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Sample records for coastal biogeochemical modelling

  1. An offline unstructured biogeochemical model (UBM) for complex estuarine and coastal environments

    SciTech Connect

    Kim, Tae Yun; Khangaonkar, Tarang

    2012-05-01

    Due to increased pollutant loads and water use from coastal development and population growth, occurrences of low-dissolved oxygen and "hypoxic zones" have increased. Reports of fish kills and water quality impairment are also becoming more frequent in many coastal waters. Water quality managers and regulatory agencies rely on numerical modeling tools to quantify the relative contributions of anthropogenic and "natural" pollutant loads (nutrients and biochemical oxygen demand) on dissolved oxygen levels and use the results for remedial activities and source control. The ability to conduct seasonlong simulations with sufficient nearshore resolution is therefore a key requirement. Mesh flexibility and the ability to increase site specific resolution without disturbing the larger domain setup and calibration are critical. The objective of this effort was to develop a robust biogeochemical model suitable for simulation of water quality dynamics including dissolved oxygen in complex coastal environments with multiple tidal channels, tidal flats, and density-driven circulation using unstructured-grid formulation. This paper presents an offline unstructured biogeochemical model that uses the Finite Volume Coastal Ocean Model (FVCOM) discretization of the study domain and the corresponding hydrodynamic solution to drive biogeochemical kinetics based on a water quality model CE-QUAL-ICM. In this paper, the linkage between selected hydrodynamic and water quality models is subjected to several scalar transport and biogeochemical module tests (plume transport and dilution, BOD/DO sag, and phytoplankton/nutrients reaction), and results are compared to their analytical solutions as part of model validation. A preliminary application of the biogeochemical model with a year-long simulation of Hood Canal basin in Puget Sound, USA, is presented as an example and a test of the tool in a real estuary setting. The model reproduced the dynamics and seasonal variations in the

  2. Use of a coastal biogeochemical model to select environmental monitoring sites

    NASA Astrophysics Data System (ADS)

    Wild-Allen, Karen; Thompson, Peter A.; Volkman, John K.; Parslow, John

    2011-10-01

    A method for the spatial selection of sites for a coastal environmental monitoring system is described. The study was completed in southeastern Tasmania, Australia, but the method can be applied in all regions with validated biogeochemical models. A 3-dimensional coupled hydrodynamic, sediment and biogeochemical model with high spatial and temporal resolution was validated against observations collected throughout 2002 and found to capture the essential features of the biogeochemical dynamics of the system. The model was used to predict the possible quantitative environmental impact of a projected increase in fish farming activity in the region. Integrated impacts of fish farm waste on labile nitrogen, phosphorus, chlorophyll and dissolved oxygen concentrations in the water column were spatially ranked to identify the most likely places to detect environmental change due to fish farming activities. Priority sites were found to be grouped in the Huon Estuary and northern part of the D'Entrecasteaux Channel consistent with the residual northward current in the region. The final monitoring program synthesized model and field understanding to ensure adequate spatial and temporal sampling of the region.

  3. Development of a 3D Coupled Physical-Biogeochemical Model for the Marseille Coastal Area (NW Mediterranean Sea): What Complexity Is Required in the Coastal Zone?

    PubMed Central

    Fraysse, Marion; Pinazo, Christel; Faure, Vincent Martin; Fuchs, Rosalie; Lazzari, Paolo; Raimbault, Patrick; Pairaud, Ivane

    2013-01-01

    Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007–2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the biogeochemical model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the biogeochemical model. PMID:24324589

  4. Applied coastal biogeochemical modelling to quantify the environmental impact of fish farm nutrients and inform managers

    NASA Astrophysics Data System (ADS)

    Wild-Allen, Karen; Herzfeld, Mike; Thompson, Peter A.; Rosebrock, Uwe; Parslow, John; Volkman, John K.

    2010-04-01

    A 3D biogeochemical model is validated against regional observations and used to quantify the fluxes and transformations of natural and anthropogenic nutrients in an oligotrophic marine channel and micro-tidal estuary in southern Tasmania. The model reproduces the seasonal cycle of pelagic phytoplankton biomass and dissolved inorganic nutrient concentrations observed in 2002 and is not excessively sensitive to the parameterization of the key biogeochemical processes of phytoplankton light absorption, zooplankton grazing or denitrification. Simulations indicate that in 2002, 66% of total nitrogen influx to the region was supplied from marine sources, 20% from rivers and 14% from salmon farms operating in the region. Fish farm loads of labile dissolved and particulate nitrogen have greatest impact on water quality in summer and autumn when they supply labile nutrient to seasonally depleted surface waters and fuel additional phytoplankton growth. Bays in the northern part of the region are more vulnerable to farm nutrient enrichment due, in part, to the residual northward circulation. It is estimated that in 2002 12% of the region had changed from oligotrophic to mesotrophic status due to salmon farm nutrient enrichment. Analysis of a future scenario simulation with 3 fold increase in farm loads quantified the spatial and temporal impact of farms on water quality and indicated that mesotrophic conditions could extend to 54% of the region. Statistical summaries and visualisation methods were used to communicate model results to stakeholders. Management action has been taken to limit future fish farm loads into the region and implement an environmental monitoring program.

  5. Coastal-zone biogeochemical dynamics under global warming

    SciTech Connect

    Mackenzie, F.T.; Ver, L.M.; Lerman, A.

    2000-03-01

    The coastal zone, consisting of the continental shelves to a depth of 200 meters, including bays, lagoons, estuaries, and near-shore banks, is an environment that is strongly affected by its biogeochemical and physical interactions with reservoirs in the adjacent domains of land, atmosphere, open ocean, and marine sediments. Because the coastal zone is smaller in volume and area coverage relative to the open ocean, it traditionally has been studied as an integral part of the global oceans. In this paper, the authors show by numerical modeling that it is important to consider the coastal zone as an entity separate from the open ocean in any assessment of future Earth-system response under human perturbation. Model analyses for the early part of the 21st century suggest that the coastal zone plays a significant modifying role in the biogeochemical dynamics of the carbon cycle and the nutrient cycles coupled to it. This role is manifested in changes in primary production, storage, and/or export of organic matter, its remineralization, and calcium carbonate precipitation--all of which determine the state of the coastal zone with respect to exchange of CO{sub 2} with the atmosphere. Under a scenario of future reduced or complete cessation of the thermohaline circulation (THC) of the global oceans, coastal waters become an important sink for atmospheric CO{sub 2}, as opposed to the conditions in the past and present, when coastal waters are believed to be a source of CO{sub 2} to the atmosphere. Profound changes in coastal-zone primary productivity underscore the important role of phosphorus as a limiting nutrient. In addition, calculations indicate that the saturation state of coastal waters with respect to carbonate minerals will decline by {approximately}15% by the year 2030. Any future slowdown in the THC of the oceans will increase slightly the rate of decline in saturation state.

  6. Phytoplankton versus macrophyte contribution to primary production and biogeochemical cycles of a coastal mesotidal system. A modelling approach

    NASA Astrophysics Data System (ADS)

    Plus, M.; Auby, I.; Maurer, D.; Trut, G.; Del Amo, Y.; Dumas, F.; Thouvenin, B.

    2015-11-01

    This study presents an assessment of the contributions of various primary producers to the global annual production and N/P cycles of a coastal system, namely the Arcachon Bay, by means of a numerical model. This 3D model fully couples hydrodynamic with ecological processes and simulates nitrogen, silicon and phosphorus cycles as well as phytoplankton, macroalgae and seagrasses. Total annual production rates for the different components were calculated for different years (2005, 2007 and 2009) during a time period of drastic reduction in seagrass beds since 2005. The total demand of nitrogen and phosphorus was also calculated and discussed with regards to the riverine inputs. Moreover, this study presents the first estimation of particulate organic carbon export to the adjacent open ocean. The calculated annual net production for the Arcachon Bay (except microphytobenthos, not included in the model) ranges between 22,850 and 35,300 tons of carbon. The main producers are seagrasses in all the years considered with a contribution ranging from 56% to 81% of global production. According to our model, the -30% reduction in seagrass bed surface between 2005 and 2007, led to an approximate 55% reduction in seagrass production, while during the same period of time, macroalgae and phytoplankton enhanced their productions by about +83% and +46% respectively. Nonetheless, the phytoplankton production remains about eightfold higher than the macroalgae production. Our results also highlight the importance of remineralisation inside the Bay, since riverine inputs only fulfill at maximum 73% nitrogen and 13% phosphorus demands during the years 2005, 2007 and 2009. Calculated advection allowed a rough estimate of the organic matter export: about 10% of the total production in the bay was exported, originating mainly from the seagrass compartment, since most of the labile organic matter was remineralised inside the bay.

  7. Biogeochemical classification of South Florida's estuarine and coastal waters.

    PubMed

    Briceño, Henry O; Boyer, Joseph N; Castro, Joffre; Harlem, Peter

    2013-10-15

    South Florida's watersheds have endured a century of urban and agricultural development and disruption of their hydrology. Spatial characterization of South Florida's estuarine and coastal waters is important to Everglades' restoration programs. We applied Factor Analysis and Hierarchical Clustering of water quality data in tandem to characterize and spatially subdivide South Florida's coastal and estuarine waters. Segmentation rendered forty-four biogeochemically distinct water bodies whose spatial distribution is closely linked to geomorphology, circulation, benthic community pattern, and to water management. This segmentation has been adopted with minor changes by federal and state environmental agencies to derive numeric nutrient criteria. PMID:23968989

  8. Mangrove forests: a potent nexus of coastal biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Barr, J. G.; Fuentes, J. D.; Shoemaker, B.; O'Halloran, T. L.; Lin, G., Sr.; Engel, V. C.

    2014-12-01

    Mangrove forests cover just 0.1% of the Earth's terrestrial surface, yet they provide a disproportionate source (~10 % globally) of terrestrially derived, refractory dissolved organic carbon to the oceans. Mangrove forests are biogeochemical reactors that convert biomass into dissolved organic and inorganic carbon at unusually high rates, and many studies recognize the value of mangrove ecosystems for the substantial amounts of soil carbon storage they produce. However, questions remain as to how mangrove forest ecosystem services should be valuated and quantified. Therefore, this study addresses several objectives. First, we demonstrate that seasonal and annual net ecosystem carbon exchange in three selected mangrove forests, derived from long-term eddy covariance measurements, represent key quantities in defining the magnitude of biogeochemical cycling and together with other information on carbon cycle parameters serves as a proxy to estimate ecosystem services. Second, we model ecosystem productivity across the mangrove forests of Everglades National Park and southern China by relating net ecosystem exchange values to remote sensing data. Finally, we develop a carbon budget for the mangrove forests in the Everglades National Park for the purposes of demonstrating that these forests and adjacent estuaries are sites of intense biogeochemical cycling. One conclusion from this study is that much of the carbon entering from the atmosphere as net ecosystem exchange (~1000 g C m-2 yr-1) is not retained in the net ecosystem carbon balance. Instead, a substantial fraction of the carbon entering the system as net ecosystem exchange is ultimately exported to the oceans or outgassed as reaction products within the adjacent estuary.

  9. Modelling Marine Biological and Biogeochemical Data

    NASA Astrophysics Data System (ADS)

    Soetaert, Karline; van Oevelen, Dick

    2011-09-01

    In the environmental sciences, mathematic models are commonly applied to analyze ecological and biogeochemical data. The technique where a model is used to interpret available measurements such as to retrieve unmeasured information on the system being observed is called "inverse modelling". In this paper we will discuss and give examples of two modeling techniques used to analyse ecological and biogeochemical data. On the one hand are mechanistic mathematical models that are written as a set of non-linear differential equations. On the other hand are so-called linear inverse models (LIMs) that consist of a set of linear equations that need to be solved for the unknowns.

  10. Interannual Variability of Coastal Nutrient Fluxes Along the U.S. Eastern Continental Shelf (USECoS): Results from a Land-Ocean-Biogeochemical Modeling System

    NASA Astrophysics Data System (ADS)

    Hofmann, E. E.

    2014-12-01

    Understanding of nitrogen cycling on continental shelves, a critical component of global nutrient cycling, is often hampered by limited observations compared to the strong variability apparent on relatively small time and space scales. Numerical models are able to partially alleviate this issue by filling temporal and spatial data gaps and hence resolving annual area-integrated nutrient fluxes. Here a land-ocean-biogeochemical modeling system was implemented to simulate the nitrogen budget during 2004-2007 on the U.S. eastern continental shelf. Quantitative model skill assessment was conducted via extensive comparisons to satellite observations, and in situ data where available. Model simulations demonstrate that denitrification and burial fluxes have pronounced seasonal variation but change little from year to year. In contrast, annual net community production (NCP) varies significantly between years, but overall is positive indicating a net autotrophic system. Whereas the advective influx of nitrogen from the bays and rivers on the western boundary of the shelf changes only slightly among the four years examined, the advective fluxes across the eastern and northern boundaries change dramatically. These changes are associated with changes in the positions of the relatively high-nutrient Labrador Sea waters advecting into the shelf from the north, and the relatively low-nutrient Gulf Stream waters advecting into the region from the southeast. Tests varying the initial conditions (reduced spin-up) and simplifying the modeled plankton structure showed distinct impacts on these nitrogen fluxes: the former strongly affected the advective fluxes, but had little impact on denitrification, burial or NCP, whereas the latter significantly reduced denitrification, burial, and NCP but did not significantly impact the advective fluxes.

  11. Modelling the global coastal ocean.

    PubMed

    Holt, Jason; Harle, James; Proctor, Roger; Michel, Sylvain; Ashworth, Mike; Batstone, Crispian; Allen, Icarus; Holmes, Robert; Smyth, Tim; Haines, Keith; Bretherton, Dan; Smith, Gregory

    2009-03-13

    Shelf and coastal seas are regions of exceptionally high biological productivity, high rates of biogeochemical cycling and immense socio-economic importance. They are, however, poorly represented by the present generation of Earth system models, both in terms of resolution and process representation. Hence, these models cannot be used to elucidate the role of the coastal ocean in global biogeochemical cycles and the effects global change (both direct anthropogenic and climatic) are having on them. Here, we present a system for simulating all the coastal regions around the world (the Global Coastal Ocean Modelling System) in a systematic and practical fashion. It is based on automatically generating multiple nested model domains, using the Proudman Oceanographic Laboratory Coastal Ocean Modelling System coupled to the European Regional Seas Ecosystem Model. Preliminary results from the system are presented. These demonstrate the viability of the concept, and we discuss the prospects for using the system to explore key areas of global change in shelf seas, such as their role in the carbon cycle and climate change effects on fisheries. PMID:19087928

  12. Biogeochemical responses of shallow coastal lagoons to Climate Change

    NASA Astrophysics Data System (ADS)

    Brito, A.; Newton, A.; Tett, P.; Fernandes, T.

    2009-04-01

    The importance of climate change and global warming in the near future is becoming consensual within the scientific community (e.g. Kerr et al., 2008; Lloret et al., 2008). The surface temperature and sea level have increased during the last few years in the northern hemisphere (IPCC, 2007). Predictions for future changes include an increase of surface temperature and sea level for Europe. Moreover, the global warming phenomenon will also change the hydrological cycle and increase precipitation in northern and central Europe (IPCC, 2007). Sea level rise already threatens to overwhelm some lagoons, such as Venice and Moroccan lagoons (Snoussi et al., 2008). Shallow coastal lagoons are some of the most vulnerable systems that will be impacted by these changes (Eisenreich, 2005). Environmental impacts on coastal lagoons include an increase of water turbidity and therefore light attenuation. If these effects are strong enough, the lighted bottoms of shallow lagoons may loose a significant part of the benthic algal community. These communities are highly productive and are essential to control nutrient dynamics of the system by uptaking large amounts of nutrients both from the water column and from the sediments. A decrease in benthic algal communities and photosynthetic oxygen production will also contribute to increasing the vulnerability of the lagoons to hypoxia and anoxia. The flux of nutrients such as phosphate from the sediments may increase dramatically, further disrupting the nutrient balance and condition and promoting cyanobacterial blooms. Microbial activity is temperature dependent, therefore, the increase of temperature will increase the concentrations of ammonium within sediments. The release of phosphate and silicate will also increase with temperature. Coastal lagoons are valuable ecosystems and may be severely impacted, both ecologically and economically, by global change. Shallow coastal lagoons should be considered as sentinel systems and should be

  13. Biogeochemical modeling at mass extinction boundaries

    NASA Technical Reports Server (NTRS)

    Rampino, M. R.; Caldeira, K. G.

    1991-01-01

    The causes of major mass extinctions is a subject of considerable interest to those concerned with the history and evolution of life on earth. The primary objectives of the proposed plan of research are: (1) to develop quantitative time-dependent biogeochemical cycle models, coupled with an ocean atmosphere in order to improve the understanding of global scale physical, chemical, and biological processes that control the distribution of elements important for life at times of mass extinctions; and (2) to develop a comprehensive data base of the best available geochemical, isotopic, and other relevant geologic data from sections across mass extinction boundaries. These data will be used to constrain and test the biogeochemical model. These modeling experiments should prove useful in: (1) determining the possible cause(s) of the environmental changes seen at bio-event boundaries; (2) identifying and quantifying little-known feedbacks among the oceans, atmosphere, and biosphere; and (3) providing additional insights into the possible responses of the earth system to perturbations of various timescales. One of the best known mass extinction events marks the Cretaceous/Tertiary (K/T) boundary (66 Myr ago). Data from the K/T boundary are used here to constrain a newly developed time-dependent biogeochemical cycle model that is designed to study transient behavior of the earth system. Model results predict significant fluctuations in ocean alkalinity, atmospheric CO2, and global temperatures caused by extinction of calcareous plankton and reduction in the sedimentation rates of pelagic carbonates and organic carbon. Oxygen-isotome and other paleoclimatic data from K/T time provide some evidence that such climatic fluctuations may have occurred, but stabilizing feedbacks may have acted to reduce the ocean alkalinity and carbon dioxide fluctuations.

  14. Effects of Climate-Induced Hydrologic Modifications on Biogeochemical Cycling of Trace Metals in Alluvial and Coastal Watersheds

    NASA Astrophysics Data System (ADS)

    Lee, M.; Natter, M. G.; Keevan, J. P.; Guerra, K.; Saunders, J.; Uddin, A.; Humayun, M.; Wang, Y.; Keimowitz, A. R.

    2013-12-01

    Assessing the impacts of climate changes on water quality requires an understanding of the biogeochemical cycling of trace metals. Evidence from research on alluvial aquifers and coastal watersheds shows direct impacts of climate change on the fate and transformation of trace metals in natural environments. This study employs field data and numerical modeling techniques to test assumptions about the effects of climate change on natural arsenic contamination of groundwater in alluvial aquifers and mercury bioaccumulation in coastal saltmarshes. The results show that the rises of sea level and river base during the warm Holocene period has led to an overall increase in groundwater arsenic concentration due to the development of reducing geochemical conditions and sluggish groundwater movement. Modeling results indicate that the intrusion of seawater occurring during high sea-level stand may lead to desorption of arsenic from the surfaces of hydrous oxides due to pH effects and ionic competition for mineral sorbing sites. Our results also show that contamination and bioaccumulation of Hg and other metals in estuarine and coastal ecosystems may be influenced by climate-induced hydrologic modifications (atmospheric deposition, riverine input, salinity level, etc.). An integrated research framework consisting of numerical modeling, long-term monitoring, laboratory experiments will be necessary for building a comprehensive understanding of the complex response of biogeochemical cycling of trace metals to climate change.

  15. Plant Nitrogen Uptake in Terrestrial Biogeochemical Models

    NASA Astrophysics Data System (ADS)

    Marti Donati, A.; Cox, P.; Smith, M. J.; Purves, D.; Sitch, S.; Jones, C. D.

    2013-12-01

    Most terrestrial biogeochemical models featured in the last Intergovernmental Panel on Climate Change (IPPC) Assessment Report highlight the importance of the terrestrial Carbon sequestration and feedbacks between the terrestrial Carbon cycle and the climate system. However, these models have been criticized for overestimating predicted Carbon sequestration and its potential climate feedback when calculating the rate of future climate change because they do not account for the Carbon sequestration constraints caused by nutrient limitation, particularly Nitrogen (N). This is particularly relevant considering the existence of a substantial deficit of Nitrogen for plants in most areas of the world. To date, most climate models assume that plants have access to as much Nitrogen as needed, but ignore the nutrient requirements for new vegetation growth. Determining the natural demand and acquisition for Nitrogen and its associated resource optimization is key when accounting for the Carbon sequestration constrains caused by nutrient limitation. The few climate models that include C-N dynamics have illustrated that the stimulation of plant growth over the coming century may be significantly smaller than previously predicted. However, models exhibit wide differences in their predictive accuracy and lead to widely diverging and inconsistent projections accounting for an uncertain Carbon sequestration decrease due to Nitrogen limitation ranging from 7 to 64%. This reduction in growth is partially offset by an increase in the availability of nutrients resulting from an accelerated rate of decomposition of dead plants and other organic matter that occurring with a rise in temperature. However, this offset does not counterbalance the reduced level of plant growth calculated by natural nutrient limitations. Additionally, Nitrogen limitation is also expected to become more pronounced in some ecosystems as atmospheric CO2 concentration increases; resulting in less new growth and

  16. Parameterization of biogeochemical sediment-water fluxes using in-situ measurements and a steady-state diagenetic model

    NASA Astrophysics Data System (ADS)

    Laurent, Arnaud; Fennel, Katja; Wilson, Robin; Lehrter, John; Devereux, Richard

    2014-05-01

    Sediment biogeochemical processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be an important driver of bottom water oxygen depletion in hypoxic systems, and sediment-water nutrient fluxes support primary productivity in the overlying water column. Yet, biogeochemical sediment-water fluxes are often parameterized crudely and only poorly constrained in coupled physical-biogeochemical models. Here, we present a method for parameterizing biogeochemical sediment-water fluxes realistically and efficiently, using in-situ measurements and a steady state diagenetic model. We apply this method to the Louisiana Shelf where high primary production induced by excess nutrient loads from the Mississippi-Atchafalaya River system promotes the development of hypoxic bottom waters in summer. The implementation of the parameterizations in a coupled circulation-biogeochemical model of the northern Gulf of Mexico results in realistic sediment-water fluxes that enable a sediment-water column feedback at low bottom oxygen concentrations.

  17. Study of the Impact of Submarine Groundwater Discharge on the Bio-Geochemical Parameters of Coastal Waters off Southern Portugal

    NASA Astrophysics Data System (ADS)

    Kontar, A. Y.; Newton, A.

    2009-12-01

    We are working on the estimation of the impact of submarine groundwater discharge (SGD) on the bio-geochemical parameters of coastal waters in Atlantic off Portugal. It is important to obtain reliable quantitative estimates of both in coming and outgoing fluxes of fresh cold waters. In situation that incoming groundwater is cold enough to occupy the lower part of the stratified water column on the shelf, transport processes in the bottom boundary layer dominate the removal of discharged water from the coastal zone. Physical mechanisms of such removal seem to be similar to the mechanisms of dense water cascades off the continental shelf over the shelf break. Cascading is a specific type of thermohaline circulation, in which dense water formed over the continental shelf descends down the continental slope to a greater depth. This process is a major component of ventilation of intermediate and abyssal waters, hence affecting thermohaline circulation and global climate. The resulting flows produce an irreversible exchange of oceanic and shelf waters and take an important role in bio-geochemical cycles by removal of phytoplankton, carbon and chlorophyll from productive areas. Because it can take decades or more for the subducted water to re-surface, water cascades contribute to long term climatic variability. It is common to consider formation of dense water by cooling, evaporation or freezing in the surface layer. SGD can provide an alternative mechanism of dense water formation on the shelf. In the framework of the ERASMUS MANDUS project we investigate the physical mechanisms of the removal of SGD water from the Algarve coastal zone to try to get a quantification of off-shore fluxes and transport pathways for SGD and chemical species from the shelf through numerical modeling of the processes in the bottom boundary layer. We are using numerical modeling of the SGD fluxes and transport pathways of dense water flow in the bottom boundary layer using a set of process

  18. Biogeochemical controls on carbonate saturation and pH in coastal oceans influenced by large rivers

    NASA Astrophysics Data System (ADS)

    Huang, W.; Hu, X.; Cai, W.

    2010-12-01

    Recent studies have suggested that river influenced coastal oceans may be more sensitive to further acidification caused by both atmospheric CO2 and acidification of the rivers themselves, the later mostly caused by anthropogenic activities. Here we present a study that focuses on examining biogeochemical controls on the carbonate system in the coastal waters that are dominated by large rivers in tropical and subtropical areas across the globe. Geochemical compositions of these rivers vary from high alkalinity/pH to low alkalinity/pH. Our findings indicate that low carbonate saturation states and low pH do not occur ubiquitously in these large river-dominated coastal oceans. Instead, both the characteristics of river water and biological influences, i.e., primary production using river exported nutrients, control the carbonate system parameters. Under current trend of nutrient export at projected river discharge, the present condition is not going to alter in a significant way as what the open ocean responds to atmospheric CO2 intrusion.

  19. Using Stable Isotope Analysis to Determine Zooplankton Trophic Response to the Biogeochemical Gradient in a Coastal Tributary

    EPA Science Inventory

    The goal of our research is to identify energy inputs that support lower food web production in a coastal tributary using the biogeochemical gradient that arises from the mixing of river and Great Lake water. We characterized the food web along the lower 35 km of the St. Louis Ri...

  20. Sedimentary Biogeochemical Indicators for Assessing the Impacts of the Deepwater Horizon Blowout on Coastal Wetlands

    NASA Astrophysics Data System (ADS)

    McNeal, K. S.; Guthrie, C. L.; Mishra, D.

    2013-05-01

    The impact of the Deepwater Horizon blowout on coastal wetlands can be understood through investigating carbon loading and microbial activity in salt marsh sediments. Carbon influx causes porewater sulfide to increase in wetland sediment, making it toxic and inhospitable to marsh vegetation. High sulfide levels due to increased microbial activity can lead to plant browning and mortality. Preliminary analyses at Marsh Point, MS indicated that sulfate reducing bacteria are more active in contaminated grass, producing sulfide concentrations 100x higher than in non-contaminated grass. Sediment electrode profiles, hydrocarbon contamination, and microbial community profiles were measured at three additional locations to capture the spatial sedimentary geochemical processes impacting salt marsh dieback. Findings indicate that response to contamination is variable due to physical and biogeochemical processes specific to each marsh. Temporal evaluation indicates that there is a lag in maximum response to contamination due to seasonal effects on microbial activity.

  1. Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin

    NASA Astrophysics Data System (ADS)

    Hagens, M.; Slomp, C. P.; Meysman, F. J. R.; Seitaj, D.; Harlay, J.; Borges, A. V.; Middelburg, J. J.

    2015-03-01

    Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity in any hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands). Monthly water-column chemistry measurements were complemented with estimates of primary production and respiration using O2 light-dark incubations, in addition to sediment-water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting data set was used to set up a proton budget on a seasonal scale. Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air-sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment-water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid-base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid-base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.

  2. Wastewater injection, aquifer biogeochemical reactions, and resultant groundwater N fluxes to coastal waters: Kā'anapali, Maui, Hawai'i.

    PubMed

    Fackrell, Joseph K; Glenn, Craig R; Popp, Brian N; Whittier, Robert B; Dulai, Henrietta

    2016-09-15

    We utilize N and C species concentration data along with δ(15)N values of NO3(-) and δ(13)C values of dissolved inorganic C to evaluate the stoichiometry of biogeochemical reactions (mineralization, nitrification, anammox, and denitrification) occurring within a subsurface wastewater plume that originates as treated wastewater injection and enters the coastal waters of Maui as submarine groundwater discharge. Additionally, we compare wastewater effluent time-series data, injection rates, and treatment history with submarine spring discharge time-series data. We find that heterotrophic denitrification is the primary mechanism of N loss within the groundwater plume and that chlorination for pathogen disinfection suppresses microbial activity in the aquifer responsible for N loss, resulting in increased coastal ocean N loading. Replacement of chlorination with UV disinfection may restore biogeochemical reactions responsible for N loss within the aquifer and return N-attenuating conditions in the effluent plume, reducing N loading to coastal waters. PMID:27339740

  3. Arctic Coastal Erosion Modeling

    NASA Astrophysics Data System (ADS)

    Ravens, T. M.; Jones, B.; Zhang, J.; Tweedie, C. E.; Erikson, L. H.; Gibbs, A.; Richmond, B. M.

    2011-12-01

    A process-based coastal erosion/shoreline change model has been developed for Arctic coastal bluffs subject to niche erosion/block collapse. The model explicitly accounts for many environmental/geographic variables including: water temperature, water level, wave height, and bluff height. The model was originally developed for a small coastal segment near Drew Point, Beaufort Sea, Alaska. This coastal setting has experienced a dramatic increase in erosion since the early 2000's. The bluffs at this site are 3-4 m tall and consist of ice-wedge bounded blocks of fine-grained sediments cemented by ice-rich permafrost and capped with a thin organic layer. The bluffs are typically fronted by a narrow (~ 5 m wide) beach or none at all. During a storm surge, the sea contacts the base of the bluff and a niche is formed through thermal and mechanical erosion. The niche grows both vertically and laterally and eventually undermines the bluff, leading to block failure or collapse. The fallen block is then eroded both thermally and mechanically by waves and currents, which must occur before a new niche forming episode may begin. The model has been calibrated based on shoreline change data at Drew Point for two time periods: 1979-2002 and 2002-2007. Measured and modeled shoreline change rates were about 8 m/yr and 16 m/yr, for the earlier and later periods, respectively. In this paper, this work is extended to include modeling and measurement of coastal erosion at Drew Point on an annual basis for the period 2007-2010. In addition, the model is applied at three other Arctic coastal locations - Elson Lagoon, Cape Halkett, and Barter Island - where niche erosion/block collapse prevails.

  4. Model for Coastal Restoration

    SciTech Connect

    Thom, Ronald M.; Judd, Chaeli

    2007-07-27

    Successful restoration of wetland habitats depends on both our understanding of our system and our ability to characterize it. By developing a conceptual model, looking at different spatial scales and integrating diverse data streams: GIS datasets and NASA products, we were able to develop a dynamic model for site prioritization based on both qualitative and quantitative relationships found in the coastal environment.

  5. Coupling a terrestrial biogeochemical model to the common land model

    SciTech Connect

    Shi, Xiaoying; Mao, Jiafu; Wang, Yingping; Dai, Yongjiu; Tang, Xuli

    2011-01-01

    A terrestrial biogeochemical model (CASACNP) was coupled to a land surface model (the Common Land Model, CoLM) to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration. The combined model, CoLM-CASACNP, was able to predict long-term carbon sources and sinks that CoLM alone could not. The coupled model was tested using measurements of belowground respiration and surface fluxes from two forest ecosystems. The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange, as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study. However, the agreement between model simulations and actual measurements was poorer under dry conditions. The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.

  6. Incorporating nitrogen fixing cyanobacteria in the global biogeochemical model HAMOCC

    NASA Astrophysics Data System (ADS)

    Paulsen, Hanna; Ilyina, Tatiana; Six, Katharina

    2015-04-01

    Nitrogen fixation by marine diazotrophs plays a fundamental role in the oceanic nitrogen and carbon cycle as it provides a major source of 'new' nitrogen to the euphotic zone that supports biological carbon export and sequestration. Since most global biogeochemical models include nitrogen fixation only diagnostically, they are not able to capture its spatial pattern sufficiently. Here we present the incorporation of an explicit, dynamic representation of diazotrophic cyanobacteria and the corresponding nitrogen fixation in the global ocean biogeochemical model HAMOCC (Hamburg Ocean Carbon Cycle model), which is part of the Max Planck Institute for Meteorology Earth system model (MPI-ESM). The parameterization of the diazotrophic growth is thereby based on available knowledge about the cyanobacterium Trichodesmium spp., which is considered as the most significant pelagic nitrogen fixer. Evaluation against observations shows that the model successfully reproduces the main spatial distribution of cyanobacteria and nitrogen fixation, covering large parts of the tropical and subtropical oceans. Besides the role of cyanobacteria in marine biogeochemical cycles, their capacity to form extensive surface blooms induces a number of bio-physical feedback mechanisms in the Earth system. The processes driving these interactions, which are related to the alteration of heat absorption, surface albedo and momentum input by wind, are incorporated in the biogeochemical and physical model of the MPI-ESM in order to investigate their impacts on a global scale. First preliminary results will be shown.

  7. Ecological, biogeochemical and salinity changes in coastal lakes and wetlands over the last 200 years

    NASA Astrophysics Data System (ADS)

    Roberts, Lucy; Holmes, Jonathan; Horne, David

    2016-04-01

    Shallow lakes provide extensive ecosystem services and are ecologically important aquatic resources supporting a diverse flora and fauna. In marginal-marine areas, where such lakes are subjected to the multiple pressures of coastal erosion, sea level rise, increasing sea surface temperature and increasing frequency and intensity of storm surges, environments are complex and unstable. They are characterised by physico-chemical variations due to climatic (precipitation/evaporation cycles) and dynamic factors (tides, currents, freshwater drainage and sea level changes). Combined with human activity in the catchment these processes can alter the salinity, habitat and ecology of coastal fresh- to brackish water ecosystems. In this study the chemical and biological stability of coastal lakes forming the Upper Thurne catchment in the NE of the Norfolk Broads, East Anglia, UK are seriously threatened by long-term changes in salinity resulting from storm surges, complex hydrogeology and anthropogenic activity in the catchment. Future management decisions depend on a sound understanding of the potential ecological impacts, but such understanding is limited by short-term observations and measurements. This research uses palaeolimnological approaches, which can be validated and calibrated with historical records, to reconstruct changes in the aquatic environment on a longer time scale than can be achieved by observations alone. Here, salinity is quantitatively reconstructed using the trace-element geochemistry (Sr/Ca and Mg/Ca) of low Mg-calcite shells of Ostracoda (microscopic bivalved crustaceans) and macrophyte and macroinvertebrate macrofossil remains are used as a proxy to assess ecological change in response to variations in salinity. δ13C values of Cladocera (which are potentially outcompeted by the mysid Neomysis integer with increasing salinity and eutrophication) can be used to reconstruct carbon cycling and energy pathways in lake food webs, which alongside

  8. A Generic Biogeochemical Module for Earth System Models: Next Generation BioGeoChemical Module (NGBGC), Version 1.0

    SciTech Connect

    Fang, Yilin; Huang, Maoyi; Liu, Chongxuan; Li, Hongyi; Leung, Lai-Yung R.

    2013-11-13

    Physical and biogeochemical processes regulate soil carbon dynamics and CO2 flux to and from atmosphere, influencing global climate changes. Integration of these processes into earth system models (e.g., community land models (CLM)), however, currently faces three major challenges: 1) extensive efforts are required to modify modeling structures and to rewrite computer programs to incorporate new or updated processes as new knowledge is being generated, 2) computational cost is prohibitively expensive to simulate biogeochemical processes in land models due to large variations in the rates of biogeochemical processes, and 3) various mathematical representations of biogeochemical processes exist to incorporate different aspects of fundamental mechanisms, but systematic evaluation of the different mathematical representations is difficult, if not possible. To address these challenges, we propose a new computational framework to easily incorporate physical and biogeochemical processes into land models. The new framework consists of a new biogeochemical module with a generic algorithm and reaction database so that new and updated processes can be incorporated into land models without the need to manually set up the ordinary differential equations to be solved numerically. The reaction database consists of processes of nutrient flow through the terrestrial ecosystems in plants, litter and soil. This framework facilitates effective comparison studies of biogeochemical cycles in an ecosystem using different conceptual models under the same land modeling framework. The approach was first implemented in CLM and benchmarked against simulations from the original CLM-CN code. A case study was then provided to demonstrate the advantages of using the new approach to incorporate a phosphorus cycle into the CLM model. To our knowledge, the phosphorus-incorporated CLM is a new model that can be used to simulate phosphorus limitation on the productivity of terrestrial ecosystems.

  9. Simulating aggregate dynamics in ocean biogeochemical models

    NASA Astrophysics Data System (ADS)

    Jackson, George A.; Burd, Adrian B.

    2015-04-01

    The dynamics of elements in the water column is complex, depending on multiple biological and physical processes operating at very different physical scales. Coagulation of particulate material is important for transforming particles and moving them in the water column. Mechanistic models of coagulation processes provide a means to predict these processes, help interpret observations, and provide insight into the processes occurring. However, most model applications have focused on describing simple marine systems and mechanisms. We argue that further model development, in close collaboration with field and experimental scientists, is required in order to extend the models to describe the large-scale elemental distributions and interactions being studied as part of GEOTRACES. Models that provide a fundamental description of trace element-particle interactions are required as are experimental tests of the mechanisms involved and the predictions arising from models. However, a comparison between simple and complicated models of aggregation and trace metal provides a means for understanding the implications of simplifying assumptions and providing guidance as to which simplifications are needed.

  10. Implementing high-latitude biogeochemical processes into Earth System Models

    NASA Astrophysics Data System (ADS)

    Brovkin, Victor; Kleinen, Thomas; Cresto-Aleina, Fabio; Kloster, Silvia; Ilyina, Tatiana

    2016-04-01

    Projections of future climate changes suggest that air temperatures in the Arctic could rise to the levels unprecedented in the last million years. Sensitivity of carbon storages on land and shelves to climate change of that scale is highly uncertain. Earth System models (ESMs), consisting of atmosphere, ocean, land, and cryosphere components are the main tools to understand interactions between carbon cycle and climate. However, ESM representation of ecological and biogeochemical processes in the Arctic is extremely simplistic. For example, all ESMs agree that tree cover in the future warming scenarios will move northwards to the Arctic coast, but they ignore interactions between vegetation, permafrost, and disturbances such as fires, which are critical for vegetation dynamics in this region. Improving modeling of interactions between model components and their evaluation against growing observational evidence is a promising research area. The first attempts to account for the permafrost carbon dynamics in the ESM framework suggest that CO2 and CH4 emissions from high-latitude regions in the 21st century are relatively small, but they become much more significant afterwards due to committed climate changes. Therefore, extension of ESM simulations beyond 2100 is essential to estimate a proper scale of frozen carbon pool response to human-induced climate change. Additionally, inclusion of sub-sea permafrost component into ESMs is an active research area that brings together terrestrial and marine biogeochemical communities, as well as geologists analyzing climate proxies on glacial timescales. Another challenging aspect of biogeochemical interactions in Arctic is an extreme land surface heterogeneity. A mixture of wetlands, lakes, and vegetation-covered surfaces on fine local scale is not properly reflected in the model structure. A promising approach of dealing with scaling gaps in modeling high-latitude biogeochemical processes in ESMs will be presented.

  11. Modeling the biogeochemical seasonal cycle in the Strait of Gibraltar

    NASA Astrophysics Data System (ADS)

    Ramírez-Romero, E.; Vichi, M.; Castro, M.; Macías, J.; Macías, D.; García, C. M.; Bruno, M.

    2014-11-01

    A physical-biological coupled model was used to estimate the effect of the physical processes at the Strait of Gibraltar over the biogeochemical features of the Atlantic Inflow (AI) towards the Mediterranean Sea. This work was focused on the seasonal variation of the biogeochemical patterns in the AI and the role of the Strait; including primary production and phytoplankton features. As the physical model is 1D (horizontal) and two-layer, different integration methods for the primary production in the Biogeochemical Fluxes Model (BFM) have been evaluated. An approach based on the integration of a production-irradiance function was the chosen method. Using this Plankton Functional Type model (BFM), a simplified phytoplankton seasonal cycle in the AI was simulated. Main results included a principal bloom in spring dominated by nanoflagellates, whereas minimum biomass (mostly picophytoplankton) was simulated during summer. Physical processes occurring in the Strait could trigger primary production and raise phytoplankton biomass (during spring and autumn), mainly due to two combined effects. First, in the Strait a strong interfacial mixing (causing nutrient supply to the upper layer) is produced, and, second, a shoaling of the surface Atlantic layer occurs eastward. Our results show that these phenomena caused an integrated production of 105 g C m- 2 year- 1 in the eastern side of the Strait, and would also modify the proportion of the different phytoplankton groups. Nanoflagellates were favored during spring/autumn while picophytoplankton is more abundant in summer. Finally, AI could represent a relevant source of nutrients and biomass to Alboran Sea, fertilizing the upper layer of this area with 4.95 megatons nitrate year- 1 (79.83 gigamol year- 1) and 0.44 megatons C year- 1. A main advantage of this coupled model is the capability of solving relevant high-resolution processes as the tidal forcing without expensive computing requirements, allowing to assess the

  12. The Dynamic Watershed and the Coastal Ocean: Biogeochemical Linkages and Interannual Variability

    NASA Astrophysics Data System (ADS)

    Olhsson, E.; Powell, T. M.

    2013-12-01

    What is the fate of riverine nutrients in the coastal ocean? To what extent does the timing and magnitude of river discharge influence coastal primary productivity? What mechanisms link biological variability to changes within a given watershed? And how might climate change alter these relationships? To test the advantages of using regional scale model coupling to explore these questions, an example river was selected for study: the Eel River. The Eel River discharges into the North Pacific at 40° 38.5' in Northern California. Its annual discharge (~200 m3/s) is about 1% that of the Mississippi, but its sediment yield (15 million tons/yr) is the highest for its drainage area (9500 km2) in the entire continental US. It is an advantageous choice for a test case to model because its annual behavior is dramatic and potentially very sensitive to changes in climate. Driven by the Mediterranean climate of northern California, it is characterized by low flow during the long dry season. Then, each winter and spring, storm events flush sediments, nutrients, organic matter and organisms down the river to the ocean, in large pulses. The storm flows are out of phase with the other major nutrient input to local coastal biology: late spring and summer upwelling of cold, nutrient-rich ocean water to the photosynthetically active surface. The timing and magnitude of these storm events, and thus of Eel riverine nutrient delivery, have a great deal of interannual variability and may be altered by climate change. Furthermore, satellite ocean color imagery suggests that the fluxes from the Eel River may contribute to phytoplankton blooms offshore, demonstrating spatial, seasonal and interannual variability of ocean color, north and south of the Eel River's mouth. This study constructs a detailed modeling framework to examine the connections between variability in weather (modulated, slowly, by climate trends), river nutrient delivery to the ocean, and coastal phytoplankton

  13. Towards bridging biogeochemical and fish-production models

    NASA Astrophysics Data System (ADS)

    Fennel, Wolfgang

    The paper presents a theoretical approach to formulate a model which comprises the full food web. The lower part of the food web is represented by a biogeochemical model which interacts explicitly with a fish-production model. The fish-production model component builds on existing theories but was substantially reformulated in order to facilitate the model coupling. The dynamics of the fish-production model is basically driven by the predator-prey interaction. We use the example of the Baltic Sea, which has a relatively simple foodweb structure. The fish biomass is dominated by three groups, sprat, herring and cod, which represent about 80% of fish biomass in the Baltic. The zooplanktivors sprat and herring are eaten by cod. In this paper we start the construction of the model as a simple box system, which can be considered as an isolated water column of 10 × 10 km 2 times the water depth in the central Bornholm basin of the Baltic Sea. The stepwise building up of the model is illustrated by example simulations, which allow to assess the consistence of the theoretical approach and the choices of parameters. As last step we introduce a simple biogeochemical model and link it with the fish model. The resulting model system is strictly mass conserving without unspecified sources of food or so. We conduct experiments with the model system and show that it can reproduce features such as interannual variation in fish catches and trophic cascades.

  14. Biogeochemical metabolic modeling of methanogenesis by Methanosarcina barkeri

    NASA Astrophysics Data System (ADS)

    Jensvold, Z. D.; Jin, Q.

    2015-12-01

    Methanogenesis, the biological process of methane production, is the final step of natural organic matter degradation. In studying natural methanogenesis, important questions include how fast methanogenesis proceeds and how methanogens adapt to the environment. To address these questions, we propose a new approach - biogeochemical reaction modeling - by simulating the metabolic networks of methanogens. Biogeochemical reaction modeling combines geochemical reaction modeling and genome-scale metabolic modeling. Geochemical reaction modeling focuses on the speciation of electron donors and acceptors in the environment, and therefore the energy available to methanogens. Genome-scale metabolic modeling predicts microbial rates and metabolic strategies. Specifically, this approach describes methanogenesis using an enzyme network model, and computes enzyme rates by accounting for both the kinetics and thermodynamics. The network model is simulated numerically to predict enzyme abundances and rates of methanogen metabolism. We applied this new approach to Methanosarcina barkeri strain fusaro, a model methanogen that makes methane by reducing carbon dioxide and oxidizing dihydrogen. The simulation results match well with the results of previous laboratory experiments, including the magnitude of proton motive force and the kinetic parameters of Methanosarcina barkeri. The results also predict that in natural environments, the configuration of methanogenesis network, including the concentrations of enzymes and metabolites, differs significantly from that under laboratory settings.

  15. A coupled biogeochemical-Dynamic Energy Budget model as a tool for managing fish production ponds.

    PubMed

    Serpa, Dalila; Pousão-Ferreira, Pedro; Caetano, Miguel; Cancela da Fonseca, Luís; Dinis, Maria Teresa; Duarte, Pedro

    2013-10-01

    The sustainability of semi-intensive aquaculture relies on management practices that simultaneously improve production efficiency and minimize the environmental impacts of this activity. The purpose of the present work was to develop a mathematical model that reproduced the dynamics of a semi-intensive fish earth pond, to simulate different management scenarios for optimizing fish production. The modeling approach consisted of coupling a biogeochemical model that simulated the dynamics of the elements that are more likely to affect fish production and cause undesirable environmental impacts (nitrogen, phosphorus and oxygen) to a fish growth model based on the Dynamic Energy Budget approach. The biogeochemical sub-model successfully simulated most water column and sediment variables. A good model fit was also found between predicted and observed white seabream (Diplodus sargus) growth data over a production cycle. In order to optimize fish production, different management scenarios were analysed with the model (e.g. increase stocking densities, decrease/increase water exchange rates, decrease/increase feeding rates, decrease phosphorus content in fish feeds, increase food assimilation efficiency and decrease pellets sinking velocity) to test their effects on the pond environment as well as on fish yields and effluent nutrient discharges. Scenarios were quantitatively evaluated and compared using the Analytical Hierarchical Process (AHP) methodology. The best management options that allow the maximization of fish production while maintaining a good pond environment and minimum impacts on the adjacent coastal system were to double standard stocking densities and to improve food assimilation efficiency. PMID:23872182

  16. Tidal Marsh Outwelling of Dissolved Organic Matter and Resulting Temporal Variability in Coastal Water Optical and Biogeochemical Properties

    NASA Technical Reports Server (NTRS)

    Tzortziou, Maria; Neale, Patrick J.; Megonigal, J. Patrick; Butterworth, Megan; Jaffe, Rudolf; Yamashita, Youhei

    2010-01-01

    Coastal wetlands are highly dynamic environments at the land-ocean interface where human activities, short-term physical forcings and intense episodic events result in high biological and chemical variability. Long being recognized as among the most productive ecosystems in the world, tidally-influenced coastal marshes are hot spots of biogeochemical transformation and exchange. High temporal resolution observations that we performed in several marsh-estuarine systems of the Chesapeake Bay revealed significant variability in water optical and biogeochemical characteristics at hourly time scales, associated with tidally-driven hydrology. Water in the tidal creek draining each marsh was sampled every hour during several semi-diurnal tidal cycles using ISCO automated samplers. Measurements showed that water leaving the marsh during ebbing tide was consistently enriched in dissolved organic carbon (DOC), frequently by more than a factor of two, compared to water entering the marsh during flooding tide. Estimates of DOC fluxes showed a net DOC export from the marsh to the estuary during seasons of both low and high biomass of marsh vegetation. Chlorophyll amounts were typically lower in the water draining the marsh, compared to that entering the marsh during flooding tide, suggesting that marshes act as transformers of particulate to dissolved organic matter. Moreover, detailed optical and compositional analyses demonstrated that marshes are important sources of optically and chemically distinctive, relatively complex, high molecular weight, aromatic-rich and highly colored dissolved organic compounds. Compared to adjacent estuarine waters, marsh-exported colored dissolved organic matter (CDOM) was characterized by considerably stronger absorption (more than a factor of three in some cases), larger DOC-specific absorption, lower exponential spectral slope, larger fluorescence signal, lower fluorescence per unit absorbance, and higher fluorescence at visible wavelengths

  17. Modelling benthic biophysical drivers of ecosystem structure and biogeochemical response

    NASA Astrophysics Data System (ADS)

    Stephens, Nicholas; Bruggeman, Jorn; Lessin, Gennadi; Allen, Icarus

    2016-04-01

    The fate of carbon deposited at the sea floor is ultimately decided by biophysical drivers that control the efficiency of remineralisation and timescale of carbon burial in sediments. Specifically, these drivers include bioturbation through ingestion and movement, burrow-flushing and sediment reworking, which enhance vertical particulate transport and solute diffusion. Unfortunately, these processes are rarely satisfactorily resolved in models. To address this, a benthic model that explicitly describes the vertical position of biology (e.g., habitats) and biogeochemical processes is presented that includes biological functionality and biogeochemical response capturing changes in ecosystem structure, benthic-pelagic fluxes and biodiversity on inter-annual timescales. This is demonstrated by the model's ability to reproduce temporal variability in benthic infauna, vertical pore water nutrients and pelagic-benthic solute fluxes compared to in-situ data. A key advance is the replacement of bulk parameterisation of bioturbation by explicit description of the bio-physical processes responsible. This permits direct comparison with observations and determination of key parameters in experiments. Crucially, the model resolves the two-way interaction between sediment biogeochemistry and ecology, allowing exploration of the benthic response to changing environmental conditions, the importance of infaunal functional traits in shaping benthic ecological structure and the feedback the resulting bio-physical processes exert on pore water nutrient profiles. The model is actively being used to understand shelf sea carbon cycling, the response of the benthos to climatic change, food provision and other societal benefits.

  18. Converting copepod vital rates into units appropriate for biogeochemical models

    NASA Astrophysics Data System (ADS)

    Frangoulis, C.; Carlotti, F.; Eisenhauer, L.; Zervoudaki, S.

    2010-01-01

    The conversion of units is one of the difficulties of model parameterisation. Conversion errors may result not only from incorrect choices of conversion factors, but also from incorrect choices of the value itself. In biogeochemical models, mesozooplankton, is the highest trophic level of the food web, and it is very often reduced to a single variable generally considered as a representation of the copepod community, the dominant taxa in mesozooplankton. If this simplifies the information to be obtained for the stock, a correct parameterisation of the processes related to the copepod community is already a tricky task due to the wide range of copepod species, sizes, stages and behaviour. The goal of this paper is to improve the communication between experimentalists and modellers by giving indications for the conversion of copepod vital rates from experimental to biogeochemical model units. This includes the choice of values, conversion factors, terminology distinction and the scale transfer. To begin with, we briefly address the common problem of the conversion of a rate per individual to a rate per mass. Then, we focus on unit conversion problems for each specific rate and give recommendations. Finally, we discuss the problem of scale transfer between the level of organisation at which the rate value is measured at characteristic time and space-scales versus the level of representation of the corresponding process in the model, with its different characteristic time and space-scales .

  19. Modeling basic features of biogeochemical structure of water column, bottom boundary layer and benthic boundary layer in changeable redox conditions

    NASA Astrophysics Data System (ADS)

    Yakushev, Evgeniy

    2013-04-01

    Climate Change affects oxygen depletion and leads to spreading of the bottom areas with hypoxic and anoxic conditions in the coastal areas of the seas and inland waters. This work aimed in estimation of a role of changes of redox conditions in the biogeochemical structure there. We use a 1-dimensional C-N-P-Si-O-S-Mn-Fe vertical transport-reaction model describing the water column, bottom boundary layer and benthic boundary layer with biogeochemical block simulating redox conditions changeability. A biogeochemical block is based on ROLM (RedOx Layer Model), that was constructed to simulate basic features of the water column biogeochemical structure changes in oxic, anoxic and changeable conditions (Yakushev et al., 2007). Organic matter formation and decay, reduction and oxidation of species of nitrogen, sulfur, manganese, iron, and the transformation of phosphorus species are parameterized in the model. ROLM includes a simplified ecological model with phytoplankton, zooplankton, aerobic autotrophic and heterotrophic bacteria, anaerobic autotrophic and heterotrophic bacteria. We simulate changes in the parameters distributions and fluxes connected with the vertical displacement of redox interface from the sediments to the water.

  20. Using Existing Coastal Models To Address Ocean Acidification Modeling Needs: An Inside Look at Several East and Gulf Coast Regions

    NASA Astrophysics Data System (ADS)

    Jewett, E.

    2013-12-01

    Ecosystem forecast models have been in development for many US coastal regions for decades in an effort to understand how certain drivers, such as nutrients, freshwater and sediments, affect coastal water quality. These models have been used to inform coastal management interventions such as imposition of total maximum daily load allowances for nutrients or sediments to control hypoxia, harmful algal blooms and/or water clarity. Given the overlap of coastal acidification with hypoxia, it seems plausible that the geochemical models built to explain hypoxia and/or HABs might also be used, with additional terms, to understand how atmospheric CO2 is interacting with local biogeochemical processes to affect coastal waters. Examples of existing biogeochemical models from Galveston, the northern Gulf of Mexico, Tampa Bay, West Florida Shelf, Pamlico Sound, Chesapeake Bay, and Narragansett Bay will be presented and explored for suitability for ocean acidification modeling purposes.

  1. Parameterization of biogeochemical sediment-water fluxes using in situ measurements and a diagenetic model

    NASA Astrophysics Data System (ADS)

    Laurent, A.; Fennel, K.; Wilson, R.; Lehrter, J.; Devereux, R.

    2016-01-01

    Diagenetic processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be a significant contributor to oxygen depletion in hypoxic systems, and sediment-water nutrient fluxes support primary productivity in the overlying water column. Moreover, nonlinearities develop between bottom water conditions and sediment-water fluxes due to loss of oxygen-dependent processes in the sediment as oxygen becomes depleted in bottom waters. Yet, sediment-water fluxes of chemical species are often parameterized crudely in coupled physical-biogeochemical models, using simple linear parameterizations that are only poorly constrained by observations. Diagenetic models that represent sediment biogeochemistry are available, but rarely are coupled to water column biogeochemical models because they are computationally expensive. Here, we apply a method that efficiently parameterizes sediment-water fluxes of oxygen, nitrate and ammonium by combining in situ measurements, a diagenetic model and a parameter optimization method. As a proof of concept, we apply this method to the Louisiana Shelf where high primary production, stimulated by excessive nutrient loads from the Mississippi-Atchafalaya River system, promotes the development of hypoxic bottom waters in summer. The parameterized sediment-water fluxes represent nonlinear feedbacks between water column and sediment processes at low bottom water oxygen concentrations, which may persist for long periods (weeks to months) in hypoxic systems such as the Louisiana Shelf. This method can be applied to other systems and is particularly relevant for shallow coastal and estuarine waters where the interaction between sediment and water column is strong and hypoxia is prone to occur due to land-based nutrient loads.

  2. Biogeochemical and Optical Analysis of Coastal DOM for Satellite Retrieval of Terrigenous DOM in the U.S. Middle Atlantic Bight

    NASA Technical Reports Server (NTRS)

    Mannino, A.; Dyda, R. Y.; Hernes, P. J.; Hooker, Stan; Hyde, Kim; Novak, Mike

    2012-01-01

    Estuaries and coastal ocean waters experience a high degree of variability in the composition and concentration of particulate and dissolved organic matter (DOM) as a consequence of riverine/estuarine fluxes of terrigenous DOM, sediments, detritus and nutrients into coastal waters and associated phytoplankton blooms. Our approach integrates biogeochemical measurements (elemental content, molecular analyses), optical properties (absorption) and remote sensing to examine terrestrial DOM contributions into the U.S. Middle Atlantic Bight (MAB). We measured lignin phenol composition, DOC and CDOM absorption within the Chesapeake and Delaware Bay mouths, plumes and adjacent coastal ocean waters to derive empirical relationships between CDOM and biogeochemical measurements for satellite remote sensing application. Lignin ranged from 0.03 to 6.6 ug/L between estuarine and outer shelf waters. Our results demonstrate that satellite-derived CDOM is useful as a tracer of terrigenous DOM in the coastal ocean

  3. Chesapeake Bay nitrogen fluxes derived from a land-estuarine ocean biogeochemical modeling system: Model description, evaluation, and nitrogen budgets

    NASA Astrophysics Data System (ADS)

    Feng, Yang; Friedrichs, Marjorie A. M.; Wilkin, John; Tian, Hanqin; Yang, Qichun; Hofmann, Eileen E.; Wiggert, Jerry D.; Hood, Raleigh R.

    2015-08-01

    The Chesapeake Bay plays an important role in transforming riverine nutrients before they are exported to the adjacent continental shelf. Although the mean nitrogen budget of the Chesapeake Bay has been previously estimated from observations, uncertainties associated with interannually varying hydrological conditions remain. In this study, a land-estuarine-ocean biogeochemical modeling system is developed to quantify Chesapeake riverine nitrogen inputs, within-estuary nitrogen transformation processes and the ultimate export of nitrogen to the coastal ocean. Model skill was evaluated using extensive in situ and satellite-derived data, and a simulation using environmental conditions for 2001-2005 was conducted to quantify the Chesapeake Bay nitrogen budget. The 5 year simulation was characterized by large riverine inputs of nitrogen (154 × 109 g N yr-1) split roughly 60:40 between inorganic:organic components. Much of this was denitrified (34 × 109 g N yr-1) and buried (46 × 109 g N yr-1) within the estuarine system. A positive net annual ecosystem production for the bay further contributed to a large advective export of organic nitrogen to the shelf (91 × 109 g N yr-1) and negligible inorganic nitrogen export. Interannual variability was strong, particularly for the riverine nitrogen fluxes. In years with higher than average riverine nitrogen inputs, most of this excess nitrogen (50-60%) was exported from the bay as organic nitrogen, with the remaining split between burial, denitrification, and inorganic export to the coastal ocean. In comparison to previous simulations using generic shelf biogeochemical model formulations inside the estuary, the estuarine biogeochemical model described here produced more realistic and significantly greater exports of organic nitrogen and lower exports of inorganic nitrogen to the shelf.

  4. Biogeochemical Modeling of the Second Rise of Atmospheric Oxygen

    NASA Astrophysics Data System (ADS)

    Smith, M.; Catling, D. C.; Claire, M.

    2014-12-01

    The second rise of atmospheric oxygen (~600 Ma) marked an increase of atmospheric pO2 from a poorly constrained value of 0.1% < pO2 < 10% of present atmospheric level (PAL) in the early and mid Proterozoic to >10%PAL1. The event is important because it ushered in the modern era of animal life. To understand the evolution of Earth's habitability, it is therefore key to understand the cause of this 2nd rise. Here, we quantitatively examine possible causes for the 2nd rise of oxygen. We use a biogeochemical box model2 originally developed to calculate the oxygen evolution before and after the 1st rise of oxygen (~2.4 Ga). The Claire et al. (2006) model calculates the evolution of atmospheric oxygen and methane given production and loss fluxes associated with the oxygen, carbon, and iron cycles. Because the model was unable to drive pO2 to end-Proterozoic levels, the authors suggested that another buffer, such as sulfur, is needed to explain the 2nd rise of oxygen. The sulfur and oxygen cycles are tied through various biogeochemical interactions; therefore, once sulfur (as sulfate) began to accumulate in Proterozoic oceans, it likely began to heavily influence the oxygen cycle. We have added a sulfur biogeochemical cycle to this model, enabling exploration of mechanisms that buffer pO2 at intermediate levels in the Proterozoic and fail to do so in the Phanerozoic. Preliminary results show evolution of oxygen and methane that are consistent with geologic proxies. However, the model-generated 2nd rise of oxygen is dependent upon sulfur fluxes that have uncertain magnitudes, so we will present the sensitivity of our results to model assumptions while constraining scenarios for the 2nd rise of atmospheric O2. In the future, we will also integrate isotopic fractionation effects, which will allow comparison with isotopic data from sedimentary sulfides, carbonates, and organic carbon. 1Canfield, C., 2014, Treatise on Geochemistry, 197 2Claire, M.W., et al., 2006, Geobiology

  5. Biogeochemical cycling in terrestrial ecosystems - Modeling, measurement, and remote sensing

    NASA Technical Reports Server (NTRS)

    Peterson, D. L.; Matson, P. A.; Lawless, J. G.; Aber, J. D.; Vitousek, P. M.

    1985-01-01

    The use of modeling, remote sensing, and measurements to characterize the pathways and to measure the rate of biogeochemical cycling in forest ecosystems is described. The application of the process-level model to predict processes in intact forests and ecosystems response to disturbance is examined. The selection of research areas from contrasting climate regimes and sites having a fertility gradient in that regime is discussed, and the sites studied are listed. The use of remote sensing in determining leaf area index and canopy biochemistry is analyzed. Nitrous oxide emission is investigated by using a gas measurement instrument. Future research projects, which include studying the influence of changes on nutrient cycling in ecosystems and the effect of pollutants on the ecosystems, are discussed.

  6. Regional-Scale Biogeochemical Modeling of Greenhouse Gas (GHG) Emissions from Wetland Ecosystems

    NASA Astrophysics Data System (ADS)

    Abdul-Aziz, O.; Liu, S.; Young, C. J.; Huang, S.

    2010-12-01

    Wetlands can play an important role in carbon sequestration, greenhouse gas (GHG) emissions, and global warming. Biogeochemical models are valuable tools to quantify emissions of major GHGs such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from wetland ecosystems. Although several models can be found in literature, most of them are mainly site-scale models and only few have been developed at the global scale. Current global-scale models incorporate over-simplified process descriptions and assumptions, and fail to capture the regional or mesoscale phenomena. On the other hand, site-scale models generally involve highly detailed process descriptions that increase the model complexity while not being notably rewarding at the regional scale. Further, calibration of the site-scale models (even if slightly modified for the regional-scale applications) requires data for many input variables and parameters that may not be available at larger scales. We developed a ‘Unit Wetland Ecosystem’ framework, which incorporates a zero-dimensional, conceptual modeling approach that can be applied in any spatial (site, regional, and global) and temporal (e.g., daily, weekly, monthly) scales. The framework is used here to develop a regional-scale model that involves a simple structure, minimum input variables, and parsimonious parameterizations based on data availability, synthesis of existing literature, and new developments, as appropriate. We applied this model to simulate the regional GHG emissions from the wetlands of the Prairie Pothole Region of the United States. The wetland biogeochemical modeling framework will also be applied to quantify wetland GHG emissions from both freshwater and coastal wetlands nationwide. This research is a part of the United States Geological Survey’s ecological carbon sequestration project that aims to quantify carbon sequestration and GHG emissions of the U.S. lands and waters under changing climate, land use/land cover

  7. Traceable components of terrestrial carbon storage capacity in biogeochemical models.

    PubMed

    Xia, Jianyang; Luo, Yiqi; Wang, Ying-Ping; Hararuk, Oleksandra

    2013-07-01

    Biogeochemical models have been developed to account for more and more processes, making their complex structures difficult to be understood and evaluated. Here, we introduce a framework to decompose a complex land model into traceable components based on mutually independent properties of modeled biogeochemical processes. The framework traces modeled ecosystem carbon storage capacity (Xss ) to (i) a product of net primary productivity (NPP) and ecosystem residence time (τE ). The latter τE can be further traced to (ii) baseline carbon residence times (τ'E ), which are usually preset in a model according to vegetation characteristics and soil types, (iii) environmental scalars (ξ), including temperature and water scalars, and (iv) environmental forcings. We applied the framework to the Australian Community Atmosphere Biosphere Land Exchange (CABLE) model to help understand differences in modeled carbon processes among biomes and as influenced by nitrogen processes. With the climate forcings of 1990, modeled evergreen broadleaf forest had the highest NPP among the nine biomes and moderate residence times, leading to a relatively high carbon storage capacity (31.5 kg cm(-2) ). Deciduous needle leaf forest had the longest residence time (163.3 years) and low NPP, leading to moderate carbon storage (18.3 kg cm(-2) ). The longest τE in deciduous needle leaf forest was ascribed to its longest τ'E (43.6 years) and small ξ (0.14 on litter/soil carbon decay rates). Incorporation of nitrogen processes into the CABLE model decreased Xss in all biomes via reduced NPP (e.g., -12.1% in shrub land) or decreased τE or both. The decreases in τE resulted from nitrogen-induced changes in τ'E (e.g., -26.7% in C3 grassland) through carbon allocation among plant pools and transfers from plant to litter and soil pools. Our framework can be used to facilitate data model comparisons and model intercomparisons via tracking a few traceable components for all terrestrial carbon

  8. Sustainable Management of Coastal Environments Through Coupled Terrestrial-Coastal Ocean Models

    NASA Astrophysics Data System (ADS)

    Lohrenz, S. E.; Cai, W.; Tian, H.; He, R.; Xue, Z.; Fennel, K.; Hopkinson, C.; Howden, S. D.

    2012-12-01

    Changing climate and land use practices have the potential to dramatically alter coupled hydrologic-biogeochemical processes and associated movement of water, carbon and nutrients through various terrestrial reservoirs into rivers, estuaries, and coastal ocean waters. Consequences of climate- and land use-related changes will be particularly evident in large river basins and their associated coastal outflow regions. The large spatial extent of such systems necessitates a combination of satellite observations and model-based approaches coupled with targeted ground-based site studies to adequately characterize relationships among climate forcing (e.g., wind, precipitation, temperature, solar radiation, humidity, extreme weather), land use practice/land cover change, and transport of materials through watersheds and, ultimately, to coastal regions. Here, we describe a NASA Interdisciplinary Science project that employs an integrated suite of models in conjunction with remotely sensed as well as targeted in situ observations with the objectives of describing processes controlling fluxes on land and their coupling to riverine, estuarine and ocean ecosystems. The objectives of this effort are to 1) assemble and evaluate long term datasets for the assessment of impacts of climate variability, extreme weather events, and land use practices on transport of water, carbon and nitrogen within terrestrial systems and the delivery of materials to waterways and rivers; 2) using the Mississippi River as a testbed, develop and evaluate an integrated suite of models to describe linkages between terrestrial and riverine systems, transport of carbon and nutrients in the Mississippi river and its tributaries, and associated cycling of carbon and nutrients in coastal ocean waters; and 3) evaluate uncertainty in model products and parameters and identify areas where improved model performance is needed through model refinement and data assimilation. The effort employs the Dynamic Land

  9. Eastern Mediterranean biogeochemical flux model - Simulations of the pelagic ecosystem

    NASA Astrophysics Data System (ADS)

    Petihakis, G.; Triantafyllou, G.; Tsiaras, K.; Korres, G.; Pollani, A.; Hoteit, I.

    2009-02-01

    During the second phase (2003-2006) of the Mediterranean ocean Forecasting System Project (MFS) named Toward Environmental Predictions (MFSTEP) one of the three major aims was the development of numerical forecasting systems. In this context a generic Biogeochemical Flux Model (BFM) was developed and coupled with hydrodynamic models already operating at basin scale as well as in regional areas. In the Eastern Mediterranean basin the BFM was coupled with the Aegean Levantine Eddy Resolving MOdel (ALERMO). The BFM is a generic highly complex model based on ERSEM and although a detailed description of the model and its components is beyond the scope of this work, a short overview of the main processes, laying emphasis on the parameter values used is presented. In addition the performance of the model is evaluated with some preliminary results being qualitatively compared against field observations. The model in its present form is rather promising and reproduces all important major features although there are some slight inefficiencies mostly related to primary and bacterial productivity rates.

  10. A 3-D variational assimilation scheme in coupled transport-biogeochemical models: Forecast of Mediterranean biogeochemical properties

    NASA Astrophysics Data System (ADS)

    Teruzzi, Anna; Dobricic, Srdjan; Solidoro, Cosimo; Cossarini, Gianpiero

    2014-01-01

    Increasing attention is dedicated to the implementation of suitable marine forecast systems for the estimate of the state of the ocean. Within the framework of the European MyOcean infrastructure, the pre-existing short-term Mediterranean Sea biogeochemistry operational forecast system has been upgraded by assimilating remotely sensed ocean color data in the coupled transport-biogeochemical model OPATM-BFM using a 3-D variational data assimilation (3D-VAR) procedure. In the present work, the 3D-VAR scheme is used to correct the four phytoplankton functional groups included in the OPATM-BFM in the period July 2007 to September 2008. The 3D-VAR scheme decomposes the error covariance matrix using a sequence of different operators that account separately for vertical covariance, horizontal covariance, and covariance among biogeochemical variables. The assimilation solution is found in a reduced dimensional space, and the innovation for the biogeochemical variables is obtained by the sequential application of the covariance operators. Results show a general improvement in the forecast skill, providing a correction of the basin-scale bias of surface chlorophyll concentration and of the local-scale spatial and temporal dynamics of typical bloom events. Further, analysis of the assimilation skill provides insights into the functioning of the model. The computational costs of the assimilation scheme adopted are low compared to other assimilation techniques, and its modular structure facilitates further developments. The 3D-VAR scheme results especially suitable for implementation within a biogeochemistry operational forecast system.

  11. Atmospheric nitrogen deposition in estuarine and coastal waters: Biogeochemical and water quality impacts

    SciTech Connect

    Paerl, H.W.; Peierls, B.L.; Fogel, M.L.; Aguilar, C. |

    1994-12-31

    Atmospheric deposition (AD) is a significant source of biologically-available ``new`` nitrogen in N-limited estuarine and coastal ocean waters. From 10 to over 50% of ``new`` N inputs are attributable to AD in waters ``downwind`` of emissions. In situ microcosm and mesocosm bioassays indicate that this ``new`` N source can enhance microalgal primary production and may alter community composition. Relative to terrestrial and regenerated N inputs, the dominant AD-N sources, NO{sub 3}k{sup {minus}}, NH{sub 4}{sup {plus}}, and dissolves organic nitrogen (DON) reveal stable N isotope ratios ({delta}{sup 15}N) generally deplete in {sup 15}N. The relatively low {delta}{sup 15}N ratio of AD-N has been used as a tracer of the incorporation and fate of this ``new`` N source in receiving water. Diagnostic biomarker molecules, including proteins and pigments (chlorophylls), indicate rapid algal utilization and transformation of AD-N. Seasonal production and N isotope studies in mixed and stratified North Carolina Atlantic coastal and offshore (i.e. Gulf Stream) waters indicate a marked impact of AD-N on microbial production. AD-N is an important and thus far poorly recognized source of ``new`` N in N-limited waters; these waters characterized a large proportion of the world`s estuarine and coastal zones. AD-N may additionally play a role in recently-noted coastal eutrophication and algal nuisance bloom dynamics.

  12. Hyporheic flow and transport processes: mechanisms, models, and biogeochemical implications

    USGS Publications Warehouse

    Boano, Fulvio; Harvey, Judson W.; Marion, Andrea; Packman, Aaron I.; Revelli, Roberto; Ridolfi, Luca; Anders, Wörman

    2014-01-01

    Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed."

  13. Hyporheic flow and transport processes: Mechanisms, models, and biogeochemical implications

    NASA Astrophysics Data System (ADS)

    Boano, F.; Harvey, J. W.; Marion, A.; Packman, A. I.; Revelli, R.; Ridolfi, L.; Wörman, A.

    2014-12-01

    Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed.

