scholarly journals Systematic variation in marine dissolved organic matter stoichiometry and remineralization ratios as a function of lability

2019 ◽  
Author(s):  
Emily J. Zakem ◽  
Naomi M. Levine
Keyword(s):  
Organic Matter ◽  
Ecosystem Model ◽  
Nutrient Supply ◽  
Biological Pump ◽  
Elemental Ratios ◽  
Carbon Production ◽  
Proportional Increase ◽  
Ocean Carbon ◽  
Biological Sequestration ◽  
Heterotrophic Biomass

AbstractRemineralization of organic matter by heterotrophic organisms regulates the biological sequestration of carbon, thereby mediating atmospheric CO2. While surface nutrient supply impacts the elemental ratios of primary production, stoichiometric control by remineralization remains unclear. Here we develop a mechanistic description of remineralization and its stoichiometry in a marine microbial ecosystem model. The model simulates the observed elemental plasticity of phytoplankton and the relatively constant, lower C:N of heterotrophic biomass. In addition, the model captures the observed decreases in DOC:DON and the C:N remineralization ratio with depth for more labile substrates, which are driven by a switch in the dominant source of labile DOM from phytoplankton to heterotrophic biomass. Only a model version with targeted remineralization of N-rich components is able to simulate the observed profiles of preferential remineralization of DON relative to DOC and the elevated C:N of bulk DOM. The model suggests that more labile substrates are associated with C-limited heterotrophic growth and not with preferential remineralization, while more recalcitrant substrates are associated with growth limited by processing rates and with preferential remineralization. The resulting patterns of variable remineralization stoichiometry mediate the extent to which a proportional increase in carbon production resulting from changes in phytoplankton stoichiometry can increase the efficiency of the biological pump. Results emphasize the importance of understanding the physiology of both phytoplankton and heterotrophs for anticipating changes in biologically driven ocean carbon storage.

scholarly journals Resolving ecological feedbacks on the ocean carbon sink in Earth system models

2020 ◽  
Author(s):  
David I. Armstrong McKay ◽  
Sarah E. Cornell ◽  
Katherine Richardson ◽  
Johan Rockström
Keyword(s):  
Climate Change ◽  
Carbon Sink ◽  
Biological Pump ◽  
Earth System ◽  
Temperature Dependent ◽  
System Models ◽  
Plankton Ecology ◽  
Ocean Carbon ◽  
The Impact ◽  
Earth System Models

Abstract. The Earth’s oceans are one of the largest sinks in the Earth system for anthropogenic CO2 emissions, acting as a negative feedback on climate change. Earth system models predict, though, that climate change will lead to a weakening ocean carbon uptake rate as warm water holds less dissolved CO2 and biological productivity declines. However, most Earth system models do not incorporate the impact of warming on bacterial remineralisation and rely on simplified representations of plankton ecology that do not resolve the potential impact of climate change on ecosystem structure or elemental stoichiometry. Here we use a recently-developed extension of the cGEnIE Earth system model (ecoGEnIE) featuring a trait-based scheme for plankton ecology (ECOGEM), and also incorporate cGEnIE's temperature-dependent remineralisation (TDR) scheme. This enables evaluation of the impact of both ecological dynamics and temperature-dependent remineralisation on the soft-tissue biological pump in response to climate change. We find that including TDR strengthens the biological pump relative to default runs due to increased nutrient recycling, while ECOGEM weakens the biological pump by enabling a shift to smaller plankton classes. However, interactions with concurrent ocean acidification cause opposite sign responses for the carbon sink in both cases: TDR leads to a smaller sink relative to default runs whereas ECOGEM leads to a larger sink. Combining TDR and ECOGEM results in a net strengthening of the biological pump and a small net reduction in carbon sink relative to default. These results clearly illustrate the substantial degree to which ecological dynamics and biodiversity modulate the strength of climate-biosphere feedbacks, and demonstrate that Earth system models need to incorporate more ecological complexity in order to resolve carbon sink weakening.

scholarly journals The influence of the ocean circulation state on ocean carbon storage and CO<sub>2</sub> drawdown potential in an Earth system model

2017 ◽  
Author(s):  
Malin Ödalen ◽  
Jonas Nycander ◽  
Kevin I. C. Oliver ◽  
Laurent Brodeau ◽  
Andy Ridgwell
Keyword(s):  
Carbon Storage ◽  
Wind Stress ◽  
Ocean Circulation ◽  
System Model ◽  
Biological Pump ◽  
Earth System ◽  
Heat Diffusivity ◽  
Initial States ◽  
Ocean Carbon ◽  
Atmospheric Heat

