean surface areas. Coastal uptake is weakened due to a bottleneck in offshore transport, which is inadequate to reduce the mean anthropogenic carbon concentration of coastal waters to the mean level found in the open-ocean mixed layer.

scholarly journals A reactivity continuum of particulate organic matter in a global ocean biogeochemical model

2016 ◽  
Author(s):  
Olivier Aumont ◽  
Marco van Hulten ◽  
Matthieu Roy-Barman ◽  
Jean-Claude Dutay ◽  
Christian Ethé ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Critical Role ◽  
Oxygen Demand ◽  
Sediment Oxygen Demand ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Mesopelagic Zone ◽  
Ocean Biogeochemical Model ◽  
The Impact ◽  
Reactivity Continuum

Abstract. The marine biological carbon pump is dominated by the vertical transfer of Particulate Organic Carbon (POC) from the surface ocean to its interior. The efficiency of this transfer plays an important role in controlling the amount of atmospheric carbon that is sequestered in the ocean. Furthermore, the abundance and composition of POC is critical for the removal of numerous trace elements by scavenging, a number of which such as iron are essential for the growth of marine organisms, including phytoplankton. Observations and laboratory experiments have shown that POC is composed of numerous organic compounds that can have very different reactivities. Yet, this variable reactivity of POC has never been extensively considered, especially in modeling studies. Here, we introduced in the global ocean biogeochemical model NEMO-PISCES a description of the variable composition of POC based on the theoretical Reactivity Continuum Model proposed by (Boudreau and Ruddick, 1991). Our model experiments show that accounting for a variable lability of POC increases POC concentrations in the ocean’s interior by one to two orders of magnitude. This increase is mainly the consequence of a better preservation of small particles that sink slowly from the surface. Comparison with observations is significantly improved both in abundance and in size distribution. Furthermore, the amount of carbon that reaches the sediments is increased by more than a factor of two, which is in better agreement with global estimates of the sediment oxygen demand. The impact on the major macro-nutrients (nitrate and phosphate) remains modest. However, iron (Fe) distribution is strongly altered, especially in the upper mesopelagic zone as a result of more intense scavenging: Vertical gradients in Fe are milder in the upper ocean which appears to be closer to observations. Thus, our study shows that the variable lability of POC can play a critical role in the marine biogeochemical cycles which advocates for more dedicated in situ and laboratory experiments.

scholarly journals Simulation of anthropogenic CO<sub>2</sub> uptake in the CCSM3.1 ocean circulation-biogeochemical model: comparison with data-based estimates

2011 ◽  
Vol 8 (6) ◽  
pp. 10895-10933
Author(s):  
S. Wang ◽  
J. K. Moore ◽  
F. W. Primeau ◽  
S. Khatiwala
Keyword(s):  
Ocean Circulation ◽  
Model Comparison ◽  
Industrial Revolution ◽  
Large Fraction ◽  
Detailed Comparison ◽  
Global Ocean ◽  
Inversion Method ◽  
Biogeochemical Model ◽  
Climate System Model ◽  
Anthropogenic Carbon

Abstract. The global ocean has taken up a large fraction of the CO2 released by human activities since the industrial revolution. Quantifying the oceanic anthropogenic carbon (Cant) inventory and its variability is important for predicting the future global carbon cycle. The detailed comparison of data-based and model-based estimates is essential for the validation and continued improvement of our prediction capabilities. So far, three global estimates of oceanic Cant inventory that are "data-based" and independent of global ocean circulation models have been produced: one based on the ΔC* method, and two are based on reconstructions of the Green function for the surface-to-interior transport, the TTD method and the maximum entropy inversion method (KPH). The KPH method, in particular, is capable of reconstructing the history of Cant inventory through the industrial era. In the present study we use forward model simulations of the Community Climate System Model (CCSM3.1) to estimate the Cant inventory and compare the results with the data-based estimates. We also use the simulations to test several assumptions of the KPH method, including the assumption of constant climate and circulation, which is common to all the data-based estimates. Though the integrated estimates of global Cant inventories are consistent with each other, the regional estimates show discrepancies up to 50 %. The CCSM3 model underestimates the total Cant inventory, in part due to weak mixing and ventilation in the North Atlantic and Southern Ocean. Analyses of different simulation results suggest that key assumptions about ocean circulation and air-sea disequilibrium in the KPH method are generally valid on the global scale, but may introduce significant errors in Cant estimates on regional scales. The KPH method should also be used with caution when predicting future oceanic anthropogenic carbon uptake.

