scholarly journals Evolution of primary production and its drivers on the Lebanese coast between 1986 and 2013

2020 ◽  
Vol 20 (4) ◽  
pp. 207-217
Author(s):  
Ali Fadel ◽  
Lama Salameh ◽  
Malak Kanj ◽  
Ahmad Kobaissi
Keyword(s):  
Primary Production ◽  
Phytoplankton Community ◽  
Controlling Factors ◽  
Sea Surface ◽  
Biogeochemical Model ◽  
Average Temperature ◽  
Biogeochemical Models ◽  
Increasing Trend ◽  
Production Dynamics ◽  
Lebanese Coast

AbstractPhysical-biogeochemical models help us to understand the dynamics and the controlling factors of primary production. In this study, the outputs of a validated hydrodynamic and biogeochemical model were used to elucidate the primary production dynamics between 1992 and 2012 for three studied sites on the Lebanese coast: Naqoura, Beirut, and Tripoli. The results showed that primary production presents a homogeneous spatial distribution along the Lebanese coastline. The phytoplankton community has a low optimal temperature. The thermocline develops in March, with maximum stratification in August and fades in October. Chlorophyll, dissolved oxygen and salinity were positively correlated throughout the water column. A significant increasing trend of sea surface temperature was found on the Lebanese coast over 27 years, between 1986 and 2013. Annual averages increased from 22°C in 1986 to 23.1°C in 2013 with the highest recorded average temperature of 23.7 °C in 2010.

scholarly journals Biogeochemical versus ecological consequences of modeled ocean physics

2016 ◽  
Author(s):  
Sophie Clayton ◽  
Stephanie Dutkiewicz ◽  
Oliver Jahn ◽  
Christopher Hill ◽  
Patrick Heimbach ◽  
...  
Keyword(s):  
Primary Production ◽  
Ocean Circulation ◽  
Mixed Layer ◽  
Phytoplankton Biomass ◽  
Phytoplankton Community ◽  
Nutrient Supply ◽  
Zooplankton Biomass ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Biogeochemical Models

Abstract. Regional and idealized modeling studies have shown that increasing the physical resolution of biogeochemical models to include mesoscale and submesoscale dynamics can result in both increases and decreases in phytoplankton biomass and primary production, as well as changes in phytoplankton community structure. Here we present a systematic study of the differences generated by coupling the same ecological-biogeochemical model to a 1°, coarse-resolution, and 1/6°, eddy-permitting, global ocean circulation model. Surprisingly, we find that the modeled phytoplankton community is largely unchanged, with the same phenotypes dominating in both cases. Conversely, there are large regional variations in integrated primary production, phytoplankton and zooplankton biomass. In the subtropics, mixed layer depths are, on average, deeper in the eddy-permitting model, resulting in higher nutrient supply driving increases in primary production and phytoplankton biomass. In the higher latitudes, deeper spring mixed layer depths in the eddy-permitting model result in increased light limitation during the spring bloom. Counter-intuitively, this does not drive a decrease in phytoplankton biomass, but is reflected in decreased primary production and zooplankton biomass. We explain these similarities and differences in the model using the framework of resource competition theory, and find that they are the consequence of changes in the regional and seasonal nutrient supply and light environment, mediated by differences in the modeled mixed layer depths. Although previous work has suggested that complex models may respond chaotically and unpredictably to changes in forcing, we find that our model responds in a predictable way to different ocean circulation forcing, despite its complexity.

scholarly journals Seasonal patterns in phytoplankton biomass across the northern and deep Gulf of Mexico: a numerical model study

2018 ◽  
Vol 15 (11) ◽  
pp. 3561-3576 ◽  
Author(s):  
Fabian A. Gomez ◽  
Sang-Ki Lee ◽  
Yanyun Liu ◽  
Frank J. Hernandez Jr. ◽  
Frank E. Muller-Karger ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Primary Production ◽  
Phytoplankton Biomass ◽  
Mississippi Delta ◽  
Three Dimensional ◽  
Rate Of Change ◽  
Integrated Analysis ◽  
Biogeochemical Model ◽  
Seasonal Patterns ◽  
Biogeochemical Models