Abstract. During the four most recent glacial cycles, atmospheric CO2 during glacial maxima has been lowered by about 90–100 ppm with respect to interglacials. There is widespread consensus that most of this carbon was partitioned in the ocean. It is however still debated which processes were dominant in achieving this increased carbon storage. In this paper, we use an Earth system model of intermediate complexity to constrain the range in ocean carbon storage for an ensemble of ocean circulation equilibrium states. We do a set of simulations where we run the model to pre-industrial equilibrium, but where we achieve different ocean circulation by changing forcing parameters such as wind stress, ocean diffusivity and atmospheric heat diffusivity. As a consequence, the ensemble members also have different ocean carbon reservoirs, global ocean average temperatures, biological pump efficiencies and conditions for air-sea CO2 disequilibrium. We analyse changes in total ocean carbon storage and separate it into contributions by the solubility pump, the biological pump and the CO2 disequilibrium component. We also relate these contributions to differences in strength of ocean overturning circulation. In cases with weaker circulation, we see that the ocean's capacity for carbon storage is larger. Depending on which ocean forcing parameter that is tuned, the origin of the change in carbon storage is different. When wind stress or ocean vertical diffusivity is changed, the response of the biological pump gives the most important effect on ocean carbon storage, whereas when atmospheric heat diffusivity or ocean horizontal diffusivity is changed, the solubility pump and the disequilibrium component are also important and sometimes dominant. Finally, we do a drawdown experiment, where we investigate the capacity for increased carbon storage by maximising the efficiency of the biological pump in our ensemble members. We conclude that different initial states for an ocean model result in different capacities for ocean carbon storage, due to differences in the ocean circulation state. This could explain why it is difficult to achieve comparable responses of the ocean carbon pumps in model intercomparison studies, where the initial states vary between models. The drawdown experiment highlights the importance of the strength of the biological pump in the control state for model studies of increased biological efficiency.

scholarly journals Variability in air-sea O<sub>2</sub> and CO<sub>2</sub> fluxes and its impact on atmospheric potential oxygen (APO) and the partitioning of land and ocean carbon sinks

2007 ◽  
Vol 4 (4) ◽  
pp. 2877-2914 ◽  
Author(s):  
C. D. Nevison ◽  
N. M. Mahowald ◽  
S. C. Doney ◽  
I. D. Lima
Keyword(s):  
Transport Model ◽  
Atmospheric Transport ◽  
Three Dimensional ◽  
Ecosystem Model ◽  
Large Error ◽  
Accurate Estimate ◽  
Carbon Sinks ◽  
Fossil Carbon ◽  
Ocean Carbon ◽  
Potential Oxygen

Abstract. A three dimensional, time-evolving field of atmospheric potential oxygen (APO ~ O2/N2 + CO2) is estimated using surface O2, N2 and CO2 fluxes from the WHOI ocean ecosystem model to force the MATCH atmospheric transport model. Land and fossil carbon fluxes are also run in MATCH and translated into O2 tracers using assumed O2:CO2 stoichiometries. The model seasonal cycles in APO agree well with the observed cycles at 13 global monitoring stations, with agreement helped by the inclusion of oceanic CO2 in the APO calculation. The model latitudinal gradient in APO is strongly influenced by seasonal rectifier effects in atmospheric transport, which appear at least partly unrealistic based on comparison to observations. An analysis of the APO vs.~CO2 method for partitioning land and ocean carbon sinks is performed in the controlled context of the MATCH simulation, in which the true surface carbon and oxygen fluxes are known exactly. This analysis suggests uncertainty ranging up to ±0.2 PgC in the inferred sinks due to transport-induced variability. It also shows that interannual variability in oceanic O2 fluxes can cause increasingly large error in the sink partitioning when the method is applied over increasingly short timescales. However, when decadal or longer averages are used, the variability in the oceanic O2 flux is relatively small, allowing carbon sinks to be partitioned to within a standard deviation of 0.1 Pg C/yr of the true values, provided one has an accurate estimate of long-term mean O2 outgassing.

scholarly journals Impact of variable air-sea O<sub>2</sub> and CO<sub>2</sub> fluxes on atmospheric potential oxygen (APO) and land-ocean carbon sink partitioning

2008 ◽  
Vol 5 (3) ◽  
pp. 875-889 ◽  
Author(s):  
C. D. Nevison ◽  
N. M. Mahowald ◽  
S. C. Doney ◽  
I. D. Lima ◽  
N. Cassar
Keyword(s):  
Transport Model ◽  
Atmospheric Transport ◽  
Carbon Sink ◽  
Three Dimensional ◽  
Ecosystem Model ◽  
Accurate Estimate ◽  
Carbon Sinks ◽  
Fossil Carbon ◽  
Ocean Carbon ◽  
Potential Oxygen