scholarly journals Role of jellyfish in the plankton ecosystem revealed using a global ocean biogeochemical model

2021 ◽  
Vol 18 (4) ◽  
pp. 1291-1320
Author(s):  
Rebecca M. Wright ◽  
Corinne Le Quéré ◽  
Erik Buitenhuis ◽  
Sophie Pitois ◽  
Mark J. Gibbons
Keyword(s):  
Temporal Dynamics ◽  
Marine Ecosystem ◽  
Zooplankton Community ◽  
Ocean Model ◽  
Plankton Community ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Ocean Biogeochemical Model ◽  
Spatio Temporal ◽  
Plankton Community Structure

Abstract. Jellyfish are increasingly recognised as important components of the marine ecosystem, yet their specific role is poorly defined compared to that of other zooplankton groups. This paper presents the first global ocean biogeochemical model that includes an explicit representation of jellyfish and uses the model to gain insight into the influence of jellyfish on the plankton community. The Plankton Type Ocean Model (PlankTOM11) model groups organisms into plankton functional types (PFTs). The jellyfish PFT is parameterised here based on our synthesis of observations on jellyfish growth, grazing, respiration and mortality rates as functions of temperature and jellyfish biomass. The distribution of jellyfish is unique compared to that of other PFTs in the model. The jellyfish global biomass of 0.13 PgC is within the observational range and comparable to the biomass of other zooplankton and phytoplankton PFTs. The introduction of jellyfish in the model has a large direct influence on the crustacean macrozooplankton PFT and influences indirectly the rest of the plankton ecosystem through trophic cascades. The zooplankton community in PlankTOM11 is highly sensitive to the jellyfish mortality rate, with jellyfish increasingly dominating the zooplankton community as its mortality diminishes. Overall, the results suggest that jellyfish play an important role in regulating global marine plankton ecosystems across plankton community structure, spatio-temporal dynamics and biomass, which is a role that has been generally neglected so far.

Estuarine–Coastal Interactions

2006 ◽  
Author(s):  
Thomas S. Bianchi
Keyword(s):  
Organic Matter ◽  
High Water ◽  
Coastal Ocean ◽  
Global Ocean ◽  
International Programs ◽  
The European Union ◽  
Fish Catch ◽  
Estuarine Coastal ◽  
Core Project ◽  
Offshore Transport

The coastal ocean is a dynamic region where the rivers, estuaries, ocean, land, and the atmosphere interact (Walsh, 1988; Mantoura et al., 1991; Alongi, 1998; Wollast, 1998). Coastlines extend over an estimated 350,000 km worldwide, and the coastal ocean, typically defined as a region that extends from the high water mark to the shelf break (figure 16.1; Alongi, 1998), covers approximately 7% (26 × 106 km2) of the surface global ocean (Gattuso et al., 1998). Although relatively small in area, this highly productive region (30% of the total net oceanic productivity) supports as much as 90% of the global fish catch (Holligan, 1992). In recent years, the coastal ocean has been recognized for its global importance with both national and international programs such as the Land–Ocean Interactions in the Coastal Zone (LOICZ) program, a subprogram of the International Global Change Program (IGBP) started in 1993 (Pernetta and Milliman, 1995), the European Union coastal core project (European Land–Ocean Interaction Studies, ELOISE) (Cadée et al., 1994), and in the U.S. Shelf Edge Exchange Processes Program (SEEP I and SEEP II) (Walsh et al., 1988; Anderson et al., 1994), the Coastal Ocean Processes (CoOP) program, Ocean Margins Program (OMP), and Land–Margin Ecosystem Research (LMER), to name a few. SEEP I and SEEP II were designed to test the Walsh et al. (1985) hypothesis that increased anthropogenic nutrient supply to the coastal ocean would result in enhanced burial of organic matter in continental margins due to higher offshore export of new productivity in the nearshore waters. While the hypothesis of offshore transport and burial was shown to be valid along certain regions of the eastern U.S. coast, other regions showed a more along-shelf transport (Walsh, 1994). More recent work in the OMP, which revisited some of the objectives of SEEP I and SEEP II, found that the accumulation of organic matter in upper slope sediments was only <1% of the total primary production in the entire continental margin of North Carolina (DeMaster et al., 2002). There are many factors that will ultimately determine if and how much nearshore production is exported offshore from the coastal ocean.