  14. Effects of changing glacial coverage on the physical and biogeochemical properties of coastal streams in southeastern Alaska

    NASA Astrophysics Data System (ADS)

    Hood, Eran; Berner, Logan

    2009-09-01

    Runoff from mountain glaciers and icecaps is a critical control on physical and chemical conditions of aquatic ecosystems in glaciated watersheds. To date, there has been little research on the biogeochemistry of proglacial streams. Here we use a space for time substitution to evaluate how stream water physical conditions and concentrations of carbon, nitrogen, and phosphorus may be altered by diminishing glacial coverage. For a full annual hydrograph, we sampled six watersheds in southeastern Alaska that ranged in glacier coverage from 0 to 55%. We found that during the summer runoff season (May-October), stream water temperature and specific conductivity were negatively correlated with the percentage of the watershed covered by glacial ice, while stream water turbidity showed a significant positive correlation. Stream water concentrations of dissolved organic carbon (DOC) were typically low (0.5-3.0 mg C L-1) and showed a significant trend toward higher concentrations as watershed glacier coverage decreased. Concentrations of dissolved organic nitrogen (DON) and dissolved inorganic nitrogen also increased significantly with decreasing glacial coverage. In contrast, concentrations of soluble reactive phosphorus decreased with lower glacial coverage. Interestingly, we found that the DOC:DON ratio of stream water dissolved organic matter (DOM) decreased with increasing glacier coverage, suggesting that glaciers may be a source of N-rich DOM. During winter low flows (November-April) there were few differences in stream water physical and biogeochemical conditions across the six watersheds as glacial inputs diminished and streamflow was dominated by groundwater. Our findings suggest that in southeastern Alaska ongoing glacial recession and the associated land cover change will impact physical and biogeochemical conditions in coastal streams, with implications for salmon spawning habitat, aquatic ecosystem productivity, and fluxes of reactive nutrients to downstream

  15. Biogeochemical dynamics in 20 m deep coastal sediments: The transition between the shallow subsurface and the marine deep biosphere

    NASA Astrophysics Data System (ADS)

    Beck, Melanie; Riedel, Thomas; Graue, Jutta; Brumsack, Hans-Jürgen; Engelen, Bert

    2010-05-01

    At present a large tidal flat area extends along the coastline of the southern North Sea. On longer geological time scales this area has, however, transformed from a terrestrial- to a marine-dominated landscape owing to changes in sea level. Biogeochemistry and microbial abundance have been intensively studied in the present tidal-flat sediments, down to about 5 m depth. However, very little is known about biogeochemical and microbial processes in deeper sediment layers, which were deposited before the establishment of today's tidal flat area. To study whether the geological history of sediment accumulation and thus the paleo-environment has an impact on pore water biogeochemistry and microbial abundance, Quaternary coastal deposits were investigated down to 20 m depth. In the tidal flat area of Spiekeroog Island (NW Germany) two geological settings were selected which are located close to each other but differ in sediment age and paleo-environmental conditions: A paleo-channel filled with mainly Holocene sediments and a sedimentary succession with the oldest sediments deposited during the Saalian glaciation ca. 130,000 years ago. The interdisciplinary analysis clearly shows that microorganisms are more abundant in the Holocene sediments. Here, almost all Archaea appear to be methanogenic as indicated by the presence of the mcrA-gene. About 12% of the Bacteria harbor the key gene for sulfate reduction. In contrast, only 1% methanogens and 0.5% sulfate-reducing bacteria were found in the older sediments. Furthermore, this study supports the concept that certain biogeochemical and microbiological features show astonishing similarities between the upper 5 meters of tidal-flat sediments and the upper hundred meters of deep-sea sediments. In the investigated 20 m-long sediment cores, the microbiological and geochemical response to sedimentary settings is transitional between the shallow subsurface of tidal-flat sediments and the marine deep biosphere.

  16. Biogeochemical modeling of tundra recovery following thermal erosion of permafrost

    NASA Astrophysics Data System (ADS)

    Pearce, A. R.; Rastetter, E. B.; Bowden, W. B.

    2011-12-01

    We simulate the biogeochemical recovery of tundra from a thermal erosion disturbance using the Multiple Element Limitation model (MEL) and compare model results with soil organic matter and nutrient chemistry measurements collected across a chronosequence of thermal erosion features. Thermal erosion of permafrost initially depletes the tundra of much of its vegetation and shallow soil organic matter. However, several decades later, there is often little distinguishing these scars from the surrounding undisturbed tundra. As thermal erosion features become more abundant on the arctic landscape, we desire to understand how the pools of carbon and nutrients rebuild after these disturbances. MEL is a plot-scale, process-based model that optimizes the acquisition of eight resources (light, water, CO2, PO4, NH4, NO3, DON and N-fixation) by vegetation based on how much of each is required and the effort needed to acquire it. Model output includes pool sizes of carbon, nitrogen and phosphorus in vegetation, litter, young soil organic matter and old soil organic matter and the fluxes among these pools over time. This calibration of MEL, operating on a daily timestep, was created with published data collected at or near the Toolik Field Station (Toolik Lake, AK, USA) from moist acidic tussock tundra sites. We corroborate our calibration with data from plot manipulations (N and P fertilization, greenhouse, and shade house) performed as part of the NSF Arctic LTER project. The initial conditions for the recovery simulations reflect post-failure observations of some of the variation in soil organic matter, and soil and water nutrient chemistry. With sufficient nutrients from residual soil or supplied in soil water from upslope, the model indicates that vegetation can recover within several decades, but recovery of C and nutrients lost from soils may take hundreds of years.

  17. A quantitative model of the biogeochemical transport of iodine

    NASA Astrophysics Data System (ADS)

    Weng, H.; Ji, Z.; Weng, J.

    2010-12-01

    Iodine deficiency disorders (IDD) are among the world’s most prevalent public health problems yet preventable by dietary iodine supplements. To better understand the biogeochemical behavior of iodine and to explore safer and more efficient ways of iodine supplementation as alternatives to iodized salt, we studied the behavior of iodine as it is absorbed, accumulated and released by plants. Using Chinese cabbage as a model system and the 125I tracing technique, we established that plants uptake exogenous iodine from soil, most of which are transported to the stem and leaf tissue. The level of absorption of iodine by plants is dependent on the iodine concentration in soil, as well as the soil types that have different iodine-adsorption capacity. The leaching experiment showed that the remainder soil content of iodine after leaching is determined by the iodine-adsorption ability of the soil and the pH of the leaching solution, but not the volume of leaching solution. Iodine in soil and plants can also be released to the air via vaporization in a concentration-dependent manner. This study provides a scientific basis for developing new methods to prevent IDD through iodized vegetable production.

  18. Nitrous Oxide Emissions from Biofuel Crops and Parameterization in the EPIC Biogeochemical Model

    EPA Science Inventory

    This presentation describes year 1 field measurements of N2O fluxes and crop yields which are used to parameterize the EPIC biogeochemical model for the corresponding field site. Initial model simulations are also presented.

  19. A 3-D variational assimilation scheme in coupled transport-biogeochemical models: Forecast of Mediterranean biogeochemical properties

    PubMed Central

    Teruzzi, Anna; Dobricic, Srdjan; Solidoro, Cosimo; Cossarini, Gianpiero

    2014-01-01

    [1] Increasing attention is dedicated to the implementation of suitable marine forecast systems for the estimate of the state of the ocean. Within the framework of the European MyOcean infrastructure, the pre-existing short-term Mediterranean Sea biogeochemistry operational forecast system has been upgraded by assimilating remotely sensed ocean color data in the coupled transport-biogeochemical model OPATM-BFM using a 3-D variational data assimilation (3D-VAR) procedure. In the present work, the 3D-VAR scheme is used to correct the four phytoplankton functional groups included in the OPATM-BFM in the period July 2007 to September 2008. The 3D-VAR scheme decomposes the error covariance matrix using a sequence of different operators that account separately for vertical covariance, horizontal covariance, and covariance among biogeochemical variables. The assimilation solution is found in a reduced dimensional space, and the innovation for the biogeochemical variables is obtained by the sequential application of the covariance operators. Results show a general improvement in the forecast skill, providing a correction of the basin-scale bias of surface chlorophyll concentration and of the local-scale spatial and temporal dynamics of typical bloom events. Further, analysis of the assimilation skill provides insights into the functioning of the model. The computational costs of the assimilation scheme adopted are low compared to other assimilation techniques, and its modular structure facilitates further developments. The 3D-VAR scheme results especially suitable for implementation within a biogeochemistry operational forecast system. PMID:26213670

  20. Mechanisms driving estuarine water quality: A 3D biogeochemical model for informed management

    NASA Astrophysics Data System (ADS)

    Wild-Allen, Karen; Skerratt, Jenny; Whitehead, Jason; Rizwi, Farhan; Parslow, John

    2013-12-01

    Estuaries are amongst the most productive marine ecosystems of the world but are also some of the most degraded due to coastal urban development. Sparse sampling of complex interactions between estuarine physics, sediment transport, chemistry, and biology limits understanding of the processes controlling estuarine water quality and confounds active management. We use a 3D coupled hydrodynamic, sediment and biogeochemical model to identify the key mechanisms driving fine-scale fluctuations in water quality in a temperate micro-tidal salt wedge estuary [Derwent Estuary, Tasmania]. Model results are dynamically consistent with relatively sparse monitoring data collected over a seasonal cycle and are considered to be a plausible hypothesis of sub-monitoring scale processes occurring in the estuary. The model shows enhanced mixing of nutrients across the pycnocline downstream of the salt wedge front that supports a persistent phytoplankton bloom. The length and flow regime of the estuary results in nutrient recycling and retention in the estuarine circulation driving a decline in bottom water dissolved oxygen in the mid- and upper-reaches. A budget analysis of modelled nitrogen suggests high levels of denitrification are critical to the maintenance of existing water quality. Active estuarine management focused on the improvement of bottom water dissolved oxygen for ecological health reasons must either concurrently reduce anthropogenic nitrogen loads or be sure to maintain high levels of microbial denitrification for net water quality improvement.

  1. The general ensemble biogeochemical modeling system (GEMS) and its applications to agriculture systems in the United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The General Ensemble Biogeochemical Modeling System (GEMS) was developed for a proper integration of well-established ecosystem biogeochemical models with various spatial databases to simulate biogeochemical cycles over large areas. Major driving variables include land cover and land use, climate, s...

  2. CALIBRATION OF SUBSURFACE BATCH AND REACTIVE-TRANSPORT MODELS INVOLVING COMPLEX BIOGEOCHEMICAL PROCESSES

    EPA Science Inventory

    In this study, the calibration of subsurface batch and reactive-transport models involving complex biogeochemical processes was systematically evaluated. Two hypothetical nitrate biodegradation scenarios were developed and simulated in numerical experiments to evaluate the perfor...

  3. Biogeochemical Insights into B-Vitamins in the Coastal Marine Sediments of San Pedro Basin, CA

    NASA Astrophysics Data System (ADS)

    Monteverde, D.; Berelson, W.; Baronas, J. J.; Sanudo-Wilhelmy, S. A.

    2015-12-01

    Coastal marine sediments support a high abundance of mircoorganisms which play key roles in the cycling of nutrients, trace metals, and carbon, yet little is known about many of the cofactors essential for their growth, such as the B-vitamins. The suite of B-vitamins (B1, B2, B6, B7, B12) are essential across all domains of life for both primary and secondary metabolism. Therefore, studying sediment concentrations of B-vitamins can provide a biochemical link between microbial processes and sediment geochemistry. Here we present B-vitamin pore water concentrations from suboxic sediment cores collected in September 2014 from San Pedro Basin, a silled, low oxygen, ~900 m deep coastal basin in the California Borderlands. We compare the B-vitamin concentrations (measured via LCMS) to a set of geochemical profiles including dissolved Fe (65-160 μM), dissolved Mn (30-300 nM), TCO2, solid phase organic carbon, and δ13C. Our results show high concentrations (0.8-3nM) of biotin (B7), commonly used for CO2 fixation as a cofactor in carboxylase enzymes. Thiamin (B1) concentrations were elevated (20-700nM), consistent with previous pore water measurements showing sediments could be a source of B1 to the ocean. Cobalamin (B12), a cofactor required for methyl transfers in methanogens, was also detected in pore waters (~4-40pM). The flavins (riboflavin [B2] and flavin mononucleotide[FMN]), molecules utilized in external electron transfer, showed a distinct increase with depth (10-90nM). Interestingly, the flavin profiles showed an inverse trend to dissolved Fe (Fe decreases with depth) providing a potential link to culture experiments which have shown extracellular flavin release to be a common trait in some metal reducers. As some of the first B-vitamin measurements made in marine sediments, these results illustrate the complex interaction between the microbial community and surrounding geochemical environment and provide exciting avenues for future research.

  4. Inconsistent Strategies to Spin up Models in CMIP5: Implications for Ocean Biogeochemical Model Performance Assessment

    NASA Technical Reports Server (NTRS)

    Seferian, Roland; Gehlen, Marion; Bopp, Laurent; Resplandy, Laure; Orr, James C.; Marti, Olivier; Dunne, John P.; Christian, James R.; Doney, Scott C.; Ilyina, Tatiana; Romanou, Anastasia

    2015-01-01

    During the fifth phase of the Coupled Model Intercomparison Project (CMIP5) substantial efforts were made to systematically assess the skill of Earth system models. One goal was to check how realistically representative marine biogeochemical tracer distributions could be reproduced by models. In routine assessments model historical hindcasts were compared with available modern biogeochemical observations. However, these assessments considered neither how close modeled biogeochemical reservoirs were to equilibrium nor the sensitivity of model performance to initial conditions or to the spin-up protocols. Here, we explore how the large diversity in spin-up protocols used for marine biogeochemistry in CMIP5 Earth system models (ESMs) contributes to model-to-model differences in the simulated fields. We take advantage of a 500-year spin-up simulation of IPSL-CM5A-LR to quantify the influence of the spin-up protocol on model ability to reproduce relevant data fields. Amplification of biases in selected biogeochemical fields (O2, NO3, Alk-DIC) is assessed as a function of spin-up duration. We demonstrate that a relationship between spin-up duration and assessment metrics emerges from our model results and holds when confronted with a larger ensemble of CMIP5 models. This shows that drift has implications for performance assessment in addition to possibly aliasing estimates of climate change impact. Our study suggests that differences in spin-up protocols could explain a substantial part of model disparities, constituting a source of model-to- model uncertainty. This requires more attention in future model intercomparison exercises in order to provide quantitatively more correct ESM results on marine biogeochemistry and carbon cycle feedbacks.

  5. Inconsistent strategies to spin up models in CMIP5: implications for ocean biogeochemical model performance assessment

    NASA Astrophysics Data System (ADS)

    Séférian, Roland; Gehlen, Marion; Bopp, Laurent; Resplandy, Laure; Orr, James C.; Marti, Olivier; Dunne, John P.; Christian, James R.; Doney, Scott C.; Ilyina, Tatiana; Lindsay, Keith; Halloran, Paul R.; Heinze, Christoph; Segschneider, Joachim; Tjiputra, Jerry; Aumont, Olivier; Romanou, Anastasia

    2016-05-01

    During the fifth phase of the Coupled Model Intercomparison Project (CMIP5) substantial efforts were made to systematically assess the skill of Earth system models. One goal was to check how realistically representative marine biogeochemical tracer distributions could be reproduced by models. In routine assessments model historical hindcasts were compared with available modern biogeochemical observations. However, these assessments considered neither how close modeled biogeochemical reservoirs were to equilibrium nor the sensitivity of model performance to initial conditions or to the spin-up protocols. Here, we explore how the large diversity in spin-up protocols used for marine biogeochemistry in CMIP5 Earth system models (ESMs) contributes to model-to-model differences in the simulated fields. We take advantage of a 500-year spin-up simulation of IPSL-CM5A-LR to quantify the influence of the spin-up protocol on model ability to reproduce relevant data fields. Amplification of biases in selected biogeochemical fields (O2, NO3, Alk-DIC) is assessed as a function of spin-up duration. We demonstrate that a relationship between spin-up duration and assessment metrics emerges from our model results and holds when confronted with a larger ensemble of CMIP5 models. This shows that drift has implications for performance assessment in addition to possibly aliasing estimates of climate change impact. Our study suggests that differences in spin-up protocols could explain a substantial part of model disparities, constituting a source of model-to-model uncertainty. This requires more attention in future model intercomparison exercises in order to provide quantitatively more correct ESM results on marine biogeochemistry and carbon cycle feedbacks.

  6. A skill assessment of the biogeochemical model REcoM2 coupled to the finite element sea-ice ocean model (FESOM 1.3)

    NASA Astrophysics Data System (ADS)

    Schourup-Kristensen, V.; Sidorenko, D.; Wolf-Gladrow, D. A.; Völker, C.

    2014-07-01

    In coupled ocean-biogeochemical models, the choice of numerical schemes in the ocean circulation component can have a large influence on the distribution of the biological tracers. Biogeochemical models are traditionally coupled to ocean general circulation models (OGCMs), which are based on dynamical cores employing quasi regular meshes, and therefore utilize limited spatial resolution in a global setting. An alternative approach is to use an unstructured-mesh ocean model, which allows variable mesh resolution. Here, we present initial results of a coupling between the Finite Element Sea-ice Ocean Model (FESOM) and the biogeochemical model REcoM2, with special focus on the Southern Ocean. Surface fields of nutrients, chlorophyll a and net primary production were compared to available data sets with focus on spatial distribution and seasonal cycle. The model produced realistic spatial distributions, especially regarding net primary production and chlorophyll a, whereas the iron concentration became too low in the Pacific Ocean. The modelled net primary production was 32.5 Pg C yr-1 and the export production 6.1 Pg C yr-1. This is lower than satellite-based estimates, mainly due to the excessive iron limitation in the Pacific along with too little coastal production. Overall, the model performed better in the Southern Ocean than on the global scale, though the assessment here is hindered by the lower availability of observations. The modelled net primary production was 3.1 Pg C yr-1 in the Southern Ocean and the export production 1.1 Pg C yr-1. All in all, the combination of a circulation model on an unstructured grid with an ocean biogeochemical model shows similar performance to other models at non-eddy-permitting resolution. It is well suited for studies of the Southern Ocean, but on the global scale deficiencies in the Pacific Ocean would have to be taken into account.

  7. Study of the Tagus estuarine plume using coupled hydro and biogeochemical models

    NASA Astrophysics Data System (ADS)

    Vaz, Nuno; Leitão, Paulo C.; Juliano, Manuela; Mateus, Marcos; Dias, João. Miguel; Neves, Ramiro

    2010-05-01

    Plumes of buoyant water produced by inflow from rivers and estuaries are common on the continental shelf. Buoyancy associated with estuarine waters is a key mediating factor in the transport and transformation of dissolved and particulate materials in coastal margins. The offshore displacement of the plume is influenced greatly by the local alongshore wind, which will tend to advect the plume either offshore or onshore, consistently with the Ekman transport. Other factor affecting the propagation of an estuarine plume is the freshwater inflow on the landward boundary. In this paper, a coupled three-dimensional ocean circulation and biogeochemical model with realistic high and low frequency forcing is used to get insight on how the Tagus River plume responds to wind and freshwater discharge during winter and spring. A nesting approach based on the MOHID numerical system was implemented for the Tagus estuary near shelf. Realistic hindcast simulations were performed, covering a period from January to June 2007. Model results were evaluated using in-situ and satellite imagery data. The numerical model was implemented using a three level nesting model. The model domain includes the whole Portuguese coast, the Tagus estuary near shelf and the Tagus River estuary, using a realistic coastline and bottom topography. River discharge and wind forcing are considered as landward and surface boundary conditions, respectively. Initial ocean stratification is from the MERCATOR solution. Ambient shelf conditions include tidal motion. As a prior validation, models outputs of salinity and water temperature were compared to available data (January 30th and May 30th, 2007) and were found minor differences between model outputs and data. On January 30th, outside the estuary, the model results reveal a stratified water column, presenting salinity stratification of the order of 3-4. The model also reproduces the hydrography for the May 30th observations. In May, near the Tagus mouth

  8. Simulation of land-atmosphere gaseous exchange using a coupled land surface-biogeochemical model

    NASA Astrophysics Data System (ADS)

    Gu, C.; Riley, W. J.; Perez, T. J.; Pan, L.

    2009-12-01

    It is important to develop and evaluate biogeochemical models that on the one hand represent vegetation and soil dynamics and on the other hand provide energy and water fluxes in a temporal resolution suitable for biogeochemical processes. In this study, we present a consistent coupling between a common land surface model (CLM3.0) and a recently developed biogeochemical model (TOUGHREACT-N). The model TOUGHREACT-N (TR-N) is one of the few process-based models that simulate green house gases fluxes by using an implicit scheme to solve the diffusion equations governing soil heat and water fluxes. By coupling with CLM3.0, we have significantly improved TR-N by including realistic representations of surface water, energy, and momentum exchanges, through the use of improved formulations for soil evaporation, plant transpiration, vegetation growth, and plant nitrogen uptake embedded in CLM3.0. The coupled CLMTR-N model is a first step for a full coupling of land surface and biogeochemical processes. The model is evaluated with measurements of soil temperature, soil water content, and N2O and N2 gaseous emission data from fallow, corn, and forest sites in Venezuela. The results demonstrate that the CLMTR-N model simulates realistic diurnal variation of soil temperature, soil water content, and N gaseous fluxes. For example, mean differences between predicted and observed midday near-surface soil water content were 8, 11, and 4 % in July, August, and September. The sensitivity of the biogeochemical processes and resulting N emissions to variation in environmental drivers is high, which indicates the need to calculate biogeochemical processes in, at least, two hourly time steps using dynamically updated (rather than daily averaged) soil environmental conditions. The development in CLMTR-N of such a complex representation of processes will allow us to characterize relevant processes and simplifications appropriate for regional to global-scale coupled biogeochemical and

  9. The Water, Energy, and Biogeochemical Model (WEBMOD): A TOPMODEL application developed within the Modular Modeling System

    NASA Astrophysics Data System (ADS)

    Webb, R. M.; Wolock, D. M.; Linard, J. I.; Wieczorek, M. E.

    2004-12-01

    Process-based flow and transport simulation models can help increase understanding of how hydrologic flow paths affect biogeochemical mixing and reactions in watersheds. This presentation describes the Water, Energy, and Biogeochemical Model (WEBMOD), a new model designed to simulate water and chemical transport in both pristine and agricultural watersheds. WEBMOD simulates streamflow using TOPMODEL algorithms and also simulates irrigation, canopy interception, snowpack, and tile-drain flow; these are important processes for successful multi-year simulations of agricultural watersheds. In addition, the hydrologic components of the model are linked to the U.S. Geological Survey's (USGS) geochemical model PHREEQC such that solute chemistry for the hillslopes and streams also are computed. Model development, execution, and calibration take place within the USGS Modular Modeling System. WEBMOD is being validated at ten research watersheds. Five of these watersheds are nearly pristine and comprise the USGS Water, Energy, and Biogeochemical Budget (WEBB) Program field sites: Loch Vale, Colorado; Trout Lake, Wisconsin; Sleepers River, Vermont; Panola Mountain, Georgia; and the Luquillo Experimental Forest, Puerto Rico. The remaining five watersheds contain intensely cultivated fields being studied by USGS National Water Quality Assessment Program: Merced River, California; Granger Drain, Washington; Maple Creek, Nebraska; Sugar Creek, Indiana; and Morgan Creek, Delaware. Model calibration improved understanding of observed variations in soil moisture, solute concentrations, and stream discharge at the five WEBB watersheds and is now being set up to simulate the processes at the five agricultural watersheds that are now ending their first year of data collection.

  10. Improving National Capability in Biogeochemical Flux Modelling: the UK Environmental Virtual Observatory (EVOp)

    NASA Astrophysics Data System (ADS)

    Johnes, P.; Greene, S.; Freer, J. E.; Bloomfield, J.; Macleod, K.; Reaney, S. M.; Odoni, N. A.

    2012-12-01

    The best outcomes from watershed management arise where policy and mitigation efforts are underpinned by strong science evidence, but there are major resourcing problems associated with the scale of monitoring needed to effectively characterise the sources rates and impacts of nutrient enrichment nationally. The challenge is to increase national capability in predictive modelling of nutrient flux to waters, securing an effective mechanism for transferring knowledge and management tools from data-rich to data-poor regions. The inadequacy of existing tools and approaches to address these challenges provided the motivation for the Environmental Virtual Observatory programme (EVOp), an innovation from the UK Natural Environment Research Council (NERC). EVOp is exploring the use of a cloud-based infrastructure in catchment science, developing an exemplar to explore N and P fluxes to inland and coastal waters in the UK from grid to catchment and national scale. EVOp is bringing together for the first time national data sets, models and uncertainty analysis into cloud computing environments to explore and benchmark current predictive capability for national scale biogeochemical modelling. The objective is to develop national biogeochemical modelling capability, capitalising on extensive national investment in the development of science understanding and modelling tools to support integrated catchment management, and supporting knowledge transfer from data rich to data poor regions, The AERC export coefficient model (Johnes et al., 2007) has been adapted to function within the EVOp cloud environment, and on a geoclimatic basis, using a range of high resolution, geo-referenced digital datasets as an initial demonstration of the enhanced national capacity for N and P flux modelling using cloud computing infrastructure. Geoclimatic regions are landscape units displaying homogenous or quasi-homogenous functional behaviour in terms of process controls on N and P cycling

  11. Southern Alaska Coastal Relief Model

    NASA Astrophysics Data System (ADS)

    Lim, E.; Eakins, B.; Wigley, R.

    2009-12-01

    The National Geophysical Data Center (NGDC), an office of the National Oceanic and Atmospheric Administration (NOAA), in conjunction with the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado at Boulder, has developed a 24 arc-second integrated bathymetric-topographic digital elevation model of Southern Alaska. This Coastal Relief Model (CRM) was generated from diverse digital datasets that were obtained from NGDC, the United States Geological Survey, and other U.S. and international agencies. The CRM spans 170° to 230° E and 48.5° to 66.5° N, including the Gulf of Alaska, Bering Sea, Aleutian Islands, and Alaska’s largest communities: Anchorage, Fairbanks, and Juneau. The CRM provides a framework for enabling scientists to refine tsunami propagation and ocean circulation modeling through increased resolution of geomorphologic features. It may also be useful for benthic habitat research, weather forecasting, and environmental stewardship. Shaded-relief image of the Southern Alaska Coastal Relief Model.

  12. Development of assimilative biogeochemical ocean models for operational and research applications

    NASA Astrophysics Data System (ADS)

    Brasseur, Pierre

    The Green-Mercator project (2007-2009, http://mercator-vert.ipsl.jussieu.fr/) aims at implementing the marine biogeochemical model PISCES at global scale into the MERCATOR operational monitoring and forecasting system. Besides the development of the model system itself, this project relies on two major research activities to improve biogeochemical simulations: (1) the refinement of process resolution to investigate the impact of the transition between eddy permitting to eddy resolving on biogeochemical simulations at global scale, and (2) the assimilation of physical and biogeochemical data (such as ocean color) into the model. The project also includes research activities to demonstrate the potential of an operational biogeochemical model for regional downscaling and extension towards marine resources. In this talk, we will focus on developments achieved in the framework of the E.U. MERSEA project (2004-2008) to assimilate satellite and in situ data into coupled models. Experiments using the SEEK filter in a North Atlantic prototype at 1/4° resolution illustrate the feasability of the approach. The results show that traditional methods such as the Kalman filter may lead to physical inconsistencies originating from the gaussian nature of the KF analysis scheme. A new scheme based on truncated gaussian pdfs is therefore developed (TGF) to integrate inequality constraints during the assimilation process. This new scheme represents a major step toward the assimilation of a variety of satellite data, such as sea-ice thickness and ocean colour data, into coupled models.

  13. Isotopes and Isoscapes: Tools for Testing Hydrological and Biogeochemical Models

    NASA Astrophysics Data System (ADS)

    Kendall, C.

    2014-12-01

    In the 21st century, the importance of high quality water resources cannot be overstated. New approaches are needed to pinpoint sources and ages of multiple contaminants, and to better understand critical hydrologic systems. Stable isotopic compositions of materials often show strong spatial and temporal distributions related to combinations of sources and processes. Isoscapes (spatial and/or temporal maps) of riverine and atmospheric data are increasingly being found to be effective means for assessing the effects of different land uses and biogeochemical processes on water resources. Hence, isotopes and isoscapes are a potentially powerful component of monitoring and assessment programs that are aimed at quantifying and mitigating alterations to environments from human activities (anthropogenic disturbances). Locations exhibiting unusually high rates of biogeochemical cycling or elevated pollution levels usually have distinctive isotopic compositions that are suggestive or diagnostic of specific reactions and pollution sources. Isotopes can be more effective at identifying hot spots and hot moments than concentrations alone because isotopic ratios may change even when concentrations do not. Hence, isotopes provide valuable additions to standard chemical and hydrological mass balance methods. This presentation will examine how the field of isotope hydrology has evolved over my 40+ year career as an isotope geochemist, highlight several exciting recent research thrusts, and share some thoughts on future research directions.

  14. Dynamic modeling of nitrogen losses in river networks unravels the coupled effects of hydrological and biogeochemical processes

    USGS Publications Warehouse

    Alexander, R.B.; Böhlke, J.K.; Boyer, E.W.; David, M.B.; Harvey, J.W.; Mulholland, P.J.; Seitzinger, S.P.; Tobias, C.R.; Tonitto, C.; Wollheim, W.M.

    2009-01-01

    The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction of nitrogen in streamflow is removed to the atmosphere via denitrification with the remainder exported in streamflow as nitrogen loads. At the watershed scale, there is a keen interest in understanding the factors that control the fate of nitrogen throughout the stream channel network, with particular attention to the processes that deliver large nitrogen loads to sensitive coastal ecosystems. We use a dynamic stream transport model to assess biogeochemical (nitrate loadings, concentration, temperature) and hydrological (discharge, depth, velocity) effects on reach-scale denitrification and nitrate removal in the river networks of two watersheds having widely differing levels of nitrate enrichment but nearly identical discharges. Stream denitrification is estimated by regression as a nonlinear function of nitrate concentration, streamflow, and temperature, using more than 300 published measurements from a variety of US streams. These relations are used in the stream transport model to characterize nitrate dynamics related to denitrification at a monthly time scale in the stream reaches of the two watersheds. Results indicate that the nitrate removal efficiency of streams, as measured by the percentage of the stream nitrate flux removed via denitrification per unit length of channel, is appreciably reduced during months with high discharge and nitrate flux and increases during months of low-discharge and flux. Biogeochemical factors, including land use, nitrate inputs, and stream concentrations, are a major control on reach-scale denitrification, evidenced by the disproportionately lower nitrate removal efficiency in streams of the highly nitrate-enriched watershed as compared with that in similarly sized streams in the less nitrate-enriched watershed. Sensitivity analyses reveal that these important biogeochemical factors and physical hydrological factors contribute nearly

  15. A skill assessment of the biogeochemical model REcoM2 coupled to the Finite Element Sea Ice-Ocean Model (FESOM 1.3)

    NASA Astrophysics Data System (ADS)

    Schourup-Kristensen, V.; Sidorenko, D.; Wolf-Gladrow, D. A.; Völker, C.

    2014-11-01

    In coupled biogeochmical-ocean models, the choice of numerical schemes in the ocean circulation component can have a large influence on the distribution of the biological tracers. Biogeochemical models are traditionally coupled to ocean general circulation models (OGCMs), which are based on dynamical cores employing quasi-regular meshes, and therefore utilize limited spatial resolution in a global setting. An alternative approach is to use an unstructured-mesh ocean model, which allows variable mesh resolution. Here, we present initial results of a coupling between the Finite Element Sea Ice-Ocean Model (FESOM) and the biogeochemical model REcoM2 (Regulated Ecosystem Model 2), with special focus on the Southern Ocean. Surface fields of nutrients, chlorophyll a and net primary production (NPP) were compared to available data sets with a focus on spatial distribution and seasonal cycle. The model produces realistic spatial distributions, especially regarding NPP and chlorophyll a, whereas the iron concentration becomes too low in the Pacific Ocean. The modelled NPP is 32.5 Pg C yr-1 and the export production 6.1 Pg C yr-1, which is lower than satellite-based estimates, mainly due to excessive iron limitation in the Pacific along with too little coastal production. The model performs well in the Southern Ocean, though the assessment here is hindered by the lower availability of observations. The modelled NPP is 3.1 Pg C yr-1 in the Southern Ocean and the export production 1.1 Pg C yr-1. All in all, the combination of a circulation model on an unstructured grid with a biogeochemical-ocean model shows similar performance to other models at non-eddy-permitting resolution. It is well suited for studies of the Southern Ocean, but on the global scale deficiencies in the Pacific Ocean would have to be taken into account.

  16. ANALYTICAL ELEMENT MODELING OF COASTAL AQUIFERS

    EPA Science Inventory

    Four topics were studied concerning the modeling of groundwater flow in coastal aquifers with analytic elements: (1) practical experience was obtained by constructing a groundwater model of the shallow aquifers below the Delmarva Peninsula USA using the commercial program MVAEM; ...

  17. Hierarchical framework for coupling a biogeochemical trace gas model to a general circulation model

    SciTech Connect

    Miller, N.L.; Foster, I.T.

    1994-04-01

    A scheme is described for the computation of terrestrial biogeochemical trace gas fluxes in the context of a general circulation model. This hierarchical system flux scheme (HSFS) incorporates five major components: (1) a general circulation model (GCM), which provides a medium-resolution (i.e., 1{degrees} by 1{degrees}) simulation of the atmospheric circulation; (2) a procedure for identifying regions of defined homogeneity of surface type within GCM grid cells; (3) a set of surface process models, to be run within each homogeneous region, which include a biophysical model, the Biosphere Atmospheric Transfer Scheme (BATS), and a biogeochemical model (BGCM); (4) an interpolation/integration system that transfers information between the GCM and surface process models with finer resolution; and (5) an interactive data array based on a geographic information system (GIS), which provides land characteristic information via the interpolator. The goals of this detailed investigation are to compute the local and global sensitivities of trace gas fluxes to GCM and BATS variables, the effects of trace gas fluxes on global climate, and the effects of global climate on specific biomes.

  18. Biogeochemical Controls on Biodegradation of MC252 Oil:Sand Aggregates on a Rapidly Eroding Coastal Headland Beach

    NASA Astrophysics Data System (ADS)

    Pardue, J.; Elango, V.; Urbano, M.; Lemelle, K.

    2012-12-01

    The research described below was conducted on Fourchon Beach, a coastal headland consisting of nine miles of fairly pristine sandy beaches and dunes, backed by wetlands and tidal channels, located between Belle Pass tidal inlet on the west and Elmer's Island on the east in Lafourche Parish, Louisiana. MC252 oil first arrived in large quantities on Fourchon Beach on or around May 20, 2010. A unique oil form created under these conditions was an aggregate of sand and emulsified oil, typically 0.1-10 cm in diameter, termed small surface residue balls (SSRBs). The work from this project made critical measurements on the factors controlling biodegradability of these SSRB aggregates. SSRB aggregates were sampled across transects perpendicular to the beach from the intertidal to the supratidal. Areas in the supratidal that were sampled initially were set aside for research purposes and not altered by any clean-up activities. Chemical composition of SSRBs was measured including concentrations of n-alkanes, PAHs, hopanes, nutrients (nitrate, nitrite, ammonium and orthophosphate measured on water extracts of SSRBs), and electron acceptor concentrations (O2 microprofiles measured on intact SSRBs and sulfate). Physical characterization of the SSRBs including length and area dimensions, mass, density, porosity, moisture content, and salinity using standard methods. Microbial characterization of SSRBs was also conducted using denaturing gradient gel electrophoresis and sequencing of dominant bands. SSRBs were sampled from various locations across the beach profile deposited by 2 significant tropical events in 2010; Hurricane Alex and TS Bonnie, and one event in 2011, TS Lee. Sampling focused on comparing and contrasting impacts of biogeochemistry on weathering of oil stranded in three beach microenvironments; supratidal surface; subtidal subsurface which is permanently inundated and intertidal subsurface samples which are intermittently inundated. The three types of oil are

  19. Towards coupled physical-biogeochemical models of the ocean carbon cycle

    NASA Technical Reports Server (NTRS)

    Rintoul, Stephen R.

    1992-01-01

    The purpose of this review is to discuss the critical gaps in our knowledge of ocean dynamics and biogeochemical cycles. It is assumed that the ultimate goal is the design of a model of the earth system that can predict the response to changes in the external forces driving climate.

  20. Coupling Isotopic Fractionation to Multiple-Continuum Reactive Transport Models of Biogeochemical Systems

    NASA Astrophysics Data System (ADS)

    Sonnenthal, E. L.; Wanner, C.

    2014-12-01

    Stable isotopic systems often show an unexpected range in observed fractionation factors associated with biogeochemical systems. In particular, the ranges in such isotopic systems as Cr, Ca, Li, and C have often been attributed to kinetic effects as well as different biogeochemical mechanisms. Reactive transport models developed to capture the sub-micron-scale transport and reaction processes within the macroscale system (e.g., biofilm to cm-scale) have been successful in simulating the biogeochemical processes associated with bacterial growth and the resultant changes in pore-fluid chemistry and redox conditions. Once such multicontinuum reactive transport models are extended to include equilibrium and kinetic isotopic fractionation, diffusive transport, and fluid-gas equilibria, it becomes possible to quantitatively interpret the isotopic changes observed in experimental and natural or engineered biogeochemical systems. We combine a solid-solution approach for isotopic substitution in minerals with the multiple-continuum reactive-transport approach to interpret the effective fractionation factor observed in experimental systems. Although such systems often have poorly constrained inputs (such as the equilibrium fractionation factor and many of the parameters associated with bacterial growth), by combining several independent contraints on reaction rates (such as lactate consumption, 13C/12C and 87Sr/86Sr in calcite), the range of possible interpretations can often be greatly narrowed. Here we present examples of the modeling approaches and their application to experimental systems to examine why the observed fractionation factors are often different from the theoretical values.

  1. Towards an assessment of simple global marine biogeochemical models of different complexity

    NASA Astrophysics Data System (ADS)

    Kriest, I.; Khatiwala, S.; Oschlies, A.

    2010-09-01

    We present a suite of experiments with a hierarchy of biogeochemical models of increasing complexity coupled to an offline global ocean circulation model based on the “transport matrix method”. Biogeochemical model structures range from simple nutrient models to more complex nutrient-phytoplankton-zooplankton-detritus-DOP models. The models’ skill is assessed by various misfit functions with respect to observed phosphate and oxygen distributions. While there is generally good agreement between the different metrics employed, an exception is a cost function based on the relative model-data misfit. We show that alterations in parameters and/or structure of the models - especially those that change particle export or remineralization profile - affect subsurface and mesopelagic phosphate and oxygen, particularly in the upwelling regions. Visual inspection of simulated biogeochemical tracer distributions as well as the evaluation of different cost functions suggest that increasing complexity of untuned, unoptimized models, simulated with parameters commonly used in large-scale model studies does not necessarily improve performance. Instead, variations in individual model parameters may be of equal, if not greater, importance.

  2. High resolution modelling of the biogeochemical processes in the eutrophic Loire River (France)

    NASA Astrophysics Data System (ADS)

    Minaudo, Camille; Moatar, Florentina; Curie, Florence; Gassama, Nathalie; Billen, Gilles

    2016-04-01

    A biogeochemical model was developed, coupling a physically based water temperature model (T-NET) with a semi-mechanistic biogeochemical model (RIVE, used in ProSe and Riverstrahler models) in order to assess at a fine temporal and spatial resolution the biogeochemical processes in the eutrophic Middle Loire hydrosystem (≈10 000 km², 3361 river segments). The code itself allows parallelized computing, which decreased greatly the calculation time (5 hours for simulating 3 years hourly). We conducted a daily survey during the period 2012-2014 at 2 sampling stations located in the Middle Loire of nutrients, chlorophyll pigments, phytoplankton and physic-chemical variables. This database was used as both input data (upstream Loire boundary) and validation data of the model (basin outlet). Diffuse and non-point sources were assessed based on a land cover analysis and WWTP datasets. The results appeared very sensible to the coefficients governing the dynamic of suspended solids and of phosphorus (sorption/desorption processes) within the model and some parameters needed to be estimated numerically. Both the Lagrangian point of view and fluxes budgets at the seasonal and event-based scale evidenced the biogeochemical functioning of the Loire River. Low discharge levels set up favorable physical conditions for phytoplankton growth (long water travel time, limited water depth, suspended particles sedimentation). Conversely, higher discharge levels highly limited the phytoplankton biomass (dilution of the colony, washing-out, limited travel time, remobilization of suspended sediments increasing turbidity), and most biogeochemical species were basically transferred downstream. When hydrological conditions remained favorable for phytoplankton development, P-availability was the critical factor. However, the model evidenced that most of the P in summer was recycled within the water body: on one hand it was assimilated by the algae biomass, and on the other hand it was

  3. Modelling physical and biogeochemical state of the Mediterranean Sea under contemporary and future climate

    NASA Astrophysics Data System (ADS)

    Solidoro, Cosimo; Lazzari, Paolo; Cossarini, Gianpiero; Melaku Canu, Donata; Lovato, Tomas; Vichi, Marcello

    2014-05-01

    A validated 3D coupled transport-biogeochemical model is used to assess the impact of future climatic and management scenarios on biogeochemical and ecological properties of the Mediterranean Sea. Results are discussed in term of temporal and spatial distribution of parameters and indicators related to the carbonate system and the cycles of carbon and inorganic nutrients through dissolved and particulate phases, as simulated by a multi nutrient multi plankton numerical model under current and future conditions. Simulations span the period 2000-2040 and are performed by forcing a three-dimensional off-line coupled eco-hydrodynamical model (BFM and OPA-tracer model, http://bfm-community.eu/) with marine circulation fields produced by ad hoc implementation of the NEMO modelling system and with river input of nutrient and freshwater computed in recent European fp7 projects. The model properly describes available experimental information on contemporary seasonal dynamic and spatial distribution at the basin and sub-basin scale of major biogeochemical parameters, as well as primary production and carbon fluxes at the air-ocean interface. Model projections suggest that future Mediterranean sea will be globally warmer, more productive, and more acidic, but with significant space variability. The relative importance of different biotic and abiotic parameters in defining such a change is explored through several numerical experiments. Potential implications in terms of ecological and higher trophic level organisms dynamics are explored as well, by integrating niche properties of selected organisms and suggestions provided by food web models.

  4. Stochastic modeling of nutrient losses in streams: Interactions of climatic, hydrologic, and biogeochemical controls

    NASA Astrophysics Data System (ADS)

    Botter, G.; Basu, N. B.; Zanardo, S.; Rao, P. S. C.; Rinaldo, A.

    2010-08-01

    We present an analytical, stochastic approach for quantifying intra-annual fluctuations of in-stream nutrient losses induced by naturally variable hydrologic conditions. The relevance of the problem we address lies in the growing concern for the major environmental impacts of increasing nutrient loads from watersheds to freshwater bodies and coastal waters. Here we express the first-order nutrient loss rate constant, ke, as a function of key biogeochemical and hydrologic controls, in particular the stream depth (h). The stage h modulates the impact of natural streamflow temporal fluctuations (induced by intermittent rainfall forcings) on the underlying biogeochemical processes and thus represents the major driver of at-a-site fluctuations of ke. Novel expressions for the probability distribution function (pdf) of h and ke are derived as a function of a few eco-hydrologic, morphologic and biogeochemical parameters. The shape of such pdf's chiefly depends on the following attributes: (1) the average frequency of streamflow-producing rainfall events, λ; (2) the inverse of mean catchment residence time, k; and (3) a stream channel shape factor, identified through the discharge rating curve exponent b. For λ/(kb) > 1, h and ke have lower intra-annual variability and lower sensitivity to climatic and morphologic controls, leading to improved predictability and ease of measurement of these attributes. Moment analyses suggest that the variability of ke, relative to that of h, is attenuated for λ/(kb) > 1. Thus, the interplay between climate-landscape parameters and the stream shape factor b controls the temporal variability induced by stochastic rainfall forcings on stream stages and nutrient removal rates.

  5. Coastal erosion problem, modelling and protection

    NASA Astrophysics Data System (ADS)

    Yılmaz, Nihal; Balas, Lale; İnan, Asu

    2015-09-01

    Göksu Delta, located in the south of Silifke County of Mersin on the coastal plain formed by Göksu River, is one of the Specially Protected Areas in Turkey. Along the coastal area of the Delta, coastline changes at significant rates are observed, concentrating especially at four regions; headland of İncekum, coast of Paradeniz Lagoon, river mouth of Göksu and coast of Altınkum. The coast of Paradeniz Lagoon is suffering significantly from erosion and the consequent coastal retreating problem. Therefore, the narrow barrier beach which separates Paradeniz Lagoon from the Mediterranean Sea is getting narrower, creating a risk of uniting with the sea, thus causing the disappearance of the Lagoon. The aim of this study was to understand the coastal transport processes along the coastal area of Göksu Delta to determine the coastal sediment transport rates, and accordingly, to propose solutions to prevent the loss of coastal lands in the Delta. To this end, field measurements of currents and sediment grain sizes were carried out, and wind climate, wave climate, circulation patterns and longshore sediment transport rates were numerically modeled by HYDROTAM-3D, which is a three dimensional hydrodynamic transport model. Finally, considering its special importance as an environmentally protected region, some coastal structures of gabions were proposed as solutions against the coastal erosion problems of the Delta. The effects of proposed structures on future coastline changes were also modeled, and the coastlines predicted for the year 2017 are presented and discussed in the paper.

  6. Modeling Nitrogen Leaching With A Biogeochemical Model Coupled With Soil Hydrology Model

    NASA Astrophysics Data System (ADS)

    Barman, R.; Yang, X.; Jain, A.; Post, W. M.; Sivapalan, M.

    2008-12-01

    Land use changes for cropland, excessive application of fertilizers in agriculture, and increase in anthropogenic activities such as fossil fuel burning have lead to widespread increases in anthropogenic production of reactive N and NH3 emissions, and N deposition rates. An important consequence of these processes is intensification of soil nutrient leaching activities, leading to serious ground water contamination problems. The current study focuses on the issue of nitrogen (nitrate and ammonium) leaching due to land cover changes for cropland, excess N fertilizer application, and atmospheric nitrogen deposition on nitrogen leaching at a global scale. Simulations of nitrogen leaching require integration of processes involving soil hydrology and biogeochemical cycles. An existing terrestrial coupled carbon-nitrogen cycle model, Integrated Science Assessment Model (ISAM), was used to estimate nitrogen leaching. The N-cycle in ISAM includes the major processes associated with nitrogen (immobilization, mineralization, nitrification, denitrification, leaching, nitrogen fixation, and vegetation nitrogen uptake). ISAM also considers how carbon and nitrogen dynamics are influenced by the effects of human perturbations to the N cycle including atmospheric deposition and fertilizer application, and the fate of N in land use activities, i.e., deforestation and agricultural harvest. In this study, the ISAM soil hydrology was extended and improved with CLM 3.5 hydrology processes and algorithms, which extended the modeling capabilities to consider the prediction of nitrogen leaching. The model performance was evaluated with flow and nutrient data at several locations within the Upper Sangamon River Basin in Illinois, and flow data in contrasting watersheds in Oklahoma. This talk will focus on describing the results of a series of modeling experiments examining the influence of land management changes for cropland and nitrogen deposition on nitrogen leaching at a global scale

  7. A Coupled Model of Multiphase Flow, Reactive Biogeochemical Transport, Thermal Transport and Geo-Mechanics.

    NASA Astrophysics Data System (ADS)

    Tsai, C. H.; Yeh, G. T.

    2015-12-01

    In this investigation, a coupled model of multiphase flow, reactive biogeochemical transport, thermal transport and geo-mechanics in subsurface media is presented. It iteratively solves the mass conservation equation for fluid flow, thermal transport equation for temperature, reactive biogeochemical transport equations for concentration distributions, and solid momentum equation for displacement with successive linearization algorithm. With species-based equations of state, density of a phase in the system is obtained by summing up concentrations of all species. This circumvents the problem of having to use empirical functions. Moreover, reaction rates of all species are incorporated in mass conservation equation for fluid flow. Formation enthalpy of all species is included in the law of energy conservation as a source-sink term. Finite element methods are used to discretize the governing equations. Numerical experiments are presented to examine the accuracy and robustness of the proposed model. The results demonstrate the feasibility and capability of present model in subsurface media.

  8. Monitoring and Modelling Lakes and Coastal Environments

    NASA Astrophysics Data System (ADS)

    Odada, Eric

    2009-01-01

    The monitoring and modeling of lakes and coastal environments is becoming ever more important, particularly because these environments bear heavy loads in terms of human population, and their resources are critical to the livelihoods and well-being of coastal inhabitants and ecosystems. Monitoring and Modelling Lakes and Coastal Environments is a collection of 18 papers arising from the Lake 2004 International Conference on Conservation, Restoration and Management of Lakes and Coastal Wetlands, held in Bhubaneswar, Orissa, India, 9-13 December 2004. Consequently, 15 of the papers are concerned with studies on the Indian subcontinent, and many of the papers focus on India's Lake Chilika, the site of a special session during the conference. Two papers concern Japan, and one focuses on North America's Great Lakes region. Although the book has a regional bias, the replication of best practices that can be drawn from these studies may be useful for an international audience.

  9. Expanding the Role of Reactive Transport Modeling in Biogeochemical Sciences

    NASA Astrophysics Data System (ADS)

    Li, Li; Maher, Katherine M.; Navarre-Sitchler, Alexis

    2014-09-01

    Earth systems are complex due to the intimate coupling of physical, chemical, and biological processes in the subsurface. Field observation and data analysis have provided significant insights into the coupling of these processes. However, mechanistic understanding often requires advanced modeling tools to quantify the role of individual processes while maintaining the process coupling that determines the overall system behavior. As a result, reactive transport modeling (RTM) has been used extensively to interrogate complex subsurface processes relevant to energy and the environment. Existing work has shown the significant research and educational advantages of RTM in elucidating mechanisms, integrating large data sets, testing hypotheses, and guiding the stewardship and management of water and energy resources.

  10. Modeling seawater intrusion and the associated reactive solute transport in fractured coastal aquifers

    NASA Astrophysics Data System (ADS)

    Nick, Hamid M.; Regnier, Pierre; Thullner, Martin

    2013-04-01

    In coastal aquifers seawater and terrestrial water get into contact and the reactive mixing between these water bodies controls the water quality of submarine groundwater discharge. The rates of such mixing controlled reactions are depending not only on the properties of the reactive species but also on the density driven flow dynamics and the resulting transport patterns. A prediction of these flow and transport processes and thus of the fate of reactive species is specifically challenged in fracture aquifers as it depends on the focusing of the flow and the local balance of viscous and gravitational forces. To study the influence of fractures on mixing and reactive transport in coastal aquifers we present a reactive discrete fracture and matrix (DFM) model using unstructured spatially adaptively refined finite-element meshes. This model is developed by coupling the Complex System Modelling Platform (CSMP++) utilizing a hybrid FEFV scheme, and a Biogeochemical Reaction Network Simulator (BRNS) capable of solving for kinetically and thermodynamically constrained biogeochemical reactions [1]. The model is applied to simulate the reactive transport in fracture networks embedded in a permeable rock matrix. For virtual coastal aquifers, different fracture data sets are employed to study the effect of fractures and their characteristics on the reactive mixing between fresh water and seawater in coastal aquifers. Obtained results show that the presence of fractures enhances reactive mixing for most cases due to the combined effect of fracture induced flow channeling and dispersion. The magnitude of this effect depends highly on fracture density, spacing and orientation. Furthermore the results indicate that reactive mixing in fractured aquifers is not well described using an effective parameterization of a homogeneous aquifer setup. This suggests that structural information on the fracture network is needed for a sufficient description of reactive transport processes in

  11. Modeling biogeochemical processes of phosphorus for global food supply.

    PubMed

    Dumas, Marion; Frossard, Emmanuel; Scholz, Roland W

    2011-08-01

    Harvests of crops, their trade and consumption, soil erosion, fertilization and recycling of organic waste generate fluxes of phosphorus in and out of the soil that continuously change the worldwide spatial distribution of total phosphorus in arable soils. Furthermore, due to variability in the properties of the virgin soils and the different histories of agricultural practices, on a planetary scale, the distribution of total soil phosphorus is very heterogeneous. There are two key relationships that determine how this distribution and its change over time affect crop yields. One is the relationship between total soil phosphorus and bioavailable soil phosphorus and the second is the relationship between bioavailable soil phosphorus and yields. Both of these depend on environmental variables such as soil properties and climate. We propose a model in which these relationships are described probabilistically and integrated with the dynamic feedbacks of P cycling in the human ecosystem. The model we propose is a first step towards evaluating the large-scale effects of different nutrient management scenarios. One application of particular interest is to evaluate the vulnerability of different regions to an increased scarcity in P mineral fertilizers. Another is to evaluate different regions' deficiency in total soil phosphorus compared with the level at which they could sustain their maximum potential yield without external mineral inputs of phosphorus but solely by recycling organic matter to close the nutrient cycle. PMID:21463882

  12. Modeling the Natural Biogeochemical Cycle of Mercury in the Global Ocean

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Jaegle, L.; Thompson, L.; Emerson, S. R.; Deutsch, C. A.; Trossman, D. S.; Shao, A.

    2012-12-01

    The ocean plays an important role in the biogeochemical cycling of mercury (Hg) because of its large reservoir mass and re-emission flux via evasion. The currently available Hg models, including 2D slab, 1D column and 0D box model cannot fully resolve the marine Hg cycle because of the lack of the proper spatial resolution. In this work, we have implemented Hg biogeochemistry in a state-of-the-art 3D offline ocean tracer model (OFFTRAC). OFFTRAC simulates the evolution of three Hg species (Hg0aq, HgIIaq and HgPaq), which are diffused and advected in the ocean. Hg0aq and HgII aq are interconverted in the surface ocean via parameterized photochemical and biological redox processes. The partitioning between HgIIaq and HgPaq depends on the local levels of particulate organic carbon (POC). The sinking of HgPaq is parameterized by coupling with the nutrient phosphorous cycle simulated in OFFTRAC. The reduction of HgIIaq to Hg0aq in the anaerobic subsurface water is proportional to the remineralizaiton of POC. OFFTRAC is coupled to a global simulation of the natural atmospheric Hg cycle in the GEOS-Chem chemical transport model. The GEOS-Chem simulation includes a geogenic source and provides the atmospheric deposition flux of HgII to the ocean and atmospheric Hg0 concentrations. The riverine input of Hg is calculated based on the climatological monthly mean fresh water discharge from continental to ocean and the average soil concentrations near the river mouth. The results show that the riverine input enhances Hg concentrations at surface by a factor of 2-3 near large river mouths and nearby coastal regions. The riverine input approximately doubles surface Hg concentration over the Arctic because of the small basin volume. In the deep ocean, which is not influenced by anthropogenic emissions, the model results (1.1±0.3 pM) generally agree with the observed present-day total Hg concentration profiles (1.4±0.9 pM). In the surface ocean, observations show average total Hg

  13. Modeling biogeochemical processes in subterranean estuaries: Effect of flow dynamics and redox conditions on submarine groundwater discharge of nutrients

    NASA Astrophysics Data System (ADS)

    Spiteri, Claudette; Slomp, Caroline P.; Tuncay, Kagan; Meile, Christof

    2008-02-01

    A two-dimensional density-dependent reactive transport model, which couples groundwater flow and biogeochemical reactions, is used to investigate the fate of nutrients (NO3-, NH4+, and PO4) in idealized subterranean estuaries representing four end-members of oxic/anoxic aquifer and seawater redox conditions. Results from the simplified model representations show that the prevalent flow characteristics and redox conditions in the freshwater-seawater mixing zone determine the extent of nutrient removal and the input of nitrogen and phosphorus to coastal waters. At low to moderate groundwater velocities, simultaneous nitrification and denitrification can lead to a reversal in the depth of freshwater NO3- and NH4+-PO4 plumes, compared to their original positions at the landward source. Model results suggest that autotrophic denitrification pathways with Fe2+ or FeS2 may provide an important, often overlooked link between nitrogen and phosphorus biogeochemistry through the precipitation of iron oxides and subsequent binding of phosphorus. Simulations also highlight that deviations of nutrient data from conservative mixing curves do not necessarily indicate nutrient removal.

  14. Nitrous oxide emissions from cropland: A procedure for calibrating the DayCent biogeochemical model using inverse modelling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    DayCent is a biogeochemical model of intermediate complexity widely used to simulate greenhouse gases (GHG), soil organic carbon (SOC) and nutrients in crop, grassland, forest and savannah ecosystems. Although this model has been applied to a wide range of ecosystems, it is still typically parameter...

  15. Integrating remotely sensed land cover observations and a biogeochemical model for estimating forest ecosystem carbon dynamics

    USGS Publications Warehouse

    Liu, J.; Liu, S.; Loveland, T.R.; Tieszen, L.L.

    2008-01-01

    Land cover change is one of the key driving forces for ecosystem carbon (C) dynamics. We present an approach for using sequential remotely sensed land cover observations and a biogeochemical model to estimate contemporary and future ecosystem carbon trends. We applied the General Ensemble Biogeochemical Modelling System (GEMS) for the Laurentian Plains and Hills ecoregion in the northeastern United States for the period of 1975-2025. The land cover changes, especially forest stand-replacing events, were detected on 30 randomly located 10-km by 10-km sample blocks, and were assimilated by GEMS for biogeochemical simulations. In GEMS, each unique combination of major controlling variables (including land cover change history) forms a geo-referenced simulation unit. For a forest simulation unit, a Monte Carlo process is used to determine forest type, forest age, forest biomass, and soil C, based on the Forest Inventory and Analysis (FIA) data and the U.S. General Soil Map (STATSGO) data. Ensemble simulations are performed for each simulation unit to incorporate input data uncertainty. Results show that on average forests of the Laurentian Plains and Hills ecoregion have been sequestrating 4.2 Tg C (1 teragram = 1012 gram) per year, including 1.9 Tg C removed from the ecosystem as the consequences of land cover change. ?? 2008 Elsevier B.V.

  16. Linking sediment structure, hydrological functioning and biogeochemical cycling in disturbed coastal saltmarshes and implications for vegetation development

    NASA Astrophysics Data System (ADS)

    Spencer, Kate; Harvey, Gemma; James, Tempest; Simon, Carr; Michelle, Morris

    2014-05-01

    Saltmarsh restoration undoubtedly provides environmental enhancement, with vegetation quickly re-establishing following the breach of sea walls and subsequent tidal inundation of previously defended areas. Yet evidence increasingly suggests that the restored saltmarshes do not have the same biological characteristics as their natural counterparts (Mossman et al. 2012) and this may be in part be due to physicochemical parameters at the site including anoxia and poor drainage. Hence, restored saltmarshes may not offer the range and quality of ecosystem services anticipated. These environments will have been 'disturbed' by previous land use and there is little understanding of the impacts of this disturbance on the wider hydrogeomorphic and biogeochemical functioning in restored saltmarshes and the implications for saltmarsh vegetation development. This study examines linkages between physical sediment characteristics, sediment structure (using X-ray microtomography), sub-surface hydrology (using pressure transducers and time series analysis), and sediment and porewater geochemistry (major and trace elements, major anions) in sediment cores collected from undisturbed saltmarshes and those restored by de-embankment. Sub-surface sediments in restored saltmarshes have lower organic matter content, lower moisture content and higher bulk density than undisturbed sites. Using X-ray tomography a clear horizon can be observed which separates relict agricultural soils at depth with less dense and structureless sediments deposited since de-embankment. Ratios of open to closed pore space suggest that while undisturbed saltmarshes have the highest porosity, restored saltmarshes have larger void spaces, but limited pore connectivity. Sub-surface hydrological response to tidal flooding was subdued in the restored compared to the undisturbed site, suggesting that porewater flow may be impeded. Time series analysis indicated that flow pathways differ in restored saltmarsh sediments

  17. ANALYTIC ELEMENT MODELING OF COASTAL AQUIFERS

    EPA Science Inventory

    Four topics were studied concerning the modeling of ground-water flow in coastal aquifers with analytic elements: (1) practical experience was obtained by constructing a ground-water model of the shallow aquifers below the Delmarva Peninsula USA using the commercial program MVAEM...

  18. Assessing the utility of frequency dependent nudging for reducing biases in biogeochemical models

    NASA Astrophysics Data System (ADS)

    Lagman, Karl B.; Fennel, Katja; Thompson, Keith R.; Bianucci, Laura

    2014-09-01

    Bias errors, resulting from inaccurate boundary and forcing conditions, incorrect model parameterization, etc. are a common problem in environmental models including biogeochemical ocean models. While it is important to correct bias errors wherever possible, it is unlikely that any environmental model will ever be entirely free of such errors. Hence, methods for bias reduction are necessary. A widely used technique for online bias reduction is nudging, where simulated fields are continuously forced toward observations or a climatology. Nudging is robust and easy to implement, but suppresses high-frequency variability and introduces artificial phase shifts. As a solution to this problem Thompson et al. (2006) introduced frequency dependent nudging where nudging occurs only in prescribed frequency bands, typically centered on the mean and the annual cycle. They showed this method to be effective for eddy resolving ocean circulation models. Here we add a stability term to the previous form of frequency dependent nudging which makes the method more robust for non-linear biological models. Then we assess the utility of frequency dependent nudging for biological models by first applying the method to a simple predator-prey model and then to a 1D ocean biogeochemical model. In both cases we only nudge in two frequency bands centered on the mean and the annual cycle, and then assess how well the variability in higher frequency bands is recovered. We evaluate the effectiveness of frequency dependent nudging in comparison to conventional nudging and find significant improvements with the former.

  19. Implementation ambiguity: The fifth element long lost in uncertainty budgets for land biogeochemical modeling

    NASA Astrophysics Data System (ADS)

    Tang, J.; Riley, W. J.

    2015-12-01

    Previous studies have identified four major sources of predictive uncertainty in modeling land biogeochemical (BGC) processes: (1) imperfect initial conditions (e.g., assumption of preindustrial equilibrium); (2) imperfect boundary conditions (e.g., climate forcing data); (3) parameterization (type I equifinality); and (4) model structure (type II equifinality). As if that were not enough to cause substantial sleep loss in modelers, we propose here a fifth element of uncertainty that results from implementation ambiguity that occurs when the model's mathematical description is translated into computational code. We demonstrate the implementation ambiguity using the example of nitrogen down regulation, a necessary process in modeling carbon-climate feedbacks. We show that, depending on common land BGC model interpretations of the governing equations for mineral nitrogen, there are three different implementations of nitrogen down regulation. We coded these three implementations in the ACME land model (ALM), and explored how they lead to different preindustrial and contemporary land biogeochemical states and fluxes. We also show how this implementation ambiguity can lead to different carbon-climate feedback estimates across the RCP scenarios. We conclude by suggesting how to avoid such implementation ambiguity in ESM BGC models.

  20. Benthic-Pelagic Coupling in Biogeochemical and Climate Models: Existing Approaches, Recent developments and Roadblocks

    NASA Astrophysics Data System (ADS)

    Arndt, Sandra

    2016-04-01

    Marine sediments are key components in the Earth System. They host the largest carbon reservoir on Earth, provide the only long term sink for atmospheric CO2, recycle nutrients and represent the most important climate archive. Biogeochemical processes in marine sediments are thus essential for our understanding of the global biogeochemical cycles and climate. They are first and foremost, donor controlled and, thus, driven by the rain of particulate material from the euphotic zone and influenced by the overlying bottom water. Geochemical species may undergo several recycling loops (e.g. authigenic mineral precipitation/dissolution) before they are either buried or diffuse back to the water column. The tightly coupled and complex pelagic and benthic process interplay thus delays recycling flux, significantly modifies the depositional signal and controls the long-term removal of carbon from the ocean-atmosphere system. Despite the importance of this mutual interaction, coupled regional/global biogeochemical models and (paleo)climate models, which are designed to assess and quantify the transformations and fluxes of carbon and nutrients and evaluate their response to past and future perturbations of the climate system either completely neglect marine sediments or incorporate a highly simplified representation of benthic processes. On the other end of the spectrum, coupled, multi-component state-of-the-art early diagenetic models have been successfully developed and applied over the past decades to reproduce observations and quantify sediment-water exchange fluxes, but cannot easily be coupled to pelagic models. The primary constraint here is the high computation cost of simulating all of the essential redox and equilibrium reactions within marine sediments that control carbon burial and benthic recycling fluxes: a barrier that is easily exacerbated if a variety of benthic environments are to be spatially resolved. This presentation provides an integrative overview of

  1. A Coupled Land Surface-Subsurface Biogeochemical Model for Aqueous and Gaseous Nitrogen Losses

    NASA Astrophysics Data System (ADS)

    Gu, C.; Maggi, F.; Riley, W.; Pan, L.; Xu, T.; Oldenburg, C.; Miller, N.

    2008-12-01

    In recent years concern has grown over the contribution of nitrogen (N) fertilizers to nitrate (NOB3PB-P) water pollution and atmospheric pollution of nitrous oxide (NB2BO), nitric oxide (NO), and ammonia (NHB3B). Characterizing the amount and species of N losses is therefore essential in developing a strategy to estimate and mitigate N leaching and emission to the atmosphere. Indeed, transformations of nitrogen depend strongly on water content, soil temperature, and nitrogen concentration. Land surface processes therefore have to be taken into account to properly characterize N biogeochemical cycling. However, most current nitrogen biogeochemical models take the land surface as the upper boundary by lumping the complex processes above the surface as known boundary conditions. In this study, an extant subsurface mechanistic N cycle model (TOUGHREACT-N) was coupled with the community land model (CLM). The resulting coupled model extends the modeling capability of TOUGHREACT-N to include the important energy, momentum, and moisture dynamics provided by CLM. The coupled model showed a significant impact of land-surface diurnal forcing on soil temperature and moisture and on nitrogen fluxes. We also discuss field applications of the model and discuss how temporal dynamics of nitrogen fluxes are affected by land surface processes.

  2. PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Blodau, C.

    2013-08-01

    Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

  3. PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Blodau, C.

    2013-03-01

    Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

  4. Dramatic variability of the carbonate system of the coastal ocean is regulated by physical and biogeochemical processes on multiple timescales

    NASA Astrophysics Data System (ADS)

    Johnson, Z. I.; Hunt, D.

    2013-12-01

    Increased atmospheric carbon dioxide (CO2) from anthropogenic sources is acidifying marine environments with potentially dramatic implications for the physical, chemical and biological functioning of these ecosystems. If current trends continue, mean ocean pH is expected to decrease by ~0.2 units over the next ~50 years. Yet, at the same time there is substantial spatial and temporal variability in pH and other carbon system parameters in the ocean resulting in regions that already exceed long term projected pH changes, suggesting that short-term variability is an important layer of complexity on top of long term acidification. Thus, in order to develop predictions of future climate change impacts including ocean acidification, there is a critical need to characterize the natural range and variability of the marine CO2 system and the mechanisms responsible for this variability. Here we examine pH and dissolved inorganic carbon (DIC) variability at time intervals spanning 1 hour to >1 year in a dynamic coastal marine system to quantify variability of the carbon system at multiple time scales. Daily and seasonal variability of the carbon system is largely driven by temperature, alkalinity and the balance between primary production and respiration, but high frequency variability (hours to days) is further influenced by water mass movement (e.g. tides) and stochastic events (e.g. storms). Both annual variability (~0.3 units) and diurnal variability (~0.1 units) in coastal ocean acidity are similar in magnitude to long term projections associated with increasing atmospheric CO2 and their drivers highlight the importance of characterizing the complete carbonate system (and not just pH). Short term variability of ocean carbon parameters may already exert significant pressure on some coastal marine ecosystems with implications for ecology, biogeochemistry and evolution and this shorter term variability layers additive effects and complexity, including extreme values, on

  5. Parameter estimation and uncertainty quantification in a biogeochemical model using optimal experimental design methods

    NASA Astrophysics Data System (ADS)

    Reimer, Joscha; Piwonski, Jaroslaw; Slawig, Thomas

    2016-04-01

    The statistical significance of any model-data comparison strongly depends on the quality of the used data and the criterion used to measure the model-to-data misfit. The statistical properties (such as mean values, variances and covariances) of the data should be taken into account by choosing a criterion as, e.g., ordinary, weighted or generalized least squares. Moreover, the criterion can be restricted onto regions or model quantities which are of special interest. This choice influences the quality of the model output (also for not measured quantities) and the results of a parameter estimation or optimization process. We have estimated the parameters of a three-dimensional and time-dependent marine biogeochemical model describing the phosphorus cycle in the ocean. For this purpose, we have developed a statistical model for measurements of phosphate and dissolved organic phosphorus. This statistical model includes variances and correlations varying with time and location of the measurements. We compared the obtained estimations of model output and parameters for different criteria. Another question is if (and which) further measurements would increase the model's quality at all. Using experimental design criteria, the information content of measurements can be quantified. This may refer to the uncertainty in unknown model parameters as well as the uncertainty regarding which model is closer to reality. By (another) optimization, optimal measurement properties such as locations, time instants and quantities to be measured can be identified. We have optimized such properties for additional measurement for the parameter estimation of the marine biogeochemical model. For this purpose, we have quantified the uncertainty in the optimal model parameters and the model output itself regarding the uncertainty in the measurement data using the (Fisher) information matrix. Furthermore, we have calculated the uncertainty reduction by additional measurements depending on time

  6. A new implementation of the Biogeochemical Flux Model in sea ice

    NASA Astrophysics Data System (ADS)

    Tedesco, L.; Vichi, M.

    2009-04-01

    The Biogeochemical Flux Model (BFM) is a direct descendent of the European Regional Seas Ecosystem Model (ERSEM) and it has been widely used and validated among the scientific community. The BFM view of the of the marine ecosystem is based upon the recognition that the major ecological functions of producers, decomposers and consumers and their specific trophic interactions can be expressed in terms of material flows of basic elements. The concentration and characteristics of organic and inorganic compounds are thus seen under a stoichiometrical perspective. This functional approach brings to the definition of Chemical Functional Families (CFF) and Living Functional Groups (LFG). The BFM is thus a set of biogeochemical equations describing the cycling of carbon, the macro-nutrients and oxygen through the lower trophic levels of marine ecosystems. A Sea-Ice system has now been implemented in the BFM and the new BFM-SI consists of three new LFG (sea ice algae, heterotrophic zooplankton, bacterioplankton), one new non-living organic functional group (sea ice DOM and POM) and two new inorganic functional groups: dissolved gases (sea ice CO2 and O2) and four nutrients (sea ice PO4, NH3, NO3 and SiO4). The innovative approach consists in simulating the biogeochemistry of the sea ice Biologically-Active-Layer (BAL), where the majority of the biomass (bottom communities) concentrates. The BFM-SI requires the physical properties of the BAL in order to be able to simulate the physiological and ecological response of the biological community to the physical environment. This is currently done by using an Enhanced 1-D thermo-halodynamic Sea Ice Model (ESIM2), developed to be suitable for biogeochemical studies. Since the biogeochemistry of sea ice is largely unknown, the BFM-SI is a useful tool that allow us to test hypotheses on the functioning of the sea ice ecosystem. By initially setting the sea ice community as having the same characteristics than the pelagic community

  7. Use of Combined Biogeochemical Model Approaches and Empirical Data to Assess Critical Loads of Nitrogen

    SciTech Connect

    Fenn, Mark E.; Driscoll, Charles; Zhou, Qingtao; Rao, Leela E.; Meixner, Tom; Allen, Edith B.; Yuan, Fengming; Sullivan, Timothy J.

    2015-01-01

    Empirical and dynamic biogeochemical modelling are complementary approaches for determining the critical load (CL) of atmospheric nitrogen (N) or other constituent deposition that an ecosystem can tolerate without causing ecological harm. The greatest benefits are obtained when these approaches are used in combination. Confounding environmental factors can complicate the determination of empirical CLs across depositional gradients, while the experimental application of N amendments for estimating the CL does not realistically mimic the effects of chronic atmospheric N deposition. Biogeochemical and vegetation simulation models can provide CL estimates and valuable ecosystem response information, allowing for past and future scenario testing with various combinations of environmental factors, pollutants, pollutant control options, land management, and ecosystem response parameters. Even so, models are fundamentally gross simplifications of the real ecosystems they attempt to simulate. Empirical approaches are vital as a check on simulations and CL estimates, to parameterize models, and to elucidate mechanisms and responses under real world conditions. In this chapter, we provide examples of empirical and modelled N CL approaches in ecosystems from three regions of the United States: mixed conifer forest, desert scrub and pinyon- juniper woodland in California; alpine catchments in the Rocky Mountains; and lakes in the Adirondack region of New York state.