Abstract. A three dimensional, time-evolving field of atmospheric potential oxygen (APO ~O2/N2+CO2) was estimated using surface O2, N2 and CO2 fluxes from the WHOI ocean ecosystem model to force the MATCH atmospheric transport model. Land and fossil carbon fluxes were also run in MATCH and translated into O2 tracers using assumed O2:CO2 stoichiometries. The modeled seasonal cycles in APO agree well with the observed cycles at 13 global monitoring stations, with agreement helped by including oceanic CO2 in the APO calculation. The modeled latitudinal gradient in APO is strongly influenced by seasonal rectifier effects in atmospheric transport. An analysis of the APO-vs.-CO2 mass-balance method for partitioning land and ocean carbon sinks was performed in the controlled context of the MATCH simulation, in which the true surface carbon and oxygen fluxes were known exactly. This analysis suggests uncertainty of up to ±0.2 PgC in the inferred sinks due to variability associated with sparse atmospheric sampling. It also shows that interannual variability in oceanic O2 fluxes can cause large errors in the sink partitioning when the method is applied over short timescales. However, when decadal or longer averages are used, the variability in the oceanic O2 flux is relatively small, allowing carbon sinks to be partitioned to within a standard deviation of 0.1 Pg C/yr of the true values, provided one has an accurate estimate of long-term mean O2 outgassing.

scholarly journals Ocean carbon inventory under warmer climate conditions – the case of the Last Interglacial

2018 ◽  
Vol 14 (12) ◽  
pp. 1961-1976 ◽  
Author(s):  
Augustin Kessler ◽  
Eirik Vinje Galaasen ◽  
Ulysses Silas Ninnemann ◽  
Jerry Tjiputra
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Carbon Sources ◽  
Climatic Conditions ◽  
Interglacial Period ◽  
Quasi Equilibrium ◽  
Biological Pump ◽  
Last Interglacial ◽  
Climate Conditions ◽  
Ocean Carbon ◽  
Carbon Inventory

Abstract. During the Last Interglacial period (LIG), the transition from 125 to 115 ka provides a case study for assessing the response of the carbon system to different levels of high-latitude warmth. Elucidating the mechanisms responsible for interglacial changes in the ocean carbon inventory provides constraints on natural carbon sources and sinks and their climate sensitivity, which are essential for assessing potential future changes. However, the mechanisms leading to modifications of the ocean's carbon budget during this period remain poorly documented and not well understood. Using a state-of-the-art Earth system model, we analyze the changes in oceanic carbon dynamics by comparing two quasi-equilibrium states: the early, warm Eemian (125 ka) versus the cooler, late Eemian (115 ka). We find considerably reduced ocean dissolved inorganic carbon (DIC; −314.1 PgC) storage in the warm climate state at 125 ka as compared to 115 ka, mainly attributed to changes in the biological pump and ocean DIC disequilibrium components. The biological pump is mainly driven by changes in interior ocean ventilation timescales, but the processes controlling the changes in ocean DIC disequilibrium remain difficult to assess and seem more regionally affected. While the Atlantic bottom-water disequilibrium is affected by the organization of sea-ice-induced southern-sourced water (SSW) and northern-sourced water (NSW), the upper-layer changes remain unexplained. Due to its large size, the Pacific accounts for the largest DIC loss, approximately 57 % of the global decrease. This is largely associated with better ventilation of the interior Pacific water mass. However, the largest simulated DIC differences per unit volume are found in the SSWs of the Atlantic. Our study shows that the deep-water geometry and ventilation in the South Atlantic are altered between the two climate states where warmer climatic conditions cause SSWs to retreat southward and NSWs to extent further south. This process is mainly responsible for the simulated DIC reduction by restricting the extent of DIC-rich SSW, thereby reducing the storage of biological remineralized carbon at depth.

scholarly journals BPOP-v1 model: exploring the impact of changes in the biological pump on the shelf sea and ocean nutrient and redox state

2019 ◽  
Author(s):  
Elisa Lovecchio ◽  
Timothy M. Lenton
Keyword(s):  
Organic Matter ◽  
Deep Ocean ◽  
Biological Pump ◽  
Promising Tool ◽  
Biogeochemical Fluxes ◽  
Structure Changes ◽  
Large Particles ◽  
Shelf Sea ◽  
Slope Sediment ◽  
The Impact