scholarly journals A derivative-free optimisation method for global ocean biogeochemical models

2021 ◽  
Author(s):  
Sophy Elizabeth Oliver ◽  
Coralia Cartis ◽  
Iris Kriest ◽  
Simon F. B. Tett ◽  
Samar Khatiwala
Keyword(s):  
Global Ocean ◽  
Biogeochemical Model ◽  
Biogeochemical Models ◽  
Derivative Free ◽  
Observational Uncertainty ◽  
Parameter Configuration ◽  
Ocean Biogeochemical Model ◽  
Observational Noise ◽  
Parameter Values ◽  
Earth System Models

Abstract. The performance of global ocean biogeochemical models, and the Earth System Models in which they are embedded, can be improved by systematic calibration of the parameter values against observations. However, such tuning is seldom undertaken as these models are computationally very expensive. Here we investigate the performance of DFO-LS, a local, derivative-free optimisation algorithm which has been designed for computationally expensive models with irregular model-data misfit landscapes typical of biogeochemical models. We use DFO-LS to calibrate six parameters of a relatively complex global ocean biogeochemical model (MOPS) against synthetic dissolved oxygen, inorganic phosphate and inorganic nitrate observations from a reference run of the same model with a known parameter configuration. The performance of DFO-LS is compared with that of CMA-ES, another derivative-free algorithm that was applied in a previous study to the same model in one of the first successful attempts at calibrating a global model of this complexity. We find that DFO-LS successfully recovers 5 of the 6 parameters in approximately 40 evaluations of the misfit function (each one requiring a 3000 year run of MOPS to equilibrium), while CMA-ES needs over 1200 evaluations. Moreover, DFO-LS reached a baseline misfit, defined by observational noise, in just 11–14 evaluations, whereas CMA-ES required approximately 340 evaluations. We also find that the performance of DFO-LS is not significantly affected by observational sparsity, however fewer parameters were successfully optimised in the presence of observational uncertainty. The results presented here suggest that DFO-LS is sufficiently inexpensive and robust to apply to the calibration of complex, global ocean biogeochemical models.

scholarly journals Impacts of physical data assimilation on the Global Ocean Carbonate System

2014 ◽  
Vol 11 (4) ◽  
pp. 5399-5441 ◽  
Author(s):  
L. Visinelli ◽  
S. Masina ◽  
M. Vichi ◽  
A. Storto
Keyword(s):  
Data Assimilation ◽  
Circulation Model ◽  
Global Scale ◽  
Ocean Basin ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Global Circulation Model ◽  
Carbonate System ◽  
Physical Data ◽  
Ocean Biogeochemical Model

Abstract. Prognostic simulations of ocean carbon distribution are largely dependent on an adequate representation of physical dynamics. In this work we show that the assimilation of temperature and salinity in a coupled ocean-biogeochemical model significantly improves the reconstruction of the carbonate system variables over the last two decades. For this purpose, we use the NEMO ocean global circulation model, coupled to the Biogeochemical Flux Model (BFM) in the global PELAGOS configuration. The assimilation of temperature and salinity is included into the coupled ocean-biogeochemical model by using a variational assimilation method. The use of ocean physics data assimilation improves the simulation of alkalinity and dissolved organic carbon against the control run as assessed by comparing with independent time series and gridded datasets. At the global scale, the effects of the assimilation of physical variables in the simulation of pCO2 improves the seasonal cycle in all basins, getting closer to the SOCAT estimates. Biases in the partial pressure of CO2 with respect to data that are evident in the control run are reduced once the physical data assimilation is used. The root mean squared errors in the pCO2 are reduced by up to 30% depending on the ocean basin considered. In addition, we quantify the relative contribution of biological carbon uptake on surface pCO2 by performing another simulation in which biology is neglected in the assimilated run.

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