  8. Investigating the initial stages of soil formation in glacier forefields using the new biogeochemical model: SHIMMER

    NASA Astrophysics Data System (ADS)

    Bradley, James; Anesio, Alexandre; Arndt, Sandra; Sabacka, Marie; Barker, Gary; Benning, Liane; Blacker, Joshua; Singarayer, Joy; Tranter, Martyn; Yallop, Marian

    2016-04-01

    Glaciers and ice sheets in Polar and alpine regions are retreating in response to recent climate warming, exposing terrestrial ecosystems that have been locked under the ice for thousands of years. Exposed soils exhibit successional characteristics that can be characterised using a chronosequence approach. Decades of empirical research in glacier forefields has shown that soils are quickly colonised by microbes which drive biogeochemical cycling of elements and affect soil properties including nutrient concentrations, carbon fluxes and soil stability (Bradley et al, 2014). The characterisation of these soils is important for our understanding of the cycling of organic matter under extreme environmental and nutrient limiting conditions, and their potential contribution to global biogeochemical cycles. This is particularly important as these new areas will become more geographically expansive with continued ice retreat. SHIMMER (Soil biogeocHemIcal Model of Microbial Ecosystem Response) (Bradley et al, 2015) is a new mathematical model that simulates biogeochemical and microbial dynamics in glacier forefields. The model captures, explores and predicts the growth of different microbial groups (classified by function), and the associated cycling of carbon, nitrogen and phosphorus along a chronosequence. SHIMMER improves typical soil model formulations by including explicit representation of microbial dynamics, and those processes which are shown to be important for glacier forefields. For example, we categorise microbial groups by function to represent the diversity of soil microbial communities, and include the different metabolic needs and physiological pathways of microbial organisms commonly found in glacier forefields (e.g. microbes derived from underneath the glacier, typical soil bacteria, and microbes that can fix atmospheric nitrogen and assimilate soil nitrogen). Here, we present data from a study where we integrated modelling using SHIMMER with empirical

  9. Ocean biogeochemical response to phytoplankton-light feedback in a global model

    NASA Astrophysics Data System (ADS)

    Manizza, Manfredi; Le QuéRé, Corinne; Watson, Andrew J.; Buitenhuis, Erik T.

    2008-10-01

    Oceanic phytoplankton, absorbing solar radiation, can influence the bio-optical properties of seawater and hence upper ocean physics. We include this process in a global ocean general circulation model (OGCM) coupled to a dynamic green ocean model (DGOM) based on multiple plankton functional types (PFT). We not only study the impact of this process on ocean physics but we also explore the biogeochemical response due to this biophysical feedback. The phytoplankton-light feedback (PLF) impacts the dynamics of the upper tropical and subtropical oceans. The change in circulation enhances both the vertical supply in the tropics and the lateral supply of nutrients from the tropics to the subtropics boosting the subtropical productivity by up to 60 gC m-2 a-1. Physical changes, due to the PLF, impact on light and nutrient availability causing shifts in the ocean ecosystems. In the extratropics, increased stratification favors calcifiers (by up to ˜8%) at the expense of mixed phytoplankton. In the Southern Ocean, silicifiers increase their biomass (by up to ˜10%) because of the combined alleviation of iron and light limitation. The PLF has a small effect globally on air-sea fluxes of carbon dioxide (CO2, 72 TmolC a-1 outgassing) and oxygen (O2, 46 TmolO2 a-1 ingassing) because changes in biogeochemical processes (primary production, biogenic calcification, and export production) highly vary regionally and can also oppose each other. From our study it emerges that the main impact of the PLF is an amplification of the seasonal cycle of physical and biogeochemical properties of the high-latitude oceans mostly driven by the amplification of the SST seasonal cycle.

  10. A new biogeochemical model to simulate regional scale carbon emission from lakes, ponds and wetlands

    NASA Astrophysics Data System (ADS)

    Bayer, Tina; Brakebusch, Matthias; Gustafsson, Erik; Beer, Christian

    2016-04-01

    Small aquatic systems are receiving increasing attention for their role in global carbon cycling. For instance, lakes and ponds in permafrost are net emitters of carbon to the atmosphere, and their capacity to process and emit carbon is significant on a landscape scale, with a global flux of 8-103 Tg methane per year which amounts to 5%-30% of all natural methane emissions (Bastviken et al 2011). However, due to the spatial and temporal highly localised character of freshwater methane emissions, fluxes remain poorly qualified and are difficult to upscale based on field data alone. While many models exist to model carbon cycling in individual lakes and ponds, we perceived a lack of models that can work on a larger scale, over a range of latitudes, and simulate regional carbon emission from a large number of lakes, ponds and wetlands. Therefore our objective was to develop a model that can simulate carbon dioxide and methane emission from freshwaters on a regional scale. Our resulting model provides an additional tool to assess current aquatic carbon emissions as well as project future responses to changes in climatic drivers. To this effect, we have combined an existing large-scale hydrological model (the Variable Infiltration Capacity Macroscale Hydrologic Model (VIC), Liang & Lettenmaier 1994), an aquatic biogeochemical model (BALTSEM, Savchuk et al., 2012; Gustafsson et al., 2014) and developed a new methane module for lakes. The resulting new process-based biogeochemical model is designed to model aquatic carbon emission on a regional scale, and to perform well in high-latitude environments. Our model includes carbon, oxygen and nutrient cycling in lake water and sediments, primary production and methanogenesis. Results of calibration and validation of the model in two catchments (Torne-Kalix in Northern Sweden and of a large arctic river catchment) will be presented.

  11. Characterizing biogeochemical processes in the hyporheic zone using flume experiments and reactive transport modeling

    NASA Astrophysics Data System (ADS)

    Quick, A. M.; Reeder, W. J.; Farrell, T. B.; Feris, K. P.; Tonina, D.; Benner, S. G.

    2015-12-01

    The hyporheic zones of streams are hotspots of biogeochemical cycling, where reactants from surface water and groundwater are continually brought into contact with microbial populations on the surfaces of stream sediments and reaction products are removed by hyporheic flow and degassing. Using large flume experiments we have documented the complex redox dynamics associated with dune-scale hyporheic flow. Observations, coupled with reactive transport modeling, provide insight into how flow dictates spatio-temporal distribution of redox reactions and the associated consumption and production of reactants and products. Dune hyporheic flow was experimentally produced by maintaining control over flow rates, slopes, sediment grain size, bedform geomorphology, and organic carbon content. An extensive in-situ monitoring array combined with sampling events over time elucidated redox-sensitive processes including constraints on the spatial distribution and magnitude of aerobic respiration, organic carbon consumption, sulfide deposition, and denitrification. Reactive transport modeling reveals further insight into the influence of system geometry and reaction rate. As an example application of the model, the relationship between residence times and reaction rates may be used to generate Damköhler numbers that are related to biogeochemical processes, such as the potential of streambed morphology and nitrate loading to influence production of the greenhouse gas nitrous oxide via incomplete denitrification.

  12. Modeling carbon cycle responses to tree mortality: linking microbial and biogeochemical changes

    NASA Astrophysics Data System (ADS)

    Moore, D. J.; Trahan, N. A.; Dynes, E. L.; Zobitz, J. M.; Gallery, R.

    2013-12-01

    Amid a worldwide increase in tree mortality, mountain pine beetles (Dendroctonus ponderosae Hopkins) have killed billions of trees from Mexico to Alaska in the last 13 years. This mortality is predicted to influence important carbon, water and energy balance feedbacks on the Earth system. We studied changes in soil biogeochemical cycling and microbial community structure after tree mortality. We show, using a decade long chronosequence, that tree mortality causes no increase in total respiration from local to watershed scales, with corresponding changes in biogeochemical pools of nitrogen and phosphorus. We also found comparable declines in both gross primary productivity and respiration suggesting little change in net flux. We tested the mechanisms controlling these patterns using an ecosystem model; contrasting a simplified microbial subroutine with a 'dead soil' model. We coupled our modeling work with direct measurements of microbial biomass, enzyme kinetics and community structure. The transitory recovery of respiration 6-7 years after mortality was associated with increased microbial biomass, increased incorporation of leaf litter carbon into soil organic matter, and was followed by a secondary decline in respiration during years 8-10. Our findings are consistent with the mechanism of reduced input of new carbon causing a decline in microbial biomass rather than an increased output of older carbon.

  13. How to `Elk-test' biogeochemical models in a data rich world? (Invited)

    NASA Astrophysics Data System (ADS)

    Reichstein, M.; Ciais, P.; Seneviratne, S. I.; Carvalhais, N.; Dalmonech, D.; Jung, M.; Luo, Y.; Mahecha, M. D.; Moffat, A. M.; Tomelleri, E.; Zaehle, S.

    2010-12-01

    Process-oriented biogeochemical models are a primary tool that has been used to project future states of climate and ecosystems in the earth system in response to anthropogenic and other forcing, and receive tremendous attention also in the context us the planned assessment report AR5 by the IPCC. However, model intercomparison and data-model comparison studies indicate large uncertainties regarding predictions of global interactions between atmosphere and biosphere. Rigorous scientific testing of these models is essential but very challenging, largely because neither it is technically and ethically possible to perform global earth-scale experiments, nor do we have replicate Earths for hypothesis testing. Hence, model evaluations have to rely on monitoring data such as ecological observation networks, global remote sensing or short-term and small-scale experiments. Here, we critically examine strategies of how model evaluations have been performed with a particular emphasis on terrestrial ecosystems. Often weak ‘validations’ are being presented which do not take advantage of all the relevant information in the observed data, but also apparent falsifications are made, that are hampered by a confusion of system processes with system behavior. We propose that a stronger integration of recent advances in pattern-oriented and system-oriented methodologies will lead to more satisfying earth system model evaluation and development, and show a few enlightening examples from terrestrial biogeochemical modeling and other disciplines. Moreover it is crucial to take advantage of the multidimensional nature of arising earth observation data sets which should be matched by models simultaneously, instead of relying on univariate simple comparisons. A new critical model evaluation is needed to improve future IPCC assessments in order to reduce uncertainties by distinguishing plausible simulation trajectories from fairy tales.

  14. Biogeochemical modeling of phosphorus cycling in the ocean: response to long-term perturbations

    NASA Astrophysics Data System (ADS)

    Palastanga, Virginia; Slomp, Caroline; Heinze, Christoph; Winguth, Arne

    2010-05-01

    Phosphorus (P) is likely the limiting nutrient for marine primary productivity on geological time scales. Therefore, insight into the mechanisms that control P cycling and burial in marine sediments is of importance for our understanding of global biogeochemical cycling and climate. Here, we use a version of the Hamburg Oceanic Carbon Cycle biogeochemical ocean model (HAMOCC2) expanded with the sedimentary P cycle, i.e. burial of organic P and formation and burial of Fe-oxide bound P and authigenic Ca-P minerals. We also include anaerobic degradation of organic matter in the sediment and a description of the oceanic Fe cycle which takes into account aeolian input and scavenging of iron onto sinking particles. For present-day climate forcing, the model predictions for the solid forms of sediment P and benthic P fluxes are compared to observations from global surface sediments. In a sensitivity study, the relationships between primary productivity, nutrient cycling, and organic C and P burial are analyzed for scenarios of increased input of P from rivers as well as for changes in aeolian deposition and circulation forcing that represent Last Glacial Maximum conditions.

  15. A Thermodynamically-consistent FBA-based Approach to Biogeochemical Reaction Modeling

    NASA Astrophysics Data System (ADS)

    Shapiro, B.; Jin, Q.

    2015-12-01

    Microbial rates are critical to understanding biogeochemical processes in natural environments. Recently, flux balance analysis (FBA) has been applied to predict microbial rates in aquifers and other settings. FBA is a genome-scale constraint-based modeling approach that computes metabolic rates and other phenotypes of microorganisms. This approach requires a prior knowledge of substrate uptake rates, which is not available for most natural microbes. Here we propose to constrain substrate uptake rates on the basis of microbial kinetics. Specifically, we calculate rates of respiration (and fermentation) using a revised Monod equation; this equation accounts for both the kinetics and thermodynamics of microbial catabolism. Substrate uptake rates are then computed from the rates of respiration, and applied to FBA to predict rates of microbial growth. We implemented this method by linking two software tools, PHREEQC and COBRA Toolbox. We applied this method to acetotrophic methanogenesis by Methanosarcina barkeri, and compared the simulation results to previous laboratory observations. The new method constrains acetate uptake by accounting for the kinetics and thermodynamics of methanogenesis, and predicted well the observations of previous experiments. In comparison, traditional methods of dynamic-FBA constrain acetate uptake on the basis of enzyme kinetics, and failed to reproduce the experimental results. These results show that microbial rate laws may provide a better constraint than enzyme kinetics for applying FBA to biogeochemical reaction modeling.

  16. In Situ Biostimulation at a Former Uranium Mill Tailings Site: Multicomponent Biogeochemical Reactive Transport Modeling

    NASA Astrophysics Data System (ADS)

    Yabusaki, S.; Fang, Y.; Long, P.

    2005-12-01

    In situ biostimulation at a Former Uranium Mill Tailings Site: Multicomponent Biogeochemical Reactive Transport Modeling Field experiments conducted at a former uranium mill tailings site in western Colorado are being used to investigate microbially mediated immobilization of uranium as a potential future remediation option for such sites. While the general principle of biostimulating microbial communities to reduce aqueous hexavalent uranium to immobile uraninite has been demonstrated in the laboratory and field, the ability to predictably engineer long lasting immobilization will require a more complete understanding of field-scale processes and properties. For this study, numerical simulation of the flow field, geochemical conditions, and micriobial communities is used to interpret field-scale biogeochemical reactive transport observed during experiments performed in 2002 to 2004. One key issue is identifying bioavailable Fe(III) oxide, which is the principal electron acceptor utilized by the acetate- oxidizing Geobacter sp. These organisms are responsible for uranium bioreduction that results in the removal of sufficient U(VI) to lower uranium groundwater concentrations to at or near applicable standards. The depletion of bioavailable Fe(III) leads to succession by sulfate reducers that are considerably less effective at uranium bioreduction. An important modeling consideration are the abiotic reactions (e.g., mineral precipitation and dissolution, aqueous and surface complexation) involving the Fe(II) and sulfide produced during biostimulation. These components, strongly associated with the solid phases, may play an important role in the evolving reactivity of the mineral surfaces that are likely to impact long-term uranium immobilization.

  17. Empirical approaches to more accurately predict benthic-pelagic coupling in biogeochemical ocean models

    NASA Astrophysics Data System (ADS)

    Dale, Andy; Stolpovsky, Konstantin; Wallmann, Klaus

    2016-04-01

    The recycling and burial of biogenic material in the sea floor plays a key role in the regulation of ocean chemistry. Proper consideration of these processes in ocean biogeochemical models is becoming increasingly recognized as an important step in model validation and prediction. However, the rate of organic matter remineralization in sediments and the benthic flux of redox-sensitive elements are difficult to predict a priori. In this communication, examples of empirical benthic flux models that can be coupled to earth system models to predict sediment-water exchange in the open ocean are presented. Large uncertainties hindering further progress in this field include knowledge of the reactivity of organic carbon reaching the sediment, the importance of episodic variability in bottom water chemistry and particle rain rates (for both the deep-sea and margins) and the role of benthic fauna. How do we meet the challenge?

  18. Geoelectrical measurement and modeling of biogeochemical breakthrough behavior during microbial activity

    USGS Publications Warehouse

    Slater, L.D.; Day-Lewis, F. D.; Ntarlagiannis, D.; O'Brien, M.; Yee, N.

    2009-01-01

    We recorded bulk electrical conductivity (??b) along a soil column during microbially-mediated selenite oxyanion reduction. Effluent fluid electrical conductivity and early time ??b were modeled according to classic advectivedispersive transport of the nutrient medium. However, ??b along the column exhibited strongly bimodal breakthrough which cannot be explained by changes in the electrical conductivity of the pore fluid. We model the anomalous breakthrough by adding a conduction path in parallel with the fluid phase, with a time dependence described by a microbial population-dynamics model. We incorporate a delay time to show that breakthrough curves along the column satisfy the same growth model parameters and offer a possible explanation based on biomass-limited growth that is delayed with distance from influent of the nutrient medium. Although the mechanism causing conductivity enhancement in the presence of biomass is uncertain, our results strongly , suggest that biogeochemical breakthrough curves have been captured in geoelectrical datasets. Copyright 2009 by the American Geophysical Union.

  19. Biogeochemical and Hydrological Controls on Mercury and Methylmercury in First Order Coastal Plain Watersheds of the Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Heyes, A.; Gilmour, C. C.; Bell, J. T.; Butera, D.; McBurney, A. W.

    2015-12-01

    Over the past 7 years we made use of the long-term research site at the Smithsonian Environmental Research Center (SERC) in central Maryland to study the fluxes of mercury (Hg) and methylmercury (MeHg) in three small first-order mid-Atlantic coastal plain watersheds. One watershed is entirely forested, one watershed is primarily agriculture with a forested stream buffer, and one watershed is mixed land use but contains a beaver produced wetland pond. Our initial goals were to assess watershed Hg yields in the mid-Atlantic and to establish a baseline prior to implementation of Hg emissions controls. All three studied watersheds produced relatively high yields of Hg, with the greatest yield coming from the forested watershed. Our initial evaluation of three watersheds showed that MeHg production and flux could also be high, but varied dramatically among watersheds and across years and seasons. During each year we observed episodic MeHg production in the spring and sometimes during prolonged high-flow storm events in the fall. The observed spring maxima of MeHg release coincided with development of anoxia in riparian groundwater. MeHg accumulation in riparian groundwater began once nitrate was depleted and either iron accumulation or sulfate depletion of groundwater began. We propose the presence of nitrate was modulating MeHg production through the suppression of sulfate and iron reducers and perhaps methanogens. As sulfate is not limiting in any of the watersheds owing to the sediments marine origin, we hypothesize the depletion of nitrate allows sulfate reducing bacteria to now utilize available carbon. Although wetlands are generally thought of as the primary zones of MeHg production in watersheds, shallow riparian groundwaters very close to the stream appear to play that role in SERC Coastal Plain watersheds. We hypothesize that the balance between nitrate, sulfate and other microbial electron acceptors in watersheds is a major control on MeHg production. Land

  20. Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models

    SciTech Connect

    Sarmiento, Jorge L.; Gnanadesikan, Anand; Gruber, Nicolas; Jin, Xin; Armstrong, Robert

    2007-06-21

    This final report summarizes research undertaken collaboratively between Princeton University, the NOAA Geophysical Fluid Dynamics Laboratory on the Princeton University campus, the State University of New York at Stony Brook, and the University of California, Los Angeles between September 1, 2000, and November 30, 2006, to do fundamental research on ocean iron fertilization as a means to enhance the net oceanic uptake of CO2 from the atmosphere. The approach we proposed was to develop and apply a suite of coupled physical-ecological-biogeochemical models in order to (i) determine to what extent enhanced carbon fixation from iron fertilization will lead to an increase in the oceanic uptake of atmospheric CO2 and how long this carbon will remain sequestered (efficiency), and (ii) examine the changes in ocean ecology and natural biogeochemical cycles resulting from iron fertilization (consequences). The award was funded in two separate three-year installments: September 1, 2000 to November 30, 2003, for a project entitled “Ocean carbon sequestration by fertilization: An integrated biogeochemical assessment.” A final report was submitted for this at the end of 2003 and is included here as Appendix 1; and, December 1, 2003 to November 30, 2006, for a follow-on project under the same grant number entitled “Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models.” This report focuses primarily on the progress we made during the second period of funding subsequent to the work reported on in Appendix 1. When we began this project, we were thinking almost exclusively in terms of long-term fertilization over large regions of the ocean such as the Southern Ocean, with much of our focus being on how ocean circulation and biogeochemical cycling would interact to control the response to a given fertilization scenario. Our research on these types of scenarios, which was carried out largely during the

  1. Numerical modeling of watershed-scale radiocesium transport coupled with biogeochemical cycling in forests

    NASA Astrophysics Data System (ADS)

    Mori, K.; Tada, K.; Tawara, Y.; Tosaka, H.; Ohno, K.; Asami, M.; Kosaka, K.

    2015-12-01

    Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, intensive monitoring and modeling works on radionuclide transfer in environment have been carried out. Although Cesium (Cs) concentration has been attenuating due to both physical and environmental half-life (i.e., wash-off by water and sediment), the attenuation rate depends clearly on the type of land use and land cover. In the Fukushima case, studying the migration in forest land use is important for predicting the long-term behavior of Cs because most of the contaminated region is covered by forests. Atmospheric fallout is characterized by complicated behavior in biogeochemical cycle in forests which can be described by biotic/abiotic interactions between many components. In developing conceptual and mathematical model on Cs transfer in forest ecosystem, defining the dominant components and their interactions are crucial issues (BIOMASS, 1997-2001). However, the modeling of fate and transport in geosphere after Cs exports from the forest ecosystem is often ignored. An integrated watershed modeling for simulating spatiotemporal redistribution of Cs that includes the entire region from source to mouth and surface to subsurface, has been recently developed. Since the deposited Cs can migrate due to water and sediment movement, the different species (i.e., dissolved and suspended) and their interactions are key issues in the modeling. However, the initial inventory as source-term was simplified to be homogeneous and time-independent, and biogeochemical cycle in forests was not explicitly considered. Consequently, it was difficult to evaluate the regionally-inherent characteristics which differ according to land uses, even if the model was well calibrated. In this study, we combine the different advantages in modeling of forest ecosystem and watershed. This enable to include more realistic Cs deposition and time series of inventory can be forced over the land surface. These processes are integrated

  2. Biogeochemical mass balances in a turbid tropical reservoir. Field data and modelling approach

    NASA Astrophysics Data System (ADS)

    Phuong Doan, Thuy Kim; Némery, Julien; Gratiot, Nicolas; Schmid, Martin

    2014-05-01

    The turbid tropical Cointzio reservoir, located in the Trans Mexican Volcanic Belt (TMVB), behaves as a warm monomictic water body (area = 6 km2, capacity 66 Mm3, residence time ~ 1 year). It is strategic for the drinking water supply of the city of Morelia, capital of the state of Michoacán, and for downstream irrigation during the dry season. This reservoir is a perfect example of a human-impacted system since its watershed is mainly composed of degraded volcanic soils and is subjected to high erosion processes and agricultural loss. The reservoir is threatened by sediment accumulation and nutrients originating from untreated waters in the upstream watershed. The high content of very fine clay particles and the lack of water treatment plants lead to serious episodes of eutrophication (up to 70 μg chl. a L-1), high levels of turbidity (Secchi depth < 30 cm) and a long period of anoxia (from May to October). Based on intensive field measurements in 2009 (deposited sediment, benthic chamber, water vertical profiles, reservoir inflow and outflow) we determined suspended sediment (SS), carbon (C), nitrogen (N) and phosphorus (P) mass balances. Watershed SS yields were estimated at 35 t km2 y-1 of which 89-92 % were trapped in the Cointzio reservoir. As a consequence the reservoir has already lost 25 % of its initial storage capacity since its construction in 1940. Nutrient mass balances showed that 50 % and 46 % of incoming P and N were retained by sedimentation, and mainly eliminated through denitrification respectively. Removal of C by 30 % was also observed both by sedimentation and through gas emission. To complete field data analyses we examined the ability of vertical one dimensional (1DV) numerical models (Aquasim biogeochemical model coupled with k-ɛ mixing model) to reproduce the main biogeochemical cycles in the Cointzio reservoir. The model can describe all the mineralization processes both in the water column and in the sediment. The values of the

  3. One-dimensional model for biogeochemical interactions and permeability reduction in soils during leachate permeation

    NASA Astrophysics Data System (ADS)

    Singhal, Naresh; Islam, Jahangir

    2008-02-01

    This paper uses the findings from a column study to develop a reactive model for exploring the interactions occurring in leachate-contaminated soils. The changes occurring in the concentrations of acetic acid, sulphate, suspended and attached biomass, Fe(II), Mn(II), calcium, carbonate ions, and pH in the column are assessed. The mathematical model considers geochemical equilibrium, kinetic biodegradation, precipitation-dissolution reactions, bacterial and substrate transport, and permeability reduction arising from bacterial growth and gas production. A two-step sequential operator splitting method is used to solve the coupled transport and biogeochemical reaction equations. The model gives satisfactory fits to experimental data and the simulations show that the transport of metals in soil is controlled by multiple competing biotic and abiotic reactions. These findings suggest that bioaccumulation and gas formation, compared to chemical precipitation, have a larger influence on hydraulic conductivity reduction.

  4. Biotic Interactions in Microbial Communities as Modulators of Biogeochemical Processes: Methanotrophy as a Model System

    PubMed Central

    Ho, Adrian; Angel, Roey; Veraart, Annelies J.; Daebeler, Anne; Jia, Zhongjun; Kim, Sang Yoon; Kerckhof, Frederiek-Maarten; Boon, Nico; Bodelier, Paul L. E.

    2016-01-01

    Microbial interaction is an integral component of microbial ecology studies, yet the role, extent, and relevance of microbial interaction in community functioning remains unclear, particularly in the context of global biogeochemical cycles. While many studies have shed light on the physico-chemical cues affecting specific processes, (micro)biotic controls and interactions potentially steering microbial communities leading to altered functioning are less known. Yet, recent accumulating evidence suggests that the concerted actions of a community can be significantly different from the combined effects of individual microorganisms, giving rise to emergent properties. Here, we exemplify the importance of microbial interaction for ecosystem processes by analysis of a reasonably well-understood microbial guild, namely, aerobic methane-oxidizing bacteria (MOB). We reviewed the literature which provided compelling evidence for the relevance of microbial interaction in modulating methane oxidation. Support for microbial associations within methane-fed communities is sought by a re-analysis of literature data derived from stable isotope probing studies of various complex environmental settings. Putative positive interactions between active MOB and other microbes were assessed by a correlation network-based analysis with datasets covering diverse environments where closely interacting members of a consortium can potentially alter the methane oxidation activity. Although, methanotrophy is used as a model system, the fundamentals of our postulations may be applicable to other microbial guilds mediating other biogeochemical processes. PMID:27602021

  5. Biotic Interactions in Microbial Communities as Modulators of Biogeochemical Processes: Methanotrophy as a Model System.

    PubMed

    Ho, Adrian; Angel, Roey; Veraart, Annelies J; Daebeler, Anne; Jia, Zhongjun; Kim, Sang Yoon; Kerckhof, Frederiek-Maarten; Boon, Nico; Bodelier, Paul L E

    2016-01-01

    Microbial interaction is an integral component of microbial ecology studies, yet the role, extent, and relevance of microbial interaction in community functioning remains unclear, particularly in the context of global biogeochemical cycles. While many studies have shed light on the physico-chemical cues affecting specific processes, (micro)biotic controls and interactions potentially steering microbial communities leading to altered functioning are less known. Yet, recent accumulating evidence suggests that the concerted actions of a community can be significantly different from the combined effects of individual microorganisms, giving rise to emergent properties. Here, we exemplify the importance of microbial interaction for ecosystem processes by analysis of a reasonably well-understood microbial guild, namely, aerobic methane-oxidizing bacteria (MOB). We reviewed the literature which provided compelling evidence for the relevance of microbial interaction in modulating methane oxidation. Support for microbial associations within methane-fed communities is sought by a re-analysis of literature data derived from stable isotope probing studies of various complex environmental settings. Putative positive interactions between active MOB and other microbes were assessed by a correlation network-based analysis with datasets covering diverse environments where closely interacting members of a consortium can potentially alter the methane oxidation activity. Although, methanotrophy is used as a model system, the fundamentals of our postulations may be applicable to other microbial guilds mediating other biogeochemical processes. PMID:27602021

  6. Simulating temporal variations of nitrogen losses in river networks with a dynamic transport model unravels the coupled effects of hydrological and biogeochemical processes

    SciTech Connect

    Mulholland, Patrick J; Alexander, Richard; Bohlke, John; Boyer, Elizabeth; Harvey, Judson; Seitzinger, Sybil; Tobias, Craig; Tonitto, Christina; Wollheim, Wilfred

    2009-01-01

    The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction of nitrogen in streamflow is removed to the atmosphere via denitrification with the remainder exported in streamflow as nitrogen loads. At the watershed scale, there is a keen interest in understanding the factors that control the fate of nitrogen throughout the stream channel network, with particular attention to the processes that deliver large nitrogen loads to sensitive coastal ecosystems. We use a dynamic stream transport model to assess biogeochemical (nitrate loadings, concentration, temperature) and hydrological (discharge, depth, velocity) effects on reach-scale denitrification and nitrate removal in the river networks of two watersheds having widely differing levels of nitrate enrichment but nearly identical discharges. Stream denitrification is estimated by regression as a nonlinear function of nitrate concentration, streamflow, and temperature, using more than 300 published measurements from a variety of US streams. These relations are used in the stream transport model to characterize nitrate dynamics related to denitrification at a monthly time scale in the stream reaches of the two watersheds. Results indicate that the nitrate removal efficiency of streams, as measured by the percentage of the stream nitrate flux removed via denitrification per unit length of channel, is appreciably reduced during months with high discharge and nitrate flux and increases during months of low-discharge and flux. Biogeochemical factors, including land use, nitrate inputs, and stream concentrations, are a major control on reach-scale denitrification, evidenced by the disproportionately lower nitrate removal efficiency in streams of the highly nitrate-enriched watershed as compared with that in similarly sized streams in the less nitrate-enriched watershed. Sensitivity analyses reveal that these important biogeochemical factors and physical hydrological factors contribute nearly

  7. Marine regime shifts in ocean biogeochemical models: a case study in the Gulf of Alaska

    NASA Astrophysics Data System (ADS)

    Beaulieu, Claudie; Cole, Harriet; Henson, Stephanie; Yool, Andrew; Anderson, Tom; de Mora, Lee; Buitenhuis, Erik T.; Butenschön, Momme; Totterdell, Ian J.; Icarus Allen, J.

    2016-08-01

    Regime shifts have been reported in many marine ecosystems, and are often expressed as an abrupt change occurring in multiple physical and biological components of the system. In the Gulf of Alaska, a regime shift in the late 1970s was observed, indicated by an abrupt increase in sea surface temperature and major shifts in the catch of many fish species. A thorough understanding of the extent and mechanisms leading to such regime shifts is challenged by data paucity in time and space. We investigate the ability of a suite of ocean biogeochemistry models of varying complexity to simulate regime shifts in the Gulf of Alaska by examining the presence of abrupt changes in time series of physical variables (sea surface temperature and mixed-layer depth), nutrients and biological variables (chlorophyll, primary productivity and plankton biomass) using change-point analysis. Our results show that some ocean biogeochemical models are capable of simulating the late 1970s shift, manifested as an abrupt increase in sea surface temperature followed by an abrupt decrease in nutrients and biological productivity. Models from low to intermediate complexity simulate an abrupt transition in the late 1970s (i.e. a significant shift from one year to the next) while the transition is smoother in higher complexity models. Our study demonstrates that ocean biogeochemical models can successfully simulate regime shifts in the Gulf of Alaska region. These models can therefore be considered useful tools to enhance our understanding of how changes in physical conditions are propagated from lower to upper trophic levels.

  8. Evaluation of Boundless Biogeochemical Cycle through Development of Process-Based Eco-Hydrological and Biogeochemical Cycle Model to Incorporate Terrestrial-Aquatic Continuum

    NASA Astrophysics Data System (ADS)

    Nakayama, T.; Maksyutov, S. S.

    2014-12-01

    Inland water might act as important transport pathway for continental biogeochemical cycle although its contribution has remained uncertain yet due to a paucity of data (Battin et al. 2009). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which incorporates surface-groundwater interactions, includes up- and down-scaling processes between local-regional-global scales, and can simulate iteratively nonlinear feedback between hydrologic-geomorphic-ecological processes. Because NICE incorporates 3-D groundwater sub-model and expands from previous 1- or 2-D or steady state, the model can simulate the lateral transport pronounced at steeper-slope or riparian/floodplain with surface-groundwater connectivity. River discharge and groundwater level simulated by NICE agreed reasonably with those in previous researches (Niu et al., 2007; Fan et al., 2013) and extended to clarify lateral subsurface also has important role on global hydrologic cycle (Nakayama, 2011b; Nakayama and Shankman, 2013b) though the resolution was coarser. NICE was further developed to incorporate biogeochemical cycle including reaction between inorganic and organic carbons in terrestrial and aquatic ecosystems. The missing role of carbon cycle simulated by NICE, for example, CO2 evasion from inland water (global total flux was estimated as about 1.0 PgC/yr), was relatively in good agreement in that estimated by empirical relation using previous pCO2 data (Aufdenkampe et al., 2011; Laruelle et al., 2013). The model would play important role in identification of greenhouse gas balance of the biosphere and spatio-temporal hot spots, and bridging gap between top-down and bottom-up approaches (Cole et al. 2007; Frei et al. 2012).

  9. Marine regime shifts in ocean biogeochemical models: a case study in the Gulf of Alaska

    NASA Astrophysics Data System (ADS)

    Beaulieu, C.; Cole, H.; Henson, S.; Yool, A.; Anderson, T. R.; de Mora, L.; Buitenhuis, E. T.; Butenschön, M.; Totterdell, I. J.; Allen, J. I.

    2015-08-01

    Regime shifts have been reported in many marine ecosystems, and are often expressed as an abrupt change occurring in multiple physical and biological components of the system. In the Gulf of Alaska, a regime shift in the late 1970s was observed, indicated by an abrupt increase in sea surface temperature and major shifts in the catch of many fish species. This late 1970s regime shift in the Gulf of Alaska was followed by another shift in the late 1980s, not as pervasive as the 1977 shift, but which nevertheless did not return to the prior state. A thorough understanding of the extent and mechanisms leading to such regime shifts is challenged by data paucity in time and space. We investigate the ability of a suite of ocean biogeochemistry models of varying complexity to simulate regime shifts in the Gulf of Alaska by examining the presence of abrupt changes in time series of physical variables (sea surface temperature and mixed layer depth), nutrients and biological variables (chlorophyll, primary productivity and plankton biomass) using change-point analysis. Our study demonstrates that ocean biogeochemical models are capable of simulating the late 1970s shift, indicating an abrupt increase in sea surface temperature forcing followed by an abrupt decrease in nutrients and biological productivity. This predicted shift is consistent among all the models, although some of them exhibit an abrupt transition (i.e. a significant shift from one year to the next), whereas others simulate a smoother transition. Some models further suggest that the late 1980s shift was constrained by changes in mixed layer depth. Our study demonstrates that ocean biogeochemical can successfully simulate regime shifts in the Gulf of Alaska region, thereby providing better understanding of how changes in physical conditions are propagated from lower to upper trophic levels through bottom-up controls.

  10. Study of the plankton ecosystem variability using a coupled hydrodynamics biogeochemical modelling in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Kessouri, Fayçal; Ulses, Caroline; Estournel, Claude; Marsaleix, Patrick

    2015-04-01

    The Mediterranean Sea presents a wide variety of trophic regimes since the large and intense spring bloom of the North-Western Mediterranean Sea (NWMS) that follows winter convection to the extreme oligotrophic regions of the South-eastern basin. The Mediterranean Sea displays a strong time variability revealing its high sensitivity to climate and anthropic pressures. In this context, it is crucial to develop tools allowing to understand the evolution of the Mediterranean hydrology and marine ecosystem as a response to external forcing. Numerical coupled hydrodynamic and biogeochemical modelling carefully calibrated in the different regions of the basin is the only tool that can answer this question. However, this important step of calibration is particularly difficult because of the lack of coherent sets of data describing the seasonal evolution of the main parameters characterizing the physical and biogeochemical environment in the different sub-basins. The chlorophyll satellite data from 4km MODIS products, a multiple in situ data from MerMEX MOOSE and DEWEX cruises and Bio-Argo floats from NAOS project are believed to be an opportunity to strongly improve the realism of ecosystem models. The model is a 3D coupled simulation using NemoMed12 for hydrodynamics and ECO 3MS for biogeochemistry and covers the whole Mediterranean Sea and runs at 1/12°. The relevant variables mentioned are phytoplankton, organic and inorganic matters faced to water masses dynamics, over ten years since summer 2003. After a short validation, we will expose two topics: First, through this coupling we quantify the nutrients fluxes across the Mediterranean straits over the years. For example, we found an annual net average around 150 Giga moles NO3 per year at Gibraltar, where we expect low annual fluctuations. In contrast, the Strait of Sicily shows greater annual variability going from 70 to 92 Giga moles NO3 per year. All the fluxes are resumed in a detailed diagram of the transport

  11. Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, S.; Hickman, A. E.; Jahn, O.; Gregg, W. W.; Mouw, C. B.; Follows, M. J.

    2015-02-01

    We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem in a dynamic three-dimensional physical framework. The radiative transfer component resolves spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (the phytoplankton community, detrital particles, and coloured dissolved organic matter, CDOM). The model is evaluated against in situ observed and satellite derived products. In particular we compare to concurrently measured biogeochemical, ecosystem and optical data along a north-south transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, and the crucial feedbacks between the light field and the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at short wavelengths and in more productive waters, phytoplankton absorption is especially important at the deep chlorophyll a (Chl a) maximum, and absorption by water molecules is relatively most important in the highly oligotrophic gyres. Sensitivity experiments in which absorption by any of the optical constituents was increased led to a decrease in the size of the oligotrophic regions of the subtropical gyres: lateral nutrient supplies were enhanced as a result of decreasing high latitude productivity. Scattering does not as strongly affect the ecosystem and biogeochemistry fields within the water column but is important for setting the surface upwelling irradiance, and hence sea surface reflectance. Having a model capable of capturing bio-optical feedbacks will be important for

  12. Variably saturated flow and multicomponent biogeochemical reactive transport modeling of a uranium bioremediation field experiment

    NASA Astrophysics Data System (ADS)

    Yabusaki, Steven B.; Fang, Yilin; Williams, Kenneth H.; Murray, Christopher J.; Ward, Andy L.; Dayvault, Richard D.; Waichler, Scott R.; Newcomer, Darrell R.; Spane, Frank A.; Long, Philip E.

    2011-11-01

    Three-dimensional, coupled variably saturated flow and biogeochemical reactive transport modeling of a 2008 in situ uranium bioremediation field experiment is used to better understand the interplay of transport and biogeochemical reactions controlling uranium behavior under pulsed acetate amendment, seasonal water table variation, spatially variable physical (hydraulic conductivity, porosity) and geochemical (reactive surface area) material properties. While the simulation of the 2008 Big Rusty acetate biostimulation field experiment in Rifle, Colorado was generally consistent with behaviors identified in previous field experiments at the Rifle IFRC site, the additional process and property detail provided several new insights. A principal conclusion from this work is that uranium bioreduction is most effective when acetate, in excess of the sulfate-reducing bacteria demand, is available to the metal-reducing bacteria. The inclusion of an initially small population of slow growing sulfate-reducing bacteria identified in proteomic analyses led to an additional source of Fe(II) from the dissolution of Fe(III) minerals promoted by biogenic sulfide. The falling water table during the experiment significantly reduced the saturated thickness of the aquifer and resulted in reactants and products, as well as unmitigated uranium, in the newly unsaturated vadose zone. High permeability sandy gravel structures resulted in locally high flow rates in the vicinity of injection wells that increased acetate dilution. In downgradient locations, these structures created preferential flow paths for acetate delivery that enhanced local zones of TEAP reactivity and subsidiary reactions. Conversely, smaller transport rates associated with the lower permeability lithofacies (e.g., fine) and vadose zone were shown to limit acetate access and reaction. Once accessed by acetate, however, these same zones limited subsequent acetate dilution and provided longer residence times that resulted

  13. A new post-processing tool for the source-related element tracing in biogeochemical models: A case study for the North Sea

    NASA Astrophysics Data System (ADS)

    Große, Fabian; Kreus, Markus; Pätsch, Johannes

    2015-04-01

    The mitigation of eutrophication and its concomitants, like harmful algal blooms or deoxygenation of bottom waters, is one of the major aspects of the ecological management of coastal marine ecosystems. In the past, biogeochemical models helped to significantly improve the understanding of the interaction of the physical and biological processes behind eutrophication. Nevertheless, the quantification of the influence of source-related nutrient inputs to eutrophication in a specific region remains an important issue, since it is as crucial for an efficient management as it is difficult to obtain. About a decade ago, a method applicable to biogeochemical models had been developed allowing for the tracing of elements from different sources, e.g. phosphorus and/or nitrogen from two different rivers, throughout the whole process chain of the applied model. This tracing method - often referred to as 'trans-boundary nutrient transport' (TBNT) - provides additional information about the contributions from different sources to the overall amount ('bulk') of an element in each part of the model domain. This information constitutes the basis for the quantification, evaluation and optimisation of nutrient reduction targets for the tributaries of a marine ecosystem. In the meantime, the TBNT method has been applied to a variety of different biogeochemical models, e.g. to quantify the influence of nutrient loads from different rivers or atmospheric deposition on phytoplankton blooms or to determine the source-related composition of total nitrogen in different parts of an ecosystem. However, for all of these applications the method was directly implemented into the considered model, and thus was model-dependent and required an individual solution to deal with the model specifics like grid structure, programming language etc. For the application of the TBNT method to the ECOHAM model (ECOlogical model HAMburg), we further developed the approach by creating a post

  14. Technical Note: A generic law-of-the-minimum flux limiter for simulating substrate limitation in biogeochemical models

    NASA Astrophysics Data System (ADS)

    Tang, J. Y.; Riley, W. J.

    2016-02-01

    We present a generic flux limiter to account for mass limitations from an arbitrary number of substrates in a biogeochemical reaction network. The flux limiter is based on the observation that substrate (e.g., nitrogen, phosphorus) limitation in biogeochemical models can be represented as to ensure mass conservative and non-negative numerical solutions to the governing ordinary differential equations. Application of the flux limiter includes two steps: (1) formulation of the biogeochemical processes with a matrix of stoichiometric coefficients and (2) application of Liebig's law of the minimum using the dynamic stoichiometric relationship of the reactants. This approach contrasts with the ad hoc down-regulation approaches that are implemented in many existing models (such as CLM4.5 and the ACME (Accelerated Climate Modeling for Energy) Land Model (ALM)) of carbon and nutrient interactions, which are error prone when adding new processes, even for experienced modelers. Through an example implementation with a CENTURY-like decomposition model that includes carbon, nitrogen, and phosphorus, we show that our approach (1) produced almost identical results to that from the ad hoc down-regulation approaches under non-limiting nutrient conditions, (2) properly resolved the negative solutions under substrate-limited conditions where the simple clipping approach failed, (3) successfully avoided the potential conceptual ambiguities that are implied by those ad hoc down-regulation approaches. We expect our approach will make future biogeochemical models easier to improve and more robust.

  15. Small pores in soils: Is the physico-chemical environment accurately reflected in biogeochemical models ?

    NASA Astrophysics Data System (ADS)

    Weber, Tobias K. D.; Riedel, Thomas

    2015-04-01

    Free water is a prerequesite to chemical reactions and biological activity in earth's upper crust essential to life. The void volume between the solid compounds provides space for water, air, and organisms that thrive on the consumption of minerals and organic matter thereby regulating soil carbon turnover. However, not all water in the pore space in soils and sediments is in its liquid state. This is a result of the adhesive forces which reduce the water activity in small pores and charged mineral surfaces. This water has a lower tendency to react chemically in solution as this additional binding energy lowers its activity. In this work, we estimated the amount of soil pore water that is thermodynamically different from a simple aqueous solution. The quantity of soil pore water with properties different to liquid water was found to systematically increase with increasing clay content. The significance of this is that the grain size and surface area apparently affects the thermodynamic state of water. This implies that current methods to determine the amount of water content, traditionally determined from bulk density or gravimetric water content after drying at 105°C overestimates the amount of free water in a soil especially at higher clay content. Our findings have consequences for biogeochemical processes in soils, e.g. nutrients may be contained in water which is not free which could enhance preservation. From water activity measurements on a set of various soils with 0 to 100 wt-% clay, we can show that 5 to 130 mg H2O per g of soil can generally be considered as unsuitable for microbial respiration. These results may therefore provide a unifying explanation for the grain size dependency of organic matter preservation in sedimentary environments and call for a revised view on the biogeochemical environment in soils and sediments. This could allow a different type of process oriented modelling.

  16. IIASA`s climate-vegetation-biogeochemical cycle module as a part of an integrated model for climate change

    SciTech Connect

    Ganopolski, A.V.; Jonas, M.; Krabec, J.; Olendrzynski, K.; Petoukhov, V.K.; Venevsky, S.V.

    1994-12-31

    The main objective of this study is the development of a hierarchy of coupled climate biosphere models with a full description of the global biogeochemical cycles. These models are planned for use as the core of a set of integrated models of climate change and they will incorporate the main elements of the Earth system (atmosphere, hydrosphere, pedosphere and biosphere) linked with each other (and eventually with the antroposphere) through the fluxes of heat, momentum, water and through the global biogeochemical cycles of carbon and nitrogen. This set of integrated models can be considered to fill the gap between highly simplified integrated models of climate change and very sophisticated and computationally expensive coupled models, developed on the basis of general circulation models (GCMs). It is anticipated that this range of integrated models will be an effective tool for investigating the broad spectrum of problems connected with the coexistence of human society and biosphere.

  17. Exploring a microbial ecosystem approach to modeling deep ocean biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Zakem, E.; Follows, M. J.

    2014-12-01

    Though microbial respiration of organic matter in the deep ocean governs ocean and atmosphere biogeochemistry, it is not represented mechanistically in current global biogeochemical models. We seek approaches that are feasible for a global resolution, yet still reflect the enormous biodiversity of the deep microbial community and its associated metabolic pathways. We present a modeling framework grounded in thermodynamics and redox reaction stoichiometry that represents diverse microbial metabolisms explicitly. We describe a bacterial/archaeal functional type with two parameters: a growth efficiency representing the chemistry underlying a bacterial metabolism, and a rate limitation given by the rate of uptake of each of the necessary substrates for that metabolism. We then apply this approach to answer questions about microbial ecology. As a start, we resolve two dominant heterotrophic respiratory pathways- reduction of oxygen and nitrate- and associated microbial functional types. We combine these into an ecological model and a two-dimensional ocean circulation model to explore the organization, biogeochemistry, and ecology of oxygen minimum zones. Intensified upwelling and lateral transport conspire to produce an oxygen minimum at mid-depth, populated by anaerobic denitrifiers. This modeling approach should ultimately allow for the emergence of bacterial biogeography from competition of metabolisms and for the incorporation of microbial feedbacks to the climate system.

  18. Systemic vulnerability model for coastal erosion processes

    NASA Astrophysics Data System (ADS)

    Greco, M.; Martino, G.; Guariglia, A.

    2010-09-01

    Many coastal areas constitute an extraordinary environmental worth and economic value resource continuously exposed to an unceasing transformation due to climatic and anthropic factors. The pressure factor overloads carry out an amplification of environmental degradation and economic rent decrease of these territories producing a disruption of normal and anticipated community growth. This paper copes with coastal erosion problem by a systemic vulnerability model application and environmental indicators approach. Through the definition of an original indicator depending on the observed annual rate of coastal erosion and wave climate parameters, such an approach allow scenario generation and it is useful and powerful planning and management tool. The model has been applied on the test case of Ionian Coast of Basilicata Region located in the southern part of Italy, in the middle of Mediterranean basin. The littoral area is constituted of sandy shores of about 50 km length and 5 river deltas take place. Looking at the shoreline in terms of displacements, a shift of a coastal part is a function of grain size characteristics of the shore sands and of the wave climate. Therefore the selected index taking into account the energy stress affecting the shore area, characterizing the territorial system state and finalized to vulnerability estimation, is defined through the maximum annual erosion,tE, and the surface-wave parameters (H,T) corresponding to the wave-generated bottom orbital velocities higher than critical velocity matches with the bottom incipient transport condition. The resulting coefficient ? (? = tE? ? gH2-?T) is obviously dimensionless and represents the part of the available power in the seas, dissipated by erosion processes. If ? increases, the system integrity decreases and the system vulnerability increases. Available data, in terms of topographic/bathymetric information referred to the period 1873-2008, were utilized to derive tE by the use of a GIS

  19. Reactive transport modelling of biogeochemical processes and carbon isotope geochemistry inside a landfill leachate plume

    NASA Astrophysics Data System (ADS)

    van Breukelen, Boris M.; Griffioen, Jasper; Röling, Wilfred F. M.; van Verseveld, Henk W.

    2004-06-01

    The biogeochemical processes governing leachate attenuation inside a landfill leachate plume (Banisveld, the Netherlands) were revealed and quantified using the 1D reactive transport model PHREEQC-2. Biodegradation of dissolved organic carbon (DOC) was simulated assuming first-order oxidation of two DOC fractions with different reactivity, and was coupled to reductive dissolution of iron oxide. The following secondary geochemical processes were required in the model to match observations: kinetic precipitation of calcite and siderite, cation exchange, proton buffering and degassing. Rate constants for DOC oxidation and carbonate mineral precipitation were determined, and other model parameters were optimized using the nonlinear optimization program PEST by means of matching hydrochemical observations closely (pH, DIC, DOC, Na, K, Ca, Mg, NH 4, Fe(II), SO 4, Cl, CH 4, saturation index of calcite and siderite). The modelling demonstrated the relevance and impact of various secondary geochemical processes on leachate plume evolution. Concomitant precipitation of siderite masked the act of iron reduction. Cation exchange resulted in release of Fe(II) from the pristine anaerobic aquifer to the leachate. Degassing, triggered by elevated CO 2 pressures caused by carbonate precipitation and proton buffering at the front of the plume, explained the observed downstream decrease in methane concentration. Simulation of the carbon isotope geochemistry independently supported the proposed reaction network.

  20. Reactive transport modelling of biogeochemical processes and carbon isotope geochemistry inside a landfill leachate plume.

    PubMed

    van Breukelen, Boris M; Griffioen, Jasper; Röling, Wilfred F M; van Verseveld, Henk W

    2004-06-01

    The biogeochemical processes governing leachate attenuation inside a landfill leachate plume (Banisveld, the Netherlands) were revealed and quantified using the 1D reactive transport model PHREEQC-2. Biodegradation of dissolved organic carbon (DOC) was simulated assuming first-order oxidation of two DOC fractions with different reactivity, and was coupled to reductive dissolution of iron oxide. The following secondary geochemical processes were required in the model to match observations: kinetic precipitation of calcite and siderite, cation exchange, proton buffering and degassing. Rate constants for DOC oxidation and carbonate mineral precipitation were determined, and other model parameters were optimized using the nonlinear optimization program PEST by means of matching hydrochemical observations closely (pH, DIC, DOC, Na, K, Ca, Mg, NH4, Fe(II), SO4, Cl, CH4, saturation index of calcite and siderite). The modelling demonstrated the relevance and impact of various secondary geochemical processes on leachate plume evolution. Concomitant precipitation of siderite masked the act of iron reduction. Cation exchange resulted in release of Fe(II) from the pristine anaerobic aquifer to the leachate. Degassing, triggered by elevated CO2 pressures caused by carbonate precipitation and proton buffering at the front of the plume, explained the observed downstream decrease in methane concentration. Simulation of the carbon isotope geochemistry independently supported the proposed reaction network. PMID:15134877

  1. A continuous time random walk approach to model biogeochemical processes in rivers and hyporheic water

    NASA Astrophysics Data System (ADS)

    Aubeneau, A. F.; Drummond, J. D.; Packman, A. I.

    2011-12-01

    Exchange of solutes and particles between river channels and the subsurface is critical for biogeochemical processes in rivers. Subsurface water moves slowly, delaying downstream transport and providing ample time for reactions to proceed. We present a stochastic modeling framework for the transport of reactive solutes in rivers based on continuous time random walk theory. This model includes solute transport, storage, and reactions in both the channel and the bed. Hyporheic residence times can take any distribution. The model produces realistic breakthrough curves for conservative and reactive solutes. Reactive solutes breakthrough curves exhibit characteristic late time truncation. We have also extended the model for river networks and use it to assess how the interaction of exchange rates, residence time distributions and reaction rates affect export at the watershed scale. We show that extended travel times reduce total export, but in proportions that vary with reaction kinetics relative to transport rates. When reactions are fast relative to transport rates, exchange between the surface and subsurface tend to control removal whereas for slow reactions, residence time distributions become more important.

  2. Performance and results of the high-resolution biogeochemical model PELAGOS025 within NEMO

    NASA Astrophysics Data System (ADS)

    Epicoco, I.; Mocavero, S.; Macchia, F.; Vichi, M.; Lovato, T.; Masina, S.; Aloisio, G.

    2015-12-01

    The present work aims at evaluating the scalability performance of a high-resolution global ocean biogeochemistry model (PELAGOS025) on massive parallel architectures and the benefits in terms of the time-to-solution reduction. PELAGOS025 is an on-line coupling between the physical ocean model NEMO and the BFM biogeochemical model. Both the models use a parallel domain decomposition along the horizontal dimension. The parallelisation is based on the message passing paradigm. The performance analysis has been done on two parallel architectures, an IBM BlueGene/Q at ALCF (Argonne Leadership Computing Facilities) and an IBM iDataPlex with Sandy Bridge processors at CMCC (Euro Mediterranean Center on Climate Change). The outcome of the analysis demonstrated that the lack of scalability is due to several factors such as the I/O operations, the memory contention, the load unbalancing due to the memory structure of the BFM component and, for the BlueGene/Q, the absence of a hybrid parallelisation approach.

  3. Variably Saturated Flow and Multicomponent Biogeochemical Reactive Transport Modeling of a Uranium Bioremediation Field Experiment

    SciTech Connect

    Yabusaki, Steven B.; Fang, Yilin; Williams, Kenneth H.; Murray, Christopher J.; Ward, Anderson L.; Dayvault, Richard; Waichler, Scott R.; Newcomer, Darrell R.; Spane, Frank A.; Long, Philip E.

    2011-11-01

    Field experiments at a former uranium mill tailings site have identified the potential for stimulating indigenous bacteria to catalyze the conversion of aqueous uranium in the +6 oxidation state to immobile solid-associated uranium in the +4 oxidation state. This effectively removes uranium from solution resulting in groundwater concentrations below actionable standards. Three-dimensional, coupled variably-saturated flow and biogeochemical reactive transport modeling of a 2008 in situ uranium bioremediation field experiment is used to better understand the interplay of transport rates and biogeochemical reaction rates that determine the location and magnitude of key reaction products. A comprehensive reaction network, developed largely through previous 1-D modeling studies, was used to simulate the impacts on uranium behavior of pulsed acetate amendment, seasonal water table variation, spatially-variable physical (hydraulic conductivity, porosity) and geochemical (reactive surface area) material properties. A principal challenge is the mechanistic representation of biologically-mediated terminal electron acceptor process (TEAP) reactions whose products significantly alter geochemical controls on uranium mobility through increases in pH, alkalinity, exchangeable cations, and highly reactive reduction products. In general, these simulations of the 2008 Big Rusty acetate biostimulation field experiment in Rifle, Colorado confirmed previously identified behaviors including (1) initial dominance by iron reducing bacteria that concomitantly reduce aqueous U(VI), (2) sulfate reducing bacteria that become dominant after {approx}30 days and outcompete iron reducers for the acetate electron donor, (3) continuing iron-reducer activity and U(VI) bioreduction during dominantly sulfate reducing conditions, and (4) lower apparent U(VI) removal from groundwater during dominantly sulfate reducing conditions. New knowledge on simultaneously active metal and sulfate reducers has been

  4. Parameter Sensitivity and Laboratory Benchmarking of a Biogeochemical Process Model for Enhanced Anaerobic Dechlorination

    NASA Astrophysics Data System (ADS)

    Kouznetsova, I.; Gerhard, J. I.; Mao, X.; Barry, D. A.; Robinson, C.; Brovelli, A.; Harkness, M.; Fisher, A.; Mack, E. E.; Payne, J. A.; Dworatzek, S.; Roberts, J.

    2008-12-01

    A detailed model to simulate trichloroethene (TCE) dechlorination in anaerobic groundwater systems has been developed and implemented through PHAST, a robust and flexible geochemical modeling platform. The approach is comprehensive but retains flexibility such that models of varying complexity can be used to simulate TCE biodegradation in the vicinity of nonaqueous phase liquid (NAPL) source zones. The complete model considers a full suite of biological (e.g., dechlorination, fermentation, sulfate and iron reduction, electron donor competition, toxic inhibition, pH inhibition), physical (e.g., flow and mass transfer) and geochemical processes (e.g., pH modulation, gas formation, mineral interactions). Example simulations with the model demonstrated that the feedback between biological, physical, and geochemical processes is critical. Successful simulation of a thirty-two-month column experiment with site soil, complex groundwater chemistry, and exhibiting both anaerobic dechlorination and endogenous respiration, provided confidence in the modeling approach. A comprehensive suite of batch simulations was then conducted to estimate the sensitivity of predicted TCE degradation to the 36 model input parameters. A local sensitivity analysis was first employed to rank the importance of parameters, revealing that 5 parameters consistently dominated model predictions across a range of performance metrics. A global sensitivity analysis was then performed to evaluate the influence of a variety of full parameter data sets available in the literature. The modeling study was performed as part of the SABRE (Source Area BioREmediation) project, a public/private consortium whose charter is to determine if enhanced anaerobic bioremediation can result in effective and quantifiable treatment of chlorinated solvent DNAPL source areas. The modelling conducted has provided valuable insight into the complex interactions between processes in the evolving biogeochemical systems

  5. Presence of nitrous oxide hotspots in the coastal upwelling area off central Chile: an analysis of temporal variability based on ten years of a biogeochemical time series

    NASA Astrophysics Data System (ADS)

    Farías, L.; Besoain, V.; García-Loyola, S.

    2015-04-01

    Seasonal and inter-annual variabilities of biogeochemical variables, including nitrous oxide (N2O), an important climate active gas, were analyzed during monthly observations between 2002 and 2012 at an ocean Time-Series station in the coastal upwelling area off central Chile (36° 30.8‧ 73° 15‧). Oxygen, N2O, nutrients and chlorophyll-a (Chl-a) showed clear seasonal variability associated with upwelling favorable winds (spring-summer) and also inter-annual variability, which in the case of N2O was clearly observed during the occurrence of N2O hotspots with saturation levels of up to 4849%. These hotspots consistently took place during the upwelling-favorable periods in 2004, 2006, 2008, 2010 and 2011, below the mixed layer (15-50 m depth) in waters with hypoxia and some N{{O}2}- accumulation. The N2O hotspots displayed excesses of N2O (ΔN2O) three times higher than the average monthly anomalies (2002-2012). Estimated relationships of ΔN2O versus apparent oxygen utilization (AOU), and ΔN2O versus N{{O}3}-, suggest that aerobic ammonium oxidation (AAO) and partial denitrification are the processes responsible for high N2O accumulation in subsurface water. Chl-a levels were reasonably correlated with the presence of the N2O hotspots, suggesting that microbial activities fuelled by high availability of organic matters lead to high N2O production. As a result, this causes a substantial N2O efflux into the atmosphere of up to 260 μmol m-2 d-1. The N2O hotspots are transient events or hot moments, which may occur more frequently than they are observed. If so, this upwelling area is producing and emitting greater than expected amounts of N2O and is therefore an important N2O source that should be considered in the global atmospheric N2O balance.

  6. Long-term controls on ocean phosphorus and oxygen in a global biogeochemical model

    NASA Astrophysics Data System (ADS)

    Palastanga, V.; Slomp, C. P.; Heinze, C.

    2011-09-01

    In this study, we use a biogeochemical ocean general circulation model (HAMOCC), originally developed for the carbon and silicon cycles, and expand it with a description of the sedimentary phosphorus (P) cycle. The model simulates the release of reactive P by aerobic and anaerobic degradation of organic matter in the sediment, as well as formation and burial of Fe-oxide bound P and authigenic Ca-P minerals. We also include pre-anthropogenic inputs of P from atmospheric dust, which is mostly in the form of detrital apatite. Model predicted total P concentrations and rates of reactive P burial for the deep sea agree reasonably well with observations in open ocean and near continental margin sediments. As part of a sensitivity analysis, we assess the long-term response of ocean productivity and deep water oxygenation to increases in the riverine input of P and preferential release of P from sediments. The simulations show that the feedback from preferential P regeneration accelerates the expansion of suboxia (O2 < 25 μM) along continental margins and in the naturally suboxic areas in tropical-subtropical regions on timescales of 10-100 ka. For a case in which maximum P regeneration from sediments is enabled, a large-scale pattern of bottom water suboxia (30% of the total ocean area) develops over the southeastern, tropical and northern Pacific Ocean sectors.

  7. Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, S.; Hickman, A. E.; Jahn, O.; Gregg, W. W.; Mouw, C. B.; Follows, M. J.

    2015-07-01

    We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem component in a dynamic three-dimensional physical framework. The radiative transfer component resolves the penetration of spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (different phytoplankton functional types; detrital particles; and coloured dissolved organic matter, CDOM). The model is evaluated against in situ-observed and satellite-derived products. In particular we compare to concurrently measured biogeochemical, ecosystem, and optical data along a meridional transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We find that incorporating the different optically important constituents explicitly and including spectral irradiance was crucial to capture the variability in the depth of the subsurface chlorophyll a (Chl a) maximum. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, as well as the crucial feedbacks between the light field, the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at attenuating light at short wavelengths and in more productive waters, phytoplankton absorption is relatively more important at the subsurface Chl a maximum, and water molecules have the greatest contribution when concentrations of other constituents are low, such as in the oligotrophic gyres. Scattering had less effect on attenuation, but since it is important for the amount and type of upwelling irradiance, it is crucial for setting sea surface reflectance. Strikingly, sensitivity experiments in which absorption by any of the

  8. Nitrogen transfers off Walvis Bay: a 3-D coupled physical/biogeochemical modeling approach in the Namibian upwelling system

    NASA Astrophysics Data System (ADS)

    Gutknecht, E.; Dadou, I.; Marchesiello, P.; Cambon, G.; Le Vu, B.; Sudre, J.; Garçon, V.; Machu, E.; Rixen, T.; Kock, A.; Flohr, A.; Paulmier, A.; Lavik, G.

    2013-06-01

    Eastern boundary upwelling systems (EBUS) are regions of high primary production often associated with oxygen minimum zones (OMZs). They represent key regions for the oceanic nitrogen (N) cycle. By exporting organic matter (OM) and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. However, losses of fixed inorganic N through denitrification and anammox processes take place in oxygen depleted environments such as EBUS, and can potentially mitigate the role of these regions as a source of N to the open ocean. EBUS can also represent a considerable source of nitrous oxide (N2O) to the atmosphere, affecting the atmospheric budget of N2O. In this paper a 3-D coupled physical/biogeochemical model (ROMS/BioEBUS) is used to investigate the N budget in the Namibian upwelling system. The main processes linked to EBUS and associated OMZs are taken into account. The study focuses on the northern part of the Benguela upwelling system (BUS), especially the Walvis Bay area (between 22° S and 24° S) where the OMZ is well developed. Fluxes of N off the Walvis Bay area are estimated in order to understand and quantify (1) the total N offshore export from the upwelling area, representing a possible N source that sustains primary production in the South Atlantic subtropical gyre; (2) export production and subsequent losses of fixed N via denitrification and anammox under suboxic conditions (O2 < 25 mmol O2 m-3); and (3) the N2O emission to the atmosphere in the upwelling area. In the mixed layer, the total N offshore export is estimated as 8.5 ± 3.9 × 1010 mol N yr-1 at 10° E off the Walvis Bay area, with a mesoscale contribution of 20%. Extrapolated to the whole BUS, the coastal N source for the subtropical gyre corresponds to 0.1 ± 0.04 mol N m-2 yr-1. This N flux represents a major source of N for the gyre compared with other N sources, and contributes 28% of the new primary

  9. A hydrodynamic modeling study to estimate the flushing rate in a large coastal embayment.

    PubMed

    Lee, Hye Won; Park, Seok Soon

    2013-01-30

    A three-dimensional hydrodynamics model was applied to a coastal embayment on the west coast of the Korean Peninsula to examine the potential effects of a large reclamation project (the Saemangeum Project). To understand and analyze the impacts of the coastal structures associated with the Project on the hydrodynamics, as well as the composition ratio of the saltwater to freshwater, the seasonal distribution of the residence time and flushing rate were examined using the salinity and tracer simulation as dilution indicators. The calibrated and verified model was used to examine changes in the tidal elevation, salinity, residence time and flushing rate. The results indicate that the completion of the fourth sea dike will limit circulation, and that the salinity inside the dike would be dominated by rainfall and runoff. The flushing rate was estimated to decrease after the construction of the dike, such that biogeochemical changes could occur in the sea water and sediment. From this study, it was concluded that the three-dimensional hydrodynamic model can successfully simulate the changes in elevation, residence time and flushing rate in the Saemangeum Embayment and become a useful tool for determining a management plan to maintain the water quality of coastal embayments. PMID:23291376

  10. SHIMMER (1.0): a novel mathematical model for microbial and biogeochemical dynamics in glacier forefield ecosystems

    NASA Astrophysics Data System (ADS)

    Bradley, J. A.; Anesio, A. M.; Singarayer, J. S.; Heath, M. R.; Arndt, S.

    2015-08-01

    SHIMMER (Soil biogeocHemIcal Model for Microbial Ecosystem Response) is a new numerical modelling framework which is developed as part of an interdisciplinary, iterative, model-data based approach fully integrating fieldwork and laboratory experiments with model development, testing, and application. SHIMMER is designed to simulate the establishment of microbial biomass and associated biogeochemical cycling during the initial stages of ecosystem development in glacier forefield soils. However, it is also transferable to other extreme ecosystem types (such as desert soils or the surface of glaciers). The model mechanistically describes and predicts transformations in carbon, nitrogen and phosphorus through aggregated components of the microbial community as a set of coupled ordinary differential equations. The rationale for development of the model arises from decades of empirical observation on the initial stages of soil development in glacier forefields. SHIMMER enables a quantitative and process focussed approach to synthesising the existing empirical data and advancing understanding of microbial and biogeochemical dynamics. Here, we provide a detailed description of SHIMMER. The performance of SHIMMER is then tested in two case studies using published data from the Damma Glacier forefield in Switzerland and the Athabasca Glacier in Canada. In addition, a sensitivity analysis helps identify the most sensitive and unconstrained model parameters. Results show that the accumulation of microbial biomass is highly dependent on variation in microbial growth and death rate constants, Q10 values, the active fraction of microbial biomass, and the reactivity of organic matter. The model correctly predicts the rapid accumulation of microbial biomass observed during the initial stages of succession in the forefields of both the case study systems. Simulation results indicate that primary production is responsible for the initial build-up of substrate that subsequently

  11. Marine biological feedback associated with Indian Ocean Dipole in a coupled ocean/biogeochemical model

    NASA Astrophysics Data System (ADS)

    Park, Jong-Yeon; Kug, Jong-Seong

    2014-01-01

    The impact of marine ecosystem on the tropical climate variability in the Indian Ocean is investigated by performing coupled ocean/biogeochemical model experiments, which are forced by realistic surface winds from 1951 to 2010. Results from a suite of chlorophyll perturbation experiments reveal that the presence of chlorophyll can have significant effects on the characteristics of the Indian Ocean Dipole (IOD), including its amplitude and skewness, as well as on the mean state. Specifically, chlorophyll increases mean sea surface temperature due to direct biological heating in regions where the mean mixed layer depth is generally shallow. It is also found that the presence of chlorophyll affects the IOD magnitude by two different processes: One is the amplifying effect by the mean chlorophyll, which leads to shoaling of mean thermocline depth, and the other is the damping effect by the interactively varying chlorophyll coupled with the physical model. There is also a biological impact on the skewness of the IOD, resulting in enhanced positive skewness. This skewness change is primarily caused by the phase dependency of the above two contradicting effects involving the asymmetric thermocline feedback and the nonlinear mixed layer heating.

  12. Modeling and water quality assessment during realisation of the coastal projects in Sochi region (Black sea coast of Russia)

    NASA Astrophysics Data System (ADS)

    Prokhoda-Shumskikh, L.

    2012-04-01

    Sochi region is the unique subtropical resort on the Black Sea coast of Russia. Nowadays due to Sochi is the capital of the Olympic game 2014, the government of the Russian Federation accepts the special federal program of Black Sea coast development. Program foresees the existing and creation of new coastal recreational and touristic complexes along the Russian Black Sea coast, such as complex of yacht harbors, water centers (aqua-centers), network of port localities and etc. These coastal projects are different, but the main problems of the environmental impact assessment are the same. The environmental impact and the relative damage should be assessed at the stage of construction as well as at the stage of operation. The key problem for the recreation coastal zone is water quality management. The port localities network as example is considered. To increase the accuracy and informative of forecasts for the coastal zone conditions the system-dynamic model has been developed, what allows to estimate the quality of the sea water, including that in the semi-enclosed coastal water areas with the limited water exchange. The model of water quality in the coastal zone includes the equations of deposit concentration changes and chemical substances evolution in the studied areas. The model incorporates joint description of cycles of two biogenic elements - nitrogen and phosphorus. The system is completely defined by the biogeochemical reactions. The sizes of such water areas allow the applying the full mixing and zero-dimensional models of water quality. The circulation of water inside the area is taken into account additionally. Water exchange in the semi-enclosed coastal water areas is defined by the discharge through the open parts of area border. The novelty of the offered model is its adaptation to the specific conditions of semi-enclosed coastal water areas. At the same time, the model contains details of the biogeochemical processes to complete modelling of the

  13. Robust Modeling of Greenhouse Gas (GHG) Fluxes from Coastal Wetland Ecosystems

    NASA Astrophysics Data System (ADS)

    Abdul-Aziz, O. I.; Ishtiaq, K. S.

    2014-12-01

    Many critical wetland biogeochemical processes are still largely unknown or poorly understood at best. Yet, available models for predicting wetland greenhouse gas (GHG) fluxes (e.g., CO2, CH4, and N2O) are generally mechanistic in nature. This knowledge gap leads to inappropriate process descriptions or over-parameterizations in existing mechanistic models, which often fail to provide accurate and robust predictions across time and space. We developed a systematic data-analytics and informatics method to identify the dominant controls and quantify the relative linkages of wetland GHG fluxes in relation to various hydro-climatic, sea level, biogeochemical and ecological drivers. The method was applied to data collected from 2012-14 through an extensive field campaign from different blue carbon sites of Waquoit Bay, MA. Multivariate pattern recognition techniques of principal component and factor analyses were employed to identify the dominant controls of wetland GHG fluxes; classifying and grouping process variables based on their similarity and interrelation patterns. Power-law based partial least squares regression models were developed to quantify the relative linkages of major GHGs with different process drivers and stressors, as well as to achieve site-specific predictions of GHG fluxes. Wetland biogeochemical similitude and scaling laws were also investigated to unravel emergent patterns and organizing principles of wetland GHG fluxes. The research findings will guide the development of parsimonious empirical to appropriate mechanistic models for spatio-temporally robust predictions of GHGs fluxes and carbon sequestration from coastal wetland ecosystems. The research is part of two current projects funded by the National Oceanic and Atmospheric Administration and the National Science Foundation; focusing on wetland data collections, knowledge formation, formulation of robust GHGs prediction models, and development of ecological engineering tools.

  14. Glacial-interglacial variability in ocean oxygen and phosphorus in a global biogeochemical model

    NASA Astrophysics Data System (ADS)

    Palastanga, V.; Slomp, C. P.; Heinze, C.