Abstract. The ocean’s biological pump has changed over Earth history from one dominated by prokaryotes, to one involving a mixture of prokaryotes and eukaryotes with trophic structure. Changes in the biological pump are in turn hypothesised to have caused important changes in the ocean’s nutrient and redox properties. To explore these hypotheses, we present here a new box model including oxygen (O), phosphorus (P) and a dynamical biological pump. Our Biological Pump, Oxygen and Phosphorus (BPOP) model accounts for two – small and large – organic matter species generated by production and coagulation, respectively. Export and burial of these particles are regulated by a remineralization length (zrem) scheme. We independently vary zrem of small and large particles in order to study how changes in sinking speeds and remineralization rates affect the major biogeochemical fluxes, and O and P ocean concentrations. Modelled O and P budgets and fluxes lay close to present estimates for zrem in the range of currently measured values. Our results highlight that relatively small changes in zrem of the large particles can have important impacts on the O and P ocean availability and support the idea that an early ocean dominated by small particles was nutrient rich due to inefficient removal to sediments. The results also highlight that shelf ocean anoxia can coexist with an oxygenated deep open ocean for realistic values of zrem, especially for large values of the small particle zrem. This could challenge conventional interpretations that the Proterozoic deep ocean was anoxic, which are derived from shelf and slope sediment redox data. This simple and computationally inexpensive model is a promising tool to investigate the impact of changes in the organic matter sinking and remineralization rates as well as changes in physical processes coupled to the biological pump in a variety of case studies.

Biogeosystem Technique as a methodology for overcoming the outdated theory and management principles of semiarid silviculture

2020 ◽  
Author(s):  
Valery Kalinichenko ◽  
Alexey Glinushkin ◽  
Peter Mukovoz ◽  
Abdulmalik Batukaev ◽  
Tatiana Minkina ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Consumption ◽  
Soil Layer ◽  
Long Term Results ◽  
Soil Reclamation ◽  
Biological Productivity ◽  
Dry Steppe ◽  
Greenhouse Emission ◽  
Biological Sequestration

&lt;p&gt;Forests and artificial forest lines at the climax stage are the source of greenhouse gases. Artificial forests, forest lines, recreational forest plantations can help to reduce the greenhouse emission, increase oxygen production, enlarge the soil carbon biological capacity, and improve silviculture land protective and recreational function.&amp;#160;&lt;/p&gt;&lt;p&gt;Artificial forest systems on the Chernozem and Kastanozem have the obvious signs of the climatic suppression. The adverse influence of climate on artificial forests via summer droughts is aggravated by poor soil conditions for silviculture. The lifespan of artificial forests reduces from typical for most tree species of 200-800 years to short 30-60 years. In dry steppe, the habitus and dimensions of trees are worse in comparison to natural analogue in good conditions of development. Now the artificial forests in semiarid and arid areas do not suit the task of carbon sequestration, oxygen producing and climate correction. It aggravates the current uncertainty of biosphere. Standard outdated agronomy and soil reclamation technologies fail to prepare the soil for the long-term successful forest growth. The known silviculture technology fails to provide the forest soil watering, because standard irrigation is linked to enormous water consumption, soil and landscape degradation.&lt;/p&gt;&lt;p&gt;We propose the Biogeosystem Technique (BGT*) for the semiarid and arid forestry improvement. The BGT* is a transcendental (non-imitating natural processes) approach to improve soil management including pre-planting soil processing, soil watering and fertigation (chemisation) for proper long-term artificial forestry. The BGT* provide regulation of the fluxes of energy, matter (including organic carbon), water and higher biological productivity of artificial forestry: intra-soil machining provides productive fine aggregate system of the 20-50 cm soil layer for root development; waste intra-soil dispersed recycling while intra-soil machining of the 20-50 cm soil layer provides better soil reclamation, remediation, plant nutrition, macro- and micro elements (including heavy metals), matter organic matter&amp;#160; transfer and turnover in the soil continuum; intra-soil pulse continuous-discrete plant watering reduces the transpiration rate, water consumption of trees is less for 5-20 times, and at the same time provides increased biological productivity of forest plantation, reversible biological sequestration of carbon. The BGT* methods reduce the loss of organic matter from soil into vadoze zone and atmosphere; reduce greenhouse emission from soil and forest, and improve the agro-ecological environment. Apply of the BGT* methods to the dry steppe Chernozem and Kastanozem artificial forest systems will increase the artificial forests oxygen and biomas production, prolong forest lifespan, improve the silviculture land protection function, and mitigate climate change.&lt;/p&gt;&lt;p&gt;BGT* robotic systems will be of low energy and material consumption, will improve forestry, agriculture, reduce the biosphere and climate uncertainty, insure the recreational appearance of forest, make the life attractive.&lt;/p&gt;&lt;p&gt;Objectives of the study: to show the long-term results of Russian steppe terrain silviculture system on Chernozem and Kastanozem; using BGT* methodology, to justify intra-soil 20-50 cm milling, waste intra-soil dispersed recycling while intra-soil 20-50 cm machining, intra-soil pulse continuous-discrete plant watering to provide higher artificial forest biological productivity, reversible carbon biological sequestration, soil fertility, the human and soil health.&lt;/p&gt;