Abstract. Biogeochemical models that simulate realistic lower-trophic-level dynamics, including the representation of main phytoplankton and zooplankton functional groups, are valuable tools for improving our understanding of natural and anthropogenic disturbances in marine ecosystems. Previous three-dimensional biogeochemical modeling studies in the northern and deep Gulf of Mexico (GoM) have used only one phytoplankton and one zooplankton type. To advance our modeling capability of the GoM ecosystem and to investigate the dominant spatial and seasonal patterns of phytoplankton biomass, we configured a 13-component biogeochemical model that explicitly represents nanophytoplankton, diatoms, micro-, and mesozooplankton. Our model outputs compare reasonably well with observed patterns in chlorophyll, primary production, and nutrients over the Louisiana–Texas shelf and deep GoM region. Our model suggests silica limitation of diatom growth in the deep GoM during winter and near the Mississippi delta during spring. Model nanophytoplankton growth is weakly nutrient limited in the Mississippi delta year-round and strongly nutrient limited in the deep GoM during summer. Our examination of primary production and net phytoplankton growth from the model indicates that the biomass losses, mainly due to zooplankton grazing, play an important role in modulating the simulated seasonal biomass patterns of nanophytoplankton and diatoms. Our analysis further shows that the dominant physical process influencing the local rate of change of model phytoplankton is horizontal advection in the northern shelf and vertical mixing in the deep GoM. This study highlights the need for an integrated analysis of biologically and physically driven biomass fluxes to better understand phytoplankton biomass phenologies in the GoM.

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

2014 ◽  
Vol 7 (4) ◽  
pp. 4153-4249
Author(s):  
V. Schourup-Kristensen ◽  
D. Sidorenko ◽  
D. A. Wolf-Gladrow ◽  
C. Völker
Keyword(s):  
Finite Element ◽  
Southern Ocean ◽  
Primary Production ◽  
Net Primary Production ◽  
Global Scale ◽  
Ocean Model ◽  
Biogeochemical Model ◽  
Biogeochemical Models ◽  
The Pacific ◽  
The Pacific Ocean

Abstract. 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.

scholarly journals Can assimilation of satellite observations improve subsurface biological properties in a numerical model? A case study for the Gulf of Mexico

2021 ◽  
Author(s):  
Bin Wang ◽  
Katja Fennel ◽  
Liuqian Yu
Keyword(s):  
Gulf Of Mexico ◽  
A Priori ◽  
Biological Properties ◽  
Satellite Observations ◽  
Sea Surface ◽  
Biogeochemical Model ◽  
Biological Variables ◽  
Biogeochemical Models ◽  
Optical Module ◽  
Argo Profiles

Abstract. Given current threats to ocean ecosystem health, there is a growing demand for accurate biogeochemical hindcasts, nowcasts, and predictions. Provision of such products requires data assimilation, i.e., a comprehensive strategy for incorporating observations into biogeochemical models, but current data streams of biogeochemical observations are generally considered insufficient for the operational provision of such products. This study investigates to what degree the satellite observations in combination with sparse BGC Argo profiles can improve subsurface biogeochemical properties. The multivariate Deterministic Ensemble Kalman Filter (DEnKF) has been implemented to assimilate physical and biological observations into a biogeochemical model of the Gulf of Mexico. First, the biogeochemical model component was tuned using BGC-Argo observations. Then, observations of sea surface height, sea surface temperature, and surface chlorophyll were assimilated, and profiles of both physical and biological variables were updated based on the surface information. We assessed whether this leads to improved subsurface distributions, especially of biological properties, using observations from five BGC-Argo floats that were not assimilated, but used in the a priori tuning. Results show that assimilation of the satellite data improves model representation of major circulation features, which translate into improved three-dimensional distributions of temperature and salinity. The multivariate assimilation also improves the agreement of subsurface nitrate through its tight correlation with temperature, but the improvements in subsurface chlorophyll were modest initially due to suboptimal choices of the model’s optical module. Repeating the assimilation run after adjusting light attenuation parameterization through further a priori tuning greatly improved the subsurface distribution of chlorophyll. Therefore, even sparse BGC-Argo observations can provide substantial benefits to biogeochemical prediction by enabling a priori model tuning. Given that, so far, the abundance of BGC-Argo profiles in the Gulf of Mexico and elsewhere is insufficient for sequential assimilation, updating 3D biological properties in a model that has been well calibrated is an intermediate step toward full assimilation of the new data types.

Comparing apples to oranges: Perspectives on satellite-based primary production estimates drawn from a global biogeochemical model

2019 ◽  
Vol 77 (2) ◽  
pp. 259-282
Author(s):  
Charles A. Stock
Keyword(s):  
Primary Production ◽  
Nutrient Limitation ◽  
Phytoplankton Community ◽  
Carbon Fixation ◽  
Size Structure ◽  
Net Primary Production ◽  
Maximum Growth ◽  
Inhibitory Effect ◽  
Biogeochemical Model ◽  
Small Phytoplankton