    2013-02-01

    Increased transfer of particulate matter from continental shelves to the open ocean during glacials may have had a major impact on the biogeochemistry of the ocean. Here, we assess the response of the coupled oceanic cycles of oxygen, carbon, phosphorus, and iron to the input of particulate organic carbon and reactive phosphorus from shelves. We use a biogeochemical ocean model and specifically focus on the Last Glacial Maximum (LGM). When compared to an interglacial reference run, our glacial scenario with shelf input shows major increases in ocean productivity and phosphorus burial, while mean deep-water oxygen concentrations decline. There is a downward expansion of the oxygen minimum zones (OMZs) in the Atlantic and Indian Ocean, while the extension of the OMZ in the Pacific is slightly reduced. Oxygen concentrations below 2000 m also decline but bottom waters do not become anoxic. The model simulations show when shelf input of particulate organic matter and particulate reactive P is considered, low oxygen areas in the glacial ocean expand, but concentrations are not low enough to generate wide scale changes in sediment biogeochemistry and sedimentary phosphorus recycling. Increased reactive phosphorus burial in the open ocean during the LGM in the model is related to dust input, notably over the southwest Atlantic and northwest Pacific, whereas input of material from shelves explains higher burial fluxes in continental slope and rise regions. Our model results are in qualitative agreement with available data and reproduce the strong spatial differences in the response of phosphorus burial to glacial-interglacial change. Our model results also highlight the need for additional sediment core records from all ocean basins to allow further insight into changes in phosphorus, carbon and oxygen dynamics in the ocean on glacial-interglacial timescales.

  15. DRINK: a biogeochemical source term model for low level radioactive waste disposal sites.

    PubMed

    Humphreys, P; McGarry, R; Hoffmann, A; Binks, P

    1997-07-01

    Interactions between element chemistry and the ambient geochemistry play a significant role in the control of radionuclide migration in the geosphere. These same interactions influence radionuclide release from near surface, low level radioactive waste, disposal sites once physical containment has degraded. In situations where LLW contains significant amounts of metal and organic materials such as cellulose, microbial degradation in conjunction with corrosion can significantly perturb the ambient geochemistry. These processes typically produce a transition from oxidising to reducing conditions and can influence radionuclide migration through changes in both the dominant radionuclide species and mineral phases. The DRINK (DRIgg Near field Kinetic) code is a biogeochemical transport code designed to simulate the long term evolution of the UK low level radioactive waste disposal site at Drigg. Drigg is the UK's principal solid low level radioactive waste disposal site and has been receiving waste since 1959. The interaction between microbial activity, the ambient geochemistry and radionuclide chemistry is central to the DRINK approach with the development of the ambient pH, redox potential and bulk geochemistry being directly influenced by microbial activity. This paper describes the microbial aspects of the code, site data underpinning the microbial model, the microbiology/chemistry interface and provides an example of the code in action. PMID:9340003

  16. Quantification of terrestrial ecosystem carbon dynamics in the conterminous United States combining a process-based biogeochemical model and MODIS and AmeriFlux data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Satellite remote sensing provides continuous temporal and spatial information of terrestrial ecosystems. Using these remote sensing data and eddy flux measurements and biogeochemical models, such as the Terrestrial Ecosystem Model (TEM), should provide a more adequate quantification of carbon dynami...

  17. 3D Modeling of influence of oxygenated inflows on biogeochemical structure of redox-layer of enclosed seas

    NASA Astrophysics Data System (ADS)

    Podymov, O.

    2009-04-01

    In this study we used a coupled hydrophysical-biogeochemical model. Biogeochemical processes were described with O-N-S-P-Mn-Fe ROLM model (Yakushev et al, 2007), designed to study processes of organic matter (OM) formation and decay, reduction and oxidation of species of nitrogen, sulphur, manganese and iron, transformation of phosphorus species. Phytoplankton, zooplankton and bacteria were also parameterized and divided into four groups according to their relation to particular energy source and to OM transformation. Hydrophysical processes where described with 3D General Estuarine Transport Model (Burchard et al, 2004). We modeled the influence of oxygenated intrusions on the vertical biogeochemical structure of the central Gotland Sea. The model simulations demonstrate that a complete ventilation of the Gotland Deep bottom water caused by massive inflows of oxygenated North Sea water led to substantial changes of the vertical biogeochemical structure within this basin. During the inflow events large amounts of iron and manganese precipitate and discharge from the water column. In this phase redox reactions are accelerated and growth of bacteria leads to an increase of particulate matter content and consecutive particle sedimentation. An unbalanced structure of water column exists during the period of reestablishment of anoxic conditions. Its appearance is related to the absence of Mn species that play the dominant role in the oxidation-reduction reactions at the pelagic redox interfaces. This unbalanced structure can serve as a biotope for a development of untypical microbial redox-cline reactions (i.e. anammox). According to the model simulations the duration of the reestablishment period for a steady state of biogeochemistry after a complete flushing is about 1.5 years.

  18. Microbial community dynamics in soil aggregates shape biogeochemical gas fluxes from soil profiles - upscaling an aggregate biophysical model.

    PubMed

    Ebrahimi, Ali; Or, Dani

    2016-09-01

    Microbial communities inhabiting soil aggregates dynamically adjust their activity and composition in response to variations in hydration and other external conditions. These rapid dynamics shape signatures of biogeochemical activity and gas fluxes emitted from soil profiles. Recent mechanistic models of microbial processes in unsaturated aggregate-like pore networks revealed a highly dynamic interplay between oxic and anoxic microsites jointly shaped by hydration conditions and by aerobic and anaerobic microbial community abundance and self-organization. The spatial extent of anoxic niches (hotspots) flicker in time (hot moments) and support substantial anaerobic microbial activity even in aerated soil profiles. We employed an individual-based model for microbial community life in soil aggregate assemblies represented by 3D angular pore networks. Model aggregates of different sizes were subjected to variable water, carbon and oxygen contents that varied with soil depth as boundary conditions. The study integrates microbial activity within aggregates of different sizes and soil depth to obtain estimates of biogeochemical fluxes from the soil profile. The results quantify impacts of dynamic shifts in microbial community composition on CO2 and N2 O production rates in soil profiles in good agreement with experimental data. Aggregate size distribution and the shape of resource profiles in a soil determine how hydration dynamics shape denitrification and carbon utilization rates. Results from the mechanistic model for microbial activity in aggregates of different sizes were used to derive parameters for analytical representation of soil biogeochemical processes across large scales of practical interest for hydrological and climate models. PMID:27152862

  19. MOPS-1.0: towards a model for the regulation of the global oceanic nitrogen budget by marine biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Kriest, I.; Oschlies, A.

    2015-09-01

    Global models of the oceanic nitrogen cycle are subject to many uncertainties regarding the representation of the relevant biogeochemical processes and of the feedbacks between nitrogen sources and sinks that determine space- and timescales on which the global nitrogen budget is regulated. We investigate these aspects using a global model of ocean biogeochemistry that explicitly considers phosphorus and nitrogen, including pelagic denitrification and nitrogen fixation as sink and source terms of fixed nitrogen, respectively. The model explores different parameterizations of organic matter sinking speed, oxidant affinity of oxic and suboxic remineralization, and regulation of nitrogen fixation by temperature and different stoichiometric ratios. Examination of the initial transient behavior of different model setups initialized from observed biogeochemical tracer distributions reveal changes in simulated nitrogen inventories and fluxes particularly during the first centuries. Millennial timescales have to be resolved in order to bring all biogeochemical and physical processes into a dynamically consistent steady state. Analysis of global properties suggests that not only particularly particle sinking speed but also the parameterization of denitrification determine the extent of oxygen minimum zones, global nitrogen fluxes, and hence the oceanic nitrogen inventory. However, the ways and directions in which different parameterizations of particle sinking, nitrogen fixation, and denitrification affect the global diagnostics are different suggesting that these may, in principle, be constrained independently from each other. Analysis of the model misfit with respect to observed biogeochemical tracer distributions and fluxes suggests a particle flux profile close to the one suggested by Martin et al. (1987). Simulated pelagic denitrification best agrees with the lower values between 59 and 84 Tg N yr-1 recently estimated by other authors.

  20. SHIMMER (1.0): a novel mathematical model for microbial and biogeochemical dynamics in glacier forefield ecosystems

    NASA Astrophysics Data System (ADS)

    Bradley, J. A.; Anesio, A. M.; Singarayer, J. S.; Heath, M. R.; Arndt, S.

    2015-10-01

    SHIMMER (Soil biogeocHemIcal Model for Microbial Ecosystem Response) is a new numerical modelling framework designed to simulate microbial dynamics and biogeochemical cycling during initial ecosystem development in glacier forefield soils. However, it is also transferable to other extreme ecosystem types (such as desert soils or the surface of glaciers). The rationale for model development arises from decades of empirical observations in glacier forefields, and enables a quantitative and process focussed approach. Here, we provide a detailed description of SHIMMER, test its performance in two case study forefields: the Damma Glacier (Switzerland) and the Athabasca Glacier (Canada) and analyse sensitivity to identify the most sensitive and unconstrained model parameters. Results show that the accumulation of microbial biomass is highly dependent on variation in microbial growth and death rate constants, Q10 values, the active fraction of microbial biomass and the reactivity of organic matter. The model correctly predicts the rapid accumulation of microbial biomass observed during the initial stages of succession in the forefields of both the case study systems. Primary production is responsible for the initial build-up of labile substrate that subsequently supports heterotrophic growth. However, allochthonous contributions of organic matter, and nitrogen fixation, are important in sustaining this productivity. The development and application of SHIMMER also highlights aspects of these systems that require further empirical research: quantifying nutrient budgets and biogeochemical rates, exploring seasonality and microbial growth and cell death. This will lead to increased understanding of how glacier forefields contribute to global biogeochemical cycling and climate under future ice retreat.

  1. Controllability of mixing errors in a coupled physical biogeochemical model of the North Atlantic: a nonlinear study using anamorphosis

    NASA Astrophysics Data System (ADS)

    Béal, D.; Brasseur, P.; Brankart, J.-M.; Ourmières, Y.; Verron, J.

    2009-06-01

    In biogeochemical models coupled to ocean circulation models, vertical mixing is an important physical process which governs the nutrient supply and the plankton residence in the euphotic layer. However, mixing is often poorly represented in numerical simulations because of approximate parameterizations of sub-grid scale turbulence, wind forcing errors and other mis-represented processes such as restratification by mesoscale eddies. Getting a sufficient knowledge of the nature and structure of these error sources is necessary to implement appropriate data assimilation methods and to evaluate their controllability by a given observation system. In this paper, Monte Carlo simulations are conducted to study mixing errors induced by approximate wind forcings in a three-dimensional coupled physical-biogeochemical model of the North Atlantic with a 1/4° horizontal resolution. An ensemble forecast involving 200 members is performed during the 1998 spring bloom, by prescribing realistic wind perturbations to generate mixing errors. It is shown that the biogeochemical response can be rather complex because of nonlinearities and threshold effects in the coupled model. In particular, the response of the surface phytoplankton depends on the region of interest and is particularly sensitive to the local stratification. We examine the robustness of the statistical relationships computed between the various physical and biogeochemical variables, and we show that significant information on the ecosystem can be obtained from observations of chlorophyll concentration or sea surface temperature. In order to improve the analysis step of sequential assimilation schemes, we propose to perform a simple nonlinear change of variables that operates separately on each state variable, by mapping their ensemble percentiles on the Gaussian percentiles. It is shown that this method is able to substantially reduce the estimation error with respect to the linear estimates computed by the Kalman

  2. Three-dimensional approach using two coupled models for description of hydrological and biogeochemical processes at the catchment scale

    NASA Astrophysics Data System (ADS)

    Plesca, Ina; Kraft, Philipp; Haas, Edwin; Klatt, Steffen; Butterbach-Bahl, Klaus; Frede, Hans-Georg; Breuer, Lutz

    2014-05-01

    Hydrological and biogeochemical transport through changing landscapes has been well described during the past years in literature. However, the uncertainties of combined water quality and water quantity models are still challenging, both due to a lack in process understanding as well to spatiotemporal heterogeneity of environmental conditions driving the processes. In order to reduce the uncertainty in water quality and runoff predictions at the catchment scale, a variety of different model approaches from empirical-conceptual to fully physical and process based models have been developed. In this study we present a new modelling approach for the investigation of hydrological processes and nutrient cycles, with a focus on nitrogen in a small catchment from Hessen, Germany. A hydrological model based on the model toolbox Catchment Modelling Framework (CMF) has been coupled with the process based biogeochemical model LandscapeDNDC. States, fluxes and parameters are exchanged between the models at high temporal and spatial resolution using the Python scripting language in order to obtain a 3-dimensional model application. The transport of water and nutrients through the catchment is modelled using a 3D Richards/Darcy approach for subsurface fluxes, a kinematic wave approach for surface runoff and a Penman-Monteith based calculation of evapotranspiration. Biogeochemical processes are modelled by Landscape-DNDC, including plant growth and biomass allocation, organic matter mineralisation, nitrification, denitrification and associated nitrous oxide emissions. The interactions and module connectivity between the two coupled models, as well as the model application on a 3.7 km² catchment with the runoff results and nitrogen quantification will be presented in this study.

  3. Assessment of the GHG reduction potential from energy crops using a combined LCA and biogeochemical process models: a review.

    PubMed

    Jiang, Dong; Hao, Mengmeng; Fu, Jingying; Wang, Qiao; Huang, Yaohuan; Fu, Xinyu

    2014-01-01

    The main purpose for developing biofuel is to reduce GHG (greenhouse gas) emissions, but the comprehensive environmental impact of such fuels is not clear. Life cycle analysis (LCA), as a complete comprehensive analysis method, has been widely used in bioenergy assessment studies. Great efforts have been directed toward establishing an efficient method for comprehensively estimating the greenhouse gas (GHG) emission reduction potential from the large-scale cultivation of energy plants by combining LCA with ecosystem/biogeochemical process models. LCA presents a general framework for evaluating the energy consumption and GHG emission from energy crop planting, yield acquisition, production, product use, and postprocessing. Meanwhile, ecosystem/biogeochemical process models are adopted to simulate the fluxes and storage of energy, water, carbon, and nitrogen in the soil-plant (energy crops) soil continuum. Although clear progress has been made in recent years, some problems still exist in current studies and should be addressed. This paper reviews the state-of-the-art method for estimating GHG emission reduction through developing energy crops and introduces in detail a new approach for assessing GHG emission reduction by combining LCA with biogeochemical process models. The main achievements of this study along with the problems in current studies are described and discussed. PMID:25045736

  4. Assessment of the GHG Reduction Potential from Energy Crops Using a Combined LCA and Biogeochemical Process Models: A Review

    PubMed Central

    Jiang, Dong; Hao, Mengmeng; Wang, Qiao; Huang, Yaohuan; Fu, Xinyu

    2014-01-01

    The main purpose for developing biofuel is to reduce GHG (greenhouse gas) emissions, but the comprehensive environmental impact of such fuels is not clear. Life cycle analysis (LCA), as a complete comprehensive analysis method, has been widely used in bioenergy assessment studies. Great efforts have been directed toward establishing an efficient method for comprehensively estimating the greenhouse gas (GHG) emission reduction potential from the large-scale cultivation of energy plants by combining LCA with ecosystem/biogeochemical process models. LCA presents a general framework for evaluating the energy consumption and GHG emission from energy crop planting, yield acquisition, production, product use, and postprocessing. Meanwhile, ecosystem/biogeochemical process models are adopted to simulate the fluxes and storage of energy, water, carbon, and nitrogen in the soil-plant (energy crops) soil continuum. Although clear progress has been made in recent years, some problems still exist in current studies and should be addressed. This paper reviews the state-of-the-art method for estimating GHG emission reduction through developing energy crops and introduces in detail a new approach for assessing GHG emission reduction by combining LCA with biogeochemical process models. The main achievements of this study along with the problems in current studies are described and discussed. PMID:25045736

  5. Project Summary. ANALYTICAL ELEMENT MODELING OF COASTAL AQUIFERS

    EPA Science Inventory

    Four topics were studied concerning the modeling of groundwater flow in coastal aquifers with analytic elements: (1) practical experience was obtained by constructing a groundwater model of the shallow aquifers below the Delmarva Peninsula USA using the commercial program MVAEM; ...

  6. High-resolution mineralogical characterization and biogeochemical modeling of uranium reaction pathways at the FRC

    SciTech Connect

    Chen Zhu

    2006-06-15

    High-Resolution Mineralogical Characterization and Biogeochemical Modeling of Uranium Reduction Pathways at the Oak Ridge Field-Research Center (FRC) Chen Zhu, Indiana University, David R. Veblen, Johns Hopkins University We have successfully completed a proof-of-concept, one-year grant on a three-year proposal from the former NABIR program, and here we seek additional two-year funding to complete and publish the research. Using a state-of-the-art 300-kV, atomic resolution, Field Emission Gun Transmission Electron Microscope (TEM), we have successfully identified three categories of mineral hosts for uranium in contaminated soils: (1) iron oxides; (2) mixed manganese-iron oxides; and (3) uranium phosphates. Method development using parallel electron energy loss spectroscopy (EELS) associated with the TEM shows great promise for characterizing the valence states of immobilized U during bioremediation. We have also collected 27 groundwater samples from two push-pull field biostimulation tests, which form two time series from zero to approximately 600 hours. The temporal evolution in major cations, anions, trace elements, and the stable isotopes 34S, 18O in sulfate, 15N in nitrate, and 13C in dissolved inorganic carbon (DIC) clearly show that biostimulation resulted in reduction of nitrate, Mn(IV), Fe(III), U(VI), sulfate, and Tc(VII), and these reduction reactions were intimately coupled with a complex network of inorganic reactions evident from alkalinity, pH, Na, K, Mg, and Ca concentrations. From these temporal trends, apparent zero order rates were regressed. However, our extensive suite of chemical and isotopic data sets, perhaps the first and only comprehensive data set available at the FRC, show that the derived rates from these field biostimulation experiments are composite and lump-sum rates. There were several reactions that were occurring at the same time but were masked by these pseudo-zero order rates. A reaction-path model comprising a total of nine

  7. A coastal ocean model with subgrid approximation

    NASA Astrophysics Data System (ADS)

    Walters, Roy A.

    2016-06-01

    A wide variety of coastal ocean models exist, each having attributes that reflect specific application areas. The model presented here is based on finite element methods with unstructured grids containing triangular and quadrilateral elements. The model optimizes robustness, accuracy, and efficiency by using semi-implicit methods in time in order to remove the most restrictive stability constraints, by using a semi-Lagrangian advection approximation to remove Courant number constraints, and by solving a wave equation at the discrete level for enhanced efficiency. An added feature is the approximation of the effects of subgrid objects. Here, the Reynolds-averaged Navier-Stokes equations and the incompressibility constraint are volume averaged over one or more computational cells. This procedure gives rise to new terms which must be approximated as a closure problem. A study of tidal power generation is presented as an example of this method. A problem that arises is specifying appropriate thrust and power coefficients for the volume averaged velocity when they are usually referenced to free stream velocity. A new contribution here is the evaluation of three approaches to this problem: an iteration procedure and two mapping formulations. All three sets of results for thrust (form drag) and power are in reasonable agreement.

  8. Modeled Global vs. Coastal Impacts on 1970 and 2005 Summer Daytime Temperature Trends in Coastal California

    NASA Astrophysics Data System (ADS)

    Habtezion, B. L.; Gonzalez, J.; Bornstein, R. D.

    2010-12-01

    California summertime July to August (JJA) mean monthly air temperatures (1970-2005) were analyzed for two California air basins: South Coast (SoCAB) and the San Francisco Bay Area (SFBA), which extended into the Central Valley (CV). Daily Tmin and Tmax values were used to produce average monthly values and spatial distributions of and Tmax values trends for each air basin. Results showed concurrent cooling in coastal areas and warming at further inland areas. This pattern suggests that the regional-warming of inland areas resulted in increased coastal sea breeze activity. Further investigations by use of mesoscale model simulations with the Regional Atmospheric Modeling System (RAMS) meso-met model with a horizontal grid resolution of 4 km on an inner grid over SoCAB were undertaken to investigate the effects of long-term changes due to green house gas (GHG) warming and land-use land-cover changes on coastal flows. Comparison of simulated present (2000-4) and past climate (1970-4) conditions showed significant increases in sea breeze activity and thus coastal cooling, which supports the observational analysis results that coastal cooling is an indirect “reverse reaction” of GHG warming. The magnitude and location of the simulated and observed coastal-cooling region were in good agreement. Urbanization effects on coastal environment were twofold: increased urban mechanical surface roughness retards sea breeze flows, while urban heat islands (UHIs) enhance them. Significant beneficial societal impacts will result from this observed reverse-reaction to global-warming, especially during UHI-growth periods, include decreased maximum: agricultural production, O3 levels, per-capita energy requirements for cooling, and human thermal-stress levels. Similar “reverse-reaction” effects should be found in other mid-latitude western coastal-regions.

  9. Modeling coastal current transport in the Gulf of Maine

    NASA Astrophysics Data System (ADS)

    Hetland, Robert D.; Signell, Richard P.

    2005-09-01

    A numerical simulation of the circulation in the Gulf of Maine is compared with observations taken during the spring and summer of 1994, focusing on two distinct coastal current systems. The eastern Maine coastal current is well mixed out to approximately 50m depth, with the influence of tidal mixing extending to 100m depth. In contrast, the western Maine coastal current consists mainly of a surface-trapped plume emanating from the Kennebec River. Various methods of model/data comparison are discussed, ranging from qualitative comparisons of surface temperature and currents to quantitative measurements of model skill. In particular, one primary metric of comparison is the amount and distribution of fresh water carried within the coastal current systems. In both coastal current systems, fresh-water flux has an approximately self-similar structure so that measurements taken at a single mooring location may be extrapolated to estimate the entire along-shore fresh-water flux. This self-similar structure is shown to be internally consistent within the model, and results in good model/data comparisons. The model has more skill at predicting fresh-water flux than other point-to-point surface property comparisons in all cases except surface salinity in the western Maine coastal current. This suggests fresh-water flux is a robust feature in the model, and a suitable metric for gauging the model ability to reproduce the broad-scale transport of the Maine coastal current system.

  10. HYDROBIOGEOCHEM: A coupled model of HYDROlogic transport and mixed BIOGEOCHEMical kinetic/equilibrium reactions in saturated-unsaturated media

    SciTech Connect

    Yeh, G.T.; Salvage, K.M.; Gwo, J.P.; Zachara, J.M.; Szecsody, J.E.

    1998-07-01

    The computer program HYDROBIOGEOCHEM is a coupled model of HYDROlogic transport and BIOGEOCHEMical kinetic and/or equilibrium reactions in saturated/unsaturated media. HYDROBIOGEOCHEM iteratively solves the two-dimensional transport equations and the ordinary differential and algebraic equations of mixed biogeochemical reactions. The transport equations are solved for all aqueous chemical components and kinetically controlled aqueous species. HYDROBIOGEOCHEM is designed for generic application to reactive transport problems affected by both microbiological and geochemical reactions in subsurface media. Input to the program includes the geometry of the system, the spatial distribution of finite elements and nodes, the properties of the media, the potential chemical and microbial reactions, and the initial and boundary conditions. Output includes the spatial distribution of chemical and microbial concentrations as a function of time and space, and the chemical speciation at user-specified nodes.

  11. Linking the Modern and Recent Record of Cabo Frio Upwelling with Local Climate and Biogeochemical Processes in Hypersaline Coastal Lagoons, Região dos Lagos, Rio de Janeiro, Brazil

    NASA Astrophysics Data System (ADS)

    McKenzie, J. A.; Nascimento, G. S.; Albuquerque, A. L.; Belem, A. L.; Carreira, R.; Eglinton, T. I.; Vasconcelos, C.

    2015-12-01

    A unique marine and lagoonal system along the coast east of Rio de Janeiro is being investigated to understand the impact of climatic variability on the South Atlantic carbon cycle and biomineralisation processes involved in carbonate precipitation in the hypersaline coastal lagoons. The region is dominated by a semi-arid microclimate attributed to the local coastal upwelling phenomenon near Cabo Frio. The intensity of the upwelling affects the hydrology of the annual water and biogeochemical cycles in the lagoons, as well as biogeochemical signals of environmental change recorded in both onshore and offshore sediments. Preliminary results of δ18O and δD values of water samples collected monthly in Lagoa Vermelha and Brejo do Espinho from 2011 to 2014 show lower values for waters corresponding to the wet season, reflecting increased input of meteoric water. The higher values for waters collected during the dry season reflect the greater amount of evaporation with increased seasonal aridity. Radiocarbon dating of Holocene marine and lagoonal cores indicates that Mg-carbonate precipitation in the lagoons is associated with high evaporation. Modern field observations for the last 3 years suggest that the amount of carbonate precipitation is correlated with evaporitic conditions associated with the upwelling phenomenon. A calibration study of hydrogen isotopic fractionation in the modern lagoons is underway to define a relationship between δDlipid of suspended particles and δDwater of associated water. This isotopic relationship will be applied to material obtained in cores from the lagoons. Offshore cores will be studied using well-tested paleotemperature proxies to evaluate the intensity of the upwelling during the Holocene. In summary, linking the coastal upwelling with the lagoonal hydrology has the potential to furnish important insights about the relationship between the local climate and paleoceanographic circulation associated with the regional carbon cycle.

  12. Regional impacts of iron-light colimitation in a global biogeochemical model

    NASA Astrophysics Data System (ADS)

    Galbraith, E. D.; Gnanadesikan, A.; Dunne, J. P.; Hiscock, M. R.

    2010-03-01

    Laboratory and field studies have revealed that iron has multiple roles in phytoplankton physiology, with particular importance for light-harvesting cellular machinery. However, although iron-limitation is explicitly included in numerous biogeochemical/ecosystem models, its implementation varies, and its effect on the efficiency of light harvesting is often ignored. Given the complexity of the ocean environment, it is difficult to predict the consequences of applying different iron limitation schemes. Here we explore the interaction of iron and nutrient cycles in an ocean general circulation model using a new, streamlined model of ocean biogeochemistry. Building on previously published parameterizations of photoadaptation and export production, the Biogeochemistry with Light Iron Nutrients and Gasses (BLING) model is constructed with only four explicit tracers but including macronutrient and micronutrient limitation, light limitation, and an implicit treatment of community structure. The structural simplicity of this computationally-inexpensive model allows us to clearly isolate the global effect that iron availability has on maximum light-saturated photosynthesis rates vs. the effect iron has on photosynthetic efficiency. We find that the effect on light-saturated photosynthesis rates is dominant, negating the importance of photosynthetic efficiency in most regions, especially the cold waters of the Southern Ocean. The primary exceptions to this occur in iron-rich regions of the Northern Hemisphere, where high light-saturated photosynthesis rates allow photosynthetic efficiency to play a more important role. In other words, the ability to efficiently harvest photons has little effect in regions where light-saturated growth rates are low. Additionally, we speculate that the phytoplankton cells dominating iron-limited regions tend to have relatively high photosynthetic efficiency, due to reduced packaging effects. If this speculation is correct, it would imply that

  13. Modeling Biogeochemical Reactive Transport in Fractured Granites: Implications for the Performance of a Deep Geological Repository

    NASA Astrophysics Data System (ADS)

    Molinero, J.; Samper, J.; Pedersen, K.; Puigdomenech, I.

    2003-12-01

    Several countries around the world are considering deep repositories in fractured granitic formations for the final disposal of high-level radioactive waste. Evaluating the long term safety of such repositories requires sound conceptual and numerical models which are being developed from data and knowledge gained from in situ experiments carried out at deep underground laboratories such as that of Žsp” in Sweden. One of the key aspects for performance assessment concerns to groundwater redox conditions because: (a) the presence of oxygen will affect to the corrosion of canisters, (b) possible production of hydrogen sulphide from sulphate reduction will also have a negative effect on these metallic containers, and (c) several long-lived radionuclides are much more soluble and mobile under oxidizing conditions. Several projects have been performed at Žsp” to investigate different aspects of the groundwater redox evolution. The vast amount of in situ-generated information has been used in this work to set up coupled hydrobiogeochemical models. Numerical models account for saturated groundwater flow, solute transport by advection, dispersion and molecular diffusion, geochemical reactions involving both the liquid and solid phases, and microbially-catallyzed processes. For the Žsp” site, modelling results provide quantitative support for the following conclusions. (A) At the operational phase of the repository, shallow fresh groundwater could reach the depth of the underground facility. Shallow groundwaters loose dissolved oxygen during the infiltration through soil layers and then, respiration of dissolved organic matter is induced along the flow paths through the reduction of Fe(III)-bearing minerals of the fracture zones. Microbial anaerobic respiration of DOC provides additional reducing capacity at the depth of the tunnel. (B) After repository closure, atmospheric oxygen will remain trapped within the tunnel. Abiotic consumption of this oxygen has been

  14. Simulating anchovy's full life cycle in the northern Aegean Sea (eastern Mediterranean): A coupled hydro-biogeochemical-IBM model

    NASA Astrophysics Data System (ADS)

    Politikos, D.; Somarakis, S.; Tsiaras, K. P.; Giannoulaki, M.; Petihakis, G.; Machias, A.; Triantafyllou, G.

    2015-11-01

    A 3-D full life cycle population model for the North Aegean Sea (NAS) anchovy stock is presented. The model is two-way coupled with a hydrodynamic-biogeochemical model (POM-ERSEM). The anchovy life span is divided into seven life stages/age classes. Embryos and early larvae are passive particles, but subsequent stages exhibit active horizontal movements based on specific rules. A bioenergetics model simulates the growth in both the larval and juvenile/adult stages, while the microzooplankton and mesozooplankton fields of the biogeochemical model provide the food for fish consumption. The super-individual approach is adopted for the representation of the anchovy population. A dynamic egg production module, with an energy allocation algorithm, is embedded in the bioenergetics equation and produces eggs based on a new conceptual model for anchovy vitellogenesis. A model simulation for the period 2003-2006 with realistic initial conditions reproduced well the magnitude of population biomass and daily egg production estimated from acoustic and daily egg production method (DEPM) surveys, carried out in the NAS during June 2003-2006. Model simulated adult and egg habitats were also in good agreement with observed spatial distributions of acoustic biomass and egg abundance in June. Sensitivity simulations were performed to investigate the effect of different formulations adopted for key processes, such as reproduction and movement. The effect of the anchovy population on plankton dynamics was also investigated, by comparing simulations adopting a two-way or a one-way coupling of the fish with the biogeochemical model.

  15. Decoupling of arsenic and iron release from ferrihydrite suspension under reducing conditions: a biogeochemical model

    PubMed Central

    Burnol, André; Garrido, Francis; Baranger, Philippe; Joulian, Catherine; Dictor, Marie-Christine; Bodénan, Françoise; Morin, Guillaume; Charlet, Laurent

    2007-01-01

    High levels of arsenic in groundwater and drinking water are a major health problem. Although the processes controlling the release of As are still not well known, the reductive dissolution of As-rich Fe oxyhydroxides has so far been a favorite hypothesis. Decoupling between arsenic and iron redox transformations has been experimentally demonstrated, but not quantitatively interpreted. Here, we report on incubation batch experiments run with As(V) sorbed on, or co-precipitated with, 2-line ferrihydrite. The biotic and abiotic processes of As release were investigated by using wet chemistry, X-ray diffraction, X-ray absorption and genomic techniques. The incubation experiments were carried out with a phosphate-rich growth medium and a community of Fe(III)-reducing bacteria under strict anoxic conditions for two months. During the first month, the release of Fe(II) in the aqueous phase amounted to only 3% to 10% of the total initial solid Fe concentration, whilst the total aqueous As remained almost constant after an initial exchange with phosphate ions. During the second month, the aqueous Fe(II) concentration remained constant, or even decreased, whereas the total quantity of As released to the solution accounted for 14% to 45% of the total initial solid As concentration. At the end of the incubation, the aqueous-phase arsenic was present predominately as As(III) whilst X-ray absorption spectroscopy indicated that more than 70% of the solid-phase arsenic was present as As(V). X-ray diffraction revealed vivianite Fe(II)3(PO4)2.8H2O in some of the experiments. A biogeochemical model was then developed to simulate these aqueous- and solid-phase results. The two main conclusions drawn from the model are that (1) As(V) is not reduced during the first incubation month with high Eh values, but rather re-adsorbed onto the ferrihydrite surface, and this state remains until arsenic reduction is energetically more favorable than iron reduction, and (2) the release of As

  16. Coastal Ecosystem Integrated Compartment Model (ICM): Modeling Framework

    NASA Astrophysics Data System (ADS)

    Meselhe, E. A.; White, E. D.; Reed, D.

    2015-12-01

    The Integrated Compartment Model (ICM) was developed as part of the 2017 Coastal Master Plan modeling effort. It is a comprehensive and numerical hydrodynamic model coupled to various geophysical process models. Simplifying assumptions related to some of the flow dynamics are applied to increase the computational efficiency of the model. The model can be used to provide insights about coastal ecosystems and evaluate restoration strategies. It builds on existing tools where possible and incorporates newly developed tools where necessary. It can perform decadal simulations (~ 50 years) across the entire Louisiana coast. It includes several improvements over the approach used to support the 2012 Master Plan, such as: additional processes in the hydrology, vegetation, wetland and barrier island morphology subroutines, increased spatial resolution, and integration of previously disparate models into a single modeling framework. The ICM includes habitat suitability indices (HSIs) to predict broad spatial patterns of habitat change, and it provides an additional integration to a dynamic fish and shellfish community model which quantitatively predicts potential changes in important fishery resources. It can be used to estimate the individual and cumulative effects of restoration and protection projects on the landscape, including a general estimate of water levels associated with flooding. The ICM is also used to examine possible impacts of climate change and future environmental scenarios (e.g. precipitation, Eustatic sea level rise, subsidence, tropical storms, etc.) on the landscape and on the effectiveness of restoration projects. The ICM code is publically accessible, and coastal restoration and protection groups interested in planning-level modeling are encouraged to explore its utility as a computationally efficient tool to examine ecosystem response to future physical or ecological changes, including the implementation of restoration and protection strategies.

  17. A Unified Multi-scale Model for Cross-Scale Evaluation and Integration of Hydrological and Biogeochemical Processes

    NASA Astrophysics Data System (ADS)

    Liu, C.; Yang, X.; Bailey, V. L.; Bond-Lamberty, B. P.; Hinkle, C.

    2013-12-01

    Mathematical representations of hydrological and biogeochemical processes in soil, plant, aquatic, and atmospheric systems vary with scale. Process-rich models are typically used to describe hydrological and biogeochemical processes at the pore and small scales, while empirical, correlation approaches are often used at the watershed and regional scales. A major challenge for multi-scale modeling is that water flow, biogeochemical processes, and reactive transport are described using different physical laws and/or expressions at the different scales. For example, the flow is governed by the Navier-Stokes equations at the pore-scale in soils, by the Darcy law in soil columns and aquifer, and by the Navier-Stokes equations again in open water bodies (ponds, lake, river) and atmosphere surface layer. This research explores whether the physical laws at the different scales and in different physical domains can be unified to form a unified multi-scale model (UMSM) to systematically investigate the cross-scale, cross-domain behavior of fundamental processes at different scales. This presentation will discuss our research on the concept, mathematical equations, and numerical execution of the UMSM. Three-dimensional, multi-scale hydrological processes at the Disney Wilderness Preservation (DWP) site, Florida will be used as an example for demonstrating the application of the UMSM. In this research, the UMSM was used to simulate hydrological processes in rooting zones at the pore and small scales including water migration in soils under saturated and unsaturated conditions, root-induced hydrological redistribution, and role of rooting zone biogeochemical properties (e.g., root exudates and microbial mucilage) on water storage and wetting/draining. The small scale simulation results were used to estimate effective water retention properties in soil columns that were superimposed on the bulk soil water retention properties at the DWP site. The UMSM parameterized from smaller

  18. Hydrodynamic modeling of Singapore's coastal waters: Nesting and model accuracy

    NASA Astrophysics Data System (ADS)

    Hasan, G. M. Jahid; van Maren, Dirk Sebastiaan; Ooi, Seng Keat

    2016-01-01

    The tidal variation in Singapore's coastal waters is influenced by large-scale, complex tidal dynamics (by interaction of the Indian Ocean and the South China Sea) as well as monsoon-driven low frequency variations, requiring a model with large spatial coverage. Close to the shores, the complex topography, influenced by headlands and small islands, requires a high resolution model to simulate tidal dynamics. This can be achieved through direct nesting or multi-scale nesting, involving multiple model grids. In this paper, we investigate the effect of grid resolution and multi-scale nesting on the tidal dynamics in Singapore's coastal waters, by comparing model results with observations using different statistical techniques. The results reveal that the intermediate-scale model is generally sufficiently accurate (equal to or better than the most refined model), but also that the most refined model is only more accurate when nested in the intermediate scale model (requiring multi-scale nesting). This latter is the result of the complex tidal dynamics around Singapore, where the dominantly diurnal tidal currents are decoupled from the semi-diurnal water level variations. Furthermore, different techniques to quantify model accuracy (harmonic analysis, basic statistics and more complex statistics) are inconsistent in determining which model is more accurate.

  19. A Coupled Ocean General Circulation, Biogeochemical, and Radiative Model of the Global Oceans: Seasonal Distributions of Ocean Chlorophyll and Nutrients

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)

    2000-01-01

    A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability. and the interactions among three functional phytoplankton groups (diatoms. chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (greater than 1000 km) model chlorophyll results are in overall agreement with CZCS pigments in many global regions. Seasonal variability observed in the CZCS is also represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are generally in conformance although occasional departures are apparent. Model nitrate distributions agree with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicates that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent many aspects of the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.

  20. Nitrous oxide emissions from cropland: a procedure for calibrating the DayCent biogeochemical model using inverse modelling

    USGS Publications Warehouse

    Rafique, Rashad; Fienen, Michael N.; Parkin, Timothy B.; Anex, Robert P.

    2013-01-01

    DayCent is a biogeochemical model of intermediate complexity widely used to simulate greenhouse gases (GHG), soil organic carbon and nutrients in crop, grassland, forest and savannah ecosystems. Although this model has been applied to a wide range of ecosystems, it is still typically parameterized through a traditional “trial and error” approach and has not been calibrated using statistical inverse modelling (i.e. algorithmic parameter estimation). The aim of this study is to establish and demonstrate a procedure for calibration of DayCent to improve estimation of GHG emissions. We coupled DayCent with the parameter estimation (PEST) software for inverse modelling. The PEST software can be used for calibration through regularized inversion as well as model sensitivity and uncertainty analysis. The DayCent model was analysed and calibrated using N2O flux data collected over 2 years at the Iowa State University Agronomy and Agricultural Engineering Research Farms, Boone, IA. Crop year 2003 data were used for model calibration and 2004 data were used for validation. The optimization of DayCent model parameters using PEST significantly reduced model residuals relative to the default DayCent parameter values. Parameter estimation improved the model performance by reducing the sum of weighted squared residual difference between measured and modelled outputs by up to 67 %. For the calibration period, simulation with the default model parameter values underestimated mean daily N2O flux by 98 %. After parameter estimation, the model underestimated the mean daily fluxes by 35 %. During the validation period, the calibrated model reduced sum of weighted squared residuals by 20 % relative to the default simulation. Sensitivity analysis performed provides important insights into the model structure providing guidance for model improvement.

  1. Numerical modeling of coastal polynyas in East Antarctica

    NASA Astrophysics Data System (ADS)

    Kusahara, K.; Hasumi, H.

    2008-12-01

    Coastal polynyas are the area of open water or thin ice surrounded by coastline and thick ice in winter, ranging in the horizontal scale from a few to 100 km. In coastal polynyas, large heat loss occurs due to the direct contact of open water/thin ice with the colder air. As a result of the large heat loss, coastal polynyas exhibit high sea-ice production rates. The high sea-ice production leads to formation of dense shelf water. Around Antarctica, such dense shelf water formed in the coastal polynyas plays an important role in the formation and spreading of Antarctic Bottom Water. Using a sea ice - ocean coupled model with fine horizontal resolution around East Antarctica ( ~ 15 km), sea-ice production and dense shelf water formation in the coastal polynyas are investigated. The model well reproduces the locations of coastal polynyas and high sea-ice production there. In East Antarctica, the Cape Darnley polynya (CDP) is the highest sea-ice production area and the Mertz Glacier polynya (MGP) is the second highest one in the model. Water denser than 27.88 kg m-3 over the shelf is formed in coastal polynyas. Besides the CDP and the MGP, polynyas near Barrier Bay, Shackleton Ice Shelf, Vincenness Bay, Dibble Iceberg Tongue, and Ninnis Glacier also contribute to dense shelf water formation. Sea-ice production largely depends on the value of the minimum sea-ice thickness in a grid. To model the formation of frazil ice and high sea-ice production in coastal polynyas, a large value of the minimum sea-ice thickness ( 50 cm in this study) is required. Blocking effect of sea-ice transport by grounded icebergs is also tested by the model. From a series of numerical experiments, we found that the blocking effect has a large impact on both sea-ice production and dense shelf water formation in coastal polynyas.

  2. Quantifying the Variability of CH4 Emissions from Pan-Arctic Lakes with Lake Biogeochemical and Landscape Evolution Models

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Zhuang, Q.

    2014-12-01

    Recent studies in the arctic and subarctic show that CH4 emissions from pan-arctic lakes are playing much more significant roles in the regional carbon cycling than previously estimated. Permafrost thawing due to pronounced warming at northern high latitudes affects lake morphology, changing its CH4 emissions. Thermokarst can enlarge the extent of artic lakes, exposing stable ancient carbon buried in the permafrost zone for degradation and changing a previously known carbon sink to a large carbon source. In some areas, the thawing of subarctic discontinuous and isolated permafrost can diminish thermokarst lakes. To date, few models have considered these important hydrological and biogeochemical processes to provide adequate estimation of CH4 emissions from these lakes. To fill this gap, we have developed a process-based climate-sensitive lake biogeochemical model and a landscape evolution model, which have been applied to quantify the state and variability of CH4 emissions from this freshwater system. Site-level experiments show the models are capable to capture the spatial and temporal variability of CH4 emissions from lakes across Siberia and Alaska. With the lake biogeochemical model solely, we estimate that the magnitude of CH4 emissions from lakes is 13.2 Tg yr-1 in the north of 60 ºN at present, which is on the same order of CH4 emissions from northern high-latitude wetlands. The maximum increment is 11.8 Tg CH4 yr-1 by the end of the 21st century when the worst warming scenario is assumed. We expect the landscape evolution model will improve the existing estimates.

  3. Our evolving conceptual model of the coastal eutrophication problem

    USGS Publications Warehouse

    Cloern, James E.

    2001-01-01

    A primary focus of coastal science during the past 3 decades has been the question: How does anthropogenic nutrient enrichment cause change in the structure or function of nearshore coastal ecosystems? This theme of environmental science is recent, so our conceptual model of the coastal eutrophication problem continues to change rapidly. In this review, I suggest that the early (Phase I) conceptual model was strongly influenced by limnologists, who began intense study of lake eutrophication by the 1960s. The Phase I model emphasized changing nutrient input as a signal, and responses to that signal as increased phytoplankton biomass and primary production, decomposition of phytoplankton-derived organic matter, and enhanced depletion of oxygen from bottom waters. Coastal research in recent decades has identified key differences in the responses of lakes and coastal-estuarine ecosystems to nutrient enrichment. The contemporary (Phase II) conceptual model reflects those differences and includes explicit recognition of (1) system-specific attributes that act as a filter to modulate the responses to enrichment (leading to large differences among estuarine-coastal systems in their sensitivity to nutrient enrichment); and (2) a complex suite of direct and indirect responses including linked changes in: water transparency, distribution of vascular plants and biomass of macroalgae, sediment biogeochemistry and nutrient cycling, nutrient ratios and their regulation of phytoplankton community composition, frequency of toxic/harmful algal blooms, habitat quality for metazoans, reproduction/growth/survival of pelagic and benthic invertebrates, and subtle changes such as shifts in the seasonality of ecosystem functions. Each aspect of the Phase II model is illustrated here with examples from coastal ecosystems around the world. In the last section of this review I present one vision of the next (Phase III) stage in the evolution of our conceptual model, organized around 5

  4. C-GEM (v 1.0): a new, cost-efficient biogeochemical model for estuaries and its application to a funnel-shaped system

    NASA Astrophysics Data System (ADS)

    Volta, C.; Arndt, S.; Savenije, H. H. G.; Laruelle, G. G.; Regnier, P.

    2014-07-01

    Reactive transport models (RTMs) are powerful tools for disentangling the complex process interplay that drives estuarine biogeochemical dynamics, for assessing the quantitative role of estuaries in global biogeochemical cycles and for predicting their response to anthropogenic disturbances (land-use change, climate change and water management). Nevertheless, the application of RTMs for a regional or global estimation of estuarine biogeochemical transformations and fluxes is generally compromised by their high computational and data demands. Here, we describe C-GEM (Carbon-Generic Estuary Model), a new one-dimensional, computationally efficient RTM that reduces data requirements by using a generic, theoretical framework based on the direct relationship between estuarine geometry and hydrodynamics. Despite its efficiency, it provides an accurate description of estuarine hydrodynamics, salt transport and biogeochemistry on the appropriate spatio-temporal scales. We provide a detailed description of the model, as well as a protocol for its set-up. The new model is then applied to the funnel-shaped Scheldt estuary (BE/NL), one of the best-surveyed estuarine systems in the world. Its performance is evaluated through comprehensive model-data and model-model comparisons. Model results show that C-GEM captures the dominant features of the biogeochemical cycling in the Scheldt estuary. Longitudinal steady-state profiles of oxygen, ammonium, nitrate and silica are generally in good agreement with measured data. In addition, simulated, system-wide integrated reaction rates of the main pelagic biogeochemical processes are comparable with those obtained using a high-resolved, two-dimensional RTM. A comparison of fully transient simulations results with those of a two-dimensional model shows that the estuarine net ecosystem metabolism (NEM) only differs by about 10%, while system-wide estimates of individual biogeochemical processes never diverge by more than 40%. A sensitivity

  5. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

    NASA Astrophysics Data System (ADS)

    Gutknecht, E.; Dadou, I.; Le Vu, B.; Cambon, G.; Sudre, J.; Garçon, V.; Machu, E.; Rixen, T.; Kock, A.; Flohr, A.; Paulmier, A.; Lavik, G.

    2013-06-01

    The Eastern Boundary Upwelling Systems (EBUS) contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs), EBUS represent key regions for the oceanic nitrogen (N) cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O) occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS) taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (northern Benguela) using the high-resolution hydrodynamic ROMS model. We present here a validation using in situ and satellite data as well as diagnostic metrics and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate, and chlorophyll a concentrations, and the rates of microbial processes (e.g, NH4+ and NO2- oxidation, NO3- reduction, and anammox) as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking, and nitrification play a key role for the low-oxygen water content, N loss, and N2O concentrations in the OMZ. Moreover, the explicit parameterization of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is necessary to improve the representation of microbial activity linked with the OMZ. The simulated minimum oxygen concentrations are driven by

  6. Integrating 'omic' data and biogeochemical modeling: the key to understanding the microbial regulation of matter cycling in soil

    NASA Astrophysics Data System (ADS)

    Pagel, Holger; Kandeler, Ellen; Seifert, Jana; Camarinha-Silva, Amélia; Kügler, Philipp; Rennert, Thilo; Poll, Christian; Streck, Thilo

    2016-04-01

    Matter cycling in soils and associated soil functions are intrinsically controlled by microbial dynamics. It is therefore crucial to consider functional traits of microorganisms in biogeochemical models. Tremendous advances in 'omic' methods provide a plethora of data on physiology, metabolic capabilities and ecological life strategies of microorganisms in soil. Combined with isotopic techniques, biochemical pathways and transformations can be identified and quantified. Such data have been, however, rarely used to improve the mechanistic representation of microbial dynamics in soil organic matter models. It is the goal of the Young Investigator Group SoilReg to address this challenge. Our general approach is to tightly integrate experiments and biochemical modeling. NextGen sequencing will be applied to identify key functional groups. Active microbial groups will be quantified by measurements of functional genes and by stable isotope probing methods of DNA and proteins. Based on this information a biogeochemical model that couples a mechanistic representation of microbial dynamics with physicochemical processes will be set up and calibrated. Sensitivity and stability analyses of the model as well as scenario simulations will reveal the importance of intrinsic and extrinsic controls of organic matter turnover. We will demonstrate our concept and present first results of two case studies on pesticide degradation and methane oxidation.

  7. Establishing a National Coastal Change Model for Scotland

    NASA Astrophysics Data System (ADS)

    Fitton, James; Hansom, Jim; Rennie, Alistair

    2015-04-01

    The Climate Change (Scotland) Act 2009 requires the development of an Adaptation Programme to take forward the risks identified within the UK's Climate Change Risk Assessment (UK-CCRA). The UK-CCRA anticipates increases in sea level, coastal erosion and coastal flooding to increasingly affect Scotland's soft coastlines and the assets found on these coasts. Shoreline Management Plans have been produced for only short sections of the Scottish coast which limits the information available to coastal managers. Consequently a National Coastal Change Assessment (NCCA) has been commissioned by the Scottish Government and is supported by a number of agencies. The assessment aims to create a shared evidence base to support more sustainable coastal and terrestrial planning decisions in the light of a changing climate. The NCCA aims to establish historic coastal change by extracting the georectified coastline position from OS 2nd Edition Country Series maps (1892-1905) and to then compare it to both the 1970's and current coastal position (updated by LiDAR datasets where available) in order to estimate past erosion/accretion rates. Using the historic coastal change rates the coastline position can then be projected into the future, albeit mediated by a Coastal Erosion Susceptibility Model (CESM) whose function is to limit erosion to areas where the hinterland is susceptible to erosion. The CESM is a national GIS assessment at 50 m raster resolution which models the physical susceptibility of the coast. The model uses a range of data (elevation, rockhead elevation, proximity to the coast, wave exposure, sediment accretion, and coastal defences) which are ranked and amalgamated into a single raster dataset reflecting erosion susceptibility. Using the erosion rates combined with a number of socioeconomic datasets, key assets at risk from future coastal erosion can be identified. The NCCA aims to inform existing strategic planning (Shoreline Management Plans, Flood Risk Management

  8. Prospects for improving the representation of coastal and shelf seas in global ocean models

    NASA Astrophysics Data System (ADS)

    Holt, Jason; New, Adrian; Liu, Hedong; Coward, Andrew; Ashworth, Mike; Pickles, Stephen; Harle, James; Siddorn, John

    2013-04-01

    The ability to accurately represent coastal and shelf seas in global scale ocean models represents one of the on-going challenges of ocean modelling, particularly when the global model is to be used in biogeochemical, climate and Earth System simulations. The motivation for this is, however, wide ranging and includes both upscaling and downscaling issues. The dynamic motivation includes dense water formation on high latitude shelves and cascading into the deeper ocean, lateral frictional/mixing effects, pinch points and exchange regions, whereas the biogeochemical motivation include carbon and nutrient cycling, shelf-ocean exchanges and land-sea coupling. Moreover, society interacts with the ocean at a local/regional scale for example through the exploitation of Living Marine Resources and the drive to achieve and maintain Good Environmental Status. Hence, global assessments of vulnerability to climate change and other large scale drivers require information at the scale of this interaction. Here, we review the physical processes prevalent in shelf seas globally and their scales, and provide a baseline assessment of three global model configurations (NEMO at resolutions of 1, 1/4 and 1/12 deg.) and a regional model (NEMO AMM7;~7km resolution) focusing on the NW European continental shelf. Then we discuss the options for improving on this position based on current and prospective modelling approaches. We contrast structured and unstructured (finite element and finite volume) approaches, highlighting some novel ways forward for both, including generalised grid methods and global nesting approaches. We conclude that a single solution is not available currently or on intermediate timescales that can accommodate both upscaling and downscaling for both the dynamics and biogeochemistry, particularly in an Earth Systems context; as is often the case the choice of approach remains context dependent. Instead, we match the various options with the original motivations and

  9. Sea Level Rise National Coastal Property Model

    EPA Science Inventory

    The impact of sea level rise on coastal properties depends critically on the human response to the threat, which in turn depends on several factors, including the immediacy of the risk, the magnitude of property value at risk, options for adapting to the threat and the cost of th...

  10. Sea Level Rise Coastal Property Model

    EPA Science Inventory

    The impact of sea level rise on coastal properties depends critically on the human response to the threat, which in turn depends on several factors, including the immediacy of the risk, the magnitude of property value at risk, options for adapting to the threat and the cost of th...

  11. Arsenic in New Jersey Coastal Plain streams, sediments, and shallow groundwater: effects from different geologic sources and anthropogenic inputs on biogeochemical and physical mobilization processes

    USGS Publications Warehouse

    Barringer, Julia L.; Reilly, Pamela A.; Eberl, Dennis D.; Mumford, Adam C.; Benzel, William M.; Szabo, Zoltan; Shourds, Jennifer L.; Young, Lily Y.

    2013-01-01

    With a history of agriculture in the New Jersey Coastal Plain, anthropogenic inputs of As, such as residues from former pesticide applications in soils, can amplify any geogenic As in runoff. Such inputs contribute to an increased total As load to a stream at high stages of flow. As a result of yet another anthropogenic influence, microbes that reduce and mobilize As beneath the streambeds are stimulated by inputs of dissolved organic carbon (DOC). Although DOC is naturally occurring, anthropogenic contributions from wastewater inputs may deliver increased levels of DOC to subsurface soils and ultimately groundwater. Arsenic concentrations may increase with the increases in pH of groundwater and stream water in developed areas receiving wastewater inputs, as As mobilization caused by pH-controlled sorption and desorption reactions are likely to occur in waters of neutral or alkaline pH (for example, Nimick and others, 1998; Barringer and others, 2007b). Because of the difference in As content of the geologic materials in the two sub-provinces of the Coastal Plain, the amount of As that is mobile in groundwater and stream water is, potentially, substantially greater in the Inner Coastal Plain than in the Outer Coastal Plain. In turn, streams within the Inner and Outer Coastal Plain can receive substantially more As in groundwater discharge from developed areas than from environments where DOC appears to be of natural origin.

  12. Multidecadal simulation of coastal fog with a regional climate model

    NASA Astrophysics Data System (ADS)

    O'Brien, Travis A.; Sloan, Lisa C.; Chuang, Patrick Y.; Faloona, Ian C.; Johnstone, James A.

    2013-06-01

    In order to model stratocumulus clouds and coastal fog, we have coupled the University of Washington boundary layer model to the regional climate model, RegCM (RegCM-UW). By comparing fog occurrences observed at various coastal airports in the western United States, we show that RegCM-UW has success at modeling the spatial and temporal (diurnal, seasonal, and interannual) climatology of northern California coastal fog. The quality of the modeled fog estimate depends on whether coast-adjacent ocean or land grid cells are used; for the model runs shown here, the oceanic grid cells seem to be most appropriate. The interannual variability of oceanic northern California summertime fog, from a multi-decadal simulation, has a high and statistically significant correlation with the observed interannual variability ( r = 0.72), which indicates that RegCM-UW is capable of investigating the response of fog to long-term climatological forcing. While RegCM-UW has a number of aspects that would benefit from further investigation and development, RegCM-UW is a new tool for investigating the climatology of coastal fog and the physical processes that govern it. We expect that with appropriate physical parameterizations and moderate horizontal resolution, other climate models should be capable of simulating coastal fog. The source code for RegCM-UW is publicly available, under the GNU license, through the International Centre for Theoretical Physics.

  13. Integration of the DAYCENT Biogeochemical Model within a Multi-Model Framework

    SciTech Connect

    David Muth

    2012-07-01

    Agricultural residues are the largest near term source of cellulosic 13 biomass for bioenergy production, but removing agricultural residues sustainably 14 requires considering the critical roles that residues play in the agronomic system. 15 Determining sustainable removal rates for agricultural residues has received 16 significant attention and integrated modeling strategies have been built to evaluate 17 sustainable removal rates considering soil erosion and organic matter constraints. 18 However the current integrated model does not quantitatively assess soil carbon 19 and long term crop yields impacts of residue removal. Furthermore the current 20 integrated model does not evaluate the greenhouse gas impacts of residue 21 removal, specifically N2O and CO2 gas fluxes from the soil surface. The DAYCENT 22 model simulates several important processes for determining agroecosystem 23 performance. These processes include daily Nitrogen-gas flux, daily carbon dioxide 24 flux from soil respiration, soil organic carbon and nitrogen, net primary productivity, 25 and daily water and nitrate leaching. Each of these processes is an indicator of 26 sustainability when evaluating emerging cellulosic biomass production systems for 27 bioenergy. A potentially vulnerable cellulosic biomass resource is agricultural 28 residues. This paper presents the integration of the DAYCENT model with the 29 existing integration framework modeling tool to investigate additional environment 30 impacts of agricultural residue removal. The integrated model is extended to 31 facilitate two-way coupling between DAYCENT and the existing framework. The 32 extended integrated model is applied to investigate additional environmental 33 impacts from a recent sustainable agricultural residue removal dataset. The 34 integrated model with DAYCENT finds some differences in sustainable removal 35 rates compared to previous results for a case study county in Iowa. The extended 36 integrated model with

  14. Biogeochemical Modeling of Wetland Carbon Sequestration and Greenhouse Gas Emission Factors for the U.S. Temperate Prairie Ecoregions

    NASA Astrophysics Data System (ADS)

    Abdul-Aziz, O.; WU, Y.; Liu, S.; Grangaard, L.; Liu, J.

    2011-12-01

    Wetlands are known to play a critical role in carbon sequestration and major greenhouse gas (GHG) emissions. They are important depositional systems interfacing the terrestrial and aquatic ecosystems. We included a wetland component into the well-known terrestrial soil organic carbon dynamics model, CENTURY IV to simulate/predict carbon sequestration and emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from wetland ecosystems. The CENTURY-Wetland package was incorporated into a generalized ensemble biogeochemical modeling system (GEMS) to develop a regional-scale wetland biogeochemical model. We applied the regional CENTURY-Wetland to simulate major GHG emissions and carbon sequestration of the wetlands in the U.S. Temperate Prairie Ecoregions (i.e., US EPA Level II Ecoregion 9.2). The simulations are analyzed to develop regional emissions factors of wetland CO2, CH4, and N2O under historical, as well as different land use/cover and IPCC climate change scenarios. This research is a part of the USGS efforts to quantify 'biological' carbon sequestrations under a changing climate, land use/cover, and policy scenarios. The CENTURY-Wetland will be applied to other U.S. ecoregions for quantifying the wetland carbon sequestration and GHG emissions from the continental United States.

  15. Coastal mapping and modelling of Tuktoyaktuk Harbour, Western Arctic, Canada

    NASA Astrophysics Data System (ADS)

    Manson, G. K.

    2015-12-01

    Climate models suggest that sea ice in the Arctic is expected to decrease and that the frequency of storms bringing high waves and storm surges is expected to increase. Reduced sea ice, higher waves, and higher storm surge water levels have implications for coastal infrastructure, nearshore sediment transport, and rates of coastal change. Tuktoyaktuk is an important shipping terminal servicing the petroleum industry and Inuvialuit communities in the western Canadian Arctic. The hydrodynamic model Delft3D is used to model sediment transport in Tuktoyaktuk Harbour and the approaches. For nearshore applications, Delft3D works best with a seamless coastal digital elevation model (DEM). A DEM was constructed from a variety of sources. Terrestrial LiDAR (Light Detection And Ranging) uses an infrared laser to construct a detailed elevation model of the terrestrial coastal zone. Multibeam bathymetry uses arrays of acoustic signals to collect detailed of the subaqueous coastal zone. Bathymetry data, and charts from the Canadian Hydrographic Service supplement the offshore bathymetry. The shoreline is derived from CanCoast, a nationally consistent geospatial database of Canada's marine coasts. The Coastal Information System (CIS) supplements CanCoast and describes coastal geomorphology in local areas. With these data, Delft3D delivered wave, current, and sediment transport data in a common reference frame. When compared to measurements, the model successfully simulates waves and currents. Output from Delft3D was mapped into a Geographic Information System, and combined with other data to help an Arctic community and industries adapt to potential climate-related hazards .

  16. A mass-conserving advection scheme for offline simulation of scalar transport in coastal ocean models

    NASA Astrophysics Data System (ADS)

    Gillibrand, P. A.; Herzfeld, M.

    2016-05-01

    We present a flux-form semi-Lagrangian (FFSL) advection scheme designed for offline scalar transport simulation with coastal ocean models using curvilinear horizontal coordinates. The scheme conserves mass, overcoming problems of mass conservation typically experienced with offline transport models, and permits long time steps (relative to the Courant number) to be used by the offline model. These attributes make the method attractive for offline simulation of tracers in biogeochemical or sediment transport models using archived flow fields from hydrodynamic models. We describe the FFSL scheme, and test it on two idealised domains and one real domain, the Great Barrier Reef in Australia. For comparison, we also include simulations using a traditional semi-Lagrangian advection scheme for the offline simulations. We compare tracer distributions predicted by the offline FFSL transport scheme with those predicted by the original hydrodynamic model, assess the conservation of mass in all cases and contrast the computational efficiency of the schemes. We find that the FFSL scheme produced very good agreement with the distributions of tracer predicted by the hydrodynamic model, and conserved mass with an error of a fraction of one percent. In terms of computational speed, the FFSL scheme was comparable with the semi-Lagrangian method and an order of magnitude faster than the full hydrodynamic model, even when the latter ran in parallel on multiple cores. The FFSL scheme presented here therefore offers a viable mass-conserving and computationally-efficient alternative to traditional semi-Lagrangian schemes for offline scalar transport simulation in coastal models.

  17. Modeling greenhouse gas emissions and nutrient transport in managed arable soils with a fully coupled hydrology-biogeochemical modeling system

    NASA Astrophysics Data System (ADS)

    Haas, Edwin; Klatt, Steffen; Kiese, Ralf; Butterbach-Bahl, Klaus; Kraft, Philipp; Breuer, Lutz

    2015-04-01

    evapotranspiration is based on Penman-Monteith. Biogeochemical processes are modelled by LandscapeDNDC, including soil microclimate, plant growth and biomass allocation, organic matter mineralisation, nitrification, denitrification, chemodenitrification and methanogenesis producing and consuming soil based greenhouse gases. The model application will present first results of the coupled model to simulate soil based greenhouse gas emissions as well as nitrate discharge from the Yanting catchment. The model application will also present the effects of different management practices (fertilization rates and timings, tilling, residues management) on the redistribution of N surplus within the catchment causing biomass productivity gradients and different levels of indirect N2O emissions along topographical gradients.

  18. Seasonal Distributions of Global Ocean Chlorophyll and Nutrients: Analysis with a Coupled Ocean General Circulation Biogeochemical, and Radiative Model

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.

    1999-01-01

    A coupled general ocean circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. The model is driven by climatological meteorological conditions, cloud cover, and sea surface temperature. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chorophytes, and picoplankton) and three nutrient groups (nitrate, ammonium, and silicate). Phytoplankton groups are initialized as homogeneous fields horizontally and vertically, and allowed to distribute themselves according to the prevailing conditions. Basin-scale model chlorophyll results are in very good agreement with CZCS pigments in virtually every global region. Seasonal variability observed in the CZCS is also well represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are also in good conformance, although occasional departures are apparent. Agreement of nitrate distributions with in situ data is even better, including seasonal dynamics, except for the equatorial Atlantic. The good agreement of the model with satellite and in situ data sources indicates that the model dynamics realistically simulate phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization, and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent the great diversity of physical, biological

  19. Simulation of glacial ocean biogeochemical tracer and isotope distributions based on the PMIP3 suite of climate models

    NASA Astrophysics Data System (ADS)

    Khatiwala, Samar; Muglia, Juan; Kvale, Karin; Schmittner, Andreas

    2016-04-01

    In the present climate system, buoyancy forced convection at high-latitudes together with internal mixing results in a vigorous overturning circulation whose major component is North Atlantic Deep Water. One of the key questions of climate science is whether this "mode" of circulation persisted during glacial periods, and in particular at the Last Glacial Maximum (LGM; 21000 years before present). Resolving this question is both important for advancing our understanding of the climate system, as well as a critical test of numerical models' ability to reliably simulate different climates. The observational evidence, based on interpreting geochemical tracers archived in sediments, is conflicting, as are simulations carried out with state-of-the-art climate models (e.g., as part of the PMIP3 suite), which, due to the computational cost involved, do not by and large include biogeochemical and isotope tracers that can be directly compared with proxy data. Here, we apply geochemical observations to evaluate the ability of several realisations of an ocean model driven by atmospheric forcing from the PMIP3 suite of climate models to simulate global ocean circulation during the LGM. This results in a wide range of circulation states that are then used to simulate biogeochemical tracer and isotope (13C, 14C and Pa/Th) distributions using an efficient, "offline" computational scheme known as the transport matrix method (TMM). One of the key advantages of this approach is the use of a uniform set of biogeochemical and isotope parameterizations across all the different circulations based on the PMIP3 models. We compare these simulated distributions to both modern observations and data from LGM ocean sediments to identify similarities and discrepancies between model and data. We find, for example, that when the ocean model is forced with wind stress from the PMIP3 models the radiocarbon age of the deep ocean is systematically younger compared with reconstructions. Changes in

  20. Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

    SciTech Connect

    Khangaonkar, Tarang; Sackmann, Brandon; Long, Wen; Mohamedali, Teizeen; Roberts, Mindy

    2012-08-14

    Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid Finite-Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinetics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5–20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. Finally, by late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific

  1. Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

    NASA Astrophysics Data System (ADS)

    Khangaonkar, Tarang; Sackmann, Brandon; Long, Wen; Mohamedali, Teizeen; Roberts, Mindy

    2012-09-01

    Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid Finite-Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinetics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5-20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. By late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific Ocean.

  2. Conceptual hydrogeological model of a coastal hydrosystem in the mediterranean

    NASA Astrophysics Data System (ADS)

    Mitropapas, Anastasios; Pouliaris, Christos; Apostolopoulos, Georgios; Vasileiou, Eleni; Schüth, Christoph; Vienken, Thomas; Dietrich, Peter; Kallioras, Andreas

    2016-04-01

    Groundwater resources management in the Mediterranean basin is an issue of paramount importance that becomes a necessity in the case of the coastal hydrosystems. Coastal aquifers are considered very sensitive ecosystems that are subject to several stresses being of natural or anthropogenic origin. The coastal hydrosystem of Lavrion can be used as a reference site that incorporates multi-disciplinary environmental problems, which are typical for Circum-Mediterranean. This study presents the synthesis of a wide range of field activities within the area of Lavrion including the monitoring of water resources within all hydrologic zones (surface, unsaturated and saturated) and geophysical (invasive and non-invasive) surveys. Different monitoring approaches -targeting to the collection of hydrochemical, geophysical, geological, hydrological data- were applied, that proved to provide a sound characterization of the groundwater flows within the coastal karstic system in connection to the surrounding water bodies of the study area. The above are used as input parameters process during the development of the conceptual model of the coastal hydrosystem of Lavrion. Key-words: Coastal hydrosystems, Mediterranean basin, seawater intrusion

  3. Useless arithmetic or useful scientific tools? Evaluation of the current state and future perspectives of aquatic biogeochemical modeling

    NASA Astrophysics Data System (ADS)

    Arhonditsis, G.

    2009-04-01

    What is the capacity of the current models to simulate the dynamics of environmental systems? How carefully do modelers develop their models? Which model features primarily determine our decision to utilize a specific model? How rigorously do we assess what a model can or cannot predict? The first part of my presentation is to answer some of these questions by reviewing the state of aquatic biogeochemical modeling; a research tool that has been extensively used for understanding and quantitatively describing aquatic ecosystems. Mechanistic aquatic biogeochemical models have form the scientific basis for environmental management decisions by providing a predictive link between management actions and ecosystem response; they have provided an important tool for elucidating the interactions between climate variability and plankton communities, and thus for addressing questions regarding the pace and impacts of climate change. The sizable number of aquatic ecosystem modeling studies which successfully passed the scrutiny of the peer-review process along with the experience gained from addressing a breadth of management problems can objectively reveal the systematic biases, methodological inconsistencies, and common misconceptions characterizing the modeling practice in environmental science. My arguments are that (i) models are not always developed in a consistent manner, clearly stated purpose, and predetermined acceptable model performance level, (ii) the potential "customers" select models without properly assessing their technical value, and (iii) oceanic modeling is a dynamic area of the current modeling practice whereas, model application for addressing environmental management issues on a local scale faces challenges as a scientific tool. The second part of my presentation argues that (i) the development of novel methods for rigorously assessing the uncertainty underlying model predictions should be a top priority of the modeling community, and (ii) the model

  4. Arsenic in New Jersey Coastal Plain streams, sediments, and shallow groundwater: effects from different geologic sources and anthropogenic inputs on biogeochemical and physical mobilization processes

    USGS Publications Warehouse

    Barringer, Julia L.; Reilly, Pamela A.; Eberl, Dennis D.; Mumford, Adam C.; Benzel, William M.; Szabo, Zoltan; Shourds, Jennifer L.; Young, Lily Y.

    2013-01-01

    Arsenic (As) concentrations in New Jersey Coastal Plain streams generally exceed the State Surface Water Quality Standard (0.017 micrograms per liter (µg/L)), but concentrations seldom exceed 1 µg/L in filtered stream-water samples, regardless of geologic contributions or anthropogenic inputs. Nevertheless, As concentrations in unfiltered stream water indicate substantial variation because of particle inputs from soils and sediments with differing As contents, and because of discharges from groundwater of widely varying chemistry. In the Inner Coastal Plain, streams draining to lower reaches of the Delaware River traverse As-rich glauconitic sediments of marine origin in which As contents typically are about 20 milligrams per kilogram (mg/kg) or greater. In some of these sedimentary units, As concentrations exceed the New Jersey drinking-water maximum contaminant level (5 µg/L) in shallow groundwater that discharges to streams. Microbes, fueled by organic carbon beneath the streambed, reduce iron (Fe) and As, releasing As and Fe into solution in the shallow groundwater from geologic materials that likely include (in addition to glauconite) other phyllosilicates, apatite, and siderite. When the groundwater discharges to the stream, the dissolved Fe and As are oxidized, the Fe precipitates as a hydroxide, and the As sorbs or co-precipitates with the Fe. Because of the oxidation/precipitation process, dissolved As concentrations measured in filtered stream waters of the Inner Coastal Plain are about 1 µg/L, but the total As concentrations (and loads) are greater, substantially amplified by As-bearing suspended sediment in stormflows. In the Outer Coastal Plain, streams draining to the Atlantic Ocean traverse quartz-rich sediments of mainly deltaic origin where the As content generally is low ( With a history of agriculture in the New Jersey Coastal Plain, anthropogenic inputs of As, such as residues from former pesticide applications in soils, can amplify any

  5. Simulating mesoscale coastal evolution for decadal coastal management: A new framework integrating multiple, complementary modelling approaches

    NASA Astrophysics Data System (ADS)

    van Maanen, Barend; Nicholls, Robert J.; French, Jon R.; Barkwith, Andrew; Bonaldo, Davide; Burningham, Helene; Brad Murray, A.; Payo, Andres; Sutherland, James; Thornhill, Gillian; Townend, Ian H.; van der Wegen, Mick; Walkden, Mike J. A.

