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

2017 ◽  
Vol 14 (9) ◽  
pp. 2321-2341 ◽  
Author(s):  
Olivier Aumont ◽  
Marco van Hulten ◽  
Matthieu Roy-Barman ◽  
Jean-Claude Dutay ◽  
Christian Éthé ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Critical Role ◽  
Oxygen Demand ◽  
Sediment Oxygen Demand ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Mesopelagic Zone ◽  
Modelling Studies ◽  
Ocean Biogeochemical Model ◽  
The Impact

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. However, this variable reactivity of POC has never been extensively considered, especially in modelling 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 1 to 2 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 2, which is in better agreement with global estimates of the sediment oxygen demand. The impact on the major macronutrients (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 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.

Considering the impact of intermittent discharges when modelling overflows

1998 ◽  
Vol 38 (10) ◽  
pp. 23-30
Author(s):  
Sarah Jubb ◽  
Philip Hulme ◽  
Ian Guymer ◽  
John Martin
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Preliminary Investigation ◽  
Oxygen Demand ◽  
Sediment Oxygen Demand ◽  
Combined Sewer Overflows ◽  
River Hydraulics ◽  
Combined Sewer ◽  
The Impact ◽  
Curve Equation

This paper describes a preliminary investigation that identified factors important in the prediction of river water quality, especially regarding dissolved oxygen (DO) concentration. Intermittent discharges from combined sewer overflows (CSOs) within the sewerage, and overflows at water reclamation works (WRW) cause dynamic conditions with respect to both river hydraulics and water quality. The impact of such discharges has been investigated under both wet and dry weather flow conditions. Data collected from the River Maun, UK, has shown that an immediate, transient oxygen demand exists downstream of an outfall during storm conditions. The presence of a delayed oxygen demand has also been identified. With regard to modelling, initial investigations used a simplified channel and the Streeter-Phelps (1925) dissolved oxygen sag curve equation. Later, a model taking into account hydrodynamic, transport and dispersion processes was used. This suggested that processes other than water phase degradation of organic matter significantly affect the dissolved oxygen concentration downstream of the location of an intermittent discharge. It is proposed that the dynamic rate of reaeration and the sediment oxygen demand should be the focus of further investigation.

Experimental manipulations of the biomass of introduced carp (Cyprinus carpio) in billabongs. II. Impacts on benthic properties and processes1

1997 ◽  
Vol 48 (5) ◽  
pp. 445 ◽  
Author(s):  
A. I. Robertson ◽  
M. R. Healey ◽  
A. J. King
Keyword(s):  
Algal Biomass ◽  
Solid Phase ◽  
Negative Impact ◽  
Oxygen Demand ◽  
Sediment Oxygen Demand ◽  
Sediment Surface ◽  
Nutrient Concentrations ◽  
Nutrient Ratios ◽  
Biofilm Development ◽  
The Impact

Two billabongs on the floodplain of the Murrumbidgee River, Australia, were partitioned in half with impermeable plastic barriers and the biomass of carp was manipulated to establish high- and low-carp biomass treatments in each billabong. Measurements of benthic variables (rates of particle settlement, biofilm development, sediment respiration, macrophyte detritus decomposition, sediment solid-phase nutrient concentrations and benthic algal biomass) were performed over four months from summer to winter 1995. Rates of particle settlement were greater in the high-carp treatment of each billabong throughout the experiment. High carp biomass had a negative impact on the autotrophic component of the biofilm developing on wood blocks placed at different heights above the sediment surface but the mechanism responsible differed between billabongs. Sediment oxygen demand became greater in the presence of a higher biomass of carp during the experiment but time courses differed between billabongs. Manipulations of carp biomass did not influence algal biomass on the sediment surface, the rate of decomposition of macrophyte detritus or sediment solid-phase nutrients or nutrient ratios. The impact of carp on benthic and surficial processes was significant but the mechanisms of change differed between billabongs.

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.

Sulfide production kinetics and model of stormwater retention ponds

2018 ◽  
Vol 77 (10) ◽  
pp. 2377-2387 ◽  
Author(s):  
P. M. D'Aoust ◽  
F. R. Pick ◽  
R. Wang ◽  
A. Poulain ◽  
C. Rennie ◽  
...  
Keyword(s):  
Critical Role ◽  
Oxygen Demand ◽  
Pond Water ◽  
Sediment Oxygen Demand ◽  
Sulfide Concentration ◽  
Retention Ponds ◽  
Production Of Hydrogen ◽  
Sulfide Production ◽  
Stormwater Retention

Abstract Stormwater retention ponds can play a critical role in mitigating the detrimental effects of urbanization on receiving waters that result from increases in polluted runoff. However, the benthic oxygen demand of stormwater facilities may cause significant hypoxia and trigger the production of hydrogen sulfide (H2S). This process is not well-documented and further research is needed to characterize benthic processes in stormwater retention ponds in order to improve their design and operation. In this study, sediment oxygen demand (SOD), sediment ammonia release (SAR) and sediment sulfide production (SSP) kinetics were characterized in situ and in the laboratory. In situ SOD and SSP data were utilized to develop a stormwater retention pond water sulfide concentration model which demonstrates strong correlation with sulfide concentrations observed in situ (r = 0.724, N = 91, p < 0.001) and in laboratory experiments (r = 0.691, N = 38, p < 0.001). At 4 °C, in situ rates of SOD, SAR and SSP were higher than those measured in laboratory. Sulfate-reducing bacteria (SRB) represented 4.99% of the bacteria present in the top 30 cm of the pond sediment, with Desulfobulbaceae spp., Desulfobacteraceae spp. and Desulfococcus spp. being the dominant SRB taxa identified.

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 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.

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