Net primary production (NPP) by microscopic phytoplankton underpins nearly all marine life, yet global NPP estimates differ substantially. Among satellite-based estimates, variation has been attributed to differing assumptions about the relationships between photosynthesis and sea surface temperature (SST). Maximum chlorophyll (Chl)–specific rates of carbon fixation in the water column (PBopt) increase monotonically with SST in some satellite algorithms, whereas others peak at intermediate values. Understanding and constraining such relationships is challenged by the many direct and indirect relationships between temperature and phytoplankton. In this article, the emergent PBopt-SST relationship was diagnosed in a global biogeochemical simulation and compared with widely used satellite NPP algorithms. The simulated PBopt-SST relationship for the aggregated phytoplankton community was highly significant (r2= 0.83) and increased monotonically with temperature. The PBopt-SST relationships for small and large phytoplankton, however, were distinct and weaker than the aggregate relationship (r2 = 0.52 and 0.36, respectively). For small phytoplankton, the inhibitory effect of nutrient limitation in warmer, more stratified waters was moderated by efficient nutrient scavenging. This, combined with photoacclimation and the stimulatory effect of warming on maximum growth produced steep PBopt increases with SST. For large phytoplankton, the need for higher Chl:C in productive regions (because of package effects) and the onset of severe nutrient limitation in warm, stratified regions decreased PBopt relative to small phytoplankton, though PBopt still increased modestly with SST. The PBopt-SST relationships for both small and large phytoplankton overestimated PBopt in nutrient-poor regions and underestimated it in nutrient-rich regions. This bias was greatly reduced in the aggregate relationship because the increased prominence of low-PBopt large phytoplankton in nutrient-rich environments tempered PBopt increases. Results support a strong, monotonically increasing PBopt-SST relationship but emphasize the role of the size structure of the phytoplankton community in shaping the emergent relationship. The implications of these results are discussed in relation to efforts to improve satellite NPP algorithms and partition NPP by phytoplankton size.

scholarly journals Modelling the processes driving <i>Trichodesmium</i> sp. spatial distribution and biogeochemical impact in the tropical Pacific Ocean

2018 ◽  
Author(s):  
Cyril Dutheil ◽  
Olivier Aumont ◽  
Thomas Gorguès ◽  
Anne Lorrain ◽  
Sophie Bonnet ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Spatial Distribution ◽  
Primary Production ◽  
New Caledonia ◽  
Regional Distribution ◽  
South Pacific ◽  
Tropical Pacific ◽  
Dinitrogen Fixation ◽  
Biogeochemical Model ◽  
Biogeochemical Models

Abstract. Dinitrogen fixation is now recognized as one of the major sources of bio-available nitrogen in the ocean. Thus, nitrogen fixation sustains a significant part of the global primary production by providing an input of the most common limiting nutrient for phytoplankton growth. Evidences of the Western Tropical South Pacific being a hotspot of nitrogen fixation, and a data coverage complemented by OUTPACE, lead us to develop an explicit nitrogen fixation compartment based on the Trichodesmium physiology (the most studied nitrogen fixer) within a 3D coupled dynamical-biogeochemical model (ROMS-PISCES). We performed a first 20-year tropical Pacific simulation that is able to reproduce the main physical (e.g. Sea Surface Temperature) and biogeochemical conditions (nutrients, and chlorophyll concentrations as well as dinitrogen fixation). This simulation showed a possible Trichodesmium regional distribution that extends from 150° E to 120° W in the south tropical Pacific, and from 120° E to 140° W in the north tropical Pacific. The local simulated maximums were around islands (Hawaii, Fiji, Samoa, New Caledonia, Vanuatu). We assessed that 15 % of the total primary production may be due to Trichodesmium in the Low Nutrient, Low Chlorophyll regions (LNLC). We also argue that implicit parameterization of N2 fixation (often used in biogeochemical models) leads to underestimate nitrogen fixation rates by about 25% in LNLC regions compared to our explicit formulation. Finally, we showed that iron fluxes from island sediments control the spatial distribution and the abundance of Trichodesmium in the western tropical south Pacific. Noteworthy, this last result does not take into account the iron supply from rivers and hydrothermal sources, which may well be of importance in a region known for its strong precipitation rates and volcanic activity.

scholarly journals Modelling N<sub>2</sub> fixation related to <i>Trichodesmium</i> sp.: driving processes and impacts on primary production in the tropical Pacific Ocean

2018 ◽  
Vol 15 (14) ◽  
pp. 4333-4352 ◽  
Author(s):  
Cyril Dutheil ◽  
Olivier Aumont ◽  
Thomas Gorguès ◽  
Anne Lorrain ◽  
Sophie Bonnet ◽  
...  
Keyword(s):  
Primary Production ◽  
N2 Fixation ◽  
New Caledonia ◽  
Regional Distribution ◽  
South Pacific ◽  
Tropical Pacific ◽  
Biogeochemical Model ◽  
Available Nitrogen ◽  
Biogeochemical Models ◽  
The Tropical Pacific