    2016-03-01

    Coastal and shoreline management increasingly needs to consider morphological change occurring at decadal to centennial timescales, especially that related to climate change and sea-level rise. This requires the development of morphological models operating at a mesoscale, defined by time and length scales of the order 101 to 102 years and 101 to 102 km. So-called 'reduced complexity' models that represent critical processes at scales not much smaller than the primary scale of interest, and are regulated by capturing the critical feedbacks that govern landform behaviour, are proving effective as a means of exploring emergent coastal behaviour at a landscape scale. Such models tend to be computationally efficient and are thus easily applied within a probabilistic framework. At the same time, reductionist models, built upon a more detailed description of hydrodynamic and sediment transport processes, are capable of application at increasingly broad spatial and temporal scales. More qualitative modelling approaches are also emerging that can guide the development and deployment of quantitative models, and these can be supplemented by varied data-driven modelling approaches that can achieve new explanatory insights from observational datasets. Such disparate approaches have hitherto been pursued largely in isolation by mutually exclusive modelling communities. Brought together, they have the potential to facilitate a step change in our ability to simulate the evolution of coastal morphology at scales that are most relevant to managing erosion and flood risk. Here, we advocate and outline a new integrated modelling framework that deploys coupled mesoscale reduced complexity models, reductionist coastal area models, data-driven approaches, and qualitative conceptual models. Integration of these heterogeneous approaches gives rise to model compositions that can potentially resolve decadal- to centennial-scale behaviour of diverse coupled open coast, estuary and inner

  6. The CO2 system in the Mediterranean Sea inferred from a 3D coupled physical-biogeochemical model

    NASA Astrophysics Data System (ADS)

    Ulses, Caroline; Kessouri, Fayçal; Estournel, Claude; Marsaleix, Patrick; Beuvier, Jonathan; Somot, Samuel; Touratier, Frank; Goyet, Catherine; Coppola, Laurent; Diamond, Emilie; Metzl, Nicolas

    2015-04-01

    The semi-enclosed Mediterranean Sea characterized by short residence times is considered as a region particularly sensitive to natural and anthropogenic forcing. Due to scarce CO2 measurements in the whole basin, the CO2 system, for instance the air-sea CO2 exchanges and the effects of the increase of atmospheric CO2, are poorly characterized. 3D physical-biogeochemical coupled models are unique tools that can provide integrated view and gain understanding in the temporal and spatial variation of the CO2 system variables (dissolved inorganic carbon, total alkalinity, partial pressure of CO2 and pH). An extended version of the biogeochemical model Eco3m-S (Auger et al., 2014), that describes the cycles of carbon, nitrogen, phosphorus and silica, was forced by a regional circulation model (Beuvier et al., 2012) to investigate the CO2 system in the Mediterranean Sea over a 13-years period (2001-2013). First, the quality of the modelling was evaluated through comparisons with satellite and in situ observations collected in the whole basin over the study period (Touratier and Goyet, 2009; 2011 ; Rivaro et al., 2010 ; Pujo-Pay et al., 2011 ; Alvarez et al, 2014). The model reasonably reproduced the various biological regimes (north-western phytoplanctonic bloom regime, oligotrophic eastern regime, etc.) as well as the recorded spatial distribution and temporal variations of the carbonate system variables. The coupled model was then used to estimate the air-sea pCO2 exchanges and the transport of DIC and TA towards the Atlantic Ocean at the Strait of Gibraltar.

  7. ANALYTIC ELEMENT MODELING OF COASTAL AQUIFERS - PROJECT SUMMARY

    EPA Science Inventory

    Four topics were studied concerning the modeling of groundwater flow in coastal aquifers with analytic elements: (1) practical experience was obtained by constructing a groundwater model
    of the shallow aquifers below the Delmarva Peninsula USA using the commercial program MVAE...

  8. Carbon and nitrogen stock and fluxes in coastal Atlantic Forest of southeast Brazil: potential impacts of climate change on biogeochemical functioning.

    PubMed

    Villela, D M; Mattos, E A de; Pinto, A S; Vieira, S A; Martinelli, L A

    2012-08-01

    The Atlantic Forest is one of the most important biomes of Brazil. Originally covering approximately 1.5 million of km², today this area has been reduced to 12% of its original size. Climate changes may alter the structure and the functioning of this tropical forest. Here we explore how increases in temperature and changes in precipitation distribution could affect dynamics of carbon and nitrogen in coastal Atlantic Forest of the southeast region of Brazil The main conclusion of this article is that the coastal Atlantic Forest has high stocks of carbon and nitrogen above ground, and especially, below ground. An increase in temperature may transform these forests from important carbon sinks to carbon sources by increasing loss of carbon and nitrogen to the atmosphere. However, this conclusion should be viewed with caution because it is based on limited information. Therefore, more studies are urgently needed to enable us to make more accurate predictions. PMID:23011294

  9. Modeling the primary and secondary productions of the southern Benguela upwelling system: A comparative study through two biogeochemical models

    NASA Astrophysics Data System (ADS)

    Koné, V.; Machu, E.; Penven, P.; Andersen, V.; GarçOn, V.; FréOn, P.; Demarcq, H.

    2005-12-01

    A three-dimensional primitive equation model, the Regional Ocean Modeling Systems (ROMS), coupled to two biogeochemical configurations (NPZD and N2P2Z2D2) was used to study the dynamics of the first trophic levels of the pelagic food web in the southern Benguela upwelling system. The domain extends from the Agulhas Bank bordered by the Agulhas Current to 27°S on the west coast of South Africa. The circulation is driven by monthly climatologies of atmospheric forcing fields. The NPZD ecosystem model consists of four state variables: nutrient (nitrate), phytoplankton, zooplankton and detritus. In the N2P2Z2D2 model, ammonium has been added and the three other variables have been divided into small and large organisms or detritus. Both models are able to reproduce the spatio-temporal phytoplankton distribution. Along the west coast, chlorophyll concentrations maxima are associated to surface waters. Westward dominating winds generate the lowest chlorophyll concentrations encountered in winter. The small phytoplankton organisms simulated by the N2P2Z2D2 model are responsible for a weaker chlorophyll inshore/offshore gradient, in closer agreement with observations. Transitions from a regime dominated by new production (high f ratio) to one dominated by regenerated production (low f ratio) happen to be abrupt, underlying the constant competition between small and large organisms with regard to upwelling induced nutrient inputs. On the Agulhas Bank, the summer enrichment is associated with subsurface maxima, while in winter, mixing by storms results in a homogeneous phytoplankton distribution in the water column. Regenerated production plays an important role in maintaining the total phytoplankton growth. Zooplankton biomass reflects the overall patterns of chlorophyll a concentrations with differences between the west coast and the Agulhas Bank, consistent with data, and its distribution exhibits a clear seasonal contrast. The seasonality of small and large zooplankton

  10. Assessing biogeochemical effects and best management practice for a wheat-maize cropping system using the DNDC model

    NASA Astrophysics Data System (ADS)

    Cui, F.; Zheng, X.; Liu, C.; Wang, K.; Zhou, Z.; Deng, J.

    2014-01-01

    Contemporary agriculture is shifting from a single-goal to a multi-goal strategy, which in turn requires choosing best management practice (BMP) based on an assessment of the biogeochemical effects of management alternatives. The bottleneck is the capacity of predicting the simultaneous effects of different management practice scenarios on multiple goals and choosing BMP among scenarios. The denitrification-decomposition (DNDC) model may provide an opportunity to solve this problem. We validated the DNDC model (version 95) using the observations of soil moisture and temperature, crop yields, aboveground biomass and fluxes of net ecosystem exchange of carbon dioxide, methane, nitrous oxide (N2O), nitric oxide (NO) and ammonia (NH3) from a wheat-maize cropping site in northern China. The model performed well for these variables. Then we used this model to simulate the effects of management practices on the goal variables of crop yields, NO emission, nitrate leaching, NH3 volatilization and net emission of greenhouse gases in the ecosystem (NEGE). Results showed that no-till and straw-incorporated practices had beneficial effects on crop yields and NEGE. Use of nitrification inhibitors decreased nitrate leaching and N2O and NO emissions, but they significantly increased NH3 volatilization. Irrigation based on crop demand significantly increased crop yield and decreased nitrate leaching and NH3 volatilization. Crop yields were hardly decreased if nitrogen dose was reduced by 15% or irrigation water amount was reduced by 25%. Two methods were used to identify BMP and resulted in the same BMP, which adopted the current crop cultivar, field operation schedules and full straw incorporation and applied nitrogen and irrigation water at 15 and 25% lower rates, respectively, than the current use. Our study indicates that the DNDC model can be used as a tool to assess biogeochemical effects of management alternatives and identify BMP.

  11. Assessing biogeochemical effects and best management practice for a wheat-maize cropping system using the DNDC model

    NASA Astrophysics Data System (ADS)

    Cui, F.; Zheng, X. H.; Liu, C. Y.; Wang, K.; Zhou, Z. X.; Deng, J.

    2013-05-01

    Contemporary agriculture is shifting from a single-goal to a multi-goal strategy, which in turn requires choosing best management practice (BMP) based on assessment of the biogeochemical effects of management alternatives. The bottleneck is the capacity of predicting the simultaneous effects of different management practice scenarios on multiple goals and choosing BMP among scenarios. The denitrification-decomposition (DNDC) model may provide an opportunity to solve this problem. We validated the DNDC model (version 95) using the observations of soil moisture and temperature, crop yields, aboveground biomass and fluxes of net ecosystem exchange of carbon dioxide, methane, nitrous oxide (N2O), nitric oxide (NO) and ammonia (NH3) from a wheat-maize cropping site in northern China. The model performed well for these variables. Then we used this model to simulate the effects of management practices on the goal variables of crop yields, NO emission, nitrate leaching, NH3 volatilization and net emission of greenhouse gases in the ecosystem (NEGE). Results showed that no-till and straw-incorporated practices had beneficial effects on crop yields and NEGE. Use of nitrification inhibitors decreased nitrate leaching and N2O and NO emissions, but they significantly increased NH3 volatilization. Irrigation based on crop demand significantly increased crop yield and decreased nitrate leaching and NH3 volatilization. Crop yields were hardly decreased if nitrogen dose was reduced by 15% or irrigation water amount was reduced by 25%. Two methods were used to identify BMP and resulted in the same BMP, which adopted the current crop cultivar, field operation schedules and full straw incorporation and applied nitrogen and irrigation water at 15% and 25% lower rates, respectively, than the current use. Our study indicates that the DNDC model can be used as a tool to assess biogeochemical effects of management alternatives and identify BMP.

  12. Offshore and coastal dispersion (OCD) model. Users guide

    SciTech Connect

    Hanna, S.R.; Schulman, L.L.; Paine, R.J.; Pleim, J.E.

    1984-09-01

    The Offshore and Coastal Dispersion (OCD) model was adapted from the EPA guideline model MPTER to simulate the effect of offshore emissions from point sources in coastal regions. Modifications were made to incorporate overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. Hourly meteorological data are needed from overwater and overland locations. Turbulence intensities are used but are not mandatory. For overwater dispersion, the turbulence intensities are parameterized from boundary-layer similarity relationships if they are not measured. Specifications of emission characteristics and receptor locations are the same as for MPTER; 250 point sources and 180 receptors may be used.

  13. Offshore and coastal dispersion (OCD) model. User's guide

    SciTech Connect

    Hanna, S.R.; Schulman, L.L.; Paine, R.J.; Pleim, J.E.

    1984-09-01

    The Offshore Coastal Dispersion (OCD) model was adapted from the EPA guideline model MPTER to simulate the effect of offshore emissions from point sources in coastal regions. Modifications were made to incorporate overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. Hourly meteorological data are needed from overwater and overland locations. For overwater dispersion, the turbulence intensities are parameterized from boundary layer similarity relationships if they are not measured. A virtual source technique is used to change the rate of plume growth as the overwater plume intercepts the overland internal boundary layer.

  14. Modeling Tidal Stream Energy Extraction and its Effects on Transport Processes in a Tidal Channel and Bay System Using a Three-dimensional Coastal Ocean Model

    SciTech Connect

    Yang, Zhaoqing; Wang, Taiping; Copping, Andrea E.

    2013-02-28

    This paper presents a numerical modeling study for simulating in-stream tidal energy extraction and assessing its effects on the hydrodynamics and transport processes in a tidal channel and bay system connecting to coastal ocean. A marine and hydrokinetic (MHK) module was implemented in a three-dimensional (3-D) coastal ocean model using the momentum sink approach. The MHK model was validated with the analytical solutions for tidal channels under one-dimensional (1-D) conditions. Model simulations were further carried out to compare the momentum sink approach with the quadratic bottom friction approach. The effects of 3-D simulations on the vertical velocity profile, maximum extractable energy, and volume flux reduction across the channel were investigated through a series of numerical experiments. 3-D model results indicate that the volume flux reduction at the maximum extractable power predicted by the 1-D analytical model or two-dimensional (2-D) depth-averaged numerical model may be overestimated. Maximum extractable energy strongly depends on the turbine hub height in the water column, and which reaches a maximum when turbine hub height is located at mid-water depth. Far-field effects of tidal turbines on the flushing time of the tidal bay were also investigated. Model results demonstrate that tidal energy extraction has a greater effect on the flushing time than volume flux reduction, which could negatively affect the biogeochemical processes in estuarine and coastal waters that support primary productivity and higher forms of marine life.

  15. A biogeochemical model for phosphorus and nitrogen cycling in the Eastern Mediterranean Sea. Part 1. Model development, initialization and sensitivity

    NASA Astrophysics Data System (ADS)

    Van Cappellen, P.; Powley, H. R.; Emeis, K.-C.; Krom, M. D.

    2014-11-01

    The Eastern Mediterranean Sea (EMS) is the largest marine basin whose annual primary productivity is limited by phosphorus (P) rather than nitrogen (N). The basin is nearly entirely land-locked and receives substantial external nutrient fluxes, comparable for instance to those of the Baltic Sea. The biological productivity of the EMS, however, is among the lowest observed in the oceans. The water column exhibits very low P and N concentrations with N:P ratios in excess of the Redfield value. These unique biogeochemical features are analyzed using a mass balance model of the coupled P and N cycles in the EMS. The present paper describes the conceptual basis, quantitative implementation and sensitivity of the model. The model is initialized for the year 1950, that is, prior to the large increase in anthropogenic nutrient loading experienced by the EMS during the second half of the 20th century. In the companion paper, the model is used to simulate the P and N cycles during the period 1950-2000. The 1950 model set-up and sensitivity analyses support the following conclusions. Inorganic molar N:P ratios in excess of the 16:1 Redfield value observed in the water column reflect higher-than-Redfield N:P ratios of the external inputs, combined with negligible denitrification. Model simulations imply that the denitrification flux would have to increase by at least a factor of 14, relative to the 1950 flux, in order for the inorganic N:P ratio of the deep waters to approach the Redfield value. The higher

  16. Hawaii and Beyond: Volcanic Islands as Model Systems for Biogeochemical and Human Ecodynamic Research

    NASA Astrophysics Data System (ADS)

    Chadwick, O.

    2012-12-01

    The Hawaiian Islands provide an excellent natural lab for understanding geochemical and ecosystem processes. The most important features are: a) increasing volcano age with distance from the hotspot, b) asymmetric rainfall distribution imposed by the northeasterly trade winds and orographic processes, creating wet windward and dry leeward landscapes, c) an impoverished vegetation assemblage allowing the same species to grow in strongly varying climate and soil conditions, d) the ability to hold topography relatively constant over long time scales by sampling on volcanic shield remnants that are preserved even on the oldest high island, Kauai, and e) a long-term topographic evolution that carves the gently sloping shield surfaces into steep-sided, amphitheater headed, relatively flat floored valleys. Although deeply incised valleys are well represented in Kauai, the later stages of volcanic island evolution are not well expressed in the exposed Hawaiian Islands. Therefore, I also consider examples from the Society and Gambier Islands in French Polynesia to demonstrate the biogeochemical and human ecodynamic impacts of valley expansion and subsidence leading to drowning of all but the highest elevation interfluves. In Hawaii, I and many colleagues have characterized the details of biogeochemical processes such as: a) variations in oxygen isotopes in soil water and soil minerals, b) changing nutrient sources using Sr, Ca, and Mg isotopes, c) mineral - carbon sorption and its implications for carbon storage in soils and for mineral ripening, and d) the development of leaching and redox driven pedogenic thresholds. Here, I address how these biogeochemical features influence human land-use decisions in prehistoric Hawaii and elsewhere in the Pacific. Polynesian radiation into the eastern Pacific occurred rapidly after 1300 y bp. Although they carried with them a kitchen garden each new island presented a different environmental challenge. They were sensitive to

  17. Realistic primary and new productions in a 3D global biogeochemical model: biological complexity or physical forcing?

    NASA Astrophysics Data System (ADS)

    Popova, E. E.; Coward, A. C.

    2003-04-01

    A nitrogen-based, five compartment biological model has been coupled to a one degree OCCAM (Ocean Circulation and Climate Advanced Modelling Project) model with a KPP ("K profile parameterisation") of the vertical mixing. The biological model state variables are Phytoplankton, Zooplankton, Detritus, Nitrate, and Ammonium. A comparison of the solution with global satellite ocean colour shows that the model is capable of a realistic description of the main seasonal and regional patterns of the surface chlorophyll. Agreement is also good for satellite derived estimates of primary production. In situ data available from local study sites (such as BATS, NABE, India, Papa) are used for the detailed comparison of the model output with the observed ecosystem dynamics in different biological provinces. We discuss performance of the physical and biological model in contrasting areas of the World Ocean. In spite of the biological model being a very simple one, we are able to reproduce the major differences between ecosystem dynamics of these areas. We believe that the success of any global biogeochemical model is dependent first of all on the correct representation of the upper mixed layer (UML) dynamics. Without being able to reproduce contrasting UML regimes in different areas of the World Ocean (such as difference between the North Atlantic and Southern Ocean, or North Atlantic and North Pacific), increased complexity biological models are in danger of producing the right results by the wrong reason.

  18. Estimating forest carbon fluxes in a disturbed southeastern landscape: Integration of remote sensing, forest inventory, and biogeochemical modeling

    NASA Astrophysics Data System (ADS)

    Masek, Jeffrey G.; Collatz, G. James

    2006-03-01

    Quantifying carbon fluxes between the atmosphere and land surface requires detailed knowledge of the disturbance regime as well as the photosynthetic response of vegetation to climate. In this study, we use a combination of satellite remote sensing, forest inventory data, and biogeochemical modeling to assess forest carbon fluxes from central Virginia, a landscape pervasively disturbed by harvest. Using historical Landsat imagery, we have reconstructed the disturbance history and age structure of forest stands at a resolution of 90 m, from 1973-1999. Forest inventory data provide breakdowns of forest type and age structure for older stands. These data, together with climate and vegetation greenness from advanced very high resolution radiometer (AVHRR), are used as inputs to a version of the Carnegie-Stanford-Ames (CASA) biogeochemical model, which simulates the uptake, allocation, and respiration of carbon and associated effects of disturbance. Modeling results indicate that forests in the study region have an average net ecosystem productivity (NEP) of ˜80 gC m-2 yr-1, reflecting the young age structure of rapid-rotation forests. Variability in annual forest carbon fluxes due to variations in clearing rate and climate are also examined. We find that observed variations in clearing rate may account for NEP variability of ˜30 gC m-2 yr-1, while observed variations in climate may account for NEP variability of 80-130 gC m-2 yr-1. Increased temperatures tend to drive both increased photosynthesis and increased heterotrophic respiration, buffering the system from larger swings in NEP. However, this response depends strongly on stand age.

  19. Towards a High Resolution Cellular Model for Coastal Simulation (CEMCOS)

    NASA Astrophysics Data System (ADS)

    Dearing, J.; Plater, A. J.; Richmond, N. C.

    2004-12-01

    The aim of this research is to develop a cellular model for coastal simulation in response to changing climate and sea-level, as a contribution to the UK Tyndall Centre's Research Theme 4: Sustaining the Coastal Zone. The modelling approach uses simple cell-based rules of sediment erosion, transport and deposition operating between adjacent cells. This enables the model to include the full range of processes and properties of the coastal environment, including nonlinear behaviour, using only local interactions at discrete time intervals. Tide propagation and wave action drive sediment transport, which is further conditioned by erosion thresholds related to grain size and vegetation growth. Here, we report an overview of this one-year project and details on model design and validation. This includes tide and wave parameterisation, resulting in sediment transport over a 3-D grid of cells representing estuary morphology and bathymetry. The model (CEMCOS) is being designed to be fully generic and exportable to different coastal areas, with initial testing and validation being conducted using published bathymetric and cartographic data over the last c.150 years for the Blackwater Estuary in eastern England.

  20. Widespread euxinia in the aftermath of the Lomagundi event: insights from a modeling study of ocean biogeochemical dynamics

    NASA Astrophysics Data System (ADS)

    Ozaki, Kazumi; Tajika, Eiichi

    2015-04-01

    The emergence of strongly sulphidic oceanic waters (euxinia) during the Proterozoic may have affected biological turnover, extinction, and evolution, not only because of its toxicity to eukaryotes but also because of its fundamental role on bioessential trace metal availability. From this point of view, the evidence for euxinic environments in the Lomagundi-Jatuli event (LJE) aftermath (~2.08-2.05 billion years ago) in Gabon and Karelia are notable because their low δ98/95Mo values (less than 0.95o and 0.85o respectively) imply widespread euxinia at that time. The Francevillian Group in Gabon represents the oxic-anoxic/euxinic transitional sequence, implying a fluctuation in the atmospheric redox condition from oxic to relatively reducing, possibly due to the oxidation of substantial amount of organic matter deposited during the LJE. The large positive anomaly of sulphur isotopes and a substantial contraction of marine sulphate reservoir size through the latter part of the LJE also imply a fall in surface oxidation state. Variations of the oxygenation state of the Earth's surface would have caused substantial changes in oceanic chemical composition and, in turn, would surely have impacted the biosphere. However, the nature and dynamics of oceanic biogeochemical cycles for this interval are poorly understood. To unravel cause and effect of the variations of oceanic redox state in the Paleoproteorozoic, we improved the CANOPS model (a 1-D advection-diffusion-reaction marine biogeochemical cycle model), in which coupled C-N-O-P-S marine biogeochemical cycles and a series of redox reactions were adequately taken into account. Through systematic sensitivity experiments we show that a substantial drop in atmospheric oxygen level could cause a widespread euxinia for millions of years, which provides a theoretical explanation consistent with the geological records, such as large positive anomaly of δ34S, low δ98/95Mo, and a decrease in SO4 concentration, in the

  1. Modeling coastal environmental changes by fuzzy logic approach

    NASA Astrophysics Data System (ADS)

    Zoran, Maria A.; Zoran, Liviu Florin V.

    2004-10-01

    The coastal zone contains that unique environmental triple point where the water, land and atmospheric components of the terrestrial surface converge and interact. This paper is an application of remotely sensed images in marine coastal land cover classification for change detection assessment. The nature of the gradients in coastal region land cover composition among the map classes can therefore be identified.A supervised approach uses the prior knowledge about the area and thus it is very useful in getting better results than an unsupervised classification. The study test area was North-Western Black Sea coastal region, characterized by no so fast drastic changes,as it is a slow and continuous process. Satellite images (Landsat MSS, TM, ETM, SAR ERS, ASTER, MODIS) over a period of time between 1975 and 2003 were chosen for change detection analysis.In the fuzzy approach, it is possible to describe change as a degree, this being the main reason for fuzzy approach using for classification and change detection of major land cover classes in a marine coastal area.The results can be utilized as a temporal land-use change model for a region to quantify the extent and nature of change, and aid in future prediction studies, which helps in planning environmental agencies to develop sustainable land-use practices .

  2. Benthic processes and coastal aquaculture: merging models and field data at a local scale

    NASA Astrophysics Data System (ADS)

    Brigolin, Daniele; Rabouille, Christophe; Bombled, Bruno; Colla, Silvia; Pastres, Roberto; Pranovi, Fabio

    2016-04-01

    Shellfish farming is regarded as an organic extractive aquaculture activity. However, the production of faeces and pseudofaeces, in fact, leads to a net transfer of organic matter from the water column to the surface sediment. This process, which is expected to locally affect the sediment biogeochemistry, may also cause relevant changes in coastal areas characterized by a high density of farms. In this paper, we present the result of a study recently carried out in the Gulf of Venice (northern Adriatic sea), combining mathematical modelling and field sampling efforts. The work aimed at using a longline mussel farm as an in-situ test-case for modelling the differences in soft sediments biogeochemical processes along a gradient of organic deposition. We used an existing integrated model, allowing to describe biogeochemical fluxes towards the mussel farm and to predict the extent of the deposition area underneath it. The model framework includes an individual-based population dynamic model of the Mediterranean mussel coupled with a Lagrangian deposition model and a 1D benthic model of early diagenesis. The work was articulated in 3 steps: 1) the integrated model allowed to simulate the downward fluxes of organic matter originated by the farm, and the extent of its deposition area; 2) based on the first model application, two stations were localized, at which sediment cores were collected during a field campaign, carried out in June 2015. Measurements included O2 and pH microprofiling, porosity and micro-porosity, Total Organic Carbon, and pore waters NH4, PO4, SO4, Alkalinity, and Dissolved Inorganic Carbon; 3) two distinct early diagenesis models were set-up, reproducing observed field data in the sampled cores. Observed oxygen microprofiles showed a different behavior underneath the farm with respect to the outside reference station. In particular, a remarkable decrease in the oxygen penetration depth, and an increase in the O2 influx calculated from the

  3. High-resolution wave and hydrodynamics modelling in coastal areas: operational applications for coastal planning, decision support and assessment

    NASA Astrophysics Data System (ADS)

    Samaras, Achilleas G.; Gaeta, Maria Gabriella; Moreno Miquel, Adrià; Archetti, Renata

    2016-07-01

    Numerical modelling has become an essential component of today's coastal planning, decision support and risk assessment. High-resolution modelling offers an extensive range of capabilities regarding simulated conditions, works and practices and provides with a wide array of data regarding nearshore wave dynamics and hydrodynamics. In the present work, the open-source TELEMAC suite and the commercial software MIKE21 are applied to selected coastal areas of South Italy. Applications follow a scenario-based approach in order to study representative wave conditions in the coastal field; the models' results are intercompared in order to test both their performance and capabilities and are further evaluated on the basis of their operational use for coastal planning and design. A multiparametric approach for the rapid assessment of wave conditions in coastal areas is also presented and implemented in areas of the same region. The overall approach is deemed to provide useful insights on the tested models and the use of numerical models - in general - in the above context, especially considering that the design of harbours, coastal protection works and management practices in the coastal zone is based on scenario-based approaches as well.

  4. A Mechanistically Informed User-Friendly Model to Predict Greenhouse Gas (GHG) Fluxes and Carbon Storage from Coastal Wetlands

    NASA Astrophysics Data System (ADS)

    Abdul-Aziz, O. I.; Ishtiaq, K. S.

    2015-12-01

    We present a user-friendly modeling tool on MS Excel to predict the greenhouse gas (GHG) fluxes and estimate potential carbon sequestration from the coastal wetlands. The dominant controls of wetland GHG fluxes and their relative mechanistic linkages with various hydro-climatic, sea level, biogeochemical and ecological drivers were first determined by employing a systematic data-analytics method, including Pearson correlation matrix, principal component and factor analyses, and exploratory partial least squares regressions. The mechanistic knowledge and understanding was then utilized to develop parsimonious non-linear (power-law) models to predict wetland carbon dioxide (CO2) and methane (CH4) fluxes based on a sub-set of climatic, hydrologic and environmental drivers such as the photosynthetically active radiation, soil temperature, water depth, and soil salinity. The models were tested with field data for multiple sites and seasons (2012-13) collected from the Waquoit Bay, MA. The model estimated the annual wetland carbon storage by up-scaling the instantaneous predicted fluxes to an extended growing season (e.g., May-October) and by accounting for the net annual lateral carbon fluxes between the wetlands and estuary. The Excel Spreadsheet model is a simple ecological engineering tool for coastal carbon management and their incorporation into a potential carbon market under a changing climate, sea level and environment. Specifically, the model can help to determine appropriate GHG offset protocols and monitoring plans for projects that focus on tidal wetland restoration and maintenance.

  5. OCD: The offshore and coastal dispersion model. Volume 2. Appendices

    SciTech Connect

    DiCristofaro, D.C.; Hanna, S.R.

    1989-11-01

    The Offshore and Coastal Dispersion (OCD) Model has been developed to simulate the effect of offshore emissions from point, area, or line sources on the air quality of coastal regions. The OCD model was adapted from the EPA guideline model MPTER (EPA, 1980). Modifications were made to incorporate overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. This is a revised OCD model, the fourth version to date. The volume is an appendices for the OCD documentation, included are three appendices: Appendix A the OCD computer program, Appendix B an Analysis Post-processor, Appendix C Offshore Meteorological data Collection Instrumentation, also included are general References.

  6. Modeling the Biogeochemical Response of a Flood Plain Aquifer Impacted By Seasonal Temperature and Water Table Variations

    NASA Astrophysics Data System (ADS)

    Arora, B.; Spycher, N.; Molins, S.; Steefel, C. I.

    2014-12-01

    With the overarching goal of understanding the impacts of climate and land use changes on carbon and nutrient cycles, we are developing a reactive transport model that couples hydrologic and biogeochemical processes to microbial functional distributions inferred from site-specific 'omic' data. The objective of the modeling approach is to simulate changes in carbon and nutrient fluxes and aquifer biogeochemistry over longer time periods due to changes in climate and/or land use, while also considering shorter time periods in which water table fluctuations and temperature variations are important. A 2-D reactive transport model has been developed for the unsaturated-saturated zone of the Rifle site, CO, an alluvial aquifer bordering the Colorado River. Modeling efforts focus on the April through September 2013 time frame that corresponds to the spring snow melt event that lead to an approximately 1 meter rise in the water table followed by a gradual lowering over 3 months. Temperature variations of as much as 10ºC are observed at shallow depths (< 1m), while at least some temperature variation (1ºC) occurs as deep as about 7m. A field survey of the microbial populations indicates the presence and activity of chemo(litho)autotrophic bacteria within the saturated zone of the alluvial aquifer. Model simulations are used to quantify the release of carbon dioxide and consumption of oxygen via abiotic pathways and heterotrophic microbial oxidation of reduced species (Fe(II), S(-2)) and minerals (pyrite). Results indicate that the observed oxygen profiles and/or carbon fluxes cannot be matched by considering abiotic reactions alone. The importance of including microbial contributions from chemo(litho)autotrophic processes (e.g., ammonia, sulfur and iron oxidation) is supported by both field observations and model simulations. Important conclusions from the study are to: (1) include microbially-mediated processes and contributions from the unsaturated zone, and (2) account

  7. Numerical model on the material circulation for coastal sediment in Ago Bay, Japan

    NASA Astrophysics Data System (ADS)

    Anggara Kasih, G. A.; Chiba, Satoshi; Yamagata, Youichi; Shimizu, Yasuhiro; Haraguchi, Koichi

    2009-04-01

    In this paper, we study the sediment in Ago Bay from the aspects of the biogeochemical cycle and the mass transport by means of a numerical model. We developed the model by adopting the basic idea of Berg et al. (Berg, P., Rysgaard, S., Thamdrup, B., 2003. Dynamic modeling of early diagenesis and nutrient cycling: A case study in Artic marine sediment. Am. J. Sci. 303, 905-955.), Fossing et al. [Fossing, H., Berg, P., Thamdrup, B., Rysgaard, S., Sorensen, H.M., Nielsen, K.A., 2004. Model set-up for an oxygen and nutrient flux for Aarhus Bay (Denmark). National Environmental Research Institute (NERI) Technical Report No. 483. Ministry of the Environment, Denmark, 65 pp.] and Sayama [Sayama, M., 2000. Analytical technique for the nitrogen circulation in the boundary layer of the coastal sediment. Isao Koike edited, Japan Environmental Management Association for Industry, Tokyo, pp. 51-103. (in Japanese)]. In the model, the biogeochemical processes involve five primary reactions and sixteen secondary reactions. The primary reactions describe the degradation of organic matters, and the secondary reactions describe the miscellaneous reactions such as re-oxidation of reduced species formed as a product from primary reactions, and the crystallizing process of oxidized particles. The transports process includes molecular diffusion, advection, bioturbation and bioirrigation. The model performance is verified by comparing the model predicted data to the observed data. The comparison involves data of vertical distribution of material concentrations and the material fluxes at the sediment-water interface. The comparison shows that the model can reproduce the observed vertical profile and the observed material fluxes at the sediment-water interface. The material circulation result shows that about 42% of dissolved organic matter (DOM) is mineralized by sulfate reduction, around 41% by oxygen respiration, and the remaining is mineralized by denitrification, manganese and iron

  8. Intercomparison and validation of operational coastal-scale models, the experience of the project MOMAR.

    NASA Astrophysics Data System (ADS)

    Brandini, C.; Coudray, S.; Taddei, S.; Fattorini, M.; Costanza, L.; Lapucci, C.; Poulain, P.; Gerin, R.; Ortolani, A.; Gozzini, B.

    2012-04-01

    The need for regional governments to implement operational systems for the sustainable management of coastal waters, in order to meet the requirements imposed by legislation (e.g. EU directives such as WFD, MSFD, BD and relevant national legislation) often lead to the implementation of coastal measurement networks and to the construction of computational models that surround and describe parts of regional seas without falling in the classic definition of regional/coastal models. Although these operational models may be structured to cover parts of different oceanographic basins, they can have considerable advantages and highlight relevant issues, such as the role of narrow channels, straits and islands in coastal circulation, as both in physical and biogeochemical processes such as in the exchanges of water masses among basins. Two models of this type were made in the context of cross-border European project MOMAR: an operational model of the Tuscan Archipelago sea and one around the Corsica coastal waters, which are both located between the Tyrrhenian and the Algerian-Ligurian-Provençal basins. Although these two models were based on different computer codes (MARS3D and ROMS), they have several elements in common, such as a 400 m resolution, boundary conditions from the same "father" model, and an important area of overlap, the Corsica channel, which has a key role in the exchange of water masses between the two oceanographic basins. In this work we present the results of the comparison of these two ocean forecasting systems in response to different weather and oceanographic forcing. In particular, we discuss aspects related to the validation of the two systems, and a systematic comparison between the forecast/hindcast based on such hydrodynamic models, as regards to both operational models available at larger scale, both to in-situ measurements made by fixed or mobile platforms. In this context we will also present the results of two oceanographic cruises in the

  9. Modeling the fate of nitrogen on the catchment scale using a spatially explicit hydro-biogeochemical simulation system

    NASA Astrophysics Data System (ADS)

    Klatt, S.; Butterbach-Bahl, K.; Kiese, R.; Haas, E.; Kraus, D.; Molina-Herrera, S. W.; Kraft, P.

    2015-12-01

    The continuous growth of the human population demands an equally growing supply for fresh water and food. As a result, available land for efficient agriculture is constantly diminishing which forces farmers to cultivate inferior croplands and intensify agricultural practices, e.g., increase the use of synthetic fertilizers. This intensification of marginal areas in particular will cause a dangerous rise in nitrate discharge into open waters or even drinking water resources. In order to reduce the amount of nitrate lost by surface runoff or lateral subsurface transport, bufferstrips have proved to be a valuable means. Current laws, however, promote rather static designs (i.e., width and usage) even though a multitude of factors, e.g., soil type, slope, vegetation and the nearby agricultural management, determines its effectiveness. We propose a spatially explicit modeling approach enabling to assess the effects of those factors on nitrate discharge from arable lands using the fully distributed hydrology model CMF coupled to the complex biogeochemical model LandscapeDNDC. Such a modeling scheme allows to observe the displacement of dissolved nutrients in both vertical and horizontal directions and serves to estimate both their uptake by the vegetated bufferstrip and loss to the environment. First results indicate a significant reduction of nitrate loss in the presence of a bufferstrip (2.5 m). We show effects induced by various buffer strip widths and plant cover on the nitrate retention.

  10. Seasonal coastal sea level prediction using a dynamical model

    NASA Astrophysics Data System (ADS)

    McIntosh, Peter C.; Church, John A.; Miles, Elaine R.; Ridgway, Ken; Spillman, Claire M.

    2015-08-01

    Sea level varies on a range of time scales from tidal to decadal and centennial change. To date, little attention has been focussed on the prediction of interannual sea level anomalies. Here we demonstrate that forecasts of coastal sea level anomalies from the dynamical Predictive Ocean Atmosphere Model for Australia (POAMA) have significant skill throughout the equatorial Pacific and along the eastern boundaries of the Pacific and Indian Oceans at lead times out to 8 months. POAMA forecasts for the western Pacific generally have greater skill than persistence, particularly at longer lead times. POAMA also has comparable or greater skill than previously published statistical forecasts from both a Markov model and canonical correlation analysis. Our results indicate the capability of physically based models to address the challenge of providing skillful forecasts of seasonal sea level fluctuations for coastal communities over a broad area and at a range of lead times.

  11. DEVELOPING SITE-SPECIFIC MODELS FOR FORECASTING BACTERIA LEVELS AT COASTAL BEACHES

    EPA Science Inventory

    The U.S.Beaches Environmental Assessment and Coastal Health Act of 2000 authorizes studies of pathogen indicators in coastal recreation waters that develop appropriate, accurate, expeditious, and cost-effective methods (including predictive models) for quantifying pathogens in co...

  12. Data-driven models of groundwater salinization in coastal plains

    NASA Astrophysics Data System (ADS)

    Felisa, G.; Ciriello, V.; Antonellini, M.; Di Federico, V.; Tartakovsky, D. M.

    2015-12-01

    Salinization of shallow coastal aquifers is particularly critical for ecosystems and agricultural activities. Management of such aquifers is an open challenge, because predictive models, on which science-based decisions are to be made, often fail to capture the complexity of relevant natural and anthropogenic processes. Complicating matters further is the sparsity of hydrologic and geochemical data that are required to parameterize spatially distributed models of flow and transport. These limitations often undermine the veracity of modeling predictions and raise the question of their utility. As an alternative, we employ data-driven statistical approaches to investigate the underlying mechanisms of groundwater salinization in low coastal plains. A time-series analysis and auto-regressive moving average models allow us to establish dynamic relations between key hydrogeological variables of interest. The approach is applied to the data collected at the phreatic coastal aquifer of Ravenna, Italy. We show that, even in absence of long time series, this approach succeeds in capturing the behavior of this complex system, and provides the basis for making predictions and decisions.

  13. Full uncertainty quantification of a regional N2O and NO3 inventory using the biogeochemical model LandscapeDNDC

    NASA Astrophysics Data System (ADS)

    Santabarbara, Ignacio; Haas, Edwin; Klatt, Steffen; Kiese, Ralf; Butterbach-Bahl, Klaus

    2015-04-01

    Numerical simulation models are increasingly used to estimate greenhouse gas emissions at site to regional / national scale and are outlined as the most advanced methodology (Tier 3) in the framework of UNFCCC reporting. Process-based models incorporate the major processes of the carbon and nitrogen cycle of terrestrial ecosystems and are thus thought to be widely applicable at various spatial scales. Regional inventories require high spatial resolution input data on soil properties, climate drivers and management information. The acceptance of model based inventory calculations depends on the assessment of the inventory's uncertainty (model, input data and parameter induced uncertainties). In this study we fully quantify the uncertainty in regional N2O / NO3 inventory predictions from arable soils of Saxony (Germany) using the biogeochemical model LandscapeDNDC. We address model induced uncertainty (MU) by contrasting two different soil biogeochemistry modules in conjunction with two different plant growth descriptions within LandscapeDNDC. Input data induced uncertainty (DU) was addressed by Latin Hyper Cube sampling of soil properties, climate drivers and agricultural management practices. The parameter induced uncertainty (PU) was assessed by using joint parameter distributions for key parameters describing microbial C and N turnover processes as obtained by differenct Bayesian calibration studies for each model configuration. We representatively sampled different parameter vectors from the discrete joint parameter distribution comprising all parameter combinations and used these to calculate individual realizations of the regional inventory. The spatial domain (4042 polygons) was set up with spatially explicit soil and climate information and a region-typical 3-year crop rotation consisting of winter wheat, rapeseed, and winter barley. For the MU, DU and PU we calculated several hundred regional inventories each to assess the individual uncertainty

  14. An integrated coastal model for aeolian and hydrodynamic sediment transport

    NASA Astrophysics Data System (ADS)

    Baart, F.; den Bieman, J.; van Koningsveld, M.; Luijendijk, A. P.; Parteli, E. J. R.; Plant, N. G.; Roelvink, J. A.; Storms, J. E. A.; de Vries, S.; van Thiel de Vries, J. S. M.; Ye, Q.

    2012-04-01

    Dunes are formed by aeolian and hydrodynamic processes. Over the last decades numerical models were developed that capture our knowledge of the hydrodynamic transport of sediment near the coast. At the same time others have worked on creating numerical models for aeolian-based transport. Here we show a coastal model that integrates three existing numerical models into one online-coupled system. The XBeach model simulates storm-induced erosion (Roelvink et al., 2009). The Delft3D model (Lesser et al., 2004) is used for long term morphology and the Dune model (Durán et al., 2010) is used to simulate the aeolian transport. These three models were adapted to be able to exchange bed updates in real time. The updated models were integrated using the ESMF framework (Hill et al., 2004), a system for composing coupled modeling systems. The goal of this integrated model is to capture the relevant coastal processes at different time and spatial scales. Aeolian transport can be relevant during storms when the strong winds are generating new dunes, but also under relative mild conditions when the dunes are strengthened by transporting sand from the intertidal area to the dunes. Hydrodynamic transport is also relevant during storms, when high water in combination with waves can cause dunes to avalanche and erode. While under normal conditions the hydrodynamic transport can result in an onshore transport of sediment up to the intertidal area. The exchange of sediment in the intertidal area is a dynamic interaction between the hydrodynamic transport and the aeolian transport. This dynamic interaction is particularly important for simulating dune evolution at timescales longer than individual storm events. The main contribution of the integrated model is that it simulates the dynamic exchange of sediment between aeolian and hydrodynamic models in the intertidal area. By integrating the numerical models, we hope to develop a model that has a broader scope and applicability than

  15. Surface micro-topography causes hot spots of biogeochemical activity in wetland systems: A virtual modeling experiment

    NASA Astrophysics Data System (ADS)

    Frei, S.; Knorr, K. H.; Peiffer, S.; Fleckenstein, J. H.

    2012-12-01

    Wetlands provide important ecohydrological services by regulating fluxes of nutrients and pollutants to receiving waters, which can in turn mitigate adverse effects on water quality. Turnover of redox-sensitive solutes in wetlands has been shown to take place in distinct spatial and temporal patterns, commonly referred to as hot spots and hot moments. Despite the importance of such patterns for solute fluxes the mechanistic understanding of their formation is still weak and their existence is often explained by variations in soil properties and diffusive transport only. Here we show that surface micro-topography in wetlands can cause the formation of biogeochemical hot spots solely by the advective redistribution of infiltrating water as a result of complex subsurface flow patterns. Surface and subsurface flows are simulated for an idealized section of a riparian wetland using a fully integrated numerical code for coupled surface-subsurface systems. Biogeochemical processes and transport along advective subsurface flow paths are simulated kinetically using the biogeochemical code PHREEQC. Distinct patterns of biogeochemical activity (expressed as reaction rates) develop in response to micro-topography induced subsurface flow patterns. Simulated vertical pore water profiles for various redox-sensitive species resemble profiles observed in the field. This mechanistic explanation of hot spot formation complements the more static explanations that relate hot spots solely to spatial variability in soil characteristics and can account for spatial as well as temporal variability of biogeochemical activity, which is needed to assess future changes in the biogeochemical turnover of wetland systems.

  16. Full Uncertainty Quantification of a Regional N2O and NO3 Inventory Using the Biogeochemical Model LandscapeDNDC

    NASA Astrophysics Data System (ADS)

    Haas, E.; Santabarbara, I.; Kraus, D.; Klatt, S.; Werner, C.; Kiese, R.; Butterbach-Bahl, K.

    2014-12-01

    Numerical simulation models are increasingly used to estimate greenhouse gas emissions at site to regional / national scale and are outlined as the most advanced methodology (Tier 3) in the framework of UNFCCC reporting. Process-based models incorporate the major processes of the carbon and nitrogen cycle of terrestrial ecosystems and are thus thought to be widely applicable at various spatial scales. Regional inventories require high spatial resolution input data on soil properties, climate drivers and management information. The acceptance of model based inventory calculations depends on the assessment of the inventory's uncertainty (model, input data and parameter induced uncertainties). In this study we fully quantify uncertainty in regional N2O / NO3 inventory predictions from arable soils of Saxony (Germany) using the biogeochemical model LandscapeDNDC. We address model induced uncertainty (MU) by contrasting two different soil biogeochemistry modules in conjunction with two different plant growth descriptions within LandscapeDNDC. Input data induced uncertainty (DU) was addressed by Latin Hyper Cube sampling of soil properties, climate drivers and agricultural management practices. The parameter induced uncertainty (PU) was assessed by using a joint parameter distribution for key parameters describing microbial C and N turnover processes as obtained by a Bayesian calibration study. We representatively sampled different parameter vectors from the discrete joint parameter distribution comprising all parameter combinations and used these to calculate individual realizations of the regional inventory. The spatial domain (4042 polygons) was set up with spatially explicit soil and climate information and a region-typical 3-year crop rotation consisting of winter wheat, rapeseed, and winter barley. For the MU, DU and PU we calculated several hundred regional inventories each to assess the individual uncertainty contributions. For the overall uncertainty

  17. A model of biogeochemical cycling of phosphorus, nitrogen, oxygen, and sulphur in the ocean: One step toward a global climate model

    NASA Astrophysics Data System (ADS)

    Shaffer, Gary

    1989-02-01

    An ocean model has been developed which, for prescribed physics, deals with interrelationships between chemical distributions, biogeochemical sinks and sources, chemical reactions at redox fronts, and transports across the air-sea and sediment-water interfaces. In its first application here, the model focuses on biogeochemical cycling of phosphorus, nitrogen, oxygen, and sulphur in an ocean forced by river input of nutrients. This is a natural starting point for a global climate model since ocean circulation and biology determine atmospheric CO2 concentrations for a given inventory of inorganic C and oceanic production is controlled mainly by the availability of inorganic P and/or N. A general approach is taken to look at oxic versus anoxic conditions, P versus N limitation of primary production, with or without inorganic removal of phosphate to the sediments. As demanded by this approach, the model is nonlinear and continuous in a vertical coordinate. To focus on the biogeochemical aspects, ocean physics are kept as simple as possible. Cold, oxygen-rich water sinks at high latitudes and is upwelled with a constant velocity. Turbulent mixing is parameterized with a constant, vertical diffusion coefficient. The biogeochemical processes considered are new production, burial, nitrogen fixation, phosphorite formation, and three types of organic decomposition: oxidation with O2, denitrification, and sulphate reduction. Organic matter is taken to consist of a high- and a low-reactive fraction. The chemical species considered explicitly are PO43--P, NO3--N, O2, NH4+-N and H2S-S. Results indicate that a change from oxic to weakly anoxic conditions at middepths in a P-limited ocean would lead to strong local denitrification and low nitrate concentrations throughout the water column. New production would also become dominated by nitrogen fixers. Geological evidence implies that anoxic conditions in the water column have been rare in the Phanerozoic ocean. Both phosphorite

  18. Modeling Biogeochemical-Physical Interactions and Carbon Flux in the Sargasso Sea (Bermuda Atlantic Time-series Study site)

    NASA Technical Reports Server (NTRS)

    Signorini, Sergio R.; McClain, Charles R.; Christian, James R.

    2001-01-01

    An ecosystem-carbon cycle model is used to analyze the biogeochemical-physical interactions and carbon fluxes in the Bermuda Atlantic Time-series Study (BATS) site for the period of 1992-1998. The model results compare well with observations (most variables are within 8% of observed values). The sea-air flux ranges from -0.32 to -0.50 mol C/sq m/yr, depending upon the gas transfer algorithm used. This estimate is within the range (-0.22 to -0.83 mol C/sq m/yr) of previously reported values which indicates that the BATS region is a weak sink of atmospheric CO2. The overall carbon balance consists of atmospheric CO2 uptake of 0.3 Mol C/sq m/yr, upward dissolved inorganic carbon (DIC) bottom flux of 1.1 Mol C/sq m/yr, and carbon export of 1.4 mol C/sq m/yr via sedimentation. Upper ocean DIC levels increased between 1992 and 1996 at a rate of approximately 1.2 (micro)mol/kg/yr, consistent with observations. However, this trend was reversed during 1997-1998 to -2.7 (micro)mol/kg/yr in response to hydrographic changes imposed by the El Nino-La Nina transition, which were manifested in the Sargasso Sea by the warmest SST and lowest surface salinity of the period (1992-1998).

  19. [Seasonal evolution of the biogeochemical cycle in the southwest lagoon of New Caledonia. Application of a compartmental model].

    PubMed

    Bujan, S; Grenz, C; Fichez, R; Douillet, P

    2000-02-01

    A biogeochemical box model describing the south-west lagoon of New-Caledonia was developed in order to simulate the seasonal cycle of carbon and nitrogen. We used fluxes generated by a 3D hydrodynamic model to simulate horizontal exchanges between boxes and added freshwater influxes as nitrogen sources from the land. Average residence time proved to be less than 11 days for the lagoon as a whole. Standard simulations showed baseline values of chlorophyll a between 0.2 and 0.4 microgram.L-1. Influences of freshwater influxes proved to be significant (increases up to 1 microgram.L-1) only in shallow areas protected from wind exposure and during short periods of heavy rainfall (tropical depressions). Tropical climatic events have reduced impact in space and time and long-term simulations over decades with increased nutrient inputs did not show any significant process of eutrophication. Hydrodynamics seemed to be one of the major control factors with respect to organic matter cycling in the lagoon. PMID:10763441

  20. Development and evaluation of the offshore and coastal dispersion model

    SciTech Connect

    Hanna, S.R.; Schulman, L.L.; Paine, R.J.; Pleim, J.E.; Baer, M.

    1985-10-01

    The Offshore and Coastal Dispersion (OCD) model has been developed for the Minerals Management Service (MMS) to determine the impact of offshore and onshore emissions from point sources on the air quality of coastal regions. Constructed on the framework of the EPA guideline model MPTER, the OCD model incorporates overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. Hourly meteorological data are needed from both offshore and onshore locations, including wind direction and speed, mixing height, overwater air temperature and relative humidity, and the sea surface temperature. Observed turbulence intensities are preferred by the model but are not mandatory. Dispersion coefficients are proportional to turbulence intensities. A virtual source technique is used to change the rate of plume growth as the overwater plume intercepts the overland internal boundary layer. The continuous shoreline fumigation case is treated using an approach suggested by Deardorff and Willis. Calculation of plume reflection from elevated terrain follows the Rough Terrain Dispersion Model (RTDM). The OCD model and the modified EPA model used as an interim model for overwater applications by the MMS were tested with measurements from three offshore tracer experiments. The OCD model was shown to be a clear improvement over the EPA model and was officially approved by the MMS in March 1985.

  1. Calibration of a biome-biogeochemical cycles model for modeling the net primary production of teak forests through inverse modeling of remotely sensed data

    NASA Astrophysics Data System (ADS)

    Imvitthaya, Chomchid; Honda, Kiyoshi; Lertlum, Surat; Tangtham, Nipon

    2011-01-01

    In this paper, we present the results of a net primary production (NPP) modeling of teak (Tectona grandis Lin F.), an important species in tropical deciduous forests. The biome-biogeochemical cycles or Biome-BGC model was calibrated to estimate net NPP through the inverse modeling approach. A genetic algorithm (GA) was linked with Biome-BGC to determine the optimal ecophysiological model parameters. The Biome-BGC was calibrated by adjusting the ecophysiological model parameters to fit the simulated LAI to the satellite LAI (SPOT-Vegetation), and the best fitness confirmed the high accuracy of generated ecophysioligical parameter from GA. The modeled NPP, using optimized parameters from GA as input data, was evaluated using daily NPP derived by the MODIS satellite and the annual field data in northern Thailand. The results showed that NPP obtained using the optimized ecophysiological parameters were more accurate than those obtained using default literature parameterization. This improvement occurred mainly because the model's optimized parameters reduced the bias by reducing systematic underestimation in the model. These Biome-BGC results can be effectively applied in teak forests in tropical areas. The study proposes a more effective method of using GA to determine ecophysiological parameters at the site level and represents a first step toward the analysis of the carbon budget of teak plantations at the regional scale.

  2. C-GEM (v 1.0): a new, cost-efficient biogeochemical model for estuaries and its application to a funnel-shaped system

    NASA Astrophysics Data System (ADS)

    Volta, C.; Arndt, S.; Savenije, H. H. G.; Laruelle, G. G.; Regnier, P.

    2013-11-01

    The first part of this paper describes C-GEM (Carbon - Generic Estuary Model), a new, one-dimensional, generic reactive-transport model for the biogeochemical dynamics of carbon and associated bio-elements (N, P, Si) in estuaries. C-GEM is computationally efficient and reduces data-requirements by using an idealized representation of the estuarine geometry to quantitatively predict the dominant features of the estuarine hydrodynamics, salt transport and biogeochemistry. A protocol for the set-up of C-GEM for an estuarine system is also described. The second part of this paper presents, as a proof of concept, the application of C-GEM to the funnel-shaped Scheldt estuary (Belgium, the Netherlands), one of the best-surveyed system in the world. Steady-state and transient simulations are performed and the performance of C-GEM is evaluated through model-data and model-model comparison, using integrated measures of the estuarine biogeochemical functioning, such as system-wide estimates of the Net Ecosystem Metabolism (NEM). A sensitivity analysis is also carried out to identify model parameters that exert the most important control on biogeochemical processes and to assess the sensitivity of the NEM to uncertainties in parameter values. The paper ends by a short discussion of current model limitations with respect to local, regional and global scale applications.

  3. Modeling of Natural Coastal Hazards in Puerto Rico in Support of Emergency Management and Coastal Planning

    NASA Astrophysics Data System (ADS)

    Mercado, A., Jr.

    2015-12-01

    The island of Puerto Rico is not only located in the so-called Caribbean hurricane alley, but is also located in a tsunami prone region. And both phenomena have affected the island. For the past few years we have undergone the task of upgrading the available coastal flood maps due to storm surges and tsunamis. This has been done taking advantage of new Lidar-derived, high resolution, topography and bathymetry and state-of-the-art models (MOST for tsunamis and ADCIRC/SWAN for storm surges). The tsunami inundation maps have been converted to evacuation maps. In tsunamis we are also working in preparing hazard maps due to tsunami currents inside ports, bays, and marinas. The storm surge maps include two scenarios of sea level rise: 0.5 and 1.0 m above Mean High Water. All maps have been adopted by the Puerto Rico State Emergency Management Agency, and are publicly available through the Internet. It is the purpose of this presentation to summarize how it has been done, the spin-off applications they have generated, and how we plan to improve coastal flooding predictions.

  4. Automated calibration of a stream solute transport model: Implications for interpretation of biogeochemical parameters

    USGS Publications Warehouse

    Scott, D.T.; Gooseff, M.N.; Bencala, K.E.; Runkel, R.L.

    2003-01-01

    The hydrologic processes of advection, dispersion, and transient storage are the primary physical mechanisms affecting solute transport in streams. The estimation of parameters for a conservative solute transport model is an essential step to characterize transient storage and other physical features that cannot be directly measured, and often is a preliminary step in the study of reactive solutes. Our study used inverse modeling to estimate parameters of the transient storage model OTIS (One dimensional Transport with Inflow and Storage). Observations from a tracer injection experiment performed on Uvas Creek, California, USA, are used to illustrate the application of automated solute transport model calibration to conservative and nonconservative stream solute transport. A computer code for universal inverse modeling (UCODE) is used for the calibrations. Results of this procedure are compared with a previous study that used a trial-and-error parameter estimation approach. The results demonstrated 1) importance of the proper estimation of discharge and lateral inflow within the stream system; 2) that although the fit of the observations is not much better when transient storage is invoked, a more randomly distributed set of residuals resulted (suggesting non-systematic error), indicating that transient storage is occurring; 3) that inclusion of transient storage for a reactive solute (Sr2+) provided a better fit to the observations, highlighting the importance of robust model parameterization; and 4) that applying an automated calibration inverse modeling estimation approach resulted in a comprehensive understanding of the model results and the limitation of input data.

  5. Predicting coastal cliff erosion using a Bayesian probabilistic model

    USGS Publications Warehouse

    Hapke, C.; Plant, N.

    2010-01-01

    Regional coastal cliff retreat is difficult to model due to the episodic nature of failures and the along-shore variability of retreat events. There is a growing demand, however, for predictive models that can be used to forecast areas vulnerable to coastal erosion hazards. Increasingly, probabilistic models are being employed that require data sets of high temporal density to define the joint probability density function that relates forcing variables (e.g. wave conditions) and initial conditions (e.g. cliff geometry) to erosion events. In this study we use a multi-parameter Bayesian network to investigate correlations between key variables that control and influence variations in cliff retreat processes. The network uses Bayesian statistical methods to estimate event probabilities using existing observations. Within this framework, we forecast the spatial distribution of cliff retreat along two stretches of cliffed coast in Southern California. The input parameters are the height and slope of the cliff, a descriptor of material strength based on the dominant cliff-forming lithology, and the long-term cliff erosion rate that represents prior behavior. The model is forced using predicted wave impact hours. Results demonstrate that the Bayesian approach is well-suited to the forward modeling of coastal cliff retreat, with the correct outcomes forecast in 70-90% of the modeled transects. The model also performs well in identifying specific locations of high cliff erosion, thus providing a foundation for hazard mapping. This approach can be employed to predict cliff erosion at time-scales ranging from storm events to the impacts of sea-level rise at the century-scale. ?? 2010.

  6. The Effects of Chlorophyll Assimilation on Carbon Fluxes in a Global Biogeochemical Model. [Technical Report Series on Global Modeling and Data Assimilation

    NASA Technical Reports Server (NTRS)

    Koster, Randal D. (Editor); Rousseaux, Cecile Severine; Gregg, Watson W.

    2014-01-01

    In this paper, we investigated whether the assimilation of remotely-sensed chlorophyll data can improve the estimates of air-sea carbon dioxide fluxes (FCO2). Using a global, established biogeochemical model (NASA Ocean Biogeochemical Model, NOBM) for the period 2003-2010, we found that the global FCO2 values produced in the free-run and after assimilation were within -0.6 mol C m(sup -2) y(sup -1) of the observations. The effect of satellite chlorophyll assimilation was assessed in 12 major oceanographic regions. The region with the highest bias was the North Atlantic. Here the model underestimated the fluxes by 1.4 mol C m(sup -2) y(sup -1) whereas all the other regions were within 1 mol C m(sup -2) y(sup -1) of the data. The FCO2 values were not strongly impacted by the assimilation, and the uncertainty in FCO2 was not decreased, despite the decrease in the uncertainty in chlorophyll concentration. Chlorophyll concentrations were within approximately 25% of the database in 7 out of the 12 regions, and the assimilation improved the chlorophyll concentration in the regions with the highest bias by 10-20%. These results suggest that the assimilation of chlorophyll data does not considerably improve FCO2 estimates and that other components of the carbon cycle play a role that could further improve our FCO2 estimates.

  7. A coupled hydrologic and biogeochemical model for assessing watershed responses to climate and land use

    EPA Science Inventory

    This seminar for Oregon State University’s Water Resources Graduate Program will describe the use of a spatially-distributed ecohydrological model, VELMA, for quantifying how alternative land use and climate scenarios affect tradeoffs among important ecosystem services. Sp...

  8. Quantification of sediment-water interactions in a polluted tropical river through biogeochemical modeling

    NASA Astrophysics Data System (ADS)

    Trinh, Anh Duc; Meysman, Filip; Rochelle-Newall, Emma; Bonnet, Marie Paule

    2012-09-01

    Diagenetic modeling presents an interesting and robust way to understand sediment-water column processes. Here we present the application of such a model to the Day River in Northern Vietnam, a system that is subject to high levels of domestic wastewater inputs from the Hanoi metropolitan area. Experimental data from three areas of different water and sediment quality, combined with some additional data from the river, are used to set up and calibrate a diagenetic model. The model was used to determine the role of the sediments as a sink for carbon and nutrients and shows that in the dry season, 27% of nitrogen, 25% of carbon, and 38% of phosphorus inputs into the river system are stored in sediments. The corresponding numbers during the rainy season are 15%, 10%, and 20%, respectively. The diagenetic model was then used to test the impact of an improvement in the treatment of Hanoi's municipal wastewater. We show that improved wastewater treatment could reduce by about 17.5% the load of organic matter to the sediment. These results are the first to highlight the importance of sediments as a potential removal mechanism of organic matter and nutrients from the water column in this type of highly impacted tropical urban river, further demonstrating that rivers need to be considered as reaction sites and not just as inert conduits.

  9. Phosphorus limitation reduces hypoxia in the northern Gulf of Mexico: results from a physical-biogeochemical model

    NASA Astrophysics Data System (ADS)

    Laurent, Arnaud; Fennel, Katja

    2014-05-01

    In the northern Gulf of Mexico, excess dissolved inorganic nitrogen and phosphorus loads from the Mississippi-Atchafalaya River system promote high primary production and contribute to the seasonal development of hypoxic bottom waters on the Louisiana Shelf. While phytoplankton growth is considered to be typically nitrogen-limited in marine waters, phosphorus limitation has been observed in this region during peak river discharge in spring and early summer. Here we present a synthesis of recent investigations that quantitatively assessed, using a realistic physical-biogeochemical model, the effect of phosphorus limitation on primary production and hypoxia development in the Mississippi-Atchafalaya River plume. Our model simulations indicate that phosphorus limitation delays and displaces westward a portion of river-stimulated primary production and depositional fluxes, resulting in a redistribution of respiration processes toward the western Louisiana Shelf. Despite this redistribution, phosphorus limitation did not promote a westward expansion or relocation of hypoxia, as some had previously speculated. Rather, the onset of hypoxia was delayed and the size of the hypoxic zone reduced. In other words, P limitation diluted the effects of eutrophication on the Louisiana shelf. Simulations with altered nutrient river loads show that despite phosphorus limitation, the co-reduction of nitrogen and phosphorus remains the best strategy to reduce hypoxia. Yet, a 50% reduction in both nutrients was not sufficient to meet the Gulf Hypoxia action plan goal of a 5 · 103 km2 hypoxic area in our model simulations. This result emphasizes the need for a drastic co-reduction of N and P loads from the Mississippi-Atchafalaya River system to significantly reduce hypoxia in this region.

  10. Beyond The Blueprint: Development Of Genome-Informed Trait-Based Models For Prediction Of Microbial Dynamics And Biogeochemical Rates

    NASA Astrophysics Data System (ADS)

    Brodie, E.; King, E.; Molins, S.; Karaoz, U.; Johnson, J. N.; Bouskill, N.; Hug, L. A.; Thomas, B. C.; Castelle, C. J.; Beller, H. R.; Banfield, J. F.; Steefel, C. I.

    2014-12-01

    -guild trait variability amongst other parameters and are using this model to explore abiotic controls on community emergence and impact on rates of reactions that contribute to the cycling of carbon across biogeochemical gradients from the soil to the subsurface.

  11. Assessment of global nitrogen pollution in rivers using an integrated biogeochemical modeling framework.

    PubMed

    He, Bin; Kanae, Shinjiro; Oki, Taikan; Hirabayashi, Yukiko; Yamashiki, Yosuke; Takara, Kaoru

    2011-04-01

    This study has analyzed the global nitrogen loading of rivers resulting from atmospheric deposition, direct discharge, and nitrogenous compounds generated by residential, industrial, and agricultural sources. Fertilizer use, population distribution, land cover, and social census data were used in this study. A terrestrial nitrogen cycle model with a 24-h time step and 0.5° spatial resolution was developed to estimate nitrogen leaching from soil layers in farmlands, grasslands, and natural lands. The N-cycle in this model includes the major processes of nitrogen fixation, nitrification, denitrification, immobilization, mineralization, leaching, and nitrogen absorption by vegetation. The previously developed Total Runoff Integrating Pathways network was used to analyze nitrogen transport from natural and anthropogenic sources through river channels, as well as the collecting and routing of nitrogen to river mouths by runoff. Model performance was evaluated through nutrient data measured at 61 locations in several major world river basins. The dissolved inorganic nitrogen concentrations calculated by the model agreed well with the observed data and demonstrate the reliability of the proposed model. The results indicate that nitrogen loading in most global rivers is proportional to the size of the river basin. Reduced nitrate leaching was predicted for basins with low population density, such as those at high latitudes or in arid regions. Nitrate concentration becomes especially high in tropical humid river basins, densely populated basins, and basins with extensive agricultural activity. On a global scale, agriculture has a significant impact on the distribution of nitrogenous compound pollution. The map of nitrate distribution indicates that serious nitrogen pollution (nitrate concentration: 10-50 mg N/L) has occurred in areas with significant agricultural activities and small precipitation surpluses. Analysis of the model uncertainty also suggests that the nitrate

  12. Natural biogeochemical cycle of mercury in a global three-dimensional ocean tracer model

    NASA Astrophysics Data System (ADS)

    Zhang, Yanxu; Jaeglé, Lyatt; Thompson, LuAnne

    2014-05-01

    We implement mercury (Hg) biogeochemistry in the offline global 3-D ocean tracer model (OFFTRAC) to investigate the natural Hg cycle, prior to any anthropogenic input. The simulation includes three Hg tracers: dissolved elemental (Hg0aq), dissolved divalent (HgIIaq), and particle-bound mercury (HgPaq). Our Hg parameterization takes into account redox chemistry in ocean waters, air-sea exchange of Hg0, scavenging of HgIIaq onto sinking particles, and resupply of HgIIaq at depth by remineralization of sinking particles. Atmospheric boundary conditions are provided by a global simulation of the natural atmospheric Hg cycle in the GEOS-Chem model. In the surface ocean, the OFFTRAC model predicts global mean concentrations of 0.16 pM for total Hg, partitioned as 80% HgIIaq, 14% Hg0aq, and 6% HgPaq. Total Hg concentrations increase to 0.38 pM in the thermocline/intermediate waters (between the mixed layer and 1000 m depth) and 0.82 pM in deep waters (below 1000 m), reflecting removal of Hg from the surface to the subsurface ocean by particle sinking followed by remineralization at depth. Our model predicts that Hg concentrations in the deep North Pacific Ocean (>2000 m) are a factor of 2-3 higher than in the deep North Atlantic Ocean. This is the result of cumulative input of Hg from particle remineralization as deep waters transit from the North Atlantic to the North Pacific on their ~2000 year journey. The model is able to reproduce the relatively uniform concentrations of total Hg observed in the old deep waters of the North Pacific Ocean (observations: 1.2 ± 0.4 pM; model: 1.1 ± 0.04 pM) and Southern Ocean (observations: 1.1 ± 0.2 pM; model: 0.8 ± 0.02 pM). However, the modeled concentrations are factors of 5-6 too low compared to observed concentrations in the surface ocean and in the young water masses of the deep North Atlantic Ocean. This large underestimate for these regions implies a factor of 5-6 anthropogenic enhancement in Hg concentrations.

  13. A Hierarchical Bayesian Model for Estimating Remediation-induced Biogeochemical Transformations Using Spectral Induced Polarization Data: Development and Application to the Contaminated DOE Rifle (CO) Site

    NASA Astrophysics Data System (ADS)

    Chen, J.; Hubbard, S. S.; Williams, K. H.; Tuglus, C.; Flores-Orozco, A.; Kemna, A.

    2010-12-01

    Although in-situ bioremediation is often considered as a key approach for subsurface environmental remediation, monitoring induced biogeochemical processes, needed to evaluate the efficacy of the treatments, is challenging over field relevant scales. In this study, we develop a hierarchical Bayesian model that builds on our previous framework for estimating biogeochemical transformations using geochemical and geophysical data obtained from laboratory column experiments. The new Bayesian model treats the induced biogeochemical transformations as both spatial and temporal (rather than just temporal) processes and combines time-lapse borehole ‘point’ geochemical measurements with inverted surface- or crosshole-based spectral induced polarization (SIP) data. This model consists of three levels of statistical sub-models: (1) data model (or likelihood function), which provides links between the biogeochemical end-products and geophysical attributes, (2) process model, which describes the spatial and temporal variability of biogeochemical properties in the disturbed subsurface systems, and (3) parameter model, which describes the prior distributions of various parameters and initial conditions. The joint posterior probability distribution is explored using Markov Chain Monte Carlo sampling methods to obtain the spatial and temporal distribution of the hidden parameters. We apply the developed Bayesian model to the datasets collected from the uranium-contaminated DOE Rifle site for estimating the spatial and temporal distribution of remediation-induced end products. The datasets consist of time-lapse wellbore aqueous geochemical parameters (including Fe(II), sulfate, sulfide, acetate, uranium, chloride, and bromide concentrations) and surface SIP data collected over 13 frequencies (ranging from 0.065Hz to 256Hz). We first perform statistical analysis on the multivariate data to identify possible patterns (or ‘diagnostic signatures’) of bioremediation, and then we

  14. Characterization of mixing errors in a coupled physical biogeochemical model of the North Atlantic: implications for nonlinear estimation using Gaussian anamorphosis

    NASA Astrophysics Data System (ADS)

    Béal, D.; Brasseur, P.; Brankart, J.-M.; Ourmières, Y.; Verron, J.

    2010-02-01

    In biogeochemical models coupled to ocean circulation models, vertical mixing is an important physical process which governs the nutrient supply and the plankton residence in the euphotic layer. However, vertical mixing is often poorly represented in numerical simulations because of approximate parameterizations of sub-grid scale turbulence, wind forcing errors and other mis-represented processes such as restratification by mesoscale eddies. Getting a sufficient knowledge of the nature and structure of these errors is necessary to implement appropriate data assimilation methods and to evaluate if they can be controlled by a given observation system. In this paper, Monte Carlo simulations are conducted to study mixing errors induced by approximate wind forcings in a three-dimensional coupled physical-biogeochemical model of the North Atlantic with a 1/4° horizontal resolution. An ensemble forecast involving 200 members is performed during the 1998 spring bloom, by prescribing perturbations of the wind forcing to generate mixing errors. The biogeochemical response is shown to be rather complex because of nonlinearities and threshold effects in the coupled model. The response of the surface phytoplankton depends on the region of interest and is particularly sensitive to the local stratification. In addition, the statistical relationships computed between the various physical and biogeochemical variables reflect the signature of the non-Gaussian behaviour of the system. It is shown that significant information on the ecosystem can be retrieved from observations of chlorophyll concentration or sea surface temperature if a simple nonlinear change of variables (anamorphosis) is performed by mapping separately and locally the ensemble percentiles of the distributions of each state variable on the Gaussian percentiles. The results of idealized observational updates (performed with perfect observations and neglecting horizontal correlations) indicate that the implementation

  15. Methane emissions from wetlands: biogeochemical, microbial, and modeling perspectives from local to global scales.

    PubMed

    Bridgham, Scott D; Cadillo-Quiroz, Hinsby; Keller, Jason K; Zhuang, Qianlai

    2013-05-01

    Understanding the dynamics of methane (CH4 ) emissions is of paramount importance because CH4 has 25 times the global warming potential of carbon dioxide (CO2 ) and is currently the second most important anthropogenic greenhouse gas. Wetlands are the single largest natural CH4 source with median emissions from published studies of 164 Tg yr(-1) , which is about a third of total global emissions. We provide a perspective on important new frontiers in obtaining a better understanding of CH4 dynamics in natural systems, with a focus on wetlands. One of the most exciting recent developments in this field is the attempt to integrate the different methodologies and spatial scales of biogeochemistry, molecular microbiology, and modeling, and thus this is a major focus of this review. Our specific objectives are to provide an up-to-date synthesis of estimates of global CH4 emissions from wetlands and other freshwater aquatic ecosystems, briefly summarize major biogeophysical controls over CH4 emissions from wetlands, suggest new frontiers in CH4 biogeochemistry, examine relationships between methanogen community structure and CH4 dynamics in situ, and to review the current generation of CH4 models. We highlight throughout some of the most pressing issues concerning global change and feedbacks on CH4 emissions from natural ecosystems. Major uncertainties in estimating current and future CH4 emissions from natural ecosystems include the following: (i) A number of important controls over CH4 production, consumption, and transport have not been, or are inadequately, incorporated into existing CH4 biogeochemistry models. (ii) Significant errors in regional and global emission estimates are derived from large spatial-scale extrapolations from highly heterogeneous and often poorly mapped wetland complexes. (iii) The limited number of observations of CH4 fluxes and their associated environmental variables loosely constrains the parameterization of process-based biogeochemistry

  16. Reconstructing paleo-ocean silicon chemistry and ecology during Last Glacial Maximum, a biogeochemical cycle modeling approach

    NASA Astrophysics Data System (ADS)

    Li, D. D.; Lerman, A.; Mackenzie, F. T.