scholarly journals Methods to evaluate CaCO<sub>3</sub> cycle modules in coupled global biogeochemical ocean models

2014 ◽  
Vol 7 (5) ◽  
pp. 2393-2408 ◽  
Author(s):  
W. Koeve ◽  
O. Duteil ◽  
A. Oschlies ◽  
P. Kähler ◽  
J. Segschneider
Keyword(s):  
Organic Matter ◽  
Carbon Cycle ◽  
Numerical Models ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Biogeochemical Processes ◽  
Data Set ◽  
Ocean Physics ◽  
The Difference ◽  
Ocean Carbon

Abstract. The marine CaCO3 cycle is an important component of the oceanic carbon system and directly affects the cycling of natural and the uptake of anthropogenic carbon. In numerical models of the marine carbon cycle, the CaCO3 cycle component is often evaluated against the observed distribution of alkalinity. Alkalinity varies in response to the formation and remineralization of CaCO3 and organic matter. However, it also has a large conservative component, which may strongly be affected by a deficient representation of ocean physics (circulation, evaporation, and precipitation) in models. Here we apply a global ocean biogeochemical model run into preindustrial steady state featuring a number of idealized tracers, explicitly capturing the model's CaCO3 dissolution, organic matter remineralization, and various preformed properties (alkalinity, oxygen, phosphate). We compare the suitability of a variety of measures related to the CaCO3 cycle, including alkalinity (TA), potential alkalinity and TA*, the latter being a measure of the time-integrated imprint of CaCO3 dissolution in the ocean. TA* can be diagnosed from any data set of TA, temperature, salinity, oxygen and phosphate. We demonstrate the sensitivity of total and potential alkalinity to the differences in model and ocean physics, which disqualifies them as accurate measures of biogeochemical processes. We show that an explicit treatment of preformed alkalinity (TA0) is necessary and possible. In our model simulations we implement explicit model tracers of TA0 and TA*. We find that the difference between modelled true TA* and diagnosed TA* was below 10% (25%) in 73% (81%) of the ocean's volume. In the Pacific (and Indian) Oceans the RMSE of A* is below 3 (4) mmol TA m−3, even when using a global rather than regional algorithms to estimate preformed alkalinity. Errors in the Atlantic Ocean are significantly larger and potential improvements of TA0 estimation are discussed. Applying the TA* approach to the output of three state-of-the-art ocean carbon cycle models, we demonstrate the advantage of explicitly taking preformed alkalinity into account for separating the effects of biogeochemical processes and circulation on the distribution of alkalinity. In particular, we suggest to use the TA* approach for CaCO3 cycle model evaluation.

scholarly journals Ocean fronts drive marine fishery production and biogeochemical cycling

2015 ◽  
Vol 112 (6) ◽  
pp. 1710-1715 ◽  
Author(s):  
C. Brock Woodson ◽  
Steven Y. Litvin
Keyword(s):  
Habitat Degradation ◽  
California Current ◽  
Ecosystem Model ◽  
Nutrient Supply ◽  
Ocean Fronts ◽  
High Productivity ◽  
Marine Fishery ◽  
Trophic Pathways ◽  
Biogeochemical Hotspots

Long-term changes in nutrient supply and primary production reportedly foreshadow substantial declines in global marine fishery production. These declines combined with current overfishing, habitat degradation, and pollution paint a grim picture for the future of marine fisheries and ecosystems. However, current models forecasting such declines do not account for the effects of ocean fronts as biogeochemical hotspots. Here we apply a fundamental technique from fluid dynamics to an ecosystem model to show how fronts increase total ecosystem biomass, explain fishery production, cause regime shifts, and contribute significantly to global biogeochemical budgets by channeling nutrients through alternate trophic pathways. We then illustrate how ocean fronts affect fishery abundance and yield, using long-term records of anchovy–sardine regimes and salmon abundances in the California Current. These results elucidate the fundamental importance of biophysical coupling as a driver of bottom–up vs. top–down regulation and high productivity in marine ecosystems.

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