    2012-12-01

    It has been established by a number of investigators that opal content and Si-C isotope studies in the marine sediments reveal information about paleooceanography and the impact on silicic acid utilization by marine autotrophes (diatoms, silicoflagellates) and heterotrophes (radiolarians) during the Last Glacial Maximum (LGM). Opal, as an amorphous form of SiO2, formed by marine Si-secreting organisms, has been used as a proxy to indicate chemical ocean evolution, paleoproductivity and temperature variations in the paleoenvironment and regional ocean water biogeochemical studies, both on million- and thousand-year scales. Here, we are using a model of the global silicon biogeochemical cycle to understand and reconstruct evolutionary history of the paleobiogeochemical cycle and paleoenvironment since LGM. The model is process-driven, temperature-driven, and land-ocean-sediment coupled with specific marine Si-secreting organisms that represent different trophic levels and physiological mechanisms. Specifically, Si utilization by marine silicoflagellates and radiolarians are each about 5% of that of ubiquitous marine diatoms. Available marine reactive Si is controlled by variation of diatom bioproduction that represents 5% of the total marine primary productivity (Si/C Redfield ratio in the marine organic matter is ~0.13, which is an order of magnitude higher than ratio in land organic matter). River input of Si is controlled by chemical weathering of silicate rocks and biocyling of land plant phytoliths. Decreasing dissolved and particulate Si input from land and less favorable climatic condition into LGM diminished the primary production of marine diatoms. However, because radiolarians favor deep-water habitat, where a higher level of DSi is found and that is less affected by temperature changes, a peak of relative abundance is usually observed in sedimentary record during LGM. Given that opal formation fractionated seawater δ30Si (1‰) and enriched seawater with

  17. Associations between the molecular and optical properties of dissolved organic matter in the Florida Everglades, a model coastal wetland system

    NASA Astrophysics Data System (ADS)

    Wagner, Sasha; Jaffe, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-11-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275-295, S350-400, SR, FI, freshness index and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman’s rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands.

  18. Associations Between the Molecular and Optical Properties of Dissolved Organic Matter in the Florida Everglades, a Model Coastal Wetland System

    PubMed Central

    Wagner, Sasha; Jaffé, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-01-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source, and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial, and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275−295, S350−400, SR, FI, freshness index, and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman's rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance, and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands. PMID:26636070

  19. Associations Between the Molecular and Optical Properties of Dissolved Organic Matter in the Florida Everglades, a Model Coastal Wetland System.

    PubMed

    Wagner, Sasha; Jaffé, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-01-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source, and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial, and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275-295, S350-400, SR, FI, freshness index, and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman's rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance, and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands. PMID:26636070

  20. Soil Biogeochemical Properties and Erosion Source Prediction Model Summary for the Buffalo Bayou Watershed, Houston, Texas

    NASA Astrophysics Data System (ADS)

    Ahmed, I.

    2015-12-01

    We draw conclusions on the research output and findings from a 4-year multidisciplinary USDA-CBG collaborative program in sustainable integrated monitoring of soil organic carbon (SOC) loss prediction via erosion. The underlying method uses the state-of-the-art stable isotope science of sediment tracing under uncertain hydrologic influences. The research finds are rooted in the (i) application of Bayesian Markov Chain Monte Carlo statistical models to assess the relationship between rainfall-runoff and soil erosion in space and time, (ii) capture of the episodic nature of rainfall events and its role in the spatial distribution of SOC loss from water erosion, (iii) stable isotope composition guided fingerprinting (source and quantity) of eroded soil, and (iv) the creation of an integrated watershed scale statistical soil loss monitoring model driven by spatial and temporal correlation of flow and stable isotope composition. The research theme was successfully applied on the urbanized Buffalo Bayou Watershed in Houston, Texas. The application brought to light novel future research conceptual outlines which will also be discussed in this deliverable to the AGU meeting. These include but not limited to: regional rainfall cluster research, physics of muddy river-bank soil and suspended sediment interaction, and friction & mobility that together make up the plasticity of soil aggregates that control erosion processes and landscape changes in a riparian corridor. References: Ahmed, I., Karim, A., Boutton, T.W., and Strom, K.B. (2013a). "Monitoring Soil Organic Carbon Loss from Erosion Using Stable Isotopes." Proc., Soil Carbon Sequestration, International Conference, May 26-29, Reykjavik, Iceland. Ahmed, I, Bouttom, T.W., Strom, K. B., Karim, A., and Irvin-Smith, N. (2013b). "Soil carbon distribution and loss monitoring in the urbanized Buffalo Bayou watershed, Houston, Texas." Proc., 4th Annual All Investigators Meeting of the North American Carbon Program, February 4

  1. Modeling physical and biogeochemical controls over carbon accumulation in a boreal forest soil

    USGS Publications Warehouse

    Carrasco, J.J.; Neff, J.C.; Harden, J.W.

    2006-01-01

    Boreal soils are important to the global C cycle owing to large C stocks, repeated disturbance from fire, and the potential for permafrost thaw to expose previously stable, buried C. To evaluate the primary mechanisms responsible for both short- and long-term C accumulation in boreal soils, we developed a multi-isotope (12,14C) Soil C model with dynamic soil layers that develop through time as soil organic matter burns and reaccumulates. We then evaluated the mechanisms that control organic matter turnover in boreal regions including carbon input rates, substrate recalcitrance, soil moisture and temperature, and the presence of historical permafrost to assess the importance of these factors in boreal C accumulation. Results indicate that total C accumulation is controlled by the rate of carbon input, decomposition rates, and the presence of historical permafrost. However, unlike more temperate ecosystems, one of the key mechanisms involved in C preservation in boreal soils examined here is the cooling of subsurface soil layers as soil depth increases rather than increasing recalcitrance in subsurface soils. The propagation of the 14C bomb spike into soils also illustrates the importance of historical permafrost and twentieth century warming in contemporary boreal soil respiration fluxes. Both 14C and total C simulation data also strongly suggest that boreal SOM need not be recalcitrant to accumulate; the strong role of soil temperature controls on boreal C accumulation at our modeling test site in Manitoba, Canada, indicates that carbon in the deep organic soil horizons is probably relatively labile and thus subject to perturbations that result from changing climatic conditions in the future. Copyright 2006 by the American Geophysical Union.

  2. Diagnostic modeling of dimethylsulfide production in coastal water west of the Antarctic Peninsula

    NASA Technical Reports Server (NTRS)

    Hermann, Maria; Najjar, Raymond G.; Neeley, Aimee R.; Vila-Costa, Maria; Dacey, John W. H.; DiTullio, Giacomo, R.; Kieber, David J.; Kiene, Ronald P.; Matrai, Patricia A.; Simo, Rafel; Vernet, Maria

    2012-01-01

    The rate of gross biological dimethylsulfide (DMS) production at two coastal sites west of the Antarctic Peninsula, off Anvers Island, near Palmer Station, was estimated using a diagnostic approach that combined field measurements from 1 January 2006 through 1 March 2006 and a one-dimensional physical model of ocean mixing. The average DMS production rate in the upper water column (0-60 m) was estimated to be 3.1 +/- 0.6 nM/d at station B (closer to shore) and 2.7 +/- 0.6 nM/d1 at station E (further from shore). The estimated DMS replacement time was on the order of 1 d at both stations. DMS production was greater in the mixed layer than it was below the mixed layer. The average DMS production normalized to chlorophyll was 0.5 +/- nM/d)/(mg cubic m) at station B and 0.7 +/- 0.2 (nM/d)/(mg/cubic m3) at station E. When the diagnosed production rates were normalized to the observed concentrations of total dimethylsulfoniopropionate (DMSPt, the biogenic precursor of DMS), we found a remarkable similarity between our estimates at stations B and E (0.06 +/- 0.02 and 0.04 +/- 0.01 (nM DMS / d1)/(nM DMSP), respectively) and the results obtained in a previous study from a contrasting biogeochemical environment in the North Atlantic subtropical gyre (0.047 =/- 0.006 and 0.087 +/- 0.014 (nM DMS d1)/(nM DMSP) in a cyclonic and anticyclonic eddy, respectively).We propose that gross biological DMS production normalized to DMSPt might be relatively independent of the biogeochemical environment, and place our average estimate at 0.06 +/- 0.01 (nM DMS / d)/(nM DMSPt). The significance of this finding is that it can provide a means to use DMSPt measurements to extrapolate gross biological DMS production, which is extremely difficult to measure experimentally under realistic in situ conditions.

  3. Modelling the effect of severe storms in coastal pollution

    NASA Astrophysics Data System (ADS)

    Grau, A.; Bolea, Y.; Guerra, E.

    2009-09-01

    Modelling and simulation of real events can be very useful to prevent environmental disasters, but these disasters can affect the health and life of human beings; then such tools become definitively necessary for governmental authorities to avoid population risk. In this wok we present a mathematical model that combines the effect of Mediterranean storms together with the effect of wastewater emissary dissolutions at the sea. The emissary model corresponds to a Catalan wastewater plant, the Besos plant in Barcelona. This plant throws the wastewater to the Mediterranean Sea with a 3-km pipe emissary, after a bacteriologically polluted secondary treatment. This polluted water is dissoluted in the salty water, provoking the death of all bacteria agents before they reach the coast. But in difficult conditions under violent storms, with strong East winds, the bacteriological polluted dissolution reaches the shore before the bacteria die and, therefore, a severe coastal pollution is produced. Its consequence can incur in a public health problem and the different governmental agencies activate great alarms to avoid population hazard. Storms modelling permits to evaluate the risk of coastal pollution predicting the wastewater dissolution path and velocity. Several simulations are presented under different storm conditions, making this tool very useful for the environmental protection agencies in the Catalan government.

  4. Modeling Channelization in Coastal Wetlands with Ecological Feedbacks

    NASA Astrophysics Data System (ADS)

    Hughes, Z. J.; Mahadevan, A.; Pennings, S.; FitzGerald, D.

    2014-12-01

    In coastal wetlands in Georgia and South Carolina, dendritic channel networks are actively incising headward at the rate of nearly 2 m/yr. The future geomorphic evolution of these marshes remains in question as rates of relative sea-level rise increase. Our objective is to understand the mechanisms that lead to the evolution of these channel networks through field observations and modeling. We model the geomorphological evolution of tidal creeks by viewing the wetland as a permeable medium. The porosity of the medium affects its hydraulic conductivity, which in turn is altered by erosion. Our multiphase model spontaneously generates channelization and branching networks through flow and erosion. In our field studies, we find that crabs play an active role in grazing vegetation and in the bioturbation of sediments. These effects are incorporated in our model based on field and laboratory observations of crab behavior and its effects on the marsh. We find the erosional patterns and channelization are significantly altered by the faunal feedback. Crabs enhance the growth of channels, inducing the headward erosion of creeks where flow-induced stresses are weakest. They are instrumental in generating high rates of creek extension, which channelize the marsh more effectively in response to sea-level rise. This indicates that the evolution of coastal wetlands is responding to interactions between physics and ecology and highlights the importance of the faunal contribution to these feedbacks.

  5. Modeling of coastal water contamination in Fortaleza (Northeastern Brazil).

    PubMed

    Pereira, S P; Rosman, P C C; Alvarez, C; Schetini, C A F; Souza, R O; Vieira, R H S F

    2015-01-01

    An important tool in environmental management projects and studies due to the complexity of environmental systems, environmental modeling makes it possible to integrate many variables and processes, thereby providing a dynamic view of systems. In this study the bacteriological quality of the coastal waters of Fortaleza (a state capital in Northeastern Brazil) was modeled considering multiple contamination sources. Using the software SisBaHiA, the dispersion of thermotolerant coliforms and Escherichia coli from three sources of contamination (local rivers, storm drains and submarine outfall) was analyzed. The models took into account variations in bacterial decay due to solar radiation and other environmental factors. Fecal pollution discharged from rivers and storm drains is transported westward by coastal currents, contaminating strips of beach water to the left of each storm drain or river. Exception to this condition only occurs on beaches protected by the breakwater of the harbor, where counterclockwise vortexes reverse this behavior. The results of the models were consistent with field measurements taken during the dry and the rainy season. Our results show that the submarine outfall plume was over 2 km from the nearest beach. The storm drains and the Maceió stream are the main factors responsible for the poor water quality on the waterfront of Fortaleza. The depollution of these sources would generate considerable social, health and economic gains for the region. PMID:26360752

  6. Offshore and Coastal Dispersion (OCD) Model, Version 3. 0 (revised 1988). Model-Simulation

    SciTech Connect

    Baer, M.

    1985-08-01

    The Offshore and Coastal Dispersion Model was adapted from the EPA guideline model MPTER to simulate the effect of offshore emissions from point sources in coastal regions. Modifications were made to incorporate overwater plume transport, dispersion, and changes that occur as the plume crosses the shoreline. Modifications included the use of turbulence intensities to define dispersion regimes, use of the RTDM Model to treat plume reflection in elevated terrain, use of the BLP Model to incorporate building downwash and plume rise to the model. The model is written in the FORTRAN programming language for implementation on a AMDAHL V7 Computer using the VSV7 operating system.

  7. Biogeochemical processes controlling methane in gassy coastal sediments—Part 2: groundwater flow control of acoustic turbidity in Eckernförde Bay Sediments

    NASA Astrophysics Data System (ADS)

    Albert, Daniel B.; Martens, Christopher S.; Alperin, Marc J.

    1998-12-01

    /shallower onset of methanogenesis, but they also aid loss of methane through advection. A diagenetic model that couples the biogeochemistry of sulfate and methane is used to explain the presence or absence of methane gas in these sediments in relation to the flow rate of fresh groundwater from below. Model results indicate that acoustic windows within otherwise acoustically turbid sediments of the bay are likely due to relatively higher rates of vertical advection of fresh groundwater. The gassy pockmark, however, with an even higher vertical advection rate, seems to require the input of additional reactive organic carbon to explain its vertical methane distribution.

  8. Coastal Digital Surface Model on Low Contrast Images

    NASA Astrophysics Data System (ADS)

    Rosu, A.-M.; Assenbaum, M.; De la Torre, Y.; Pierrot-Deseilligny, M.

    2015-08-01

    Coastal sandy environments are extremely dynamic and require regular monitoring that can easily be achieved by using an unmanned aerial system (UAS) including a drone and a photo camera. The acquired images have low contrast and homogeneous texture. Using these images and with very few, if any, ground control points (GCPs), it is difficult to obtain a digital surface model (DSM) by classical correlation and automatic interest points determination approach. A possible response to this problem is to work with enhanced, contrast filtered images. To achieve this, we use and tune the free open-source software MicMac.

  9. Biogeochemical cycling in an organic-rich coastal marine basin. 8. A sulfur isotopic budget balanced by differential diffusion across the sediment-water interface

    USGS Publications Warehouse

    Chanton, J.P.; Martens, C.S.; Goldhaber, M.B.

    1987-01-01

    The sulfur isotopic composition of the sulfur fluxes occurring in the anoxic marine sediments of Cape Lookout Bight, N.C., U.S.A., was determined, and the result of isotopic mass balance was obtained via the differential diffusion model. Seasonal pore water sulfate ??34S measurements yielded a calculated sulfate input of 0.6%.. Sulfate transported into the sediments via diffusion appeared to be enriched in the lighter isotope because its concentration gradient was steeper, due to the increase in the measured isotopic composition of sulfate with depth. Similarly, the back diffusion of dissolved sulfide towards the sediment-water interface appeared enriched in the heavier isotope. The isotopic composition of this flux was calculated from measurements of the ??34S of dissolved sulfide and was determined to be 15.9%.. The isotopic composition of buried sulfide was determined to be -5.2%. and the detrital sulfur input was estimated to be -6.2%.. An isotope mass balance equation based upon the fluxes at the sediment-water interface successfully predicted the isotopic composition of the buried sulfur flux within 0.5%., thus confirming that isotopes diffuse in response to their individual concentration gradients. ?? 1987.

  10. Probabilistic Downscaling of Remote Sensing Data with Applications for Multi-Scale Biogeochemical Flux Modeling.

    PubMed

    Stoy, Paul C; Quaife, Tristan

    2015-01-01

    Upscaling ecological information to larger scales in space and downscaling remote sensing observations or model simulations to finer scales remain grand challenges in Earth system science. Downscaling often involves inferring subgrid information from coarse-scale data, and such ill-posed problems are classically addressed using regularization. Here, we apply two-dimensional Tikhonov Regularization (2DTR) to simulate subgrid surface patterns for ecological applications. Specifically, we test the ability of 2DTR to simulate the spatial statistics of high-resolution (4 m) remote sensing observations of the normalized difference vegetation index (NDVI) in a tundra landscape. We find that the 2DTR approach as applied here can capture the major mode of spatial variability of the high-resolution information, but not multiple modes of spatial variability, and that the Lagrange multiplier (γ) used to impose the condition of smoothness across space is related to the range of the experimental semivariogram. We used observed and 2DTR-simulated maps of NDVI to estimate landscape-level leaf area index (LAI) and gross primary productivity (GPP). NDVI maps simulated using a γ value that approximates the range of observed NDVI result in a landscape-level GPP estimate that differs by ca 2% from those created using observed NDVI. Following findings that GPP per unit LAI is lower near vegetation patch edges, we simulated vegetation patch edges using multiple approaches and found that simulated GPP declined by up to 12% as a result. 2DTR can generate random landscapes rapidly and can be applied to disaggregate ecological information and compare of spatial observations against simulated landscapes. PMID:26067835

  11. Probabilistic Downscaling of Remote Sensing Data with Applications for Multi-Scale Biogeochemical Flux Modeling

    PubMed Central

    Stoy, Paul C.; Quaife, Tristan

    2015-01-01

    Upscaling ecological information to larger scales in space and downscaling remote sensing observations or model simulations to finer scales remain grand challenges in Earth system science. Downscaling often involves inferring subgrid information from coarse-scale data, and such ill-posed problems are classically addressed using regularization. Here, we apply two-dimensional Tikhonov Regularization (2DTR) to simulate subgrid surface patterns for ecological applications. Specifically, we test the ability of 2DTR to simulate the spatial statistics of high-resolution (4 m) remote sensing observations of the normalized difference vegetation index (NDVI) in a tundra landscape. We find that the 2DTR approach as applied here can capture the major mode of spatial variability of the high-resolution information, but not multiple modes of spatial variability, and that the Lagrange multiplier (γ) used to impose the condition of smoothness across space is related to the range of the experimental semivariogram. We used observed and 2DTR-simulated maps of NDVI to estimate landscape-level leaf area index (LAI) and gross primary productivity (GPP). NDVI maps simulated using a γ value that approximates the range of observed NDVI result in a landscape-level GPP estimate that differs by ca 2% from those created using observed NDVI. Following findings that GPP per unit LAI is lower near vegetation patch edges, we simulated vegetation patch edges using multiple approaches and found that simulated GPP declined by up to 12% as a result. 2DTR can generate random landscapes rapidly and can be applied to disaggregate ecological information and compare of spatial observations against simulated landscapes. PMID:26067835

  12. Silicon isotopic chemistry in the Changjiang Estuary and coastal regions: Impacts of physical and biogeochemical processes on the transport of riverine dissolved silica

    NASA Astrophysics Data System (ADS)

    Zhang, A. Y.; Zhang, J.; Hu, J.; Zhang, R. F.; Zhang, G. S.

    2015-10-01

    The dissolved silica (DSi) concentration and silicon isotopic composition (δ30Si) of surface water samples from the Changjiang Estuary was measured in summer and winter to study the behavior of DSi fluvial inputs into the estuary. The DSi concentration decreased away from the estuary and had a linear relationship with salinity, suggesting that mixing between river water and seawater is the dominant effect on DSi levels in the study area. Measured δ30Si in the Changjiang Estuary ranged from +1.48‰ to +2.35‰ in summer, and from +1.54‰ to +1.95‰ in winter. As a result of low light levels and abundant DSi riverine inputs, DSi remains relatively unaffected by biological utilization and fractionation in the near-shore region, and the isotopic imprint of water from the Changjiang can still be detected up to a salinity level of 20 in summer. An obvious increase in δ30Si was observed beyond this salinity level, indicating a significant increase in biological utilization and fractionation of DSi in high salinity waters. Lower water temperatures and light levels that prevail over the winter lead to the reduced fractionation of DSi compared with that in summer. The fractionation factor (30ɛ) was estimated using a steady state model to the high salinity waters, yielding a value of -0.95‰, which is in agreement with previous results obtained for Skeletonema costatum in cultivation experiments. The results of this study suggest that silicon isotopes can be used to identify the impact of biological utilization on the behavior of DSi in highly dynamic estuarine environments.

  13. Development of advanced process-based model towards evaluation of boundless biogeochemical cycles in terrestrial-aquatic continuum

    NASA Astrophysics Data System (ADS)

    Nakayama, Tadanobu; Maksyutov, Shamil

    2014-05-01

    Recent research shows inland water may play some role in continental biogeochemical cycling though its contribution has remained uncertain due to a paucity of data (Battin et al. 2009). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which incorporates surface-groundwater interactions, includes up- and down-scaling processes between local, regional and global scales, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes. In this study, NICE was extended to evaluate global hydrologic cycle by using various global datasets. The simulated result agreed reasonably with that in the previous research (Fan et al., 2013) and extended to clarify further eco-hydrological process in global scale. Then, NICE was further developed to incorporate the biogeochemical cycle including the reaction between inorganic and organic carbons (DOC, POC, DIC, pCO2, etc.) in the biosphere (terrestrial and aquatic ecosystems including surface water and groundwater). The model simulated the carbon cycle, for example, CO2 evasion from inland water in global scale, which is relatively in good agreement in that estimated by empirical relation using the previous pCO2 data (Aufdenkampe et al., 2011; Global River Chemistry Database, 2013). This simulation system would play important role in identification of full greenhouse gas balance of the biosphere and spatio-temporal hot spots in boundless biogeochemical cycle (Cole et al. 2007; Frei et al. 2012). References; Aufdenkampe, A.K., et al., Front. Ecol. Environ., doi:10.1890/100014, 2011. Battin, T.J., et al., Nat. Geosci., 2, 598-600, 2009. Cole, J.J. et al., Ecosystems, doi:10.1007/s10021-006-9013-8, 2007. Fan, Y. et al

  14. A dynamic marine iron cycle module coupled to the University of Victoria Earth System Model: the Kiel Marine Biogeochemical Model 2 for UVic 2.9

    NASA Astrophysics Data System (ADS)

    Nickelsen, L.; Keller, D. P.; Oschlies, A.

    2015-05-01

    Marine biological production as well as the associated biotic uptake of carbon in many ocean regions depends on the availability of nutrients in the euphotic zone. While large areas are limited by nitrogen and/or phosphorus, the micronutrient iron is considered the main limiting nutrient in the North Pacific, equatorial Pacific and Southern Ocean. Changes in iron availability via changes in atmospheric dust input are discussed to play an important role in glacial-interglacial cycles via climate feedbacks caused by changes in biological ocean carbon sequestration. Although many aspects of the iron cycle remain unknown, its incorporation into marine biogeochemical models is needed to test our current understanding and better constrain its role in the Earth system. In the University of Victoria Earth System Climate Model (UVic) iron limitation in the ocean was, until now, simulated pragmatically with an iron concentration masking scheme that did not allow a consistent interactive response to perturbations of ocean biogeochemistry or iron cycling sensitivity studies. Here, we replace the iron masking scheme with a dynamic iron cycle and compare the results to available observations and the previous marine biogeochemical model. Sensitivity studies are also conducted with the new model to test the sensitivity of the model to parameterized iron ligand concentrations, the importance of considering the variable solubility of iron in dust deposition, the importance of considering high-resolution bathymetry for the sediment release of iron, the effect of scaling the sedimentary iron release with temperature and the sensitivity of the iron cycle to a climate change scenario.

  15. A simple model for forecast of coastal algal blooms

    NASA Astrophysics Data System (ADS)

    Wong, Ken T. M.; Lee, Joseph H. W.; Hodgkiss, I. J.

    2007-08-01

    In eutrophic sub-tropical coastal waters around Hong Kong and South China, algal blooms (more often called red tides) due to the rapid growth of microscopic phytoplankton are often observed. Under favourable environmental conditions, these blooms can occur and subside over rather short time scales—in the order of days to a few weeks. Very often, these blooms are observed in weakly flushed coastal waters under calm wind conditions—with or without stratification. Based on high-frequency field observations of harmful algal blooms at two coastal mariculture zones in Hong Kong, a mathematical model has been developed to forecast algal blooms. The model accounts for algal growth, decay, settling and vertical turbulent mixing, and adopts the same assumptions as the classical Riley, Stommel and Bumpus model (Riley, G.A., Stommel, H., Bumpus, D.F., 1949. Quantitative ecology of the plankton of the western North Atlantic. Bulletin of the Bingham Oceanographic Collection Yale University 12, 1-169). It is shown that for algal blooms to occur, a vertical stability criterion, E < 4 μl2/ π2, must be satisfied, where E, μ, l are the vertical turbulent diffusivity, algal growth rate, and euphotic layer depth respectively. In addition, a minimum nutrient threshold concentration must be reached. Moreover, with a nutrient competition consideration, the type of bloom (caused by motile or non-motile species) can be classified. The model requires as input simple and readily available field measurements of water column transparency and nutrient concentration, and representative maximum algal growth rate of the motile and non-motile species. In addition, with the use of three-dimensional hydrodynamic circulation models, simple relations are derived to estimate the vertical mixing coefficient as a function of tidal range, wind speed, and density stratification. The model gives a quick assessment of the likelihood of algal bloom occurrence, and has been validated against field

  16. Analysis of mixing and biogeochemical effects induced by tides on the Atlantic Mediterranean flow in the Strait of Gibraltar through a physical biological coupled model

    NASA Astrophysics Data System (ADS)

    Macías, D.; Martin, A. P.; García-Lafuente, J.; García, C. M.; Yool, A.; Bruno, M.; Vázquez-Escobar, A.; Izquierdo, A.; Sein, D. V.; Echevarría, F.

    2007-08-01

    The output of a two-layer hydrodynamic model along a west-east section of the Gibraltar Strait is used to estimate tidal induced mixing between the Mediterranean and Atlantic water layers and to simulate the effects of mixing processes on biogeochemical fluxes and the pelagic community of the area. The hydrodynamic model is used to estimate interfacial mixing and water advection which drive the dynamics of the pelagic community. The model was run for 13 months, in order to analyse the effect of annual modulations in tidal amplitude on mixing. Incorporation of a third intermediate layer leads to a significant improvement in the model results, showing the necessity for a three layer circulation scheme when modelling biogeochemical processes in the Strait of Gibraltar. Pelagic processes are modelled using a simple Nutrient-Phytoplankton-Zooplankton (NPZ) model. The intense physical mixing and advection in the channel are the main influence on plankton dynamics in the area. It is found that residence times within the channel are so short that phytoplankton communities cannot grow appreciably during their transit. As a consequence, the use of a more sophisticated biogeochemical model does not lead to significant changes in the results obtained. According to the model, mixing over the Camarinal Sill causes an average of 16% of the out-flowing nutrients to be returned back to the Mediterranean. This fraction varies between 4% and 35% as a function of the tidal amplitude. The comparison of the model results with field data suggests that in order to obtain an accurate simulation of the plankton ecosystem dynamics in the strait, it is necessary to take into account the full horizontal flow, as recirculation and coast-channel interactions seems to be very important processes in explaining the biological patterns in the area.

  17. Online, On Demand Access to Coastal Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Long, J.; Bristol, S.; Long, D.; Thompson, S.

    2014-12-01

    Process-based numerical models for coastal waves, water levels, and sediment transport are initialized with digital elevation models (DEM) constructed by interpolating and merging bathymetric and topographic elevation data. These gridded surfaces must seamlessly span the land-water interface and may cover large regions where the individual raw data sources are collected at widely different spatial and temporal resolutions. In addition, the datasets are collected from different instrument platforms with varying accuracy and may or may not overlap in coverage. The lack of available tools and difficulties in constructing these DEMs lead scientists to 1) rely on previously merged, outdated, or over-smoothed DEMs; 2) discard more recent data that covers only a portion of the DEM domain; and 3) use inconsistent methodologies to generate DEMs. The objective of this work is to address the immediate need of integrating land and water-based elevation data sources and streamline the generation of a seamless data surface that spans the terrestrial-marine boundary. To achieve this, the U.S. Geological Survey (USGS) is developing a web processing service to format and initialize geoprocessing tasks designed to create coastal DEMs. The web processing service is maintained within the USGS ScienceBase data management system and has an associated user interface. Through the map-based interface, users define a geographic region that identifies the bounds of the desired DEM and a time period of interest. This initiates a query for elevation datasets within federal science agency data repositories. A geoprocessing service is then triggered to interpolate, merge, and smooth the data sources creating a DEM based on user-defined configuration parameters. Uncertainty and error estimates for the DEM are also returned by the geoprocessing service. Upon completion, the information management platform provides access to the final gridded data derivative and saves the configuration parameters

  18. Seasonal enhancement of submarine groundwater discharge (SGD)-derived nitrate loading into the Ria Formosa coastal lagoon assessed by 1-D modeling of benthic NO3- profiles

    NASA Astrophysics Data System (ADS)

    Ibánhez, J. Severino P.; Leote, Catarina; Rocha, Carlos

    2013-11-01

    The role of benthic sandy ecosystems in mitigating NO3- loads carried by Submarine Groundwater Discharge (SGD) to coastal marine ecosystems is uncertain. Benthic biogeochemical mediation of NO3--rich submarine groundwater discharge was studied at the seepage face of a barrier island site in the Ria Formosa coastal lagoon (Southern Portugal). Preliminary analysis of NO3- porewater distributions at the seepage face during discharge indicated that benthic biogeochemical processes could significantly affect the fluxes of groundwater-borne NO3- into the lagoon. In order to discriminate between the relative contribution of transport and reaction processes to shape and concentration range evidenced by in-situ porewater NO3- gradients, an advection-dispersion-reaction (ADR) model of NO3- diagenesis was applied to describe NO3- porewater profiles obtained in March, June, September and December 2006. Good agreement between modeled and measured profiles was obtained. Model-derived apparent benthic nitrification and NO3- reduction rates ranged from 0.01 to 5.2 mmol m-2 h-1, sufficient to explain gross observed changes in NO3- fluxes arriving at the seepage face (up to 70% within the surficial 20 cm depth layer). Results of the analysis indicated that the upper limit of the seepage face promoted mitigation of NO3- fluxes to the lagoon throughout the year. In contrast, the lower limit of the seepage area promoted net amplification of the NO3- fluxes into the lagoon in June and September. These results will help constrain further work aiming to clarify the role of permeable sediments in mitigating nitrogen loading of coastal ecosystems.

  19. FORWARD AND INVERSE BIO-GEOCHEMICAL MODELING OF MICROBIALLY INDUCED PRECIPITATION IN 0.5M COLUMNAR EXPERIMENTS

    NASA Astrophysics Data System (ADS)

    Barkouki, T. H.; Martinez, B.; Mortensen, B.; Dejong, J.; Weathers, T. S.; Spycher, N.; Ginn, T. R.; Fujita, Y.; Smith, R. W.

    2009-12-01

    Subsurface contamination by metals and radionuclides threatens water supplies and ecosystem health at sites worldwide. One potential solution is immobilization in calcite where mineral precipitation is induced in situ by microbially-mediated ureolysis. Specifically, immobile aerobic biophases (cells or enzymes) mediate the conversion of urea to ammonium and carbonate, raising pH and promoting calcite precipitation. Divalent species such as strontium (including 90Sr, a common radionuclide contaminant) can co-precipitate, resulting in in situ immobilization. In waters that are saturated with respect to calcite, this represents a long-term sequestration mechanism. Calcite precipitation also enables control of mechanical properties of the medium through the cementation of particles thus increasing the shear strength and stiffness, while decreasing the permeability and compressibility. Challenges in application include design of the injectate aqueous chemistry (e.g., calcium, carbonate, urea, pH buffer, microbial nutrients) and selection of injection rates in order to control the timing and rate of calcite precipitation to generate the desired spatial distribution. Modeling ultimately requires incorporation of comprehensive reaction networks into transport simulators for non-uniform flow. To develop and validate the reaction network for use in both contaminant co-precipitation and subsurface structural modification applications, multicomponent biogeochemical modeling (TOUGHREACT v2) was applied in analyses of laboratory batch and column investigations of microbially-mediated calcite precipitation using Sporosarcina pasteurii. Column experiments included continuous and repeat pulse-flows, with cumulative flux equal in both cases. Aqueous chemistry and calcite distribution were monitored, as well as seismic shear waves that correlate to the stiffness of the column and thus to precipitation extent. TOUGHREACT was coupled with the inversion code UCODE to invert on observed

  20. Bidirectional reflectance function in coastal waters: modeling and validation

    NASA Astrophysics Data System (ADS)

    Gilerson, Alex; Hlaing, Soe; Harmel, Tristan; Tonizzo, Alberto; Arnone, Robert; Weidemann, Alan; Ahmed, Samir

    2011-11-01

    The current operational algorithm for the correction of bidirectional effects from the satellite ocean color data is optimized for typical oceanic waters. However, versions of bidirectional reflectance correction algorithms, specifically tuned for typical coastal waters and other case 2 conditions, are particularly needed to improve the overall quality of those data. In order to analyze the bidirectional reflectance distribution function (BRDF) of case 2 waters, a dataset of typical remote sensing reflectances was generated through radiative transfer simulations for a large range of viewing and illumination geometries. Based on this simulated dataset, a case 2 water focused remote sensing reflectance model is proposed to correct above-water and satellite water leaving radiance data for bidirectional effects. The proposed model is first validated with a one year time series of in situ above-water measurements acquired by collocated multi- and hyperspectral radiometers which have different viewing geometries installed at the Long Island Sound Coastal Observatory (LISCO). Match-ups and intercomparisons performed on these concurrent measurements show that the proposed algorithm outperforms the algorithm currently in use at all wavelengths.

  1. Improved Sharp Interface Models in Coastal Aquifers of Finite Dimensions

    NASA Astrophysics Data System (ADS)

    Christelis, Vasileios; Mantoglou, Aristotelis

    2013-04-01

    Coastal aquifer management often involves aquifers of finite dimensions where optimal pumping rates must be calculated through a combined simulation-optimization procedure. Variable-density numerical models are considered more exact than sharp interface models as they better describe the governing flow and transport equations. However, such models are not always preferable in pumping optimization studies, due to their complexity and computational burden. On the other hand, sharp interface models are approximate and can lead to large errors if they are not applied properly, particularly when model boundaries are not treated correctly. The present paper proposes improved sharp interface models considering aquifer boundaries in a proper way. Two sharp interface models are investigated based on the single potential formulation and the Ghyben-Herzberg relation. The first model (Strack, 1976) is based on the assumption of a semi-infinite aquifer with a sea-boundary only. The second model (Mantoglou, 2003) is based on an analytical solution developed for coastal aquifers of finite size and accounts for inland and lateral aquifer boundaries. Next, both models are modified using an empirical correction factor (similar to Pool and Carrera, 2011) which accounts for mixing. A simple pumping optimization problem with a single well in a confined coastal aquifer of finite size with four boundaries (sea, inland and lateral impervious boundaries) is employed. The constraint prevents the toe of the interface to reach the well and the optimal pumping rates are calculated for different locations of the pumping well and different combinations of aquifer parameters. Then the results of the sharp interface models are compared to the 'true' results of the corresponding variable-density numerical model in order to evaluate the performance of the sharp interface models. The results indicate that when the location of the well is close to the sea-boundary, the semi-infinite and the finite

  2. Thermal and hydrocarbon maturation models for coastal California

    SciTech Connect

    Heasler, H.P.; Surdam, R.C.

    1985-02-01

    Hydrocarbon maturation models for coastal California must consider thermal and geochemical constraints imposed by plate tectonics, diagenetic reactions, and the sedimentation history of the region. Plate tectonism drastically effects the thermal history of California basins in many ways. Initially, temperatures in the crust of coastal California are suppressed during subduction of the Farallon plate. With the passage of the Mendocino triple junction, subduction ceases and a void is created into which asthenosphere moves. This elevates temperatures in the basins in a complex manner depending on the time of passage of the Mendocino triple junction and the location of a specific basin. Finite-difference numerical models were developed to approximate the thermal effects of subduction and lithospheric upwelling. Diagenetic reactions and sedimentation history affect both the maturation model and thermal history of a basin. Diagenetic reactions through time in the Miocene Monterey Formation may change thermal conductivity values by 70%. Facies changes also have an important effect on sediment thermal conductivity and hence sediment temperatures. Maturation models indicate varying levels of maturity depending on the method used. Models using the Time Temperature Index of Lopatin indicate the lowest level of maturity. Tissot and Espitalie's method, which uses multiple activation energies and varying constants for the kerogen types, results in an intermediate level of maturity. The highest level of maturity results in an intermediate level of maturity. The highest level of maturity results from the use of the Tissot and Espitalie method modified by using a single activation energy of 178.69 kJ mole/sup -1/ and a constant of 4.92 x 10/sup 13/ hour/sup -1/ as reported by M.D. Lewan for shale from the Phosphoria Formation.

  3. Modelization of highly nonlinear waves in coastal regions

    NASA Astrophysics Data System (ADS)

    Gouin, Maïté; Ducrozet, Guillaume; Ferrant, Pierre

    2015-04-01

    The proposed work deals with the development of a highly non-linear model for water wave propagation in coastal regions. The accurate modelization of surface gravity waves is of major interest in ocean engineering, especially in the field of marine renewable energy. These marine structures are intended to be settled in coastal regions where the effect of variable bathymetry may be significant on local wave conditions. This study presents a numerical model for the wave propagation with complex bathymetry. It is based on High-Order Spectral (HOS) method, initially limited to the propagation of non-linear wave fields over flat bottom. Such a model has been developed and validated at the LHEEA Lab. (Ecole Centrale Nantes) over the past few years and the current developments will enlarge its application range. This new numerical model will keep the interesting numerical properties of the original pseudo-spectral approach (convergence, efficiency with the use of FFTs, …) and enable the possibility to propagate highly non-linear wave fields over long time and large distance. Different validations will be provided in addition to the presentation of the method. At first, Bragg reflection will be studied with the proposed approach. If the Bragg condition is satisfied, the reflected wave generated by a sinusoidal bottom patch should be amplified as a result of resonant quadratic interactions between incident wave and bottom. Comparisons will be provided with experiments and reference solutions. Then, the method will be used to consider the transformation of a non-linear monochromatic wave as it propagates up and over a submerged bar. As the waves travel up the front slope of the bar, it steepens and high harmonics are generated due to non-linear interactions. Comparisons with experimental data will be provided. The different test cases will assess the accuracy and efficiency of the method proposed.

  4. Biogeochemical context impacts seawater pH changes resulting from atmospheric sulfur and nitrogen deposition

    NASA Astrophysics Data System (ADS)

    Hagens, Mathilde; Hunter, Keith A.; Liss, Peter S.; Middelburg, Jack J.

    2014-02-01

    Seawater acidification can be induced both by absorption of atmospheric carbon dioxide (CO2) and by atmospheric deposition of sulfur and nitrogen oxides and ammonia. Their relative significance, interplay, and dependency on water column biogeochemistry are not well understood. Using a simple biogeochemical model we show that the initial conditions of coastal systems are not only relevant for CO2-induced acidification but also for additional acidification due to atmospheric acid deposition. Coastal areas undersaturated with respect to CO2 are most vulnerable to CO2-induced acidification but are relatively least affected by additional atmospheric deposition-induced acidification. In contrast, the pH of CO2-supersaturated systems is most sensitive to atmospheric deposition. The projected increment in atmospheric CO2 by 2100 will increase the sensitivity of coastal systems to atmospheric deposition-induced acidification by up to a factor 4, but the additional annual change in proton concentration is at most 28%.

  5. Use of the Water, Energy, and Biogeochemical Model (WEBMOD) to Simulate Water Quality at Five U.S. Geological Survey Research Watersheds

    NASA Astrophysics Data System (ADS)

    Webb, R. M.; Leavesley, G. H.; Shanley, J. B.; Peters, N. E.; Aulenbach, B. T.; Blum, A. E.; Campbell, D. H.; Clow, D. W.; Mast, M. A.; Stallard, R. F.; Larsen, M. C.; Troester, J. W.; Walker, J. F.; White, A. F.

    2003-12-01

    The Water, Energy, and Biogeochemical Model (WEBMOD) was developed as an aid to compare and contrast basic hydrologic and biogeochemical processes active in the diverse hydroclimatic regions represented by the five U.S. Geological Survey (USGS) Water, Energy, and Biogeochemical Budget (WEBB) sites: Loch Vale, Colorado; Trout Lake, Wisconsin; Sleepers River, Vermont; Panola Mountain, Georgia; and Luquillo Experimental Forest, Puerto Rico. WEBMOD simulates solute concentrations for vegetation canopy, snow pack, impermeable ground, leaf litter, unsaturated and saturated soil zones, riparian zones and streams using selected process modules coupled within the USGS Modular Modeling System (MMS). Source codes for the MMS hydrologic modules include the USGS Precipitation Runoff Modeling System, the National Weather Service Hydro-17 snow model, and TOPMODEL. The hydrologic modules distribute precipitation and temperature to predict evapotranspiration, snow accumulation, snow melt, and streamflow. Streamflow generation mechanisms include infiltration excess, saturated overland flow, preferential lateral flow, and base flow. Input precipitation chemistry, and fluxes and residence times predicted by the hydrologic modules are input into the geochemical module where solute concentrations are computed for a series of discrete well-mixed reservoirs using calls to the geochemical engine PHREEQC. WEBMOD was used to better understand variations in water quality observed at the WEBB sites from October 1991 through September 1997. Initial calibrations were completed by fitting the simulated hydrographs with those measured at the watershed outlets. Model performance was then refined by comparing the predicted export of conservative chemical tracers such as chloride, with those measured at the watershed outlets. The model succeeded in duplicating the temporal variability of net exports of major ions from the watersheds.

  6. Calibration and validation of a one-dimensional complex marine biogeochemical flux model in different areas of the northern Adriatic shelf

    NASA Astrophysics Data System (ADS)

    Vichi, M.; Oddo, P.; Zavatarelli, M.; Coluccelli, A.; Coppini, G.; Celio, M.; Fonda Umani, S.; Pinardi, N.

    2003-01-01

    In this paper we show results from numerical simulations carried out with a complex biogeochemical fluxes model coupled with a one-dimensional high-resolution hydrodynamical model and implemented at three different locations of the northern Adriatic shelf. One location is directly affected by the Po River influence, one has more open-sea characteristics and one is located in the Gulf of Trieste with an intermediate behavior; emphasis is put on the comparison with observations and on the functioning of the northern Adriatic ecosystem in the three areas. The work has been performed in a climatological context and has to be considered as preliminary to the development of three-dimensional numerical simulations. Biogeochemical model parameterizations have been ameliorated with a detailed description of bacterial substrate utilization associated with the quality of the dissolved organic matter (DOM), in order to improve the models capability in capturing the observed DOM dynamics in the basin. The coupled model has been calibrated and validated at the three locations by means of climatological data sets. Results show satisfactory model behavior in simulating local seasonal dynamics in the limit of the available boundary conditions and the one-dimensional implementation. Comparisons with available measurements of primary and bacterial production and bacterial abundances have been performed in all locations. Model simulated rates and bacterial dynamics are in the same order of magnitude of observations and show a qualitatively correct time evolution. The importance of temperature as a factor controlling bacteria efficiency is investigated with sensitivity experiments on the model parameterizations.

  7. Integrating operational watershed and coastal models for the Iberian Coast: Watershed model implementation - A first approach

    NASA Astrophysics Data System (ADS)

    Brito, David; Campuzano, F. J.; Sobrinho, J.; Fernandes, R.; Neves, R.

    2015-12-01

    River discharges and loads are essential inputs to coastal seas, and thus for coastal seas modelling, and their properties are the result of all activities and policies carried inland. For these reasons main rivers were object of intense monitoring programs having been generated some important amount of historical data. Due to the decline in the Portuguese hydrometric network and in order to quantify and forecast surface water streamflow and nutrients to coastal areas, the MOHID Land model was applied to the Western Iberia Region with a 2 km horizontal resolution and to the Iberian Peninsula with 10 km horizontal resolution. The domains were populated with land use and soil properties and forced with existing meteorological models. This approach also permits to understand how the flows and loads are generated and to forecast their values which are of utmost importance to perform coastal ocean and estuarine forecasts. The final purpose of the implementation is to obtain fresh water quantity and quality that could be used to support management decisions in the watershed, reservoirs and also to estuaries and coastal areas. A process oriented model as MOHID Land is essential to perform this type of simulations, as the model is independent of the number of river catchments. In this work, the Mohid Land model equations and parameterisations were described and an innovative methodology for watershed modelling is presented and validated for a large international river, the Tagus River, and the largest national river of Portugal, the Mondego River. Precipitation, streamflow and nutrients modelling results for these two rivers were compared with observations near their coastal outlet in order to evaluate the model capacity to represent the main watershed trends. Finally, an annual budget of fresh water and nutrient transported by the main twenty five rivers discharging in the Portuguese coast is presented.

  8. Coastal Ecosystems and Climate Change: Is Modeling and Monitoring Enough?

    NASA Astrophysics Data System (ADS)

    Cronin, T. M.; Walker, H. A.

    2005-05-01

    Many coastal ecosystems are severely degraded due to a variety of human factors, requiring large and expensive monitoring and modeling efforts for restoration and management. Climate variability, including abrupt climate change, is seldom factored into coastal ecosystem management despite growing evidence for climate forcing of precipitation, river discharge, water quality, salinity, turbidity, faunal and phytoplankton dynamics, dissolved oxygen, and other ecosystem processes. We will review evidence from long-term monitoring records, multi-proxy paleoclimatic and paleoecological records, and climatic modeling that suggests that the effects of climate can override local and regional human activities and may potentially diminish the success of restoration efforts. Because ecosystem restoration often involves long-term objectives requiring decades to achieve, our focus will be on examples from sub-tropical and temperate estuaries in North America that show ecosystem response over decadal timescales to variability related to El Niño-Southern Oscillation, the Pacific Decadal Oscillation and the North Atlantic Oscillation. Climatic variability evident from paleo-records of the past few centuries exceeds that recorded in most 20th century monitoring records. This raises issues about the efficacy of local and regional ecosystem and hydrodynamic models designed to simulate ecosystem response to anthropogenic changes in sediment and nutrient input, fresh-water discharge, and land-use because such models, though tested with rigorous validation procedures, use calibration data sets limited to a few years. Thus, they might not be appropriate for simulating response to climatic extremes on the scale and duration of past events outside their calibration range. Understanding the complexities of ecosystem response to climatic forcing, especially in the context of local and regional ecosystem disturbance, raises formidable challenges, but attempts to integrate climate

  9. A mechanistic model of runoff-associated fecal coliform fate and transport through a coastal lagoon.

    PubMed

    Steets, B M; Holden, P A

    2003-02-01

    Fecal coliform (FC) contamination in coastal waters is an ongoing public health problem worldwide. Coastal wetlands and lagoons are typically expected to protect coastal waters by attenuating watershed pollutants including FC bacteria. However, new evidence suggests that coastal lagoons or marshes can also be a source of high indicator organism concentrations in coastal waters. We asked for a Mediterranean-type climate, what is the fate of runoff-associated FC through a coastal lagoon? To address this question, we developed a mass balance-based, mechanistic model of FC concentration through a coastal lagoon and simulated, for summer and winter conditions, FC within the lagoon water column, lagoon sediments, and in the ocean water just downstream of the lagoon mouth. Our model accounts for advective flow and dispersion, decay and sedimentation and resuspension of FC-laden sediments during high flow, erosional conditions. Under low flow conditions that occur in the summer, net FC decay and FC storage in lagoon sediments are predicted. Under high flow conditions that occur in the winter, FC-laden sediments are predicted to erode, resuspend and flow out of the lagoon where they elevate FC concentrations in the coastal ocean. For both seasonal conditions, the predicted water column FC concentrations were within an order of magnitude of field measurements for a reference site in southern California. Our results suggest that there are seasonally varying roles for coastal lagoons in mediating FC contamination to coastal waters. PMID:12688694

  10. Parameterization of biogeochemical sediment-water fluxes using in-situ measurements and a steady-state diagenetic model

    EPA Science Inventory

    Diagenetic processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be a significant contributor to oxygen depletion in hypoxic systems, and sediment–water nutrient fluxes support primary productivity in ...

  11. Significant Findings: Seasonal Distributions of Global Ocean Chlorophyll and Nutrients With a Coupled Ocean General Circulation, Biogeochemical, and Radiative Model. 2; Comparisons With Satellite and In Situ Data

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)

    2000-01-01

    A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model were determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (>1000 km) model chlorophyll seasonal distributions were statistically positively correlated with CZCS chlorophyll in 10 of 12 major oceanographic regions, and with SeaWiFS in all 12. Notable disparities in magnitudes occurred, however, in the tropical Pacific, the spring/summer bloom in the Antarctic, autumn in the northern high latitudes, and during the southwest monsoon in the North Indian Ocean. Synoptic scale (100-1000 km) comparisons of satellite and in situ data exhibited broad agreement, although occasional departures were apparent. Model nitrate distributions agreed with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicated that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on basin and synoptic scales.

  12. Performance and results of the high-resolution biogeochemical model PELAGOS025 v1.0 within NEMO v3.4

    NASA Astrophysics Data System (ADS)

    Epicoco, Italo; Mocavero, Silvia; Macchia, Francesca; Vichi, Marcello; Lovato, Tomas; Masina, Simona; Aloisio, Giovanni

    2016-06-01

    The present work aims at evaluating the scalability performance of a high-resolution global ocean biogeochemistry model (PELAGOS025) on massive parallel architectures and the benefits in terms of the time-to-solution reduction. PELAGOS025 is an on-line coupling between the Nucleus for the European Modelling of the Ocean (NEMO) physical ocean model and the Biogeochemical Flux Model (BFM) biogeochemical model. Both the models use a parallel domain decomposition along the horizontal dimension. The parallelisation is based on the message passing paradigm. The performance analysis has been done on two parallel architectures, an IBM BlueGene/Q at ALCF (Argonne Leadership Computing Facilities) and an IBM iDataPlex with Sandy Bridge processors at the CMCC (Euro Mediterranean Center on Climate Change). The outcome of the analysis demonstrated that the lack of scalability is due to several factors such as the I/O operations, the memory contention, the load unbalancing due to the memory structure of the BFM component and, for the BlueGene/Q, the absence of a hybrid parallelisation approach.

  13. Modeling fecal contamination in the Aljezur coastal stream (Portugal)

    NASA Astrophysics Data System (ADS)

    Rodrigues, Marta; Oliveira, Anabela; Guerreiro, Martha; Fortunato, André Bustorff; Menaia, José; David, Luís Mesquita; Cravo, Alexandra

    2011-06-01

    This study aims at understanding the fecal contamination behavior in a small coastal stream (Aljezur, Portugal), which has significant economic and ecological values. Like in most small coastal systems, circulation and water renewal in the Aljezur stream exhibit a strong variability due to their dependence on tides, waves, intermittent river flows, and a highly variable morphology. Hence, the problem was approached through a combination of field surveys and the development and application of a hard-coupled three-dimensional hydrodynamic and fecal contamination model. Salinity and temperature results have shown that mixing and transport in the stream are very sensitive to the river flow and wind forcing. The model is able to represent the main patterns and trends observed in Escherichia coli and fecal enterococcus concentrations along the stream, for different environmental and contamination conditions, suggesting die-off rates on the order of 0.50-0.55 day-1. Die-off rate and the representation of the sediment-associated processes were identified as the major remaining sources of uncertainty in the model. Results show that, owing to the processes that occur along the stream, fecal bacteria reach the beaches water in numbers that comply with the European Bathing Waters Directive, even during the summer periods when the upstream concentrations are larger. In particular, results suggest a direct relation between the tidal propagation upstream and the reduction of the fecal bacteria concentrations along the stream that can be relevant for the development of a strategy for the management of the system's water safety.

  14. Palaeo-modeling of coastal salt water intrusion during the Holocene: an application to the Netherlands

    NASA Astrophysics Data System (ADS)

    Delsman, J. R.; Hu-a-ng, K. R. M.; Vos, P. C.; de Louw, P. G. B.; Oude Essink, G. H. P.; Stuyfzand, P. J.; Bierkens, M. F. P.

    2013-11-01

    Management of coastal fresh groundwater reserves requires a thorough understanding of the present-day groundwater salinity distribution and its possible future development. However, coastal groundwater often still reflects a complex history of marine transgressions and regressions, and is only rarely in equilibrium with current boundary conditions. In addition, the distribution of groundwater salinity is virtually impossible to characterize satisfactorily, complicating efforts to model and predict coastal groundwater flow. A way forward may be to account for the historical development of groundwater salinity when modeling present-day coastal groundwater flow. In this paper, we construct a palaeo-hydrogeological model to simulate the evolution of groundwater salinity in the coastal area of the Netherlands throughout the Holocene. While intended as a perceptual tool, confidence in our model results is warranted by a good correspondence with a hydrochemical characterization of groundwater origin. Model results attest to the impact of groundwater density differences on coastal groundwater flow on millennial timescales and highlight their importance in shaping today's groundwater salinity distribution. Not once reaching steady-state throughout the Holocene, our results demonstrate the long-term dynamics of salinity in coastal aquifers. This stresses the importance of accounting for the historical evolution of coastal groundwater salinity when modeling present-day coastal groundwater flow, or when predicting impacts of e.g. sea level rise on coastal aquifers. Of more local importance, our findings suggest a more significant role of pre-Holocene groundwater in the present-day groundwater salinity distribution in the Netherlands than previously recognized. The implications of our results extend beyond understanding the present-day distribution of salinity, as the proven complex history of coastal groundwater also holds important clues for understanding and predicting the

  15. A generic reaction-based biogeochemical simulator

    SciTech Connect

    Fang, Yilin; Yabusaki, Steven B.; Yeh, Gour T.; C.T. Miller, M.W. Farthing, W.G. Gray, and G.F. Pinder

    2004-06-17

    This paper presents a generic biogeochemical simulator, BIOGEOCHEM. The simulator can read a thermodynamic database based on the EQ3/EQ6 database. It can also read user-specified equilibrium and kinetic reactions (reactions not defined in the format of that in EQ3/EQ6 database) symbolically. BIOGEOCHEM is developed with a general paradigm. It overcomes the requirement in most available reaction-based models that reactions and rate laws be specified in a limited number of canonical forms. The simulator interprets the reactions, and rate laws of virtually any type for input to the MAPLE symbolic mathematical software package. MAPLE then generates Fortran code for the analytical Jacobian matrix used in the Newton-Raphson technique, which are compiled and linked into the BIOGEOCHEM executable. With this feature, the users are exempted from recoding the simulator to accept new equilibrium expressions or kinetic rate laws. Two examples are used to demonstrate the new features of the simulator.

  16. Using Hyperspectral Remote Sensing Models to Determine Phytoplankton Density in the Coastal Waters of Long Bay, South Carolina

    NASA Astrophysics Data System (ADS)

    Harrington, J. E.; Ali, K.

    2013-12-01

    The southeast coastal region is one of the fastest growing regions in the United States and the increasing utilization of open water bodies has led to the deterioration of water quality and aquatic ecology, placing the future of these resources at risk. In coastal zones, a key index that can be used to assess the stress on the environment is the water quality. The shallow nearshore waters of Long Bay, South Carolina (SC) are heavily influenced by multiple biogeochemical constituents or color producing agents (CPAs) such as, phytoplankton, suspend matter, and dissolved organic carbon. The interaction of the various chemical, biological and physical components gives rise to the optical complexity observed in the coastal waters producing turbid waters. Ecological stress on these environments is reflected by the increase in the frequency and severity of Harmful Algal Blooms (HABs), a prime agent of water quality deterioration, including foul odors and tastes, deoxygenation of bottom waters (hypoxia), toxicity, fish kills, and food web alterations. These are of great concern for human health and are detrimental to the marine life. Therefore, efficient monitoring tools are required for early detection and forecasting purposes as well as to understand the state of the conditions and better protect, manage and address the question of how various natural and anthropogenic factors affect the health of these environments. This study assesses the efficiency remote sensing as a potential tool for accurate and timely detection of HABs, as well as for providing high spatial and temporal resolution information regarding the biogeodynamics in coastal water bodies. Existing blue-green and NIR-red based remote sensing algorithms are applied to the reflectance data obtained using ASD spectroradiometer to predict the amount of chlorophyll, an independent of other associated CPAs in the Long Bay waters. The pigment is the primary light harvesting pigment in all phytoplankton and is used

  17. Linking spatially distributed biogeochemical data with a two-host life-cycle pathogen:A model of whirling disease dynamics in salmonid fishes in the Intermountain West

    NASA Astrophysics Data System (ADS)

    Fytilis, N.; Lamb, R.; Stevens, L.; Morrissey, L. A.; Kerans, B.; Rizzo, D. M.

    2010-12-01

    Fish diseases are often caused by waterborne parasites, making them ideal systems for modeling the non-linear relationships between biogeochemical features and disease dynamics. Myxobolus cerebralis, the causative agent of whirling disease, has been a major contributor to the loss of wild rainbow trout populations in numerous streams within the Intermountain West (Colorado, Idaho, Montana, Utah, Wyoming). The parasite alternates between an invertebrate and vertebrate host, being transmitted between the sediment feeding worm T.Tubifex and salmonid fishes. A greater understanding of the linkage between biological stream integrity, geomorphic features, water quality parameters and whirling disease risk is needed to improve current management techniques. Biodiversity and abundance of the worm communities are influenced by biogeochemical features and linked to disease severity in fish. We collected and identified ~700 worms from eight sites using molecular genetic probes and a taxonomic key. Additionally, ~1700 worms were identified using only a taxonomic key. Our work examines the links between worm community structure and biogeochemical features. We use a modified Self-Organizing-Map (SOM), which is a non-parametric clustering method based on an artificial neural network (ANN). Clustering methods are particularly attractive for exploratory data analyses because they do not require either the target number of groupings or the data structure be specified at the outset. ANN clustering methods have been shown to be more robust and to account for more data variability than traditional methods when applied to clustering geo-hydrochemical and microbiological datasets. The SOM highlights spatial variation of worm community structure between sites; and is used in tandem with expert knowledge (Lamb and Kerans) of local worm communities and a Madison River, MT physiochemical dataset (GIS-derived layers, water quality parameters). We iteratively clustered the physiochemical data

  18. Multiresolution in CROCO (Coastal and Regional Ocean Community model)

    NASA Astrophysics Data System (ADS)

    Debreu, Laurent; Auclair, Francis; Benshila, Rachid; Capet, Xavier; Dumas, Franck; Julien, Swen; Marchesiello, Patrick

    2016-04-01

    CROCO (Coastal and Regional Ocean Community model [1]) is a new oceanic modeling system built upon ROMS_AGRIF and the non-hydrostatic kernel of SNH, gradually including algorithms from MARS3D (sediments)and HYCOM (vertical coordinates). An important objective of CROCO is to provide the possibility of running truly multiresolution simulations. Our previous work on structured mesh refinement [2] allowed us to run two-way nesting with the following major features: conservation, spatial and temporal refinement, coupling at the barotropic level. In this presentation, we will expose the current developments in CROCO towards multiresolution simulations: connection between neighboring grids at the same level of resolution and load balancing on parallel computers. Results of preliminary experiments will be given both on an idealized test case and on a realistic simulation of the Bay of Biscay with high resolution along the coast. References: [1] : CROCO : http://www.croco-ocean.org [2] : Debreu, L., P. Marchesiello, P. Penven, and G. Cambon, 2012: Two-way nesting in split-explicit ocean models: algorithms, implementation and validation. Ocean Modelling, 49-50, 1-21.

  19. Probabilistic modelling of sea surges in coastal urban areas

    NASA Astrophysics Data System (ADS)

    Georgiadis, Stylianos; Jomo Danielsen Sørup, Hjalte; Arnbjerg-Nielsen, Karsten; Nielsen, Bo Friis

    2016-04-01

    Urban floods are a major issue for coastal cities with severe impacts on economy, society and environment. A main cause for floods are sea surges stemming from extreme weather conditions. In the context of urban flooding, certain standards have to be met by critical infrastructures in order to protect them from floods. These standards can be so strict that no empirical data is available. For instance, protection plans for sub-surface railways against floods are established with 10,000 years return levels. Furthermore, the long technical lifetime of such infrastructures is a critical issue that should be considered, along with the associated climate change effects in this lifetime. We present a case study of Copenhagen where the metro system is being expanded at present with several stations close to the sea. The current critical sea levels for the metro have never been exceeded and Copenhagen has only been severely flooded from pluvial events in the time where measurements have been conducted. However, due to the very high return period that the metro has to be able to withstand and due to the expectations to sea-level rise due to climate change, reliable estimates of the occurrence rate and magnitude of sea surges have to be established as the current protection is expected to be insufficient at some point within the technical lifetime of the metro. The objective of this study is to probabilistically model sea level in Copenhagen as opposed to extrapolating the extreme statistics as is the practice often used. A better understanding and more realistic description of the phenomena leading to sea surges can then be given. The application of hidden Markov models to high-resolution data of sea level for different meteorological stations in and around Copenhagen is an effective tool to address uncertainty. For sea surge studies, the hidden states of the model may reflect the hydrological processes that contribute to coastal floods. Also, the states of the hidden Markov

  20. Coastal-ocean uptake of anthropogenic carbon

    NASA Astrophysics Data System (ADS)

    Bourgeois, Timothée; Orr, James C.; Resplandy, Laure; Terhaar, Jens; Ethé, Christian; Gehlen, Marion; Bopp, Laurent

    2016-07-01

    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.

  1. Improving the parameters of a global ocean biogeochemical model via variational assimilation of in situ data at five time series stations

    NASA Astrophysics Data System (ADS)

    Kane, A.; Moulin, C.; Thiria, S.; Bopp, L.; Berrada, M.; Tagliabue, A.; CréPon, M.; Aumont, O.; Badran, F.

    2011-06-01

    The global ocean biogeochemical models that are used in order to assess the ocean role in the global carbon cycle and estimate the impact of the climate change on marine ecosystems are getting more and more sophisticated. They now often account for several phytoplankton functional types that play particular roles in marine food webs and the ocean carbon cycle. These phytoplankton functional types have specific physiological characteristics, which are usually poorly known and therefore add uncertainties to model results. Indeed, this evolution in model complexity is not accompanied by a similar increase in the number and diversity of in situ data sets necessary for model calibration and evaluation. Thus, it is of primary importance to develop new methods to improve model performance using existing biogeochemical data sets, despite their current limitations. In this paper, we have optimized 45 physiological parameters of the PISCES global model, using a variational optimal control method. In order to bypass a global 3-D ocean variational assimilation, which would require enormous computation and memory storage, we have simplified the estimation procedure by assimilating monthly climatological in situ observations at five contrasted oceanographic stations of the JGOFS program in a 1-D version of the PISCES model. We began by estimating the weight matrix in the cost function by using heuristic considerations. Then we used this matrix to estimate the 45 parameters of the 1-D version of the PISCES model by assimilating the different monthly profiles (observed profiles at the five stations) in the same variational procedure on a time window of 1 year. This set of optimized parameters was then used in the standard 3-D global PISCES version to perform a 500 year global simulation. The results of both the standard and the optimized versions of the model were compared to satellite-derived chlorophyll-a images, which are an independent and global data set, showing that our

  2. Panel Discussion: U.S. EPA Using Modeling and Ecosystem Services to Enhance Coastal Decision Making

    EPA Science Inventory

    This panel will discuss the research being conducted, and the models being used in three current coastal EPA studies being conducted on ecosystem services in Tampa Bay, the Chesapeake Bay and the Coastal Carolinas. These studies are intended to provide a broader and more compreh...

  3. Addressing numerical challenges in introducing a reactive transport code into a land surface model: a biogeochemical modeling proof-of-concept with CLM-PFLOTRAN 1.0

    NASA Astrophysics Data System (ADS)

    Tang, Guoping; Yuan, Fengming; Bisht, Gautam; Hammond, Glenn E.; Lichtner, Peter C.; Kumar, Jitendra; Mills, Richard T.; Xu, Xiaofeng; Andre, Ben; Hoffman, Forrest M.; Painter, Scott L.; Thornton, Peter E.

    2016-03-01

    reaction network is highly nonlinear or the half saturation or residual concentration is very low, the allowable time-step cuts may need to be increased for robustness for the log transformation method, or STOL may need to be tightened for the clipping and scaling methods to avoid false convergence.As some biogeochemical processes (e.g., methane and nitrous oxide reactions) involve very low half saturation and thresholds, this work provides insights for addressing nonphysical negativity issues and facilitates the representation of a mechanistic biogeochemical description in Earth system models to reduce climate prediction uncertainty.

  4. Addressing numerical challenges in introducing a reactive transport code into a land surface model: a biogeochemical modeling proof-of-concept with CLM–PFLOTRAN 1.0

    DOE PAGESBeta

    Tang, Guoping; Yuan, Fengming; Bisht, Gautam; Hammond, Glenn E.; Lichtner, Peter C.; Kumar, Jitendra; Mills, Richard T.; Xu, Xiaofeng; Andre, Ben; Hoffman, Forrest M.; et al

    2016-03-04

    methods are efficient. When the reaction network is highly nonlinear or the half saturation or residual concentration is very low, the allowable time-step cuts may need to be increased for robustness for the log transformation method, or STOL may need to be tightened for the clipping and scaling methods to avoid false convergence.As some biogeochemical processes (e.g., methane and nitrous oxide reactions) involve very low half saturation and thresholds, this work provides insights for addressing nonphysical negativity issues and facilitates the representation of a mechanistic biogeochemical description in Earth system models to reduce climate prediction uncertainty.« less

  5. Addressing numerical challenges in introducing a reactive transport code into a land surface model: A biogeochemical modeling proof-of-concept with CLM PFLOTRAN 1.0

    DOE PAGESBeta

    Tang, Guoping; Yuan, Fengming; Bisht, Gautam; Hammond, Glenn E.; Lichtner, Peter C.; Kumar, Jitendra; Mills, Richard T.; Xu, Xiaofeng; Andre, Ben; Hoffman, Forrest M.; et al

    2016-03-04

    efficient. When the reaction network is highly nonlinear or the half saturation or residual concentration is very low, the allowable time-step cuts may need to be increased for robustness for the log transformation method, or STOL may need to be tightened for the clipping and scaling methods to avoid false convergence. As some biogeochemical processes (e.g., methane and nitrous oxide reactions) involve very low half saturation and thresholds, this work provides insights for addressing nonphysical negativity issues and facilitates the representation of a mechanistic biogeochemical description in Earth system models to reduce climate prediction uncertainty.« less

  6. Numerical Modeling to Support Floodplain Mapping in Coastal Areas

    NASA Astrophysics Data System (ADS)

    Cydzik, K.; Shrestha, P. L.; Hamilton, D.; Rezakhani, M.; Scheffner, N.; Lenaburg, R.

    2009-12-01

    A hurricane-induced flood mapping study was conducted for the State of Hawaii encompassing the six major Hawaiian Islands: Hawaii, Kauai, Lanai, Maui, Molokai, and Oahu. The objective of the study was to use numerical methods to compute storm surge frequency relationships using the Empirical Simulation Technique (EST). This paper describes the EST methodology. Ultimately, the storm surge frequency data and water surface elevations determined through the modeling effort define coastal inundation areas to revise Flood Insurance Rate Maps (FRIMs). Such information guides coastal development and highlights flood risks in coastal areas. To perform a realistic storm surge analysis, historical events impacting the islands in the study area were selected from the National Hurricane Center’s Eastern and Central North Pacific Basin Hurricane database. The database consists of hurricanes, tropical storms, and tropical depressions impacting the Hawaiian Islands from 1949 through 2005 and includes records of the latitude, longitude, maximum wind speed, and, often, the central pressure of the eye of the storm. For this study, candidate events were selected based on two criteria. Storms were required to pass within 200 nautical miles of at least two of the islands with maximum winds at that point of at least tropical storm-strength (39 mph.) Of the 794 storm events in the database, 11 events met these criteria and were used to generate wind and pressure fields for the modeling effort. An assumption of the EST analysis is that each of the 11 events has an equal probability of impacting the islands within the 200 nautical mile ellipse. Therefore, the 11events were translated by one Radius-to-Maximum winds across the ellipse so that each event impacted each island, generating 102 impacting events. The hypothetical events were used to generate wind and pressure fields for input to the ADvanced CIRCulation (ADCIRC) long-wave hydrodynamic model to compute storm surge at defined

  7. Offshore and coastal dispersion (OCD) model. Version 3. 0 (revised 1988) (for microcomputers). Model-Simulation

    SciTech Connect

    Not Available

    1990-08-23

    The Offshore and Coastal Dispersion Model was adapted from the EPA guideline model MPTER to simulate the effect of offshore emissions from point sources in coastal regions. Modifications were made to incorporate overwater plume transport, dispersion and changes that occur as the plume crosses the shoreline. Modifications included the use of turbulence intensities to define dispersion regimes, use of the RTDM Model to treat plume reflection in elevated terrain, use of the BLP Model to incorporate building downwash and plume rise to the model, partial plume penetration into elevated inversions, a virtual source to describe plume growth as the plume intercepts the overland internal boundary layer, and a continuous fumigation modular. The model is written in the FORTRAN programming language for implementation on an IBM PC or compatible microcomputer using MS DOS 3.0 operating system. A math coprocessor is required to run the program.

  8. Iron-light colimitation in a global ocean biogeochemical model and the sensitivity of oceanic CO2 uptake to dust deposition

    NASA Astrophysics Data System (ADS)

    Nickelsen, L.; Oschlies, A.

    2012-12-01

    The iron hypothesis of glacial-interglacial cycles states that glacial increases in the deposition of dust enhanced the concentrations of the micronutrient iron in the ocean where it triggered phytoplankton growth and thus CO2 uptake. Indeed, iron fertilization experiments find that phytoplankton needs iron in particular for nitrate uptake, light harvesting, synthesis of chlorophyll and in the electron transport chain of photosynthesis. Previous global biogeochemical models used to extrapolate results from local culture and field experiments have suggested that the sensitivity of ocean biogeochemistry to changes in dust deposition is too low to account for the observed glacial-interglacial changes of atmospheric CO2 concentrations. Here we show that this sensitivity is increased significantly when iron-light colimitation, i.e. the impact of iron on light harvesting capabilities and chlorophyll synthesis, is explicitly considered in a global biogeochemical ocean model. Iron-light colimitation increases the shift of export production to higher latitudes at high dust deposition and amplifies iron limitation at low dust deposition. Our results suggest that iron fertilization by increased dust deposition may explain a substantially larger portion of the observed past CO2 variability than thought previously. Our results emphasize the role of iron as a key limiting nutrient for phytoplankton in the ocean, with a high potential for changes in oceanic iron supply affecting the global carbon cycle and climate.

  9. Physical and numerical modeling of seawater intrusion in coastal aquifers

    NASA Astrophysics Data System (ADS)

    Crestani, Elena; Camporese, Matteo; Salandin, Paolo

    2016-04-01

    Seawater intrusion in coastal aquifers is a worldwide problem caused, among others factors, by aquifer overexploitation, rising sea levels, and climate changes. To limit the deterioration of both surface water and groundwater quality caused by saline intrusion, in recent years many research studies have been developed to identify possible countermeasures, mainly consisting of underground barriers. In this context, physical models are fundamental to study the saltwater intrusion, since they provide benchmarks for numerical model calibrations and for the evaluation of the effectiveness of general solutions to contain the salt wedge. This work presents a laboratory experiment where seawater intrusion was reproduced in a specifically designed sand-box. The physical model, built at the University of Padova, represents the terminal part of a coastal aquifer and consists of a flume 500 cm long, 30 cm wide and 60 cm high, filled for an height of 49 cm with glass beads characterized by a d50 of 0.6 mm and a uniformity coefficient d60/d10 ≈ 1.5. The resulting porous media is homogeneous, with porosity of about 0.37 and hydraulic conductivity of about 1.3×10‑3 m/s. Upstream from the sand-box, a tank filled by freshwater provides the recharge to the aquifer. The downstream tank simulates the sea and red food dye is added to the saltwater to easily visualize the salt wedge. The volume of the downstream tank is about five times the upstream one, and, due to the small filtration discharge, salt concentration variations (i.e., water density variations) due to the incoming freshwater flow are negligible. The hydraulic gradient during the tests is constant, due to the fixed water level in the two tanks. Water levels and discharged flow rate are continuously monitored. The experiment presented here had a duration of 36 h. For the first 24 h, the saltwater wedge was let to evolve until quasi stationary condition was obtained. In the last 12 h, water withdrawal was carried out at

  10. The numerical modeling the sensitivity of coastal wind and ozone concentration to different SST forcing

    NASA Astrophysics Data System (ADS)

    Choi, Hyun-Jung; Lee, Hwa Woon; Jeon, Won-Bae; Lee, Soon-Hwan

    2012-01-01

    This study evaluated an atmospheric and air quality model of the spatial variability in low-level coastal winds and ozone concentration, which are affected by sea surface temperature (SST) forcing with different thermal gradients. Several numerical experiments examined the effect of sea surface SST forcing on the coastal atmosphere and air quality. In this study, the RAMS-CAMx model was used to estimate the sensitivity to two different resolutions of SST forcing during the episode day as well as to simulate the low-level coastal winds and ozone concentration over a complex coastal area. The regional model reproduced the qualitative effect of SST forcing and thermal gradients on the coastal flow. The high-resolution SST derived from NGSST-O (New Generation Sea Surface Temperature Open Ocean) forcing to resolve the warm SST appeared to enhance the mean response of low-level winds to coastal regions. These wind variations have important implications for coastal air quality. A higher ozone concentration was forecasted when SST data with a high resolution was used with the appropriate limitation of temperature, regional wind circulation, vertical mixing height and nocturnal boundary layer (NBL) near coastal areas.

  11. Modelling coastal marsh stability in response to sea level rise: a case study in coastal Louisiana, USA

    USGS Publications Warehouse

    Chmura, G.L.; Costanza, R.; Kosters, E.C.

    1992-01-01

    In some regions coastal marsh stability is threatened by high rates of sea level rise. The deltaic plain of the Mississippi River is a natural laboratory for the study of marsh stability under conditions of rising sea level because it has been experiencing high rates of local submergence which cause relatively high rates of apparent sea level rise. We constructed a dynamic simulation model to study the relationship of accretion to three components of relative sea level rise: compaction, eustatic rise and submergence. The model is then used to project marsh stability under various future scenarios of sea level rise as well as enhancement of sediment supplies and marsh accretion. The model was calibrated to a 14C-dated sediment deposit which provides a long-term record of sediment accretion. Results indicate that an equilibrium between relative sea level and accretion rates can be attained, but that in this region of coastal Louisiana only the most optimistic assumptions yield coastal marshes that are stable in the long term. ?? 1992.

  12. Using Coupled Models to Study the Effects of River Discharge on Biogeochemical Cycling and Hypoxia in the Northern Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    Penta, Bradley; Ko, D.; Gould, Richard W.; Arnone, Robert A.; Greene, R.; Lehrter, J.; Hagy, James; Schaeffer, B.; Murrell, M.; Kurtz, J.; Herchenroder, B.; Green, R.; Eldridge, P.

    2009-01-01

    We describe emerging capabilities to understand physical processes and biogeoehemical cycles in coastal waters through the use of satellites, numerical models, and ship observations. Emerging capabilities provide significantly improved ability to model ecological systems and the impact of environmental management actions on them. The complex interaction of physical and biogeoehemical processes responsible for hypoxic events requires an integrated approach to research, monitoring, and modeling in order to fully define the processes leading to hypoxia. Our efforts characterizes the carbon cycle associated with river plumes and the export of organic matter and nutrients form coastal Louisiana wetlands and embayments in a spatially and temporally intensive manner previously not possible. Riverine nutrients clearly affect ecosystems in the northern Gulf of Mexico as evidenced in the occurrence of regional hypoxia events. Less known and largely unqualified is the export of organic matter and nutrients from the large areas of disappearing coastal wetlands and large embayments adjacent to the Louisiana Continental Shelf. This project provides new methods to track the river plume along the shelf and to estimate the rate of export of suspended inorganic and organic paniculate matter and dissolved organic matter form coastal habitats of south Louisiana.

  13. A new model for the vertical spectral diffuse attenuation coefficient of downwelling irradiance in turbid coastal waters: validation with in situ measurements.

    PubMed

    Simon, Arthi; Shanmugam, Palanisamy

    2013-12-01

    The vertical spectral diffuse attenuation coefficient of Kd is an important optical property related to the penetration and availability of light underwater, which is of fundamental interest in studies of ocean physics and biology. Models developed in the recent decades were mainly based on theoretical analyses and numerical (radiative transfer) simulations to estimate this property in optically deep waters, thus leaving inadequate knowledge of its variability at multiple depths and wavelengths, covering a wide range of solar incident geometry, in turbid coastal waters. In the present study, a new model is developed to quantify the vertical, spatial and temporal variability of K(d) at multiple wavelengths and to quantify its dependence with respect to solar incident geometry under differing sky conditions. Thus, the new model is derived as a function of inherent optical properties (IOPs - absorption a and backscattering b(b)), solar zenith angle and depth parameters. The model results are rigorously evaluated using time-series and discrete in situ data from clear and turbid coastal waters. The K(d) values derived from the new model are found to agree with measured data within the mean relative error 0.02~6.24% and R² 0.94~0.99. By contrast, the existing models have large errors when applied to the same data sets. Statistical results of the new model for the vertical spectral distribution of K(d) in clear oceanic waters (for different solar zenith and in-water conditions) are also good when compared to those of the existing models. These results suggest that the new model can provide an improved interpretation about the variation of the vertical spectral diffuse attenuation coefficient of downwelling irradiance, which will have important implications for ocean physics, biogeochemical cycles and underwater applications in both relatively clear and turbid coastal waters. PMID:24514558

  14. MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies

    NASA Astrophysics Data System (ADS)

    Yool, A.; Popova, E. E.; Anderson, T. R.

    2013-10-01

    MEDUSA-1.0 (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification) was developed as an "intermediate complexity" plankton ecosystem model to study the biogeochemical response, and especially that of the so-called "biological pump", to anthropogenically driven change in the World Ocean (Yool et al., 2011). The base currency in this model was nitrogen from which fluxes of organic carbon, including export to the deep ocean, were calculated by invoking fixed C:N ratios in phytoplankton, zooplankton and detritus. However, due to anthropogenic activity, the atmospheric concentration of carbon dioxide (CO2) has significantly increased above its natural, inter-glacial background. As such, simulating and predicting the carbon cycle in the ocean in its entirety, including ventilation of CO2 with the atmosphere and the resulting impact of ocean acidification on marine ecosystems, requires that both organic and inorganic carbon be afforded a more complete representation in the model specification. Here, we introduce MEDUSA-2.0, an expanded successor model which includes additional state variables for dissolved inorganic carbon, alkalinity, dissolved oxygen and detritus carbon (permitting variable C:N in exported organic matter), as well as a simple benthic formulation and extended parameterizations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal spin-up simulation (1860-2005) is performed. The biogeochemical performance of the model is evaluated using a diverse range of observational data, and MEDUSA-2.0 is assessed relative to comparable models using output from the Coupled Model Intercomparison Project (CMIP5).

  15. An Information Infrastructure for Coastal Models and Data

    NASA Astrophysics Data System (ADS)

    Hardin, D.; Keiser, K.; Conover, H.; Graves, S.

    2007-12-01

    Advances in semantics and visualization have given rise to new capabilities for the location, manipulation, integration, management and display of data and information in and across domains. An example of these capabilities is illustrated by a coastal restoration project that utilizes satellite, in-situ data and hydrodynamic model output to address seagrass habitat restoration in the Northern Gulf of Mexico. In this project a standard stressor conceptual model was implemented as an ontology in addition to the typical CMAP diagram. The ontology captures the elements of the seagrass conceptual model as well as the relationships between them. Noesis, developed by the University of Alabama in Huntsville, is an application that provides a simple but powerful way to search and organize data and information represented by ontologies. Noesis uses domain ontologies to help scope search queries to ensure that search results are both accurate and complete. Semantics are captured by refining the query terms to cover synonyms, specializations, generalizations and related concepts. As a resource aggregator Noesis categorizes search results returned from multiple, concurrent search engines such as Google, Yahoo, and Ask.com. Search results are further directed by accessing domain specific catalogs that include outputs from hydrodynamic and other models. Embedded within the search results are links that invoke applications such as web map displays, animation tools and virtual globe applications such as Google Earth. In the seagrass prioritization project Noesis is used to locate information that is vital to understanding the impact of stressors on the habitat. This presentation will show how the intelligent search capabilities of Noesis are coupled with visualization tools and model output to investigate the restoration of seagrass habitat.

  16. Offshore and Coastal Dispersion (OCD) Model, Version 3. 0. Model-Simulation

    SciTech Connect

    Marshall, C.

    1985-08-01

    The Offshore and Coastal Dispersion Model was adapted from the EPA guideline model MPTER to simulate the effect of offshore emissions from point sources in coastal regions. Modifications were made to incorporate overwater plume transport and dispersion and changes that occur as the plume crosses the shoreline. Modifications included the use of turbulence intensities to define dispersion regimes, use of the RTD Model to treat plume reflection in elevated terrain, use of the BLP Model to incorporate building downwash and plume rise to the model, partial plume penetration into elevated inversions, a virtual source to describe plume growth as the plume intercepts the overland internal boundary layer, and a continuous fumigation modular. Software Description: The system is written in the FORTRAN programming language for implementation on a AMDAHL V7 computer using the VSV7 operating system. 500K bytes of core storage are required to operate the system.

  17. Assessing the model performance of an integrated hydrological and biogeochemical model for discharge and nitrate load predictions

    NASA Astrophysics Data System (ADS)

    Pohlert, T.; Breuer, L.; Huisman, J. A.; Frede, H.-G.

    2007-03-01

    In this study, we evaluate the performance of the SWAT-N model, a modified version of the widely used SWAT version, for discharge and nitrate predictions at the mesoscale Dill catchment (Germany) for a 5-year period. The underlying question is, whether the model efficiency is sufficient for scenario analysis of land-use changes on both water quantity and quality. The Shuffled Complex Evolution (SCE-UA) algorithm is used to calibrate the model for daily discharge at the catchments outlet. Model performance is assessed with a split-sampling as well as a proxy-basin test using recorded hydrographs of four additional gauges located within the catchment. The efficiency regarding nitrate load simulation is assessed without further calibration on a daily, log-daily, weekly, and monthly basis as compared to observations derived from an intensive sampling campaign conducted at the catchments outlet. A new approach is employed to test the spatial consistency of the model, where simulated longitudinal profiles of nitrate concentrations were compared with observed longitudinal profiles. It is concluded that the model efficiency of SWAT-N is sufficient for the assessment of scenarios for daily discharge predictions. SWAT-N can be employed without further calibration for nitrate load simulations on both a weekly and monthly basis with an acceptable degree of accuracy. However, the model efficiency for daily nitrate load is insufficient, which can be attributed to both data uncertainty (i.e. point-source effluents and actual farming practise) as well as structural errors. The simulated longitudinal profiles meet the observations reasonably well, which suggests that the model is spatially consistent.

  18. Assessing the model performance of an integrated hydrological and biogeochemical model for discharge and nitrate load predictions

    NASA Astrophysics Data System (ADS)

    Pohlert, T.; Breuer, L.; Huisman, J. A.; Frede, H.-G.

    2006-09-01

    In this study, we evaluate the performance of the SWAT-N model, a modified version of the widely used SWAT version, for discharge and nitrate predictions at the mesoscale Dill catchment for a 5-year period. The underlying question is, whether the model efficiency is sufficient for scenario analysis of land-use changes on both water quantity and quality. The Shuffled Complex Evolution (SCE-UA) algorithm is used to calibrate the model for daily discharge at the catchments outlet. Model performance is assessed with a split-sampling as well as a proxy-basin test using recorded hydrographs of four additional gauges located within the catchment. The efficiency regarding nitrate load simulation is assessed without further calibration on a daily, log-daily, weekly, and monthly basis as compared to observations derived from an intensive sampling campaign conducted at the catchments outlet. A new approach is employed to test the spatial consistency of the model, where simulated longitudinal profiles of nitrate concentrations were compared with observed longitudinal profiles. It is concluded that the model efficiency of SWAT-N is sufficient for the assessment of scenarios for daily discharge predictions. SWAT-N can be employed without further calibration for nitrate load simulations on both a weekly and monthly basis with an acceptable degree of accuracy. However, the model efficiency for daily nitrate load is insufficient, which can be attributed to both data uncertainty (i.e. point-source effluents and actual farming practise) as well as structural errors. The simulated longitudinal profiles meet the observations reasonably well, which suggests that the model is spatially consistent.

  19. An integrated water system model considering hydrological and biogeochemical processes at basin scale: model construction and application

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Y.; Shao, Q. X.; Ye, A. Z.; Xing, H. T.

    2014-08-01

    Integrated water system modeling is a reasonable approach to provide scientific understanding and possible solutions to tackle the severe water crisis faced over the world and to promote the implementation of integrated river basin management. Such a modeling practice becomes more feasible nowadays due to better computing facilities and available data sources. In this study, the process-oriented water system model (HEXM) is developed by integrating multiple water related processes including hydrology, biogeochemistry, environment and ecology, as well as the interference of human activities. The model was tested in the Shaying River Catchment, the largest, highly regulated and heavily polluted tributary of Huai River Basin in China. The results show that: HEXM is well integrated with good performance on the key water related components in the complex catchments. The simulated daily runoff series at all the regulated and less-regulated stations matches observations, especially for the high and low flow events. The average values of correlation coefficient and coefficient of efficiency are 0.81 and 0.63, respectively. The dynamics of observed daily ammonia-nitrogen (NH4N) concentration, as an important index to assess water environmental quality in China, are well captured with average correlation coefficient of 0.66. Furthermore, the spatial patterns of nonpoint source pollutant load and grain yield are also simulated properly, and the outputs have good agreements with the statistics at city scale. Our model shows clear superior performance in both calibration and validation in comparison with the widely used SWAT model. This model is expected to give a strong reference for water system modeling in complex basins, and provide the scientific foundation for the implementation of integrated river basin management all over the world as well as the technical guide for the reasonable regulation of dams and sluices and environmental improvement in river basins.

  20. Use of Advanced Meteorological Model Output for Coastal Ocean Modeling in Puget Sound

    SciTech Connect

    Yang, Zhaoqing; Khangaonkar, Tarang; Wang, Taiping

    2011-06-01

    It is a great challenge to specify meteorological forcing in estuarine and coastal circulation modeling using observed data because of the lack of complete datasets. As a result of this limitation, water temperature is often not simulated in estuarine and coastal modeling, with the assumption that density-induced currents are generally dominated by salinity gradients. However, in many situations, temperature gradients could be sufficiently large to influence the baroclinic motion. In this paper, we present an approach to simulate water temperature using outputs from advanced meteorological models. This modeling approach was applied to simulate annual variations of water temperatures of Puget Sound, a fjordal estuary in the Pacific Northwest of USA. Meteorological parameters from North American Region Re-analysis (NARR) model outputs were evaluated with comparisons to observed data at real-time meteorological stations. Model results demonstrated that NARR outputs can be used to drive coastal ocean models for realistic simulations of long-term water-temperature distributions in Puget Sound. Model results indicated that the net flux from NARR can be further improved with the additional information from real-time observations.

  1. Modeling of Dense Water Production and Salt Transport from Alaskan Coastal Polynyas

    NASA Technical Reports Server (NTRS)

    Signorini, Sergio R.; Cavalieri, Donald J.

    2000-01-01

    The main significance of this paper is that a realistic, three-dimensional, high-resolution primitive equation model has been developed to study the effects of dense water formation in Arctic coastal polynyas. The model includes realistic ambient stratification, realistic bottom topography, and is forced by time-variant surface heat flux, surface salt flux, and time-dependent coastal flow. The salt and heat fluxes, and the surface ice drift, are derived from satellite observations (SSM/I and NSCAT sensors). The model is used to study the stratification, salt transport, and circulation in the vicinity of Barrow Canyon during the 1996/97 winter season. The coastal flow (Alaska coastal current), which is an extension of the Bering Sea throughflow, is formulated in the model using the wind-transport regression. The results show that for the 1996/97 winter the northeastward coastal current exports 13% to 26% of the salt produced by coastal polynyas upstream of Barrow Canyon in 20 to 30 days. The salt export occurs more rapidly during less persistent polynyas. The inclusion of ice-water stress in the model makes the coastal current slightly weaker and much wider due to the combined effects of surface drag and offshore Ekman transport.

  2. Development of high-resolution coastal DEMs: Seamlessly integrating bathymetric and topographic data to support coastal inundation modeling

    NASA Astrophysics Data System (ADS)

    Eakins, B. W.; Taylor, L. A.; Warnken, R. R.; Carignan, K. S.; Sharman, G. F.

    2006-12-01

    The National Geophysical Data Center (NGDC), an office of the National Oceanic and Atmospheric Administration (NOAA), is cooperating with the NOAA Pacific Marine Environmental Laboratory (PMEL), Center for Tsunami Research to develop high-resolution digital elevation models (DEMs) of combined bathymetry and topography. The coastal DEMs will be used as input for the Method of Splitting Tsunami (MOST) model developed by PMEL to simulate tsunami generation, propagation and inundation. The DEMs will also be useful in studies of coastal inundation caused by hurricane storm surge and rainfall flooding, resulting in valuable information for local planners involved in disaster preparedness. We present our methodology for creating the high-resolution coastal DEMs, typically at 1/3 arc-second (10 meters) cell size, from diverse digital datasets collected by numerous methods, in different terrestrial environments, and at various scales and resolutions; one important step is establishing the relationships between various tidal and geodetic vertical datums, which may vary over a gridding region. We also discuss problems encountered and lessons learned, using the Myrtle Beach, South Carolina DEM as an example.

  3. Modeling Tidal Water Levels for Canadian Coastal and Offshore waters

    NASA Astrophysics Data System (ADS)

    Robin, C. M. I.; MacAulay, P.; Nudds, S.; Godin, A.; de Lange Boom, B.; Bartlett, J.; Maltais, L.; Herron, T.; Craymer, M. R.; Veronneau, M.; Fadaie, K.

    2014-12-01

    IIn 2010, the Canadian Hydrographic Service initiated the Continuous Vertical Datum for Canadian Waters (CVDCW) project, the aim of which is to connect tidal water level datums (high and low water levels, chart datum, etc.) to a national geodetic reference frame over all Canadian tidal waters. Currently, water level datums are tied to a geodetic reference frame at approximately 400 tide stations which have been surveyed with GPS, whereas water levels vary significantly in space even a short distance away from tide stations. The CVDCW captures the relevant spatial variability between stations and offshore by integrating ocean models, gauge data (water level analyses and/or GPS observations), sea level trends, satellite altimetry, and a geoid model. The CVDCW will enable the use of Global Navigation Satellite System technologies (primarily GPS) for hydrographers and navigators. It will also be important for other users including oceanographers, environmental and climate scientists, surveyors and engineers. For instance, it will allow easier integration of hydrographic and terrestrial data, provide a baseline for storm surge modeling and climate change adaptation, and aid with practical issues such as sovereignty and the definition of the coastline. Once high and low water surfaces are complete, they will define a large portion of the vertical link between land and ocean, helping to delineate flooding thresholds and inter-tidal ecosystem zones and boundaries. Here we present an overview of the methodology using a set of prototype model results, and will outline features of interest for studies in coastal stability, climate change adaptation, and sea level change.

  4. A novel adaptive biogeochemical model, and its 3-D application for a decadal hindcast simulation of the biogeochemistry of the southern North Sea

    NASA Astrophysics Data System (ADS)

    Kerimoglu, Onur; Hofmeister, Richard; Wirtz, Kai

    2016-04-01

    Adaptation and acclimation processes are often ignored in ecosystem-scale model implementations, despite the long-standing recognition of their importance. Here we present a novel adaptive phytoplankton growth model where acclimation of the community to the changes in external resource ratios is accounted for, using optimality principles and dynamic physiological traits. We show that the model can reproduce the internal stoichiometries obtained at marginal supply ratios in chemostat experiments. The model is applied in a decadal hindcast simulation of the southern North Sea, where it is coupled to a 2-D benthic model and a 3-D hydrodynamic model in an approximately 1.5km horizontal resolution at the German Bight coast. The model is shown to have good skill in capturing the steep, coastal gradients in the German Bight, suggested by the match between the estimated and observed dissolved nutrient and chlorophyll concentrations. We then analyze the differential sensitivity of the coastal and off-shore zones to major drivers of the system, such as riverine nutrient loads. We demonstrate that the relevance of phytoplankton acclimation varies across coastal gradients and can become particularly significant in terms of summer nutrient depletion.

  5. Potential for real-time understanding of coupled hydrologic and biogeochemical processes in stream ecosystems: Future integration of telemetered data with process models for glacial meltwater streams

    NASA Astrophysics Data System (ADS)

    McKnight, Diane M.; Cozzetto, Karen; Cullis, James D. S.; Gooseff, Michael N.; Jaros, Christopher; Koch, Joshua C.; Lyons, W. Berry; Neupauer, Roseanna; Wlostowski, Adam

    2015-08-01

    While continuous monitoring of streamflow and temperature has been common for some time, there is great potential to expand continuous monitoring to include water quality parameters such as nutrients, turbidity, oxygen, and dissolved organic material. In many systems, distinguishing between watershed and stream ecosystem controls can be challenging. The usefulness of such monitoring can be enhanced by the application of quantitative models to interpret observed patterns in real time. Examples are discussed primarily from the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica. Although the Dry Valley landscape is barren of plants, many streams harbor thriving cyanobacterial mats. Whereas a daily cycle of streamflow is controlled by the surface energy balance on the glaciers and the temporal pattern of solar exposure, the daily signal for biogeochemical processes controlling water quality is generated along the stream. These features result in an excellent outdoor laboratory for investigating fundamental ecosystem process and the development and validation of process-based models. As part of the McMurdo Dry Valleys Long-Term Ecological Research project, we have conducted field experiments and developed coupled biogeochemical transport models for the role of hyporheic exchange in controlling weathering reactions, microbial nitrogen cycling, and stream temperature regulation. We have adapted modeling approaches from sediment transport to understand mobilization of stream biomass with increasing flows. These models help to elucidate the role of in-stream processes in systems where watershed processes also contribute to observed patterns, and may serve as a test case for applying real-time stream ecosystem models.

  6. A numerical scheme for coastal morphodynamic modelling on unstructured grids

    NASA Astrophysics Data System (ADS)

    Guerin, Thomas; Bertin, Xavier; Dodet, Guillaume

    2016-08-01

    Over the last decade, modelling systems based on unstructured grids have been appearing increasingly attractive to investigate the dynamics of coastal zones. However, the resolution of the sediment continuity equation to simulate bed evolution is a complex problem which often leads to the development of numerical oscillations. To overcome this problem, addition of artificial diffusion or bathymetric filters are commonly employed methods, although these techniques can potentially over-smooth the bathymetry. This study aims to present a numerical scheme based on the Weighted Essentially Non-Oscillatory (WENO) formalism to solve the bed continuity equation on unstructured grids in a finite volume formulation. The new solution is compared against a classical method, which combines a basic node-centered finite volume method with artificial diffusion, for three idealized test cases. This comparison reveals that a higher accuracy is obtained with our new method while the addition of diffusion appears inappropriate mainly due to the arbitrary choice of the diffusion coefficient. Moreover, the increased computation time associated with the WENO-based method to solve the bed continuity equation is negligible when considering a fully-coupled simulation with tides and waves. Finally, the application of the new method to the pluri-monthly evolution of an idealized inlet subjected to tides and waves shows the development of realistic bed features (e.g. secondary flood channels, ebb-delta sandbars, or oblique sandbars at the adjacent beaches), that are smoothed or nonexistent when using additional diffusion.

  7. Tampa Bay as a model estuary for examining the impact of human activities on biogeochemical processes: an introduction

    USGS Publications Warehouse

    Swarzenski, Peter W.; Baskaran, Mark; Henderson, Carl S.; Yates, Kim

    2007-01-01

    Tampa Bay is a shallow, Y-shaped coastal embayment that is located along the center of the Florida Platform – an expansive accumulation of Cretaceous–Tertiary shallow-water carbonates and evaporites that were periodically exposed during glacio–eustatic sea level fluctuations. As a consequence, extensive karstification likely had a controlling impact on the geologic evolution of Tampa Bay. Despite its large aerial size (∼ 1000 km2), Tampa Bay is relatively shallow (mean depth = 4 m) and its watershed (6700 km2) is among the smallest in the Gulf of Mexico. About 85% of all freshwater inflow (mean = 63 m3 s-1) to the bay is carried by four principal tributaries (Orlando et al., 1993). Groundwater makes up an important component of baseflow of these coastal streams and may also be important in delivering nutrients and other constituents to the bay proper by submarine groundwater discharge.

  8. Modeling SST and chlorophyll patterns in a coupled estuary-coastal system of Portugal: The Tagus case study

    NASA Astrophysics Data System (ADS)

    Vaz, N.; Mateus, M.; Plecha, S.; Sousa, M. C.; Leitão, P. C.; Neves, R.; Dias, J. M.

    2015-07-01

    This work studies the influence of the Tagus estuary, Portugal, on the near coastal system using a model application to describe the main physical and biogeochemical processes in the Region of Freshwater Influence (ROFI). It was used as nested modeling approach, downscaling the solution for the general circulation from a larger domain model (the Portuguese coast), to the local Tagus estuary domain. The model is evaluated during a very dynamic and biologic productive period of the year, corresponding to the winter and early summer (January-May 2007). Also during this period, there is a strong freshwater inflow into the Tagus estuary, which in turn modulates the estuarine outflow to the Tagus ROFI. The results focus on water temperature and chlorophyll and a skill assessment was made, given the lack of data required to perform a thorough validation. Simulation results reveal an adequate reproduction of the vertical thermal structure and chlorophyll concentrations. While a fairly reasonable agreement is seen for water temperature, showing no significant thermal stratification at the study area (average surface-to-bottom difference ranging from 1.3 °C to 1.6 °C), chlorophyll vertical profiles show some differences between the model results and the measurements. Maximum model bias for surface temperature is 1.4 °C and ranges from 1 to 2 mg m- 3 for chlorophyll, revealing an underestimation of the predicted chlorophyll and surface temperature for the area in the vicinity of the Tagus mouth. The general trends of surface chlorophyll and surface water temperature are satisfactorily reproduced by the model.

  9. Preface: Monitoring and modelling to guide coastal adaptation to extreme storm events in a changing climate

    NASA Astrophysics Data System (ADS)

    Brown, J. M.; Ciavola, P.; Masselink, G.; McCall, R.; Plater, A. J.

    2016-02-01

    Storms across the globe and their associated consequences in coastal zones (flooding and erosion), combined with the long-term geomorphic evolution of our coastlines, are a threat to life and assets, both socioeconomic and environmental. In a changing climate, with a rising global sea level, potentially changing patterns in storm tracks and storminess, and rising population density and pressures on the coastal zone, the future risk of coastal storm impacts is likely to increase. Coastal managers and policy makers therefore need to make effective and timely decisions on the use of resources for the immediate and longer Research focused on "monitoring and modelling to guide coastal adaptation to extreme storm events in a changing climate" is becoming more common; its goal is to provide science-based decision support for effective adaptation to the consequences of storm impacts, both now and under future climate scenarios at the coast. The growing transfer of information between the science community and end-users is enabling leading research to have a greater impact on the socioeconomic resilience of coastal communities. This special issue covers recent research activities relating to coastal hazard mapping in response to extreme events, economic impacts of long-term change, coastal processes influencing management decisions and the development of online decision support tools.

  10. OBSERVATIONS RELATED TO THE USE OF THE SIGMA COORDINATE TRANSFORMATION FOR ESTUARIES AND COASTAL MODELING STUDIES

    EPA Science Inventory

    One of the common techniques used in application of time-dependent, three-dimensional models addressing estuarine and coastal environmental problems is the sigma coordinate transformation. his transformation has proven useful in applications with highly irregular bottom topograph...

  11. Contributions of Participatory Modeling to Development and Support of Coastal and Marine Management Plans

    EPA Science Inventory

    The role of participatory modeling- at various scales- to assist in developing shared visions, understanding the decision landscape, identifying and selecting management options, and monitoring outcomes will be explored in the context of coastal and marine planning, ecosystem ser...

  12. Effects of coastal transport on larval patches: Models and observations

    NASA Astrophysics Data System (ADS)

    Tilburg, Charles E.; Houser, Letise T.; Steppe, Cecily N.; Garvine, Richard W.; Epifanio, Charles E.

    2006-03-01

    We used a combination of field observations and numerical modeling to examine the physical mechanisms responsible for the evolution and transport of patches of blue crab larvae in the mouth of Delaware Bay. The observations consisted of larval collections and surface salinity measurements taken along a moving spatial grid whose origin was determined by a satellite-tracked drifter. Examination of field observations revealed a slender larval patch that was aligned with salinity contours. Measurement of the salting rate of the larval patch indicated that the patch moved through the offshore edge of a buoyant plume due to wind-driven upwelling circulation. A numerical model that provided realistic simulations of the flow field at the mouth of Delaware Bay and the adjoining coastal ocean was used to examine the physical mechanisms responsible for the movement and evolution of the patch. We conducted a series of simulations in which we separately examined the effects of tides, buoyancy-driven flow, and wind-driven transport. Results showed that both tides and buoyancy-driven flow tend to elongate an initially square fluid element. Although winds alone have little effect on the shape of a patch, wind-driven flow can effectively move a patch through a complex flow field in which the deformation by tides and buoyancy-driven circulation can have significant effects. This study represents the first observation and analysis of a larval patch that remains intact while moving through the edge of a buoyant plume. It provides new insight into the shape of larval patches in Delaware Bay and any region with strong buoyancy- and tidally-driven flow, suggesting that typical larval patches may not be characterized by equal across- and alongshelf dimensions but instead tend to be slender shapes that are aligned with the flow field.

  13. An integrated coastal modeling system for analyzing beach processes and beach restoration projects, SMC

    NASA Astrophysics Data System (ADS)

    González, M.; Medina, R.; Gonzalez-Ondina, J.; Osorio, A.; Méndez, F. J.; García, E.

    2007-07-01

    A user-friendly system called coastal modeling system (SMC) has been developed by the Spanish Ministry of Environment and the University of Cantabria. The system includes several numerical models specifically developed for the application of the methodology proposed in the Spanish Beach Nourishment and Protection Manual. According to this methodology, the SMC is structured into five -modules: (1) Pre-process module; (2) Short-term module; (3) Long-term module; (4) Coastal terrain module; and (5) Tutorial module. The pre-process module allows the processing of a database of morphodynamic information used as input for the different programs and models of the SMC. Short-, Long-term modules include numerical models to analyze coastal systems on different scales of variability (hours-months-years) and are composed of morphodynamic evolution models in cross-profile 2DV and beach plan 2DH. The coastal terrain module allows the user to modify the working bathymetry and to combine bathymetries from different sources in only one working bathymetry. The tutorial module includes a comprehensive collection of coastal engineering design and analysis software. The SMC has a dynamic design and allows the incorporation of future new databases and morphodynamic models. The SMC system is freely distributed to coastal practitioners and has already been implemented in several countries.

  14. Up-scaling of process-based eco-hydrology model to global scale for identification of hot spots in boundless biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Nakayama, T.; Maksyutov, S. S.

    2013-12-01

    Recent research shows inland water may play some role in continental biogeochemical cycling though its contribution has remained uncertain due to a paucity of data (Battin et al. 2009). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which includes surface-groundwater interactions and down-scaling process from regional to local simulation with finer resolution, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes in east Asia. In this study, NICE was further extended to implement map factor and non-uniform grid through up-scaling process of coordinate transformation from rectangular to longitude-latitude system applicable to global scale. This improved model was applied to several basins in Eurasia to evaluate the impact of coordinate transformation on eco-hydrological changes. Simulated eco-hydrological process after up-scaling corresponded reasonably to that in the original there after evaluating the effect of different latitude. Then, the model was expanded to evaluate global hydrologic cycle by using various global datasets. The simulated result agreed reasonably with that in the previous research (Fan et al., 2013) and extended to clarify further eco-hydrological process in global scale. This simulation system would play important role in identification of spatio-temporal hot spots in boundless biogeochemical cycle along terrestrial-aquatic continuum for global environmental change (Cole et al. 2007; Battin et al. 2009; Frei et al. 2012).

  15. Adjoint Data Assimilative Model Study of the Gulf of Maine Coastal Circulation

    NASA Astrophysics Data System (ADS)

    He, R.; McGillicuddy, D. J.; Lynch, D. R.

    2004-12-01

    Data assimilation (DA) in the coastal ocean can be divided into category of either sequential estimation or variational adjoint. Sequential estimation techniques blend models with observations directly, using a variety of algorithms with which the relative weights of data and model are calculated. Variational adjoint techniques infer model control variables (e.g. parameters, forcing functions, boundary conditions, etc.) that minimize the misfit between observations and predictions. The advantage of the latter techniques over the former is that the resulting model solutions obey model dynamics. In this study, the Gulf of Maine coastal circulation and the material property transport are investigated with the Dartmouth variational adjoint DA modeling system, which assimilates in-situ data via inversion for the unknown sea level elevation at open boundaries. In-situ observations include ADCP currents and coastal sea levels. The adjoint DA model skill is evaluated by the inter-comparisons between modeled and observed drifter trajectories. Excellent model skill is found, demonstrating the utility and effectiveness of the adjoint DA modeling system in bridging in-situ observations with coastal ocean model simulations. Implications of the adjoint DA strategy on the emergent coastal ocean observing systems are discussed.

  16. Integrating Hydrogeological, Microbiological, and Geochemical Data Using a Multi-Component Reactive Transport Model: Quantifying the Biogeochemical Evolution of Redox Zones in a Contaminated Aquifer

    NASA Astrophysics Data System (ADS)

    McGuire, J. T.; Phanikumar, M. S.; Long, D. T.; Hyndman, D. W.

    2003-12-01

    Hydrogeological, microbiological, and geochemical processes operating in a shallow sandy aquifer contaminated by waste fuels and chlorinated solvents were integrated using high-resolution mechanistic models. A 3-D, transient, reactive transport model was developed to quantitatively describe coupled processes via thermodynamic and kinetic arguments. The model was created by linking the hydrodynamic model MODFLOW (McDonald and Harbaugh, 1988), with advection, dispersion and user defined kinetic reactions based on RT3D 2.0, (Clement and Jones, 1998) and geochemical model PHREEQC (Parkhurst and Appelo, 1999). This model, BGTK3D 2.0, describes 1) the biodegradation of organic matter based on the influence of transport processes on microbial growth, 2) the complex suite of biogeochemical reactions operating in the aquifer, and 3) sharp chemical gradients. Some key features of this model are an ability to incorporate realistic solid phases to test hypotheses regarding mineral-water interactions, and an ability to accurately describe small-scale biogeochemical cycling (cm variability) observed in the field without oscillations or excessive numerical damping. BGTK3D was used to test hypotheses regarding the evolution of redox chemistry in a contaminated aquifer. The conceptual model that terminal electron accepting processes (TEAPs) distribute themselves sequentially into redox zones down flow path in aqueous systems is often used to interpret how and at what rates organic compounds will be degraded in the environment. Geochemical and microbiological data collected from a mixed contaminant plume at the former Wurtsmith AFB in Oscoda, Michigan suggests that under steady-state, mature plume conditions, traditional redox zonation may not be a realistic model of the distribution of TEAPs and therefore may not be the best model to evaluate the potential degradation of organic compounds. Based on these data, a conceptual model of TEAP evolution in contaminated systems was

  17. Effects of meteorological forcing on coastal eutrophication: Modeling with model trees

    NASA Astrophysics Data System (ADS)

    Tamvakis, Androniki; Miritzis, John; Tsirtsis, George; Spyropoulou, Alexandra; Spatharis, Sofie

    2012-12-01

    The exploration of processes leading to coastal eutrophication is a major challenge in ecological research, particularly in light of important new policies such as the European Water Framework Directive. In the present study primary production (in terms of chlorophyll α - chl α) is modeled based on a number of abiotic parameters using model trees (MTs), a machine learning (ML) approach whereby linear regressions are induced within homogeneous subsets of samples (tree leaves). Standardized regression was applied to determine the relative weight of abiotic parameters in the MT tree leaves whereas the efficiency of the MT method in chl α prediction was tested against neural networks (NNs) which is the most frequently used ML approach, and the classical multiple linear regression (MLR). To assess the efficiency of models to describe eutrophication-related responses under different environmental conditions, the methods were applied on a coastal ecosystem affected by terrestrial runoff for two meteorologically contrasting annual cycles: a typical dry ('04-'05) and a typical wet ('09-'10). MTs showed increased predictive power in chl α prediction attributed to the discrimination of input data space into tree leaves, instead of using a uniform space as in NNs and MLR. By grouping samples of each tested annual cycle (wet and dry) on a seasonal basis into discrete groups/leaves, MTs offer a much more explanatory description of ecosystem status than NNs and MLR. The discriminating variables forming tree leaves and the weighing coefficients of Linear Models (LMs) in each leaf provided a useful scaling of abiotic parameters driving chl α dynamics. The MT method is thus proposed as an efficient tool for obtaining insights into ecosystem processes leading to eutrophication events in coastal ecosystems and a useful component in integrated coastal zone management.

  18. OCD: The offshore and coastal dispersion model. Volume 1. User's guide

    SciTech Connect

    DiCristofaro, D.C.; Hanna, S.R.

    1989-11-01

    The Offshore and Coastal Dispersion (OCD) Model has been developed to simulate the effect of offshore emissions from point, area, or line sources on the air quality of coastal regions. The OCD model was adapted from the EPA guideline model MPTER (EPA, 1980). Modifications were made to incorporate overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. This is a revised OCD model, the fourth version to date. The volume is the User's Guide which includes a Model overview, technical description, user's instructions, and notes on model evaluation and results.

  19. Comparison of ocean physical and biogeochemical mean state and climate sensitivity across ocean model resolution from 100 km to 10 km

    NASA Astrophysics Data System (ADS)

    Dunne, J. P.

    2015-12-01

    One of the representational aspirations driving current Earth System Model development is to capture the global ocean mesoscale (i.e. ocean weather) in coupled carbon-climate. The present study explores a the role of ocean model resolution (100 km to 10 km) on baseline physical and biogeochemical simulation characteristics and their response to climate change. We find the high resolution model to improve the representation of boundary currents and mesoscale phenomena, and to eliminate fictitious current structures that plague the coarse resolution models. Along with these expected improvements of smaller scales however, we also find a general lack of improvement in many of the large scale biases. With respect to sensitivity, we find the high resolution model to restrict ocean heat uptake towards the surface ocean and to exhibit somewhat less structure at the regional scale than the coarse resolution model. We find similarly more uniform patterns of carbon uptake and biogeochemicel response at high resolution consistent with a greater tendency in the high resolution model to accommodate change in the major current structures, and suggesting that some of the highly regional structure observed among CMIP5 models is due to their inability to represent the role of the mesoscale on the regional scale.

  20. Physical and biogeochemical spatial scales of variability in the East Australian Current separation zone from shelf glider measurements

    NASA Astrophysics Data System (ADS)

    Schaeffer, A.; Roughan, M.; Jones, E.; White, D.

    2015-12-01

    In contrast to physical processes, biogeochemical processes are inherently patchy in the ocean, which affects both the observational sampling strategy and the representativeness of sparse measurements in data assimilating models. In situ observations from multiple glider deployments are analyzed to characterize spatial scales of variability in both physical and biogeochemical properties, using an empirical statistical model. We find that decorrelation ranges are strongly dependent on the balance between local dynamics and mesoscale forcing. The shortest horizontal (5-10 km) and vertical (45 m) decorrelation ranges are for chlorophyll a fluorescence. Whereas those variables that are a function of regional ocean and atmosphere dynamics (temperature and dissolved oxygen) result in anisotropic patterns with longer ranges along (28-37 km) than across the shelf (8-19 km). Variables affected by coastal processes (salinity and colored dissolved organic matter) have an isotropic range similar to the baroclinic Rossby radius (10-15 km).

  1. Physical and biogeochemical spatial scales of variability in the East Australian Current separation from shelf glider measurements

    NASA Astrophysics Data System (ADS)

    Schaeffer, Amandine; Roughan, Moninya; Jones, Emlyn M.; White, Dana

    2016-03-01

    In contrast to physical processes, biogeochemical processes are inherently patchy in the ocean, which affects both the observational sampling strategy and the representativeness of sparse measurements in data assimilating models. In situ observations from multiple glider deployments are analysed to characterize spatial scales of variability in both physical and biogeochemical properties, using an empirical statistical model. We find that decorrelation ranges are strongly dependent on the balance between local dynamics and mesoscale forcing. The shortest horizontal (5-10 km) and vertical (45 m) decorrelation ranges are for chlorophyll a fluorescence, whereas those variables that are a function of regional ocean and atmosphere dynamics (temperature and dissolved oxygen) result in anisotropic patterns with longer ranges along (28-37 km) than across the shelf (8-19 km). Variables affected by coastal processes (salinity and coloured dissolved organic matter) have an isotropic range similar to the baroclinic Rossby radius (10-15 km).

  2. Inland and coastal waters

    NASA Astrophysics Data System (ADS)

    Mouw, Colleen; Greb, Steven

    2012-09-01

    Workshop for Remote Sensing of Coastal and Inland Waters;Madison, Wisconsin, 20-22 June 2012 Coastal and inland water bodies, which have great value for recreation, food supply, commerce, transportation, and human health, have been experiencing external pressure from direct human activities and climate change. Given their societal and economic value, understanding issues of water quality, water quantity, and the impact of environmental change on the ecological and biogeochemical functioning of these water bodies is of interest to a broad range of communities. Remote sensing offers one of the most spatially and temporally comprehensive tools for observing these waters. While there has been some success with remotely observing these water bodies, many challenges still remain, including algorithm performance, atmospheric correction, the relationships between optical properties and biogeochemical parameters, sufficient spatial and spectral resolution, and a lack of uncertainty estimates over the wide range of environmental conditions encountered across these coastal and inland water bodies.

  3. Atmospheric-induced variability of hydrological and biogeochemical signatures in the NW Alboran Sea. Consequences for the spawning and nursery habitats of European anchovy

    NASA Astrophysics Data System (ADS)

    Macías, D.; Catalán, I. A.; Solé, J.; Morales-Nin, B.; Ruiz, J.

    2011-12-01

    The north-western Alboran Sea is a highly dynamic region in which the hydrological processes are mainly controlled by the entrance of the Atlantic Jet (AJ) through the Strait of Gibraltar. The biological patterns of the area are also related to this variability in which atmospheric pressure distributions and wind intensity and direction play major roles. In this work, we studied how changes in atmospheric forcing (from high atmospheric pressure over the Mediterranean to low atmospheric pressure) induced alterations in the physical and biogeochemical environment by re-activating coastal upwelling on the Spanish shore. The nursery area of European anchovy ( Engraulis encrasicolus) in the NW Alboran Sea, confirmed to be the very coastal band around Malaga Bay, did not show any drastic change in its biogeochemical characteristics, indicating that this coastal region is somewhat isolated from the rest of the basin. Our data also suggests that anchovy distribution is tightly coupled to the presence of microzooplankton rather than mesozooplankton. Finally, we use detailed physical and biological information to evaluate a hydrological-biogeochemical coupled model with a specific hydrological configuration to represent the Alboran basin. This model is able to reproduce the general circulation patterns in the region forced by the AJ movements only including two variable external forcings; atmospheric pressure over the western Mediterranean and realistic wind fields.

  4. Significant Findings: Tracking the SeaWiFS Record with a Coupled Physical/Biogeochemical/Radiative Model of the Global Oceans

    NASA Technical Reports Server (NTRS)

    Watson, Gregg W.

    2000-01-01

    The Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) has observed 2.5 years of routine global chlorophyll observations from space. The mission was launched into a record El Nino event, which eventually gave way to one of the most intensive and longest-lasting La Nina events ever recorded. The SeaWiFS chlorophyll record captured the response of ocean phytoplankton to these significant events in the tropical Indo-Pacific basins, but also indicated significant interannual variability unrelated to the El Nino/La Nina events. This included large variability in the North Atlantic and Pacific basins, in the North Central and equatorial Atlantic, and milder patterns in the North Central Pacific. This SeaWiFS record was tracked with a coupled physical/biogeochemical/radiative model of the global oceans using near-real-time forcing data such as wind stresses, sea surface temperatures, and sea ice. This provided an opportunity to offer physically and biogeochemically meaningful explanations of the variability observed in the SeaWiFS data set, since the causal mechanisms and interrelationships of the model are completely understood. The coupled model was able to represent the seasonal distributions of chlorophyll during the SeaWiFS era, and was capable of differentiating among the widely different processes and dynamics occurring in the global oceans. The model was also reasonably successful in representing the interannual signal, especially when it was large, such as, the El Nino and La Nina events in the tropical Pacific and Indian Oceans. The model provided different phytoplankton group responses for the different events in these regions: diatoms were predominant in the tropical Pacific during the La Nina but other groups were predominant during El Nino. The opposite condition occurred in the tropical Indian Ocean. Both situations were due to the different responses of the basins to El Nino. The interannual variability in the North Atlantic, which was exhibited in Sea

  5. Parameter-induced uncertainty quantification of a regional N2O and NO3 inventory using the biogeochemical model LandscapeDNDC

    NASA Astrophysics Data System (ADS)

    Haas, Edwin; Klatt, Steffen; Kraus, David; Werner, Christian; Ruiz, Ignacio Santa Barbara; Kiese, Ralf; Butterbach-Bahl, Klaus

    2014-05-01

    Numerical simulation models are increasingly used to estimate greenhouse gas emissions at site to regional and national scales and are outlined as the most advanced methodology (Tier 3) for national emission inventory in the framework of UNFCCC reporting. Process-based models incorporate the major processes of the carbon and nitrogen cycle of terrestrial ecosystems like arable land and grasslands and are thus thought to be widely applicable at various spatial and temporal scales. The high complexity of ecosystem processes mirrored by such models requires a large number of model parameters. Many of those parameters are lumped parameters describing simultaneously the effect of environmental drivers on e.g. microbial community activity and individual processes. Thus, the precise quantification of true parameter states is often difficult or even impossible. As a result model uncertainty is not solely originating from input uncertainty but also subject to parameter-induced uncertainty. In this study we quantify regional parameter-induced model uncertainty on nitrous oxide (N2O) emissions and nitrate (NO3) leaching from arable soils of Saxony (Germany) using the biogeochemical model LandscapeDNDC. For this we calculate a regional inventory using a joint parameter distribution for key parameters describing microbial C and N turnover processes as obtained by a Bayesian calibration study. We representatively sampled 400 different parameter vectors from the discrete joint parameter distribution comprising approximately 400,000 parameter combinations and used these to calculate 400 individual realizations of the regional inventory. The spatial domain (represented by 4042 polygons) is set up with spatially explicit soil and climate information and a region-typical 3-year crop rotation consisting of winter wheat, rape- seed, and winter barley. Average N2O emission from arable soils in the state of Saxony across all 400 realizations was 1.43 ± 1.25 [kg N / ha] with a median

  6. Evaluating meteo marine climatic model inputs for the investigation of coastal hydrodynamics

    NASA Astrophysics Data System (ADS)

    Bellafiore, D.; Bucchignani, E.; Umgiesser, G.

    2010-09-01

    One of the major aspects discussed in the recent works on climate change is how to provide information from the global scale to the local one. In fact the influence of sea level rise and changes in the meteorological conditions due to climate change in strategic areas like the coastal zone is at the base of the well known mitigation and risk assessment plans. The investigation of the coastal zone hydrodynamics, from a modeling point of view, has been the field for the connection between hydraulic models and ocean models and, in terms of process studies, finite element models have demonstrated their suitability in the reproduction of complex coastal morphology and in the capability to reproduce different spatial scale hydrodynamic processes. In this work the connection between two different model families, the climate models and the hydrodynamic models usually implemented for process studies, is tested. Together, they can be the most suitable tool for the investigation of climate change on coastal systems. A finite element model, SHYFEM (Shallow water Hydrodynamic Finite Element Model), is implemented on the Adriatic Sea, to investigate the effect of wind forcing datasets produced by different downscaling from global climate models in terms of surge and its coastal effects. The wind datasets are produced by the regional climate model COSMO-CLM (CIRA), and by EBU-POM model (Belgrade University), both downscaling from ECHAM4. As a first step the downscaled wind datasets, that have different spatial resolutions, has been analyzed for the period 1960-1990 to compare what is their capability to reproduce the measured wind statistics in the coastal zone in front of the Venice Lagoon. The particularity of the Adriatic Sea meteo climate is connected with the influence of the orography in the strengthening of winds like Bora, from North-East. The increase in spatial resolution permits the more resolved wind dataset to better reproduce meteorology and to provide a more

  7. Analysis and modeling of decadal and long-term variability of coastal California summer temperature changes

    NASA Astrophysics Data System (ADS)

    Sequera, Pedro

    Summer average daily maximum temperature (Tmax) trends for 1950-2010 were calculated for 241 locations along all of California by use of daily max temperatures from NWS Coop sites to understand the spatial and temporal variabilities of the previously reported summer coastal-cooling. Results show that coastal-cooling appears almost continuously throughout the California coast in locations open to marine air penetrations for the period of 1970-2010. Correlations with the Pacific Decadal Oscillation (PDO) Index show that coastal-cooling disappears during the increasing PDO period (1950-1985). The most influential factor(s) on California summer coastal temperatures, i.e., Greenhouse Gas (GHG) warming, PDO and changes in Land Cover/Land Use (LCLU), were determined through numerical atmospheric modeling using the Weather Research & Forecasting (WRF) model. Combined results from observations, reanalysis and modeling lead to the conclusion that PDO is the main mechanism of decadal variability of California summer temperatures, dominating over global GHG-warming effects. PDO affects both coastal and inland temperatures by controlling the position and intensity of the two dominating global circulation patterns on California summer: the semi-permanent Pacific High Pressure System and the continental Thermal-Low. Coastal cooling will rise on decreasing PDO periods, where the warming of inland regions and cooling of nearshore Sea Surface Temperatures (SSTs) results in an increase in sea-breeze activity. Coastal-warming results in increasing periods of the PDO. Global warming induced by GHG and hyper-urbanization were found to be major sources of coastal warming over complete PDO cycles (1950-2010).

  8. Improving Coastal Ocean Color Validation Capabilities through Application of Inherent Optical Properties (IOPs)

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio

    2008-01-01

    Understanding how the different components of seawater alter the path of incident sunlight through scattering and absorption is essential to using remotely sensed ocean color observations effectively. This is particularly apropos in coastal waters where the different optically significant components (phytoplankton, detrital material, inorganic minerals, etc.) vary widely in concentration, often independently from one another. Inherent Optical Properties (IOPs) form the link between these biogeochemical constituents and the Apparent Optical Properties (AOPs). understanding this interrelationship is at the heart of successfully carrying out inversions of satellite-measured radiance to biogeochemical properties. While sufficient covariation of seawater constituents in case I waters typically allows empirical algorithms connecting AOPs and biogeochemical parameters to behave well, these empirical algorithms normally do not hold for case I1 regimes (Carder et al. 2003). Validation in the context of ocean color remote sensing refers to in-situ measurements used to verify or characterize algorithm products or any assumption used as input to an algorithm. In this project, validation capabilities are considered those measurement capabilities, techniques, methods, models, etc. that allow effective validation. Enhancing current validation capabilities by incorporating state-of-the-art IOP measurements and optical models is the purpose of this work. Involved in this pursuit is improving core IOP measurement capabilities (spectral, angular, spatio-temporal resolutions), improving our understanding of the behavior of analytical AOP-IOP approximations in complex coastal waters, and improving the spatial and temporal resolution of biogeochemical data for validation by applying biogeochemical-IOP inversion models so that these parameters can be computed from real-time IOP sensors with high sampling rates. Research cruises supported by this project provides for collection and

  9. Using model reduction to predict the soil-surface C18OO flux: an example of representing complex biogeochemical dynamics in a computationally efficient manner

    NASA Astrophysics Data System (ADS)

    Riley, W. J.

    2012-11-01

    Earth System Models (ESMs) must calculate large-scale interactions between the land and atmosphere while accurately characterizing fine-scale spatial heterogeneity in water, carbon, and nutrient dynamics. We present here a high-dimensional model representation (HDMR) approach that allows detailed process representation of a coupled carbon and water tracer (the δ18O value of the soil-surface CO2 flux (δFs)) in a computationally tractable manner. δFs depends on the δ18O value of soil water, soil moisture, soil temperature, and soil CO2 production (all of which are depth-dependent), and the δ18O value of above-surface CO2. We tested the HDMR approach over a growing season in a C4-dominated pasture using two vertical soil discretizations. The difference between the HDMR approach and the full model solution in the three-month integrated isoflux was less than 0.2% (0.5 mol m-2‰), and the approach is up to 100 times faster than the full numerical solution. This type of model reduction approach allows representation of complex coupled biogeochemical processes in regional and global climate models and can be extended to characterize subgrid-scale spatial heterogeneity.

  10. Using model reduction to predict the soil-surface C18OO flux: an example of representing complex biogeochemical dynamics in a computationally efficient manner

    NASA Astrophysics Data System (ADS)

    Riley, W. J.

    2013-03-01

    Earth system models (ESMs) must calculate large-scale interactions between the land and atmosphere while accurately characterizing fine-scale spatial heterogeneity in water, carbon, and other nutrient dynamics. We present here a high-dimension model representation (HDMR) approach that allows detailed process representation of a coupled carbon and water tracer (the δ18O value of the soil-surface CO2 flux (δ Fs)) in a computationally tractable manner. δ Fs depends on the δ18O value of soil water, soil moisture and temperature, and soil CO2 production (all of which are depth dependent), and the δ18O value of above-surface CO2. We tested the HDMR approach over a growing season in a C4-dominated pasture using two vertical soil discretizations. The difference between the HDMR approach and the full model solution in the three-month integrated isoflux was less than 0.2% (0.5 mol m-2 ‰), and the approach is up to 100 times faster than the full numerical solution. This type of model reduction approach allows representation of complex coupled biogeochemical processes in regional and global climate models and can be extended to characterize subgrid-scale spatial heterogeneity.

  11. Coastal Zone Color Scanner

    NASA Technical Reports Server (NTRS)

    Johnson, B.

    1988-01-01

    The Coastal Zone Color Scanner (CZCS) spacecraft ocean color instrument is capable of measuring and mapping global ocean surface chlorophyll concentration. It is a scanning radiometer with multiband capability. With new electronics and some mechanical, and optical re-work, it probably can be made flight worthy. Some additional components of a second flight model are also available. An engineering study and further tests are necessary to determine exactly what effort is required to properly prepare the instrument for spaceflight and the nature of interfaces to prospective spacecraft. The CZCS provides operational instrument capability for monitoring of ocean productivity and currents. It could be a simple, low cost alternative to developing new instruments for ocean color imaging. Researchers have determined that with global ocean color data they can: specify quantitatively the role of oceans in the global carbon cycle and other major biogeochemical cycles; determine the magnitude and variability of annual primary production by marine phytoplankton on a global scale; understand the fate of fluvial nutrients and their possible affect on carbon budgets; elucidate the coupling mechanism between upwelling and large scale patterns in ocean basins; answer questions concerning the large scale distribution and timing of spring blooms in the global ocean; acquire a better understanding of the processes associated with mixing along the edge of eddies, coastal currents, western boundary currents, etc., and acquire global data on marine optical properties.

  12. Unstructured-grid coastal ocean modelling in Southern Adriatic and Northern Ionian Seas

    NASA Astrophysics Data System (ADS)

    Federico, Ivan; Pinardi, Nadia; Coppini, Giovanni; Oddo, Paolo

    2016-04-01

    The Southern Adriatic Northern Ionian coastal Forecasting System (SANIFS) is a short-term forecasting system based on unstructured grid approach. The model component is built on SHYFEM finite element three-dimensional hydrodynamic model. The operational chain exploits a downscaling approach starting from the Mediterranean oceanographic-scale model MFS (Mediterranean Forecasting System, operated by INGV). The implementation set-up has been designed to provide accurate hydrodynamics and active tracer processes in the coastal waters of Southern Eastern Italy (Apulia, Basilicata and Calabria regions), where the model is characterized by a variable resolution in range of 50-500 m. The horizontal resolution is also high in open-sea areas, where the elements size is approximately 3 km. The model is forced: (i) at the lateral open boundaries through a full nesting strategy directly with the MFS (temperature, salinity, non-tidal sea surface height and currents) and OTPS (tidal forcing) fields; (ii) at surface through two alternative atmospheric forcing datasets (ECMWF and COSMOME) via MFS-bulk-formulae. Given that the coastal fields are driven by a combination of both local/coastal and deep ocean forcings propagating along the shelf, the performance of SANIFS was verified first (i) at the large and shelf-coastal scales by comparing with a large scale CTD survey and then (ii) at the coastal-harbour scale by comparison with CTD, ADCP and tide gauge data. Sensitivity tests were performed on initialization conditions (mainly focused on spin-up procedures) and on surface boundary conditions by assessing the reliability of two alternative datasets at different horizontal resolution (12.5 and 7 km). The present work highlights how downscaling could improve the simulation of the flow field going from typical open-ocean scales of the order of several km to the coastal (and harbour) scales of tens to hundreds of meters.

  13. New Insights into Fluvial Carbon Responses to Future Forest Management and Climate Change Obtained from Multi-Scale Modelling of Biogeochemical Processes

    NASA Astrophysics Data System (ADS)

    Oni, S. K.; Tiwari, T.; Futter, M. N.; Agren, A.; Teutschbein, C.; Ledesma, J.; Schelker, J.; Laudon, H.

    2014-12-01

    The boreal ecozone covers 2x107 km2 of the northern circumpolar region and includes 29% of the world's forests. The boreal consists of mosaic of forest/wetland landscape elements and stores about 500 Gt3 carbon (C) with a delicate sink-source C balance. Dissolved organic carbon (DOC) is the main form of C exported from boreal landscapes and is fundamental to global C cycling. This northern ecosystem is vulnerable to global climate change, and increasing demands for forest products threaten its surface water resources. So far, there have been no attempts to assess the combined impacts of climate change and forest management on the future DOC fluxes from boreal surface waters. While differences in model assumptions may have negligible effects on present day simulations, these differences could be amplified when projecting the future climate and land use change conditions. Here we use an ensemble of regional climate models and multi-scale models of biogeochemical processes to gain insights into uncertainties associated with climate change and forest management on C and runoff dynamics in boreal landscape. While there are significant uncertainties associated with model projections, our results show that climate change will be the main driver of long term DOC dynamics in meso- to large boreal catchments in the future. However, forestry intensifies hydrological processes and can lead to large DOC fluxes at the headwater scales.

  14. Mapping pan-Arctic CH4 emissions using an adjoint method by integrating process-based wetland and lake biogeochemical models and atmospheric CH4 concentrations

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Zhuang, Q.; Henze, D. K.; Frankenberg, C.; Dlugokencky, E. J.; Sweeney, C.; Turner, A. J.

    2015-12-01

    Understanding CH4 emissions from wetlands and lakes are critical for the estimation of Arctic carbon balance under fast warming climatic conditions. To date, our knowledge about these two CH4 sources is almost solely built on the upscaling of discontinuous measurements in limited areas to the whole region. Many studies indicated that, the controls of CH4 emissions from wetlands and lakes including soil moisture, lake morphology and substrate content and quality are notoriously heterogeneous, thus the accuracy of those simple estimates could be questionable. Here we apply a high spatial resolution atmospheric inverse model (nested-grid GEOS-Chem Adjoint) over the Arctic by integrating SCIAMACHY and NOAA/ESRL CH4 measurements to constrain the CH4 emissions estimated with process-based wetland and lake biogeochemical models. Our modeling experiments using different wetland CH4 emission schemes and satellite and surface measurements show that the total amount of CH4 emitted from the Arctic wetlands is well constrained, but the spatial distribution of CH4 emissions is sensitive to priors. For CH4 emissions from lakes, our high-resolution inversion shows that the models overestimate CH4 emissions in Alaskan costal lowlands and East Siberian lowlands. Our study also indicates that the precision and coverage of measurements need to be improved to achieve more accurate high-resolution estimates.

  15. EFFECT OF NUTRIENT LOADING ON BIOGEOCHEMICAL AND MICROBIAL PROCESSES IN A NEW ENGLAND HIGH SALT MARSH, SPARTINA PATNES, (AITON MUHL)

    EPA Science Inventory

    Coastal marshes represent an important transitional zone between uplands and estuaries and can assimilate nutrient inputs from uplands. We examined the effects of nitrogen (N) and phosphorus (P) fertilization on biogeochemical and microbial processes during the summer growing sea...

  16. Total maximum allocated load calculation of nitrogen pollutants by linking a 3D biogeochemical-hydrodynamic model with a programming model in Bohai Sea

    NASA Astrophysics Data System (ADS)

    Dai, Aiquan; Li, Keqiang; Ding, Dongsheng; Li, Yan; Liang, Shengkang; Li, Yanbin; Su, Ying; Wang, Xiulin

    2015-12-01

    The equal percent removal (EPR) method, in which pollutant reduction ratio was set as the same in all administrative regions, failed to satisfy the requirement for water quality improvement in the Bohai Sea. Such requirement was imposed by the developed Coastal Pollution Total Load Control Management. The total maximum allocated load (TMAL) of nitrogen pollutants in the sea-sink source regions (SSRs) around the Bohai Rim, which is the maximum pollutant load of every outlet under the limitation of water quality criteria, was estimated by optimization-simulation method (OSM) combined with loop approximation calculation. In OSM, water quality is simulated using a water quality model and pollutant load is calculated with a programming model. The effect of changes in pollutant loads on TMAL was discussed. Results showed that the TMAL of nitrogen pollutants in 34 SSRs was 1.49×105 ton/year. The highest TMAL was observed in summer, whereas the lowest in winter. TMAL was also higher in the Bohai Strait and central Bohai Sea and lower in the inner area of the Liaodong Bay, Bohai Bay and Laizhou Bay. In loop approximation calculation, the TMAL obtained was considered satisfactory for water quality criteria as fluctuation of concentration response matrix with pollutant loads was eliminated. Results of numerical experiment further showed that water quality improved faster and were more evident under TMAL input than that when using the EPR method

  17. A Multivariate Model for Coastal Water Quality Mapping Using Satellite Remote Sensing Images

    PubMed Central

    Su, Yuan-Fong; Liou, Jun-Jih; Hou, Ju-Chen; Hung, Wei-Chun; Hsu, Shu-Mei; Lien, Yi-Ting; Su, Ming-Daw; Cheng, Ke-Sheng; Wang, Yeng-Fung

    2008-01-01

    This study demonstrates the feasibility of coastal water quality mapping using satellite remote sensing images. Water quality sampling campaigns were conducted over a coastal area in northern Taiwan for measurements of three water quality variables including Secchi disk depth, turbidity, and total suspended solids. SPOT satellite images nearly concurrent with the water quality sampling campaigns were also acquired. A spectral reflectance estimation scheme proposed in this study was applied to SPOT multispectral images for estimation of the sea surface reflectance. Two models, univariate and multivariate, for water quality estimation using the sea surface reflectance derived from SPOT images were established. The multivariate model takes into consideration the wavelength-dependent combined effect of individual seawater constituents on the sea surface reflectance and is superior over the univariate model. Finally, quantitative coastal water quality mapping was accomplished by substituting the pixel-specific spectral reflectance into the multivariate water quality estimation model.

  18. Stage-specific distribution models can predict eel (Anguilla anguilla) occurrence during settlement in coastal lagoons

    NASA Astrophysics Data System (ADS)

    Leone, C.; Zucchetta, M.; Capoccioni, F.; Gravina, M. F.; Franzoi, P.; Ciccotti, E.

    2016-03-01

    Eel (Anguilla anguilla) is a catadromous fish species typical of Mediterranean coastal lagoons, that currently suffers from several anthropogenic and natural impacts. These are thought to be the cause of a stock-wide decline that this panmictic species is facing, in inland and coastal waters of Europe and North Africa. The decline affects both adult phases and recruitment, i.e. glass eel arrival to coastal waters and their ascent to inland waters. Quantitative features of eel recruitment reflect a transoceanic global scale, but also depend on local environmental conditions, the latter also affecting settlement dynamics in transitional waters. There is only little information on the dynamics of these two processes in coastal lagoons, notwithstanding the paramount importance of both in sustaining local stocks abundance and their demographic structure for this typical but also economically important inhabitant of Mediterranean lagoons, habitats that constitute an important share of the eel distribution area. The present study aims, therefore, to clarify space and time dynamics of local scale recruitment and of settlement in a coastal lagoon in the Mediterranean area, also by setting up a specific methodological approach. For this purpose, data from field surveys in combination with Species Distribution Models (SDMs) have been used in order to relate distribution of eel juvenile stages to the environmental conditions within the lagoon. Specifically, models were calibrated to quantify the relationship between presence of juvenile eel and the main environmental drivers, with the aim of identifying potential habitats for eel settlement within the lagoon. Results gained by modelling suggest certain spatial and temporal colonization patterns for the juvenile eel in the Fogliano lagoon, a typical Mediterranean coastal lake. The modelling approach has therefore proved to be a useful tool for predicting habitats for eel recruitment at the local scale and settlement, because

  19. Using Satellite-derived Ice Concentration to Represent Antarctic Coastal Polynyas in Ocean Climate Models

    NASA Technical Reports Server (NTRS)

    Stoessel, Achim; Markus, Thorsten

    2003-01-01

    The focus of this paper is on the representation of Antarctic coastal polynyas in global ice-ocean general circulation models (OGCMs), in particular their local, regional, and high-frequency behavior. This is verified with the aid of daily ice concentration derived from satellite passive microwave data using the NASATeam 2 (NT2) and the bootstrap (BS) algorithms. Large systematic regional and temporal discrepancies arise, some of which are related to the type of convection parameterization used in the model. An attempt is made to improve the fresh-water flux associated with melting and freezing in Antarctic coastal polynyas by ingesting (assimilating) satellite ice concentration where it comes to determining the thermodynamics of the open-water fraction of a model grid cell. Since the NT2 coastal open-water fraction (polynyas) tends to be less extensive than the simulated one in the decisive season and region, assimilating NT2 coastal ice concentration yields overall reduced net freezing rates, smaller formation rates of Antarctic Bottom Water, and a stronger southward flow of North Atlantic Deep Water across 30 S. Enhanced net freezing rates occur regionally when NT2 coastal ice concentration is assimilated, concomitant with a more realistic ice thickness distribution and accumulation of High-Salinity Shelf Water. Assimilating BS rather than NT2 coastal ice concentration, the differences to the non-assimilated simulation are generally smaller and of opposite sign. This suggests that the model reproduces coastal ice concentration in closer agreement with the BS data than with the NT2 data, while more realistic features emerge when NT2 data are assimilated.

  20. Full uncertainty quantification of a regional N2O, NO, NH3 emission and NO3 leaching inventory using the biogeochemical model LandscapeDNDC

    NASA Astrophysics Data System (ADS)

    Santabarbara, Ignacio; Haas, Edwin

    2016-04-01

    Numerical simulation models are increasingly used to estimate greenhouse gas emissions at site to regional / national scale and are outlined as the most advanced methodology (Tier 3) in the framework of UNFCCC reporting. Process-based models incorporate the major processes of the carbon and nitrogen cycle of terrestrial ecosystems and are thus thought to be widely applicable at various spatial scales. Regional inventories require high spatial resolution input data on soil properties, climate drivers and management information. The acceptance of model based inventory calculations depends on the assessment of the inventory's uncertainty (model structure, initial condition data and parameter induced uncertainties). In this study we fully quantify uncertainty in regional simulation of the N cycle in arable, grassland and forest soils of Saxony (Germany) using the biogeochemical model LandscapeDNDC. We address model structural uncertainty (MU) by contrasting with Bayes factors two different soil biogeochemistry modules within LandscapeDNDC, the DNDC versus the MeTrx biogeochemistry process description. Initial conditions induced uncertainty (IU) was addressed with the parameter distribution obtained by a Bayesian calibration of soil properties, climate drivers and management practices. The parameter induced uncertainty (PU) was assessed by using a joint parameter distribution for key parameters describing microbial C and N turnover processes as obtained also by a Bayesian calibration study. Once the representative sample size from all parameters, initial conditions and model selection is set, we sampled the different configurations and used these to calculate individual realizations of the regional inventory. The ecosystems considered in this study (forest, arable and grasslands) are given spatially discretized into 8858 polygons (16058 km-2), each representing a unique land use and homogenous soil properties. For the overall uncertainty quantification we calculated

  1. Validating high-resolution California coastal flood modeling with Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR)

    NASA Astrophysics Data System (ADS)

    O'Neill, A.

    2015-12-01

    The Coastal Storm Modeling System (CoSMoS) is a numerical modeling scheme used to predict coastal flooding due to sea level rise and storms influenced by climate change, currently in use in central California and in development for Southern California (Pt. Conception to the Mexican border). Using a framework of circulation, wave, analytical, and Bayesian models at different geographic scales, high-resolution results are translated as relevant hazards projections at the local scale that include flooding, wave heights, coastal erosion, shoreline change, and cliff failures. Ready access to accurate, high-resolution coastal flooding data is critical for further validation and refinement of CoSMoS and improved coastal hazard projections. High-resolution Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) provides an exceptional data source as appropriately-timed flights during extreme tides or storms provide a geographically-extensive method for determining areas of inundation and flooding extent along expanses of complex and varying coastline. Landward flood extents are numerically identified via edge-detection in imagery from single flights, and can also be ascertained via change detection using additional flights and imagery collected during average wave/tide conditions. The extracted flooding positions are compared against CoSMoS results for similar tide, water level, and storm-intensity conditions, allowing for robust testing and validation of CoSMoS and providing essential feedback for supporting regional and local model improvement.

  2. Renewable Energy Production and Urban Remediation: Modeling the biogeochemical cycle at contaminated urban brownfields and the potential for renewable energy production and mitigation of greenhouse gases

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, G.

    2014-12-01

    Brownfields or urban sites that have been contaminated as a result of historic practices are present throughout the world. In the United States alone, the National Research Council has estimated that there are approximately 300,000 to 400,000 sites which have been contaminated by improper use and disposal of chemicals (NRC 1993). The land available at these sites is estimated at several million acres; however, the presence of high levels of contamination in the soil and groundwater makes it difficult to utilize these sites for traditional purposes such as agriculture. Further, the time required to remediate these contaminants to regulated levels is in the order of decades, which often results in long-term economic consequences for the areas near these sites. There has been significant interest in developing these sites as potential sources of renewable energy production in order to increase the economic viability of these sites and to provide alternative land resources for renewable energy production (EPA 2012). Solar energy, wind energy, and bioenergy from lignocellulosic biomass production have been identified as the main sources of renewable energy that can be produced at these locations. However, the environmental impacts of such a policy and the implications for greenhouse gas emissions, particularly resulting from changes in land-use impacting the biogeochemical cycle at these sites, have not been studied extensively to date. This study uses the biogeochemical process-based model DNDC to simulate carbon sequestration, nitrous oxide emissions and methane emissions from typical urban brownfield systems in the United States, when renewable energy systems are deployed. Photovoltaic solar energy and lignocellulosic biomass energy systems are evaluated here. Plants modeled include those most widely used for both bioenergy and remediation such as woody trees. Model sensitivity to soil conditions, contaminant levels and local weather data and the resulting impacts on

  3. High-resolution modelling of 3D hydrodynamics in coastal archipelagos

    NASA Astrophysics Data System (ADS)

    Miettunen, Elina; Tuomi, Laura; Ropponen, Janne; Lignell, Risto

    2016-04-01

    Dynamics of the coastal seas are affected by eutrophication, over-fishing, coastal construction and climate change. To enable the sustainable development of these areas, monitoring and modelling of the state of the sea are needed. The Archipelago Sea, located in the northern part of the semi-enclosed and brackish water Baltic Sea, is one of the most complex coastal areas with over 40 000 small islands and islets. It is also very vulnerable area already heavily stressed with eutrophication. Applicable modelling tools are needed to support the decision making and to provide sufficiently reliable information on the effects of the planned actions on the state of the coastal waters. We used 3D hydrodynamic model COHERENS to model the Archipelago Sea area with high spatial resolution of 0.25 nmi. Boundary conditions for this limited area were provided from coarser resolution, 2 nmi, Baltic Sea grid. In order to evaluate the performance of the high-resolution coastal model implementation a comprehensive measurement dataset was gathered, including hydrographic data from three intensive monitoring stations and several more rarely visited monitoring or research stations. The hydrodynamic model was able to simulate the surface temperature and salinity fields and their seasonal variation with good accuracy in this complex area. The sharp depth gradients typical for this area provided some challenges to the modelling. There was some over mixing and related to too strong vertical currents in the steep slopes of the deeper fault lines. Also the water exchange between the more open sea and coastal areas through narrow channels between the islands is not sufficiently well reproduced with the current resolution, leading to too high bottom temperatures.

  4. Integrated modeling framework to quantify the coastal protection services supplied by vegetation

    NASA Astrophysics Data System (ADS)

    Guannel, Greg; Ruggiero, Peter; Faries, Joe; Arkema, Katie; Pinsky, Malin; Gelfenbaum, Guy; Guerry, Anne; Kim, Choong-Ki

    2015-01-01

    can protect communities by reducing nearshore wave height and altering sediment transport processes. However, quantitative approaches for evaluating the coastal protection services, or benefits, supplied by vegetation to people in a wide range of coastal environments are lacking. To begin to fill this knowledge gap, we propose an integrated modeling approach for quantifying how vegetation modifies nearshore processes—including the attenuation of wave height, mean and total water level—and reduces shoreline erosion during storms. We apply the model to idealized seagrass-sand and mangrove-mud cases, and illustrate its potential by quantifying how those habitats reduce water levels and sediment loss beyond what would be observed in the absence of vegetation. The integrated modeling approach provides an efficient way to quantify the coastal protection services supplied by vegetation and highlights specific research needs for improved representations of the ways in which vegetation modifies wave-induced processes.

  5. Modeling Black Sea circulation with high resolution in the coastal zone

    NASA Astrophysics Data System (ADS)

    Zalesnyi, V. B.; Gusev, A. V.; Agoshkov, V. I.

    2016-05-01

    We present a numerical model of Black Sea circulation based on primitive equations with improved spatial resolution in the coastal zone. The model equations are formulated in a two-pole orthogonal coordinate system with arbitrary locations of the poles and a vertical σ coordinate. Increased horizontal resolution is gained by displacing the pole into the vicinity of the separated subdomain. The problem is solved over a grid with a variable step. The northern coordinate pole is displaced to the vicinity of Gelendzhik; the grid step varies from 150 m in the coastal zone to 4.6 km in the main basin. We simulated the fields of currents, sea level, temperature, and salinity under the given atmospheric forcing in 2007. The model is capable of reproducing the large-scale Black Sea circulation and submesoscale variations in the coastal currents.

  6. Towards tracer-aided spatially distributed models of catchment storage and mixing to predict non-stationary hydrologic and biogeochemical response

    NASA Astrophysics Data System (ADS)

    Soulsby, Chris; van Huijgevoort, Marjolein; Dick, Jonathan; Birkel, Christian; Tetzlaff, Doerthe

    2016-04-01

    To develop a spatially distributed understanding of the linkages between storage dynamics, mixing processes and non-stationary watershed response we have used diverse, intensive data sets collected in a small montane catchment to both inform and test hydrological and water quality models. At the core of these efforts has been the use of ~6 years of daily isotope data in precipitation and stream flow to inform the calibration and testing of coupled flow-tracer models that constrain storage estimates, mixing processes and hydrologic fluxes in the dominant landscape units as well as simulating discharge and stream isotopes. LiDAR surveys have been used to extend this approach using a high resolution DTM to facilitate a Spatially distributed Tracer-Aided Rainfall-Runoff model (STARR). This provides a flexible, generic approach that allows us to track and visualise aggregated storage changes, mixing processes, and the fluxes and age distribution of water across spatio-temporal scales. The modelling framework provides a basis for assessing the effects of hydroclimatic variability on the non-stationary nature of catchment hydrological function by simulating the spatial variation in tracer composition of different source waters and flow paths. This is tested against extensive (over 120 sites) synoptic surveys of multiple-tracers in soil water, groundwater and stream water repeated under contrasting states of catchment storage when different flow paths are activated. The modelling approach can reproduce the major spatio-temporal differences in isotopes, dissolved organic (DOC) and alkalinity reasonably well and thus, has potential to be adapted for biogeochemical modelling. This potential is explored in relation to daily DOC simulations over prolonged (2 year) periods. The transferability of the modelling approach to other sites is also tested.

  7. Assessment of coastal management options by means of multilayered ecosystem models

    NASA Astrophysics Data System (ADS)

    Nobre, Ana M.; Ferreira, João G.; Nunes, João P.; Yan, Xiaojun; Bricker, Suzanne; Corner, Richard; Groom, Steve; Gu, Haifeng; Hawkins, Anthony J. S.; Hutson, Rory; Lan, Dongzhao; Silva, João D. Lencart e.; Pascoe, Philip; Telfer, Trevor; Zhang, Xuelei; Zhu, Mingyuan

    2010-03-01

    This paper presents a multilayered ecosystem modelling approach that combines the simulation of the biogeochemistry of a coastal ecosystem with the simulation of the main forcing functions, such as catchment loading and aquaculture activities. This approach was developed as a tool for sustainable management of coastal ecosystems. A key feature is to simulate management scenarios that account for changes in multiple uses and enable assessment of cumulative impacts of coastal activities. The model was applied to a coastal zone in China with large aquaculture production and multiple catchment uses, and where management efforts to improve water quality are under way. Development scenarios designed in conjunction with local managers and aquaculture producers include the reduction of fish cages and treatment of wastewater. Despite the reduction in nutrient loading simulated in three different scenarios, inorganic nutrient concentrations in the bay were predicted to exceed the thresholds for poor quality defined by Chinese seawater quality legislation. For all scenarios there is still a Moderate High to High nutrient loading from the catchment, so further reductions might be enacted, together with additional decreases in fish cage culture. The model predicts that overall, shellfish production decreases by 10%-28% using any of these development scenarios, principally because shellfish growth is being sustained by the substances to be reduced for improvement of water quality. The model outcomes indicate that this may be counteracted by zoning of shellfish aquaculture at the ecosystem level in order to optimize trade-offs between productivity and environmental effects. The present case study exemplifies the value of multilayered ecosystem modelling as a tool for Integrated Coastal Zone Management and for the adoption of ecosystem approaches for marine resource management. This modelling approach can be applied worldwide, and may be particularly useful for the application of

  8. Biogeochemical cycling in the ocean. Part 1: Introduction to the effects of upwelling along the west coast of North America

    NASA Technical Reports Server (NTRS)

    Howe, John T.

    1986-01-01

    Coastal upwelling is examined as it relates to the cycling of chemical species in coastal waters along the west coast of North America. The temporal and spatial features of upwelling phenomena in the Eastern boundary regions of the North Pacific Ocean are presented and discussed in terms of upwelling episodes. Climate conditions affecting upwelling include: thermal effects, wind-induced shear stress which moves surface layers, and the curl of the wind stress vector which is thought to affect the extent and nature of upwelling and the formation of offshore convergent downwelling fronts. These effects and the interaction of sunlight and upwelled nutrients which result in a biological bloom in surface waters is modeled analytically. The roles of biological and chemical species, including the effects of predation, are discussed in that context, and relevant remote sensing and in situ observations are presented. Climatological, oceanographic, biological, physical, chemical events, and processes that pertain to biogeochemical cycling are presented and described by a set of partial differential equations. Simple preliminary results are obtained and are compared with data. Thus a fairly general framework has been laid where the many facets of biogeochemical cycling in coastal upwelled waters can be examined in their relationship to one another, and to the whole, to whatever level of detail or approximation is warranted or desired.

  9. The Framework of a Coastal Hazards Model - A Tool for Predicting the Impact of Severe Storms

    USGS Publications Warehouse

    Barnard, Patrick L.; O'Reilly, Bill; van Ormondt, Maarten; Elias, Edwin; Ruggiero, Peter; Erikson, Li H.; Hapke, Cheryl; Collins, Brian D.; Guza, Robert T.; Adams, Peter N.; Thomas, Julie

    2009-01-01

    The U.S. Geological Survey (USGS) Multi-Hazards Demonstration Project in Southern California (Jones and others, 2007) is a five-year project (FY2007-FY2011) integrating multiple USGS research activities with the needs of external partners, such as emergency managers and land-use planners, to produce products and information that can be used to create more disaster-resilient communities. The hazards being evaluated include earthquakes, landslides, floods, tsunamis, wildfires, and coastal hazards. For the Coastal Hazards Task of the Multi-Hazards Demonstration Project in Southern California, the USGS is leading the development of a modeling system for forecasting the impact of winter storms threatening the entire Southern California shoreline from Pt. Conception to the Mexican border. The modeling system, run in real-time or with prescribed scenarios, will incorporate atmospheric information (that is, wind and pressure fields) with a suite of state-of-the-art physical process models (that is, tide, surge, and wave) to enable detailed prediction of currents, wave height, wave runup, and total water levels. Additional research-grade predictions of coastal flooding, inundation, erosion, and cliff failure will also be performed. Initial model testing, performance evaluation, and product development will be focused on a severe winter-storm scenario developed in collaboration with the Winter Storm Working Group of the USGS Multi-Hazards Demonstration Project in Southern California. Additional offline model runs and products will include coastal-hazard hindcasts of selected historical winter storms, as well as additional severe winter-storm simulations based on statistical analyses of historical wave and water-level data. The coastal-hazards model design will also be appropriate for simulating the impact of storms under various sea level rise and climate-change scenarios. The operational capabilities of this modeling system are designed to provide emergency planners with

  10. User's guide to the Offshore and Coastal Dispersion (OCD) Model; (revised 1988)

    SciTech Connect

    Hanna, S.R.; Schulman, L.L.; Paine, R.J.; Pleim, J.E.

    1988-01-01

    The Offshore Coastal Dispersion (OCD) Model was adapted from the EPA guideline model MPTER to simulate the effect of offshore emissions from point sources in coastal regions. Modifications were made to incorporate overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. Hourly meteorological data are needed from overwater and overland locations. Turbulence intensities are used but are not mandatory. For overwater dispersion, the turbulence intensities are parameterized from boundary-layer similarity relationships if they are not measured.

  11. Development of a Coupled Ocean-Hydrologic Model to Simulate Pollutant Transport in Singapore Coastal Waters

    NASA Astrophysics Data System (ADS)

    Chua, V. P.

    2015-12-01

    Intensive agricultural, economic and industrial activities in Singapore and Malaysia have made our coastal areas under high risk of water pollution. A coupled ocean-hydrologic model is employed to perform three-dimensional simulations of flow and pollutant transport in Singapore coastal waters. The hydrologic SWAT model is coupled with the coastal ocean SUNTANS model by outputting streamflow and pollutant concentrations from the SWAT model and using them as inputs for the SUNTANS model at common boundary points. The coupled model is calibrated with observed sea surface elevations and velocities, and high correlation coefficients that exceed 0.97 and 0.91 are found for sea surface elevations and velocities, respectively. The pollutants are modeled as Gaussian passive tracers, and are released at five upstream locations in Singapore coastal waters. During the Northeast monsoon, pollutants released in Source 1 (Johor River), Source 2 (Tiram River), Source 3 (Layang River) and Source 4 (Layau River) enter the Singapore Strait after 4 days of release and reach Sentosa Island within 9 days. Meanwhile, pollutants released in Source 5 (Kallang River) reach Sentosa Island after 4 days. During the Southwest monsoon, the dispersion time is roughly doubled, with pollutants from Sources 1 - 4 entering the Singapore Strait only after 12 days of release due to weak currents.

  12. Modelling coastal low-level wind-jets: does horizontal resolution matter?

    NASA Astrophysics Data System (ADS)

    Ranjha, Raza; Tjernström, Michael; Svensson, Gunilla; Semedo, Alvaro

    2016-04-01

    Atmospheric flows in coastal regions are impacted by land-sea temperature contrasts, complex terrain, shape of the coastline, among many things. Along the west coast of central North America, winds in the boundary layer are mainly from north or northwest, roughly parallel to the coastline. Frequently, the coastal low-level wind field is characterized by a sharp wind maximum along the coast in the lowest kilometre. This feature, commonly referred to as a coastal low-level jet (CLLJ), has significant impact on the climatology of the coastal region and affects many human activities in the littoral zone. Hence, a good understanding and forecasting of CLLJs are vital. This study evaluates the issue of proper mesoscale numerical model resolution to describe the physics of a CLLJ, and its impact on the upper ocean. The COAMPS® model is used for a summer event to determine the realism of the model results compared to observations, from an area of supercritical flow adjustment between Pt. Sur and Pt. Conception, California. Simulations at different model horizontal resolutions, from 54 to 2 km are performed. While the model produces realistic results with increasing details at higher resolution, the results do not fully converge even at a resolution of only few kilometres and an objective analysis of model errors do not show an increased skill with increasing resolution. Based on all available information, a compromise resolution appears to be at least 6 km. New methods may have to be developed to evaluate models at very high resolution.

  13. Biogeochemical drivers of phosphatase activity in salt marsh sediments

    NASA Astrophysics Data System (ADS)

    Freitas, Joana; Duarte, Bernardo; Caçador, Isabel

    2014-10-01

    Although nitrogen has become a major concern for wetlands scientists dealing with eutrophication problems, phosphorous represents another key element, and consequently its biogeochemical cycling has a crucial role in eutrophication processes. Microbial communities are a central component in trophic dynamics and biogeochemical processes on coastal systems, since most of the processes in sediments are microbial-mediated due to enzymatic action, including the mineralization of organic phosphorus carried out by acid phosphatase activity. In the present work, the authors investigate the biogeochemical sediment drivers that control phosphatase activities. Authors also aim to assess biogeochemical factors' influence on the enzyme-mediated phosphorous cycling processes in salt marshes. Plant rhizosediments and bare sediments were collected and biogeochemical features, including phosphatase activities, inorganic and organic phosphorus contents, humic acids content and pH, were assessed. Acid phosphatase was found to give the highest contribution for total phosphatase activity among the three pH-isoforms present in salt marsh sediments, favored by acid pH in colonized sediments. Humic acids also appear to have an important role inhibiting phosphatase activity. A clear relation of phosphatase activity and inorganic phosphorous was also found. The data presented reinforces the role of phosphatase in phosphorous cycling.

  14. A statistical model for water quality predictions from a river discharge using coastal observations

    NASA Astrophysics Data System (ADS)

    Kim, S.; Terrill, E. J.

    2007-12-01

    Understanding and predicting coastal ocean water quality has benefits for reducing human health risks, protecting the environment, and improving local economies which depend on clean beaches. Continuous observations of coastal physical oceanography increase the understanding of the processes which control the fate and transport of a riverine plume which potentially contains high levels of contaminants from the upstream watershed. A data-driven model of the fate and transport of river plume water from the Tijuana River has been developed using surface current observations provided by a network of HF radar operated as part of a local coastal observatory that has been in place since 2002. The model outputs are compared with water quality sampling of shoreline indicator bacteria, and the skill of an alarm for low water quality is evaluated using the receiver operating characteristic (ROC) curve. In addition, statistical analysis of beach closures in comparison with environmental variables is also discussed.

  15. Comparison of Greenhouse Gas Emissions between Two Dairy Farm Systems (Conventional vs. Organic Management) in New Hampshire Using the Manure DNDC Biogeochemical Model

    NASA Astrophysics Data System (ADS)

    Dorich, C.; Contosta, A.; Li, C.; Brito, A.; Varner, R. K.

    2013-12-01

    Agriculture contributes 20 to 25 % of the total anthropogenic greenhouse gas (GHG) emissions globally. These agricultural emissions are primarily in the form of methane (CH4) and nitrous oxide (N2O) with these GHG accounting for roughly 40 and 80 % of the total anthropogenic emissions of CH4 and N2O, respectively. Due to varied management and the complexities of agricultural ecosystems, it is difficult to estimate these CH4 and N2O emissions. The IPCC emission factors can be used to yield rough estimates of CH4 and N2O emissions but they are often based on limited data. Accurate modeling validated by measurements is needed in order to identify potential mitigation areas, reduce GHG emissions from agriculture, and improve sustainability of farming practices. The biogeochemical model Manure DNDC was validated using measurements from two dairy farms in New Hampshire, USA in order to quantify GHG emissions under different management systems. One organic and one conventional dairy farm operated by the University of New Hampshire's Agriculture Experiment Station were utilized as the study sites for validation of Manure DNDC. Compilation of management records started in 2011 to provide model inputs. Model results were then compared to field collected samples of soil carbon and nitrogen, above-ground biomass, and GHG fluxes. Fluxes were measured in crop, animal, housing, and waste management sites on the farms in order to examine the entire farm ecosystem and test the validity of the model. Fluxes were measured by static flux chambers, with enteric fermentation measurements being conducted by the SF6 tracer test as well as a new method called Greenfeeder. Our preliminary GHG flux analysis suggests higher emissions than predicted by IPCC emission factors and equations. Results suggest that emissions from manure management is a key concern at the conventional dairy farm while bedded housing at the organic dairy produced large quantities of GHG.

  16. Biogeochemical Modeling of In Situ U(VI) Reduction and Immobilization with Emulsified Vegetable Oil as the Electron Donor at a Field Site in Oak Ridge, Tennessee

    NASA Astrophysics Data System (ADS)

    Tang, G.; Parker, J.; Wu, W.; Schadt, C. W.; Watson, D. B.; Brooks, S. C.; Orifrc Team

    2011-12-01

    A comprehensive biogeochemical model was developed to quantitatively describe the coupled hydrologic, geochemical and microbiological processes that occurred following injection of emulsified vegetable oil (EVO) as the electron donor to immobilize U(VI) at the Oak Ridge Integrated Field Research Challenge site (ORIFRC) in Tennessee. The model couples the degradation of EVO, production and oxidation of long-chain fatty acids (LCFA), glycerol, hydrogen and acetate, reduction of nitrate, manganese, ferrous iron, sulfate and uranium, and methanoganesis with growth of multiple microbial groups. The model describes the evolution of geochemistry and microbial populations not only in the aqueous phase as typically observed, but also in the mineral phase and therefore enables us to evaluate the applicability of rates from the literature for field scale assessment, estimate the retention and degradation rates of EVO and LCFA, and assess the influence of the coupled processes on fate and transport of U(VI). Our results suggested that syntrophic bacteria or metal reducers might catalyze LCFA oxidation in the downstream locations when sulfate was consumed, and competition between methanogens and others for electron donors and slow growth of methanogen might contribute to the sustained reducing condition. Among the large amount of hydrologic, geochemical and microbiological parameter values, the initial biomass, and the interactions (e.g., inhibition) of the microbial functional groups, and the rate and extent of Mn and Fe oxide reduction appear as the major sources of uncertainty. Our model provides a platform to conduct numerical experiments to study these interactions, and could be useful for further iterative experimental and modeling investigations into the bioreductive immobiliztion of radionuclide and metal contaminants in the subsurface.

  17. Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies

    PubMed Central

    Stegen, James C.; Konopka, Allan; McKinley, James P.; Murray, Chris; Lin, Xueju; Miller, Micah D.; Kennedy, David W.; Miller, Erin A.; Resch, Charles T.; Fredrickson, Jim K.

    2016-01-01

    Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies—oxidized, reduced, and transition—within one lithofacies and elucidate relationships among facies features and microbial community biomass, richness, and composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial richness—the number of microbial taxa—was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions. PMID:27469056

  18. Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies.

    PubMed

    Stegen, James C; Konopka, Allan; McKinley, James P; Murray, Chris; Lin, Xueju; Miller, Micah D; Kennedy, David W; Miller, Erin A; Resch, Charles T; Fredrickson, Jim K

    2016-01-01

    Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies-oxidized, reduced, and transition-within one lithofacies and elucidate relationships among facies features and microbial community biomass, richness, and composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial richness-the number of microbial taxa-was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions. PMID:27469056

  19. Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies

    NASA Astrophysics Data System (ADS)

    Stegen, James C.; Konopka, Allan; McKinley, James P.; Murray, Chris; Lin, Xueju; Miller, Micah D.; Kennedy, David W.; Miller, Erin A.; Resch, Charles T.; Fredrickson, Jim K.

    2016-07-01

    Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies—oxidized, reduced, and transition—within one lithofacies and elucidate relationships among facies features and microbial community biomass, richness, and composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial richness—the number of microbial taxa—was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions.

  20. Review: Simulation-optimization models for the management and monitoring of coastal aquifers

    NASA Astrophysics Data System (ADS)

    Sreekanth, J.; Datta, Bithin

    2015-09-01

    The literature on the application of simulation-optimization approaches for management and monitoring of coastal aquifers is reviewed. Both sharp- and dispersive-interface modeling approaches have been applied in conjunction with optimization algorithms in the past to develop management solutions for saltwater intrusion. Simulation-optimization models based on sharp-interface approximation are often based on the Ghyben-Herzberg relationship and provide an efficient framework for preliminary designs of saltwater-intrusion management schemes. Models based on dispersive-interface numerical models have wider applicability but are challenged by the computational burden involved when applied in the simulation-optimization framework. The use of surrogate models to substitute the physically based model during optimization has been found to be successful in many cases. Scalability is still a challenge for the surrogate modeling approach as the computational advantage accrued is traded-off with the training time required for the surrogate models as the problem size increases. Few studies have attempted to solve stochastic coastal-aquifer management problems considering model prediction uncertainty. Approaches that have been reported in the wider groundwater management literature need to be extended and adapted to address the challenges posed by the stochastic coastal-aquifer management problem. Similarly, while abundant literature is available on simulation-optimization methods for the optimal design of groundwater monitoring networks, applications targeting coastal aquifer systems are rare. Methods to optimize compliance monitoring strategies for coastal aquifers need to be developed considering the importance of monitoring feedback information in improving the management strategies.

  1. Advanced geological modeling of coastal-marine cassiterite placers based on data on deposits in Russia'S Eastern Arctic Region

    NASA Astrophysics Data System (ADS)

    Lalomov, A. V.; Tabolich, S. E.; Chefranov, R. M.

    2016-03-01

    A mathematical model of coastal-marine tin placers formed in the alongshore drift flow is developed using the mass balance method. The physical meaning of the coefficients included in the model is considered. Coastal-marine placers are quantitatively estimated. The simulation adequacy is confirmed by the data on coastal-marine tin-bearing placer deposits at the Pevek ore cluster (Chaun Bay, East Siberian Sea). We suggest that the obtained equations be used for surveying and exploration. Identified patterns are used to estimate the tin placer potential in one of the coastal areas in the Eastern Arctic Basin.

  2. Integrated water system simulation by considering hydrological and biogeochemical processes: model development, with parameter sensitivity and autocalibration

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Y.; Shao, Q. X.; Ye, A. Z.; Xing, H. T.; Xia, J.

    2016-02-01

    Integrated water system modeling is a feasible approach to understanding severe water crises in the world and promoting the implementation of integrated river basin management. In this study, a classic hydrological model (the time variant gain model: TVGM) was extended to an integrated water system model by coupling multiple water-related processes in hydrology, biogeochemistry, water quality, and ecology, and considering the interference of human activities. A parameter analysis tool, which included sensitivity analysis, autocalibration and model performance evaluation, was developed to improve modeling efficiency. To demonstrate the model performances, the Shaying River catchment, which is the largest highly regulated and heavily polluted tributary of the Huai River basin in China, was selected as the case study area. The model performances were evaluated on the key water-related components including runoff, water quality, diffuse pollution load (or nonpoint sources) and crop yield. Results showed that our proposed model simulated most components reasonably well. The simulated daily runoff at most regulated and less-regulated stations matched well with the observations. The average correlation coefficient and Nash-Sutcliffe efficiency were 0.85 and 0.70, respectively. Both the simulated low and high flows at most stations were improved when the dam regulation was considered. The daily ammonium-nitrogen (NH4-N) concentration was also well captured with the average correlation coefficient of 0.67. Furthermore, the diffuse source load of NH4-N and the corn yield were reasonably simulated at the administrative region scale. This integrated water system model is expected to improve the simulation performances with extension to more model functionalities, and to provide a scientific basis for the implementation in integrated river basin managements.

  3. Investigating the interactions between biogeophysical and biogeochemical processes in the northern high latitudes using a land surface model; feedbacks and climatic impacts

    NASA Astrophysics Data System (ADS)

    Barman, R.; Jain, A.; Liang, M.; McGuire, A. D.

    2010-12-01

    The dynamics of carbon fluxes in the permafrost region is likely to have tremendous impacts for the future global climate. Recently, several ecosystem and land surface models have demonstrated improved permafrost modeling capabilities by incorporating deep soil layers, organic soils, and parameterizing the effects of wind compaction and depth hoar formations, which influence high latitude soil biogeophysics. However, no global study has yet incorporated the combined effects of these biogeophysical improvements. Additionally, the primary focus has been on modeling biogeophysical fluxes rather than on how biogeochemical processes and feedbacks are impacted. In this study, we evaluate how biogeochemistry (carbon and nitrogen dynamics) responds to improved biogeophysics in the high latitudes. We employ a land surface model, the Integrated Science Assessment Model (ISAM), to model the fluxes of water, energy and carbon, as well as the change in active layer depths during the historical period. The ISAM represents fully prognostic carbon and nitrogen cycles, coupled with biogeophysics schemes adapted selectively from other land surface models such as the Community Land Model (CLM3.5) and the Common Land Model (CoLM). The soil decomposition module in the ISAM was calibrated with field experiment data, which includes representation of nitrogen mineralization processes. Additionally, biogeophysical improvements such as the inclusion of deep soils, organic soils, wind compaction and depth hoar formation effects, which are critical for high-latitude soil thermal dynamics, have been incorporated into the model. The performance of the model is evaluated using observations for active layer depths and carbon fluxes, together with recent estimates for total soil carbon amount in the permafrost region. This is one of the first studies to explore the combined effects of improvements in biogeophysics, coupled with a detailed model of soil carbon and nitrogen dynamics, for the entire

  4. Catchment Legacies and Trajectories: Hydrologic and Biogeochemical Controls

    NASA Astrophysics Data System (ADS)

    Basu, N. B.; Loukinova, N. V.

    2012-04-01

    Increased nutrient loads delivered from watersheds due to agricultural intensification, industrialization, and urbanization have contributed to the persistence of large hypoxic zones in inland and coastal waters at a global scale. Watershed management practices to target these non-point source pollutants have reportedly resulted in little or no improvement in water quality, even after extensive implementation of conservation measures or Best Management Practices (BMPs). The lag time between implementation of a conservation measure and resultant water quality benefits has recently been recognized as an important factor in the "apparent" failure of these BMPs. Conservation measures are often implemented without explicit consideration of the lag time and with the expectation that they will lead to immediate benefits; the resulting failure to meet such expectations then discourages vital restoration efforts. In order to address this problem, it is important to quantify the lag times associated with watershed management efforts a priori and to implement restoration strategies that are targeted specifically at minimizing lag times as well as maximizing restoration benefits. The focus of this research is to develop an analytical framework for understanding the time lags between land use changes and stream water quality benefits. Watershed lag times are a function of coupled hydrologic and biogeochemical factors that modify pollutant loads as these pollutants are transported through the landscape. Hydrologic factors include the pathways of delivery of the solute to streams (e.g., overland flow, tile flow, or groundwater pathways), and the distribution of travel times along the pathways. Biogeochemical factors include the reactivity of the pollutant, and whether there are internal sources of the pollutant within the landscape. Results of a data synthesis effort of the MARB and the Baltic Basin indicate that landscapes having been subject to fertilizer application for

  5. Studying Uncertainties in Climate-Terrestrial Biogeochemical Feedbacks in the Northern High Latitudes using a Flexible Earth System Modeling Framework

    NASA Astrophysics Data System (ADS)

    Barman, R.; Hoffman, F. M.; Lawrence, D. M.; Song, Y.; Meiyappan, P.; Jain, A. K.; Jacob, R. L.; Vertenstein, M.

    2011-12-01

    Uncertainties in the representation of terrestrial biogeochemistry in land surface models (LSMs), together with their long spin-up time requirements, contribute to the many challenges inherent in coupled Earth system models (ESMs). Here we present a recently developed ESM framework, designed to incorporate multiple LSMs into an existing ESM. This ISAM-CESM framework provides an alternative LSM, the Integrated Science Assessment Model (ISAM), coupled to the NCAR Community Earth System Model (CESM1). The purpose of this general modeling framework is to carry out equivalent climate simulations using multiple LSMs with the rest of the component models being the same, allowing a more direct comparison of the effects of different land surface representations on corresponding feedbacks to climate change. In this presentation, we will analyze the role of different biogeochemistry representations and the effects of different land surface processes on climate-carbon cycle feedbacks using the ISAM and the NCAR Community Land Model (CLM4), the two LSMs currently available in the ISAM-CESM framework. Both ISAM and CLM4 contain fully prognostic, coupled carbon-nitrogen models, integrated with detailed representation of terrestrial biogeophysics. Biogeophysical schemes in the ISAM have been adapted from the CLM4, its precursor CLM3.5, and the Common Land Model (CoLM); however, the representation of the biogeochemistry of carbon nitrogen cycles are structurally different in the two models, making them suitable for inter-comparison. The aim of this study is to understand those differences and better attribute their roles in varying responses of the land surface to future climate change. We will compare the 20th century predictions of gross primary productivity (GPP) and annual cycle of CO2 from offline land simulations of ISAM and CLM4, using the newly available CRU-NCEP climate forcing data, in the CESM1 modeling framework to study the response of alternate land surface models

  6. The application of an integrated biogeochemical model (PnET-BGC) to five forested watersheds in the Adirondack and Catskill regions of New York

    USGS Publications Warehouse

    Chen, L.; Driscoll, C.T.; Gbondo-Tugbawa, S.; Mitchell, M.J.; Murdoch, Peter S.

    2004-01-01

    PnET-BGC is an integrated biogeochemical model formulated to simulate the response of soil and surface waters in northern forest ecosystems to changes in atmospheric deposition and land disturbances. In this study, the model was applied to five intensive study sites in the Adirondack and Catskill regions of New York. Four were in the Adirondacks: Constable Pond, an acid-sensitive watershed; Arbutus Pond, a relatively insensitive watershed; West Pond, an acid-sensitive watershed with extensive wetland coverage; and Willy's Pond, an acid-sensitive watershed with a mature forest. The fifth was Catskills: Biscuit Brook, an acid-sensitive watershed. Results indicated model-simulated surface water chemistry generally agreed with the measured data at all five sites. Model-simulated internal fluxes of major elements at the Arbutus watershed compared well with previously published measured values. In addition, based on the simulated fluxes, element and acid neutralizing capacity (ANC) budgets were developed for each site. Sulphur budgets at each site indicated little retention of inputs of sulphur. The sites also showed considerable variability in retention of NO3-. Land-disturbance history and in-lake processes were found to be important in regulating the output of NO3- via surface waters. Deposition inputs of base cations were generally similar at these sites. Various rates of base cation outputs reflected differences in rates of base cation supply at these sites. Atmospheric deposition was found to be the largest source of acidity, and cation exchange, mineral weathering and in-lake processes served as sources of ANC. ?? 2004 John Wiley and Sons, Ltd.

  7. Coastal flooding and storm protection program; field verification program. Mathematical modeling of three-dimensional coastal currents and sediment dispersion: model development and application. Final report

    SciTech Connect

    Sheng, Y.P.

    1983-09-01

    A comprehensive model of Coastal currents and sediment dispersion has been formulated and applied to the Mississippi Sound and adjacent continental shelf waters. The study combines mathematical modeling of various hydrodynamic and sedimentary processes with laboratory and field experiments. Of primary importance is the development of an efficient and comprehensive three-dimensional, finite-difference model of coastal, estuarine, and lake currents (CELC3D). The model resolves currents driven by tide, wind, and density gradient. It has been applied to the Mississippi Sound, and results agree well with measured surface displacements and currents during two episodes. Rates of entrainment and deposition of the Mississippi Sound sediments have been studied in a laboratory flume. Effects of (1) bottom shear stress, (2) bed properties, (3) salinity of water, and (4) sediment type on the erodability of sediments have been examined. Results of the laboratory study have been incorporated into the bottom boundary conditions for a three-dimensional sediment dispersion model. Gravitational settling and particle size distribution of the Mississippi Sound sediments were also studied in laboratories. Bottom boundary layer dynamics and wave effect on sediment dispersion have been studied by means of a turbulent transport model and a wave model. Model simulations of sediment dispersion in the Mississippi Sound agree well available data from ship surveys.

  8. A Dynamic Flood Inundation Model Framework to Assess Coastal Flood Risk in a Changing Climate

    NASA Astrophysics Data System (ADS)

    Bilskie, M. V.; Hagen, S. C.; Passeri, D. L.; Alizad, K.; Medeiros, S. C.; Irish, J. L.

    2015-12-01

    Coastal regions around the world are susceptible to a variety of natural disasters causing extreme inundation. It is anticipated that the vulnerability of coastal cities will increase due to the effects of climate change, and in particular sea level rise (SLR). A novel framework was developed to generate a suite of physics-based storm surge models that include projections of coastal floodplain dynamics under climate change scenarios: shoreline erosion/accretion, dune morphology, salt marsh migration, and population dynamics. First, the storm surge inundation model was extensively validated for present day conditions with respect to astronomic tides and hindcasts of Hurricane Ivan (2004), Dennis (2005), Katrina (2005), and Isaac (2012). The model was then modified to characterize the future outlook of the landscape for four climate change scenarios for the year 2100 (B1, B2, A1B, and A2), and each climate change scenario was linked to a sea level rise of 0.2 m, 0.5 m, 1.2 m, and 2.0 m. The adapted model was then used to simulate hurricane storm surge conditions for each climate scenario using a variety of tropical cyclones as the forcing mechanism. The collection of results shows the intensification of inundation area and the vulnerability of the coast to potential future climate conditions. The methodology developed herein to assess coastal flooding under climate change can be performed across any coastal region worldwide, and results provide awareness of regions vulnerable to extreme flooding in the future. Note: The main theme behind this work is to appear in a future Earth's Future publication. Bilskie, M. V., S. C. Hagen, S. C. Medeiros, and D. L. Passeri (2014), Dynamics of sea level rise and coastal flooding on a changing landscape, Geophysical Research Letters, 41(3), 927-934. Parris, A., et al. (2012), Global Sea Level Rise Scenarios for the United States National Climate AssessmentRep., 37 pp. Passeri, D. L., S. C. Hagen, M. V. Bilskie, and S. C. Medeiros

  9. Modelling of an enhanced PAH attenuation experiment and associated biogeochemical changes at a former gasworks site in southern Germany.

    PubMed

    Herold, Maria; Greskowiak, Janek; Ptak, Thomas; Prommer, Henning

    2011-01-25

    Former manufactured gas plant sites often form a widespread contaminant source in the subsurface, leading to large plumes that contain a wide variety of tar-oil related compounds. Although most of these compounds eventually degrade naturally, the relevant processes tend to be slow and inefficient, often leaving active remediation as the only viable option to eliminate the risks of toxic substances to reach potential receptors such as surface waters or drinking water wells. In this study we use a reactive transport model to analyse the fate of a contaminant plume containing acenaphthene, methylbenzofurans and dimethylbenzofurans (i) prior to the installation of an active remediation scheme and (ii) for an enhanced remediation experiment during which O(2) and H(2)O(2) were added to the contaminated groundwater through a recirculation well. The numerical model developed for this study considers the primary contaminant degradation reactions (i.e., microbially mediated redox reactions) as well as secondary and competing mineral precipitation/dissolution reactions that affect the site's hydrochemistry and/or contaminant fate. The model was calibrated using a variety of constraints to test the uncertainty on model predictions resulting from the undocumented presence of reductants such as pyrite. The results highlight the important role of reactive transport modelling for the development of a comprehensive process understanding. PMID:20947201

  10. Modelling of an enhanced PAH attenuation experiment and associated biogeochemical changes at a former gasworks site in southern Germany

    NASA Astrophysics Data System (ADS)

    Herold, Maria; Greskowiak, Janek; Ptak, Thomas; Prommer, Henning

    2011-01-01

    Former manufactured gas plant sites often form a widespread contaminant source in the subsurface, leading to large plumes that contain a wide variety of tar-oil related compounds. Although most of these compounds eventually degrade naturally, the relevant processes tend to be slow and inefficient, often leaving active remediation as the only viable option to eliminate the risks of toxic substances to reach potential receptors such as surface waters or drinking water wells. In this study we use a reactive transport model to analyse the fate of a contaminant plume containing acenaphthene, methylbenzofurans and dimethylbenzofurans (i) prior to the installation of an active remediation scheme and (ii) for an enhanced remediation experiment during which O 2 and H 2O 2 were added to the contaminated groundwater through a recirculation well. The numerical model developed for this study considers the primary contaminant degradation reactions (i.e., microbially mediated redox reactions) as well as secondary and competing mineral precipitation/dissolution reactions that affect the site's hydrochemistry and/or contaminant fate. The model was calibrated using a variety of constraints to test the uncertainty on model predictions resulting from the undocumented presence of reductants such as pyrite. The results highlight the important role of reactive transport modelling for the development of a comprehensive process understanding.

  11. Modeling for Policy Change: A Feedback Perspective on Improving the Effectiveness of Coastal and Marine Management

    ERIC Educational Resources Information Center

    Robadue, Donald D., Jr.

    2012-01-01

    Those advocating for effective management of the use of coastal areas and ecosystems have long aspired for an approach to governance that includes information systems with the capability to predict the end results of various courses of action, monitor the impacts of decisions and compare results with those predicted by computer models in order to…

  12. Linking nutrient loading and oxygen in the coastal ocean: A new global scale model

    NASA Astrophysics Data System (ADS)

    Reed, Daniel C.; Harrison, John A.

    2016-03-01

    Recent decades have witnessed an exponential spread of low-oxygen regions in the coastal ocean due at least in-part to enhanced terrestrial nutrient inputs. As oxygen deprivation is a major stressor on marine ecosystems, there is a great need to quantitatively link shifts in nutrient loading with changes in oxygen concentrations. To this end, we have developed and here describe, evaluate, and apply the Coastal Ocean Oxygen Linked to Benthic Exchange And Nutrient Supply (COOLBEANS) model, a first-of-its-kind, spatially explicit (with 152 coastal segments) model, global model of coastal oxygen and nutrient dynamics. In COOLBEANS, benthic oxygen demand (BOD) is calculated using empirical models for aerobic respiration, iron reduction, and sulfate reduction, while oxygen supply is represented by a simple parameterization of exchange between surface and bottom waters. A nutrient cycling component translates shifts in riverine nutrient inputs into changes in organic matter delivery to sediments and, ultimately, oxygen uptake. Modeled BOD reproduces observations reasonably well (Nash-Sutcliffe efficiency = 0.71), and estimates of exchange between surface and bottom waters correlate with stratification. The model examines sensitivity of bottom water oxygen to changes in nutrient inputs and vertical exchange between surface and bottom waters, highlighting the importance of this vertical exchange in defining the susceptibility of a system to oxygen depletion. These sensitivities along with estimated maximum hypoxic areas that are supported by present day nutrient loads are consistent with existing hypoxic regions. Sensitivities are put into context by applying historic changes in nitrogen loading observed in the Gulf of Mexico to the global coastal ocean, demonstrating that such loads would drive many systems anoxic or even sulfidic.

  13. FORWARD AND INVERSE BIO-GEOCHEMICAL MODELING OF MICROBIALLY INDUCED PRECIPITATION IN 0.5M COLUMNAR EXPERIMENTS

    SciTech Connect

    Tammer Barkouki; Brian Martinez; Brina Mortensen; Tess Weathers; Jason DeJong; Nic Spycher; Tim Ginn; Yoshiko Fujita; Robert Smith

    2009-09-01

    Microbial ureolysis-induced calcite precipitation may offer an in situ remediation for heavy metal and radionuclide contamination, as well as an alternative to traditional soil strengthening techniques. A microbially mediated calcite precipitation model was built in TOUGHREACT v2 and calibrated to batch and columnar experimental data. Kinetic ureolysis and calcite precipitation-rate expressions were parameterized by coupling TOUCHREACT with UCODE.

  14. Potential environmental impact of tidal energy extraction in the Pentland Firth at large spatial scales: results of a biogeochemical model

    NASA Astrophysics Data System (ADS)

    van der Molen, Johan; Ruardij, Piet; Greenwood, Naomi

    2016-05-01

    A model study was carried out of the potential large-scale (> 100 km) effects of marine renewable tidal energy generation in the Pentland Firth, using the 3-D hydrodynamics-biogeochemistry model GETM-ERSEM-BFM. A realistic 800 MW scenario and a high-impact scenario with massive expansion of tidal energy extraction to 8 GW scenario were considered. The realistic 800 MW scenario suggested minor effects on the tides, and undetectable effects on the biogeochemistry. The massive-expansion 8 GW scenario suggested effects would be observed over hundreds of kilometres away with changes of up to 10 % in tidal and ecosystem variables, in particular in a broad area in the vicinity of the Wash. There, waters became less turbid, and primary production increased with associated increases in faunal ecosystem variables. Moreover, a one-off increase in carbon storage in the sea bed was detected. Although these first results suggest positive environmental effects, further investigation is recommended of (i) the residual circulation in the vicinity of the Pentland Firth and effects on larval dispersal using a higher-resolution model and (ii) ecosystem effects with (future) state-of-the-art models if energy extraction substantially beyond 1 GW is planned.

  15. Potential environmental impact of tidal energy extraction in the Pentland Firth at large spatial scales: results of a biogeochemical model

    NASA Astrophysics Data System (ADS)

    van der Molen, J.; Ruardij, P.; Greenwood, N.

    2015-12-01

    A model study was carried out of the potential large-scale (> 100 km) effects of marine renewable tidal energy generation in the Pentland Firth, using the 3-D hydrodynamics-biogeochemistry model GETM-ERSEM-BFM. A realistic 800 MW scenario and an exaggerated academic 8 GW scenario were considered. The realistic 800 MW scenario suggested minor effects on the tides, and undetectable effects on the biogeochemistry. The academic 8 GW scenario suggested effects would be observed over hundreds of kilometres away with changes of up to 10 % in tidal and ecosystem variables, in particular in a broad area in the vicinity of The Wash. There, waters became less turbid, and primary production increased with associated increases in faunal ecosystem variables. Moreover, a one-off increase in carbon storage in the sea bed was detected. Although these first results suggest positive environmental effects, further investigation is recommended of: (i) the residual circulation in the vicinity of the Pentland Firth and effects on larval dispersal using a higher resolution model, (ii) ecosystem effects with (future) state-of-the-art models if energy extraction substantially beyond 1 GW is planned.

  16. Calibration of a coupled biological-physical model for prediction in a coastal inlet

    NASA Astrophysics Data System (ADS)

    Guarracino, M.; Dowd, M.; Sheng, J.; Cullen, J. J.

    2011-10-01

    We describe a numerical forecast system designed for prediction of physical and biological dynamics of a coastal inlet. It is based on a coastal ocean observatory that was located at Lunenburg Bay, Nova Scotia, Canada. Biological, chemical, optical, and physical measurements were collected from instrumented moorings, weekly sampling and detailed surveys from 2002 through 2007. Here we present a framework for calibration and evaluation of an ecosystem model using data from the summer of 2007. A three-dimensional hydrodynamic model was coupled to a simple biological (Nutrients-Phytoplankton-Detritus) model; a simple model was used so results could be compared directly to observed biological and chemical variables using skill scores as a first step toward data-assimilation modeling. As a complement to this analysis, variability of model output, e.g., the nutrient limitation term, was examined to understand the modeled biological response to the simulated physical environment. Skill scores based on variances in observed and simulated time-series of biological components were also investigated. Coastal upwelling/downwelling simulated through this model has been found to increase modeled biological activity in the bay. Also model skill in reproducing the observed patterns in nutrients and phytoplankton has been increased due to the restoring conditions for biology set up at the open ocean boundaries of the bay.

  17. Development of a high-resolution coastal circulation model for the ocean observatory in lunenburg bay

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Sheng, Jinyu

    2005-10-01

    An advanced ocean observatory has been established in Lunenburg Bay of Nova Scotia, Canada as part of an interdisciplinary research project of marine environmental prediction. The development of a high-resolution coastal circulation model is one of important components of the observatory. The model horizontal resolution is 60 m and the vertical resolution is about lm. The coastal circulation model is used to simulate the semi-diurnal tidal circulation and associated nonlinear dynamics with the M2 forcing specified at the model open boundaries. The model is also used to simulate the storm-induced circulation in the bay during Hurricane Juan in September 2003, with the model forcing to be the combination of tides and remotely generated waves specified at the model open boundaries and wind stress applied at the sea surface. The model results demonstrate strong interactions between the local wind stress, tidal forcing, and remotely generated waves during this period. Comparison of model results with the surface elevation and current observations demonstrates that the coastal circulation model has reasonable skills in simulating the tidal and storm-induced circulation in the bay.

  18. Integration of coastal inundation modeling from storm tides to individual waves

    NASA Astrophysics Data System (ADS)

    Li, Ning; Roeber, Volker; Yamazaki, Yoshiki; Heitmann, Troy W.; Bai, Yefei; Cheung, Kwok Fai

    2014-11-01

    Modeling of storm-induced coastal inundation has primarily focused on the surge generated by atmospheric pressure and surface winds with phase-averaged effects of the waves as setup. Through an interoperable model package, we investigate the role of phase-resolving wave processes in simulation of coastal flood hazards. A spectral ocean wave model describes generation and propagation of storm waves from deep to intermediate water, while a non-hydrostatic storm-tide model has the option to couple with a spectral coastal wave model for computation of phase-averaged processes in a near-shore region. The ocean wave and storm-tide models can alternatively provide the wave spectrum and the surface elevation as the boundary and initial conditions for a nested Boussinesq model. Additional surface-gradient terms in the Boussinesq equations maintain the quasi-steady, non-uniform storm tide for modeling of phase-resolving surf and swash-zone processes as well as combined tide, surge, and wave inundation. The two nesting schemes are demonstrated through a case study of Hurricane Iniki, which made landfall on the Hawaiian Island of Kauai in 1992. With input from a parametric hurricane model and global reanalysis and tidal datasets, the two approaches produce comparable significant wave heights and phase-averaged surface elevations in the surf zone. The nesting of the Boussinesq model provides a seamless approach to augment the inundation due to the individual waves in matching the recorded debris line along the coast.

  19. Paleo-modeling of coastal saltwater intrusion during the Holocene: an application to the Netherlands

    NASA Astrophysics Data System (ADS)

    Delsman, J. R.; Hu-a-ng, K. R. M.; Vos, P. C.; de Louw, P. G. B.; Oude Essink, G. H. P.; Stuyfzand, P. J.; Bierkens, M. F. P.

    2014-10-01

    Coastal groundwater reserves often reflect a complex evolution of marine transgressions and regressions, and are only rarely in equilibrium with current boundary conditions. Understanding and managing the present-day distribution and future development of these reserves and their hydrochemical characteristics therefore requires insight into their complex evolution history. In this paper, we construct a paleo-hydrogeological model, together with groundwater age and origin calculations, to simulate, study and evaluate the evolution of groundwater salinity in the coastal area of the Netherlands throughout the last 8.5 kyr of the Holocene. While intended as a conceptual tool, confidence in our model results is warranted by a good correspondence with a hydrochemical characterization of groundwater origin. Throughout the modeled period, coastal groundwater distribution never reached equilibrium with contemporaneous boundary conditions. This result highlights the importance of historically changing boundary conditions in shaping the present-day distribution of groundwater and its chemical composition. As such, it acts as a warning against the common use of a steady-state situation given present-day boundary conditions to initialize groundwater transport modeling in complex coastal aquifers or, more general, against explaining existing groundwater composition patterns from the currently existing flow situation. The importance of historical boundary conditions not only holds true for the effects of the large-scale marine transgression around 5 kyr BC that thoroughly reworked groundwater composition, but also for the more local effects of a temporary gaining river system still recognizable today. Model results further attest to the impact of groundwater density differences on coastal groundwater flow on millennial timescales and highlight their importance in shaping today's groundwater salinity distribution. We found free convection to drive large-scale fingered infiltration

  20. Calibration of Daycent biogeochemical model for rice paddies in three agro-ecological zones in Peninsular India to optimize cropping practices and predict GHG emissions

    NASA Astrophysics Data System (ADS)

    Rajan, S.; Kritee, K.; Keough, C.; Parton, W. J.; Ogle, S. M.

    2014-12-01

    Rice is a staple for nearly half of the world population with irrigated and rainfed lowland rice accounting for about 80% of the worldwide harvested rice area. Increased atmospheric CO2 and rising temperatures are expected to adversely affect rice yields by the end of the 21st century. In addition, different crop management practices affect methane and nitrous oxide emissions from rice paddies antagonistically warranting a review of crop management practices such that farmers can adapt to the changing climate and also help mitigate climate change. The Daily DayCent is a biogeochemical model that operates on a daily time step, driven by four ecological drivers, i.e. climate, soil, vegetation, and management practices. The model is widely used to simulate daily fluxes of various gases, plant productivity, nutrient availability, and other ecosystem parameters in response to changes in land management and climate. We employed the DayCent model as a tool to optimize rice cropping practices in Peninsular India so as to develop a set of farming recommendations to ensure a triple win (i.e. higher yield, higher profit and lower GHG emissions). We applied the model to simulate both N2O and CH4 emissions, and crop yields from four rice paddies in three different agro-ecological zones under different management practices, and compared them with measured GHG and yield data from these plots. We found that, like all process based models, the biggest constraint in using the model was input data acquisition. Lack of accurate documentation of historic land use and management practices, missing historical daily weather data, and difficulty in obtaining digital records of soil and crop/vegetation parameters related to our experimental plots came in the way of our execution of this model. We will discuss utilization of estimates based on available literature, or knowledge-based values in lieu of missing measured parameters in our simulations with DayCent which could prove to be a

  1. One-Dimensional Coupled Ecosystem-Carbon Flux Model for the Simulation of Biogeochemical Parameters at Ocean Weather Station P

    NASA Technical Reports Server (NTRS)

    Signorini, S.; McClain, C.; Christian, J.; Wong, C. S.

    2000-01-01

    In this Technical Publication, we describe the model functionality and analyze its application to the seasonal and interannual variations of phytoplankton, nutrients, pCO2 and CO2 concentrations in the eastern subarctic Pacific at Ocean Weather Station P (OWSP, 50 deg. N 145 deg. W). We use a verified one-dimensional ecosystem model, coupled with newly incorporated carbon flux and carbon chemistry components, to simulate 22 years (1958-1980) of pCO2 and CO2 variability at Ocean Weather Station P (OWS P). This relatively long period of simulation verifies and extends the findings of previous studies using an explicit approach for the biological component and realistic coupling with the carbon flux dynamics. The slow currents and the horizontally homogeneous ocean in the subarctic Pacific make OWS P one of the best available candidates for modeling the chemistry of the upper ocean in one dimension. The chlorophyll and ocean currents composite for 1998 illustrates this premise. The chlorophyll concentration map was derived from SeaWiFS data and the currents are from an OGCM simulation (from R. Murtugudde).

  2. Mechanistic site-based emulation of a global ocean biogeochemical model (MEDUSA 1.0) for parametric analysis and calibration: an application of the Marine Model Optimization Testbed (MarMOT 1.1)

    NASA Astrophysics Data System (ADS)

    Hemmings, J. C. P.; Challenor, P. G.; Yool, A.

    2015-03-01

    Biogeochemical ocean circulation models used to investigate the role of plankton ecosystems in global change rely on adjustable parameters to capture the dominant biogeochemical dynamics of a complex biological system. In principle, optimal parameter values can be estimated by fitting models to observational data, including satellite ocean colour products such as chlorophyll that achieve good spatial and temporal coverage of the surface ocean. However, comprehensive parametric analyses require large ensemble experiments that are computationally infeasible with global 3-D simulations. Site-based simulations provide an efficient alternative but can only be used to make reliable inferences about global model performance if robust quantitative descriptions of their relationships with the corresponding 3-D simulations can be established. The feasibility of establishing such a relationship is investigated for an intermediate complexity biogeochemistry model (MEDUSA) coupled with a widely used global ocean model (NEMO). A site-based mechanistic emulator is constructed for surface chlorophyll output from this target model as a function of model parameters. The emulator comprises an array of 1-D simulators and a statistical quantification of the uncertainty in their predictions. The unknown parameter-dependent biogeochemical environment, in terms of initial tracer concentrations and lateral flux information required by the simulators, is a significant source of uncertainty. It is approximated by a mean environment derived from a small ensemble of 3-D simulations representing variability of the target model behaviour over the parameter space of interest. The performance of two alternative uncertainty quantification schemes is examined: a direct method based on comparisons between simulator output and a sample of known target model "truths" and an indirect method that is only partially reliant on knowledge of the target model output. In general, chlorophyll records at a

  3. A simulation-optimization model for effective water resources management in the coastal zone

    NASA Astrophysics Data System (ADS)

    Spanoudaki, Katerina; Kampanis, Nikolaos

    2015-04-01

    Coastal areas are the most densely-populated areas in the world. Consequently water demand is high, posing great pressure on fresh water resources. Climatic change and its direct impacts on meteorological variables (e.g. precipitation) and indirect impact on sea level rise, as well as anthropogenic pressures (e.g. groundwater abstraction), are strong drivers causing groundwater salinisation and subsequently affecting coastal wetlands salinity with adverse effects on the corresponding ecosystems. Coastal zones are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes and variable-density flow conditions. Simulation of sea level rise and tidal effects on aquifer salinisation and accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands requires the use of integrated surface water-groundwater mathematical models. In the past few decades several computer codes have been developed to simulate coupled surface and groundwater flow. However, most integrated surface water-groundwater models are based on the assumption of constant fluid density and therefore their applicability to coastal regions is questionable. Thus, most of the existing codes are not well-suited to represent surface water-groundwater interactions in coastal areas. To this end, the 3D integrated surface water-groundwater model IRENE (Spanoudaki et al., 2009; Spanoudaki, 2010) has been modified in order to simulate surface water-groundwater flow and salinity interactions in the coastal zone. IRENE, in its original form, couples the 3D shallow water equations to the equations describing 3D saturated groundwater flow of constant density. A semi-implicit finite difference scheme is used to solve the surface water flow equations, while a fully implicit finite difference scheme is used for the groundwater equations. Pollution interactions are simulated by coupling the advection

  4. Investigation of model capability in capturing vertical coastal processes: A case study in the Adriatic Sea

    NASA Astrophysics Data System (ADS)

    McKiver, William; Sannino, Gianmaria; Bellafiore, Debora

    2015-04-01

    Coastal horizontal and vertical processes play an important role in ocean dynamics. Being the interface between land and sea, they are strongly influenced by winds, river inputs, tides, heat and water fluxes, topographic features, as well as human activities. In this work we perform a set of simulations using two different models, SHYFEM and MITgcm, each employing very different numerical approaches (finite elements and finite volume respectively). This allows us to access their capability to capture a number of coastal processes, specifically considering the role of upwelling and downwelling in the Northern Adriatic Sea. We focus on the Adriatic as its topography, having a very shallow northern basin becoming deeper towards the south, as well as the local atmospheric conditions and its large number of freshwater sources (about a third of the entire Mediterranean), make it prone to dense water events, when cold north-easterly winter winds induce dense water formation in the shallow northern coastal shelf. These extreme dense water events have many complex influences and thus are particularly challenging to understand and model, though their impact on the wider ocean circulation has made them an important topic of research. In this study we focus on one particularly strong dense water formation event that occurred in the beginning of 2012. This serves as an interesting test case to assess both the models strengths and weaknesses, while giving an opportunity to understand how these events affect coastal upwelling and downwelling processes. Using the two very different models we examine the impact of different resolutions (horizontal and vertical), different preconditionings as well as assessing the importance of non-hydrostatic dynamics, in order to identify the crucial model characteristics needed to best reproduce coastal processes.

  5. Mapping pan-Arctic methane emissions at high spatial resolution using an adjoint atmospheric transport and inversion method and process-based wetland and lake biogeochemical models

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Zhuang, Q.; Henze, D. K.; Frankenberg, C.; Dlugokencky, E.; Sweeney, C.; Turner, A. J.

    2015-11-01

    Understanding methane emissions from the Arctic, a fast warming carbon reservoir, is important for projecting changes in the global methane cycle under future climate scenarios. Here we optimize Arctic methane emissions with a nested-grid high-resolution inverse model by assimilating both high-precision surface measurements and column-average SCIAMACHY satellite retrievals of methane mole fraction. For the first time, methane emissions from lakes are integrated into an atmospheric transport and inversion estimate, together with prior wetland emissions estimated by six different biogeochemical models. We find that, the global methane emissions during July 2004-June 2005 ranged from 496.4 to 511.5 Tg yr-1, with wetland methane emissions ranging from 130.0 to 203.3 Tg yr-1. The Arctic methane emissions during July 2004-June 2005 were in the range of 14.6-30.4 Tg yr-1, with wetland and lake emissions ranging from 8.8 to 20.4 Tg yr-1 and from 5.4 to 7.9 Tg yr-1 respectively. Canadian and Siberian lakes contributed most of the estimated lake emissions. Due to insufficient measurements in the region, Arctic methane emissions are less constrained in northern Russia than in Alaska, northern Canada and Scandinavia. Comparison of different inversions indicates that the distribution of global and Arctic methane emissions is sensitive to prior wetland emissions. Evaluation with independent datasets shows that the global and Arctic inversions improve estimates of methane mixing ratios in boundary layer and free troposphere. The high-resolution inversions provide more details about the spatial distribution of methane emissions in the Arctic.

  6. A tsunami early warning system for the coastal area modeling

    NASA Astrophysics Data System (ADS)

    Soebroto, Arief Andy; Sunaryo, Suhartanto, Ery

    2015-04-01

    The tsunami disaster is a potential disaster in the territory of Indonesia. Indonesia is an archipelago country and close to the ocean deep. The tsunami occurred in Aceh province in 2004. Early prevention efforts have been carried out. One of them is making "tsunami buoy" which has been developed by BPPT. The tool puts sensors on the ocean floor near the coast to detect earthquakes on the ocean floor. Detection results are transmitted via satellite by a transmitter placed floating on the sea surface. The tool will cost billions of dollars for each system. Another constraint was the transmitter theft "tsunami buoy" in the absence of guard. In this study of the system has a transmission system using radio frequency and focused on coastal areas where costs are cheaper, so that it can be applied at many beaches in Indonesia are potentially affected by the tsunami. The monitoring system sends the detection results to the warning system using a radio frequency with a capability within 3 Km. Test results on the sub module sensor monitoring system generates an error of 0.63% was taken 10% showed a good quality sensing. The test results of data transmission from the transceiver of monitoring system to the receiver of warning system produces 100% successful delivery and reception of data. The test results on the whole system to function 100% properly.

  7. Prediction model of atmospheric refractive index structure parameter in coastal area

    NASA Astrophysics Data System (ADS)

    Wang, Hongxing; Li, Bifeng; Wu, Xiaojun; Liu, Chuanhui; Hu, Zhihui; Xu, Pengfei

    2015-09-01

    In this paper, we focus on the prediction of atmospheric refractive index structure parameter (?) in coastal area using the routine meteorological parameters. Based on the micrometeorology, macrometeorology and Monin-Obukhov similarity theory, three modified prediction models of ? are presented in combination with the long-term observation data of ? and meteorological parameters in coastal city, respectively. For different weather, the applicable cases of three ? prediction models are comparatively analysed and their applicable effects are comprehensively evaluated. The results indicate that the modified micrometeorology model of ? shows better applicability for overcast sky, the offshore macrometeorology model of ? displays better predictability for sunny day and the offshore Thiermann model provides better availability for overcast sky, cloudy day, overcast to sunny or sunny to overcast day.

  8. Numerical modeling experiments of coastal upwelling at the field of Arctic fjords.

    NASA Astrophysics Data System (ADS)

    Kosecki, Szymon; Dzierzbicka-Głowacka, Lidia

    2016-04-01

    Coastal upwelling is a well described, known phenomenon in theory. Nowadays there is more and more both environmental and modeling studies about it. Upwelling especially in the Arctic fjords is a process that strongly affects hydrodynamics and even more ecosystems. It is so important, that it brings detailed question about effects and needed wind driven forcing parameters. My modeling experiment studies were strongly different than the studies that are typically carried out using numerical models. Instead of searching for this phenomenon in modeled analysis or environmental data, I did several case scenarios simulations. For those I used statistically selected wind data measured in-stiu. The hi-resolution coastal mapping, the flexible mesh discretization method and the sigma-layered three dimensional model MIKE 3 by DHI allowed me to explore this phenomenon with very good accuracy. This studies have been done in Institute of Oceanology PAS in Sopot, as a part of Centre for Polar Studies.

  9. Biogeochemical Cycles in Degraded Lands

    NASA Technical Reports Server (NTRS)

    Davidson, Eric A.; Vieira, Ima Celia G.; ReisdeCarvalho, Claudio Jose; DeaneDeAbreuSa, Tatiana; deSpozaMoutinho, Paulo R.; Figueiredo, Ricardo O.; Stone, Thomas A.

    2003-01-01

    The objectives of this project were to define and describe the types of landscapes that fall under the broad category of "degraded lands" and to study biogeochemical cycles across this range of degradation found in secondary forests. We define degraded land as that which has lost part of its capacity of renovation of a productive ecosystem, either in the context of agroecosystems or as native communities of vegetation. This definition of degradation permits evaluation of biogeochemical constraints to future land uses.

  10. Biogeochemical Cycles in Degraded Lands

    NASA Technical Reports Server (NTRS)

    Davidson, Eric A.; Vieira, Ima Celia G.; ReisdeCarvalho, Claudio Jose; DeanedeAbreuSa, Tatiana; deSouzaMoutinho, Paulo R.; Figueiredo, Ricardo O.; Stone, Thomas A.

    2004-01-01

    The objectives of this project were to define and describe the types of landscapes that fall under the broad category of "degraded lands" and to study biogeochemical cycles across this range of degradation found in secondary forests. We define degraded land as that which has lost part of its capacity of renovation of a productive ecosystem, either in the context of agroecosystems or as native communities of vegetation. This definition of degradation permits evaluation of biogeochemical constraints to future land uses.

  11. Marine biogeochemical influence on primary sea spray aerosol composition in the Southern Ocean: predictions from a mechanistic model

    NASA Astrophysics Data System (ADS)

    McCoy, D.; Burrows, S. M.; Elliott, S.; Frossard, A. A.; Russell, L. M.; Liu, X.; Ogunro, O. O.; Easter, R. C.; Rasch, P. J.

    2014-12-01

    Remote marine clouds, such as those over the Southern Ocean, are particularly sensitive to variations in the concentration and chemical composition of aerosols that serve as cloud condensation nuclei (CCN). Observational evidence indicates that the organic content of fine marine aerosol is greatly increased during the biologically active season near strong phytoplankton blooms in certain locations, while being nearly constant in other locations. We have recently developed a novel modeling framework that mechanistically links the organic fraction of submicron sea spray to ocean biogeochemistry (Burrows et al., in discussion, ACPD, 2014; Elliott et al., ERL, 2014). Because of its combination of large phytoplankton blooms and high wind speeds, the Southern Ocean is an ideal location for testing our understanding of the processes driving the enrichment of organics in sea spray aerosol. Comparison of the simulated OM fraction with satellite observations shows that OM fraction is a statistically significant predictor of cloud droplet number concentration over the Southern Ocean. This presentation will focus on predictions from our modeling framework for the Southern Ocean, specifically, the predicted geographic gradients and seasonal cycles in the aerosol organic matter and its functional group composition. The timing and location of a Southern Ocean field campaign will determine its utility in observing the effects of highly localized and seasonal phytoplankton blooms on aerosol composition and clouds. Reference cited: Burrows, S. M., Ogunro, O., Frossard, A. A., Russell, L. M., Rasch, P. J., and Elliott, S.: A physically-based framework for modelling the organic fractionation of sea spray aerosol from bubble film Langmuir equilibria, Atmos. Chem. Phys. Discuss., 14, 5375-5443, doi:10.5194/acpd-14-5375-2014, 2014. Elliott, S., Burrows, S. M., Deal, C., Liu, X., Long, M., Ogunro, O., Russell, L. M., and Wingenter O.. "Prospects for simulating macromolecular surfactant

  12. Agricultural livelihoods in coastal Bangladesh under climate and environmental change--a model framework.

    PubMed

    Lázár, Attila N; Clarke, Derek; Adams, Helen; Akanda, Abdur Razzaque; Szabo, Sylvia; Nicholls, Robert J; Matthews, Zoe; Begum, Dilruba; Saleh, Abul Fazal M; Abedin, Md Anwarul; Payo, Andres; Streatfield, Peter Kim; Hutton, Craig; Mondal, M Shahjahan; Moslehuddin, Abu Zofar Md

    2015-06-01

    Coastal Bangladesh experiences significant poverty and hazards today and is highly vulnerable to climate and environmental change over the coming decades. Coastal stakeholders are demanding information to assist in the decision making processes, including simulation models to explore how different interventions, under different plausible future socio-economic and environmental scenarios, could alleviate environmental risks and promote development. Many existing simulation models neglect the complex interdependencies between the socio-economic and environmental system of coastal Bangladesh. Here an integrated approach has been proposed to develop a simulation model to support agriculture and poverty-based analysis and decision-making in coastal Bangladesh. In particular, we show how a simulation model of farmer's livelihoods at the household level can be achieved. An extended version of the FAO's CROPWAT agriculture model has been integrated with a downscaled regional demography model to simulate net agriculture profit. This is used together with a household income-expenses balance and a loans logical tree to simulate the evolution of food security indicators and poverty levels. Modelling identifies salinity and temperature stress as limiting factors to crop productivity and fertilisation due to atmospheric carbon dioxide concentrations as a reinforcing factor. The crop simulation results compare well with expected outcomes but also reveal some unexpected behaviours. For example, under current model assumptions, temperature is more important than salinity for crop production. The agriculture-based livelihood and poverty simulations highlight the critical significance of debt through informal and formal loans set at such levels as to persistently undermine the well-being of agriculture-dependent households. Simulations also indicate that progressive approaches to agriculture (i.e. diversification) might not provide the clear economic benefit from the perspective of

  13. Mercury dynamics in a Coastal Plain watershed: Insights from multiple models and empirical data

    NASA Astrophysics Data System (ADS)

    Golden, H. E.; Knightes, C. D.; Conrads, P. A.; Davis, G. M.; Feaster, T.; Benedict, S.; Journey, C.; Brigham, M. E.; Bradley, P. M.

    2011-12-01

    Interactions among atmospherically deposited mercury, abundant wetlands, and surface waters with elevated acidity and dissolved organic carbon (DOC) often lead to widespread mercury-related fish consumption advisories in the Coastal Plain of the southeastern United States (US). However, the science behind understanding mercury dynamics in these mixed land cover, Coastal Plain watersheds is just beginning to emerge. Watershed models are important tools for answering questions related to watershed mercury cycling - including the spatial and temporal variations in surface water mercury concentrations and fluxes - particularly when limited data exist and multiple models with different underlying dynamics are available. We quantify total mercury (HgT) concentrations and fluxes to the outlet of McTier Creek Watershed, located in the upper Coastal Plain of South Carolina, US, an area with more diverse land cover, a larger drainage area, and different geophysical setting than many previous mercury studies in North America (primarily from small forested headwater boreal or northern forested catchments). We apply three independently developed watershed mercury models with distinct mathematical frameworks that emphasize different system processes. Because spatially-explicit watershed scale mercury modeling is a recent advancement, the use of multiple models combined with data affords broader insights to HgT dynamics in the watershed. As a result, we employ a spatially-explicit grid based watershed mercury model (GBMM), the spatially-explicit VELMA-Hg model, and the semi-empirical TOPLOAD-Hg model for HgT concentration and flux calculations. We use the S-LOADEST model for seasonal HgT fluxes, while measured in-stream HgT concentrations and fluxes provide additional insights and data for model calibrations. Our findings begin to elucidate important abiotic processes controlling HgT, areas within the landscape where HgT at the outlet is derived, and potential governing dynamics

  14. Modelling approaches for coastal simulation based on cellular automata: the need and potential.

    PubMed

    Dearing, J A; Richmond, N; Plater, A J; Wolf, J; Prandle, D; Coulthard, T J

    2006-04-15

    The paper summarizes the theoretical and practical needs for cellular automata (CA)-type models in coastal simulation, and describes early steps in the development of a CA-based model for estuarine sedimentation. It describes the key approaches and formulae used for tidal, wave and sediment processes in a prototype integrated cellular model for coastal simulation designed to simulate estuary sedimentary responses during the tidal cycle in the short-term and climate driven changes in sea-level in the long-term. Results of simple model testing for both one-dimensional and two-dimensional models, and a preliminary parameterization for the Blackwater Estuary, UK, are shown. These reveal a good degree of success in using a CA-type model for water and sediment transport as a function of water level and wave height, but tidal current vectors are not effectively simulated in the approach used. The research confirms that a CA-type model for the estuarine sediment system is feasible, with a real prospect for coupling to existing catchment and nearshore beach/cliff models to produce integrated coastal simulators of sediment response to climate, sea-level change and human actions. PMID:16537155

  15. Limited impact of atmospheric nitrogen deposition on marine productivity due to biogeochemical feedbacks in a global ocean model

    NASA Astrophysics Data System (ADS)

    Somes, Christopher J.; Landolfi, Angela; Koeve, Wolfgang; Oschlies, Andreas

    2016-05-01

    The impact of increasing anthropogenic atmospheric nitrogen deposition on marine biogeochemistry is uncertain. We performed simulations to quantify its effect on nitrogen cycling and marine productivity in a global 3-D ocean biogeochemistry model. Nitrogen fixation provides an efficient feedback by decreasing immediately to deposition, whereas water column denitrification increases more gradually in the slowly expanding oxygen deficient zones. Counterintuitively, nitrogen deposition near oxygen deficient zones causes a net loss of marine nitrogen due to the stoichiometry of denitrification. In our idealized atmospheric deposition simulations that only account for nitrogen cycle perturbations, these combined stabilizing feedbacks largely compensate deposition and suppress the increase in global marine productivity to <2%, in contrast to a simulation that neglects nitrogen cycle feedbacks that predicts an increase of >15%. Our study emphasizes including the dynamic response of nitrogen fixation and denitrification to atmospheric nitrogen deposition to predict future changes of the marine nitrogen cycle and productivity.

  16. Crude oil in a shallow sand and gravel aquifer-III. Biogeochemical reactions and mass balance modeling in anoxic groundwater