Abstract. Dinitrogen fixation is now recognized as one of the major sources of bio-available nitrogen in the ocean. Thus, N2 fixation sustains a significant part of the global primary production by supplying the most common limiting nutrient for phytoplankton growth. The “Oligotrophy to UlTra-oligotrophy PACific Experiment” (OUTPACE) improved the data coverage of the western tropical South Pacific, an area recently recognized as a hotspot of N2 fixation. This new development leads us to develop and test an explicit N2 fixation formulation based on the Trichodesmium physiology (the most studied nitrogen fixer) within a 3-D coupled dynamical–biogeochemical model (ROMS-PISCES). We performed a climatological numerical simulation that is able to reproduce the main physical (e.g. sea surface temperature) and biogeochemical patterns (nutrient and chlorophyll concentrations, as well as N2 fixation) in the tropical Pacific. This simulation displayed a Trichodesmium regional distribution that extends from 150∘ E to 120∘ W in the south tropical Pacific, and from 120∘ E to 140∘ W in the north tropical Pacific. The local simulated maximuma were found around islands (Hawaii, Fiji, Samoa, New Caledonia, Vanuatu). We assessed that 15 % of the total primary production may be due to Trichodesmium in the low-nutrient low-chlorophyll regions (LNLC) of the tropical Pacific. Comparison between our explicit and the often used (in biogeochemical models) implicit parameterization of N2 fixation showed that the latter leads to an underestimation of N2 fixation rates by about 25 % in LNLC regions. Finally, we established that iron fluxes from island sediments control the spatial distribution of Trichodesmium biomasses in the western tropical South Pacific. Note, this last result does not take into account the iron supply from rivers and hydrothermal sources, which may well be of importance in a region known for its strong precipitation rates and volcanic activity.

scholarly journals Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kuang-Yu Chang ◽  
William J. Riley ◽  
Sara H. Knox ◽  
Robert B. Jackson ◽  
Gavin McNicol ◽  
...  
Keyword(s):  
Temperature Sensitivity ◽  
Spatial Scales ◽  
Biogeochemical Model ◽  
Spatial And Temporal Variability ◽  
Biogeochemical Models ◽  
Model Parameterization ◽  
Machine Learning Model ◽  
Meta Analyses ◽  
The Relationship ◽  
Global Carbon

AbstractWetland methane (CH4) emissions ($${F}_{{{CH}}_{4}}$$ F C H 4 ) are important in global carbon budgets and climate change assessments. Currently, $${F}_{{{CH}}_{4}}$$ F C H 4 projections rely on prescribed static temperature sensitivity that varies among biogeochemical models. Meta-analyses have proposed a consistent $${F}_{{{CH}}_{4}}$$ F C H 4 temperature dependence across spatial scales for use in models; however, site-level studies demonstrate that $${F}_{{{CH}}_{4}}$$ F C H 4 are often controlled by factors beyond temperature. Here, we evaluate the relationship between $${F}_{{{CH}}_{4}}$$ F C H 4 and temperature using observations from the FLUXNET-CH4 database. Measurements collected across the globe show substantial seasonal hysteresis between $${F}_{{{CH}}_{4}}$$ F C H 4 and temperature, suggesting larger $${F}_{{{CH}}_{4}}$$ F C H 4 sensitivity to temperature later in the frost-free season (about 77% of site-years). Results derived from a machine-learning model and several regression models highlight the importance of representing the large spatial and temporal variability within site-years and ecosystem types. Mechanistic advancements in biogeochemical model parameterization and detailed measurements in factors modulating CH4 production are thus needed to improve global CH4 budget assessments.

Manifestarea anotimpurilor în contextul schimbarilor climatice

2019 ◽  
Author(s):  
Maria Nedealcov ◽  
Keyword(s):  
Temporal Variability ◽  
Climatic Variability ◽  
Warming Trend ◽  
Climatic Parameters ◽  
Adaptation To Climate Change ◽  
Thermal Threshold ◽  
Average Temperature ◽  
Increasing Trend ◽  
Spatio Temporal ◽  
The Right

The early manifestation of the seasons and seasonal temperature's increasing trend for all seasons require adequate solutions of adaptation to climate change. Knowledge of the spatio-temporal variability of climatic parameters that characterize the seasons, focusing on the last decades - a period of time when climatic variability is even more pronounced compared to previous periods, is of particular interest. Analysis of the density of the seasonal average temperature distribution function indicates a shift to the right for the values, which demonstrates warming trend for all the seasons. The highest accelerated rhythm belongs to winters and summers, and in this context the duration of the seasons and the accumulation of daily temperatures with a certain thermal threshold is also changing.

scholarly journals New insights into aerosol and climate in the Arctic

2018 ◽  
Author(s):  
Jonathan P. D. Abbatt ◽  
W. Richard Leaitch ◽  
Amir A. Aliabadi ◽  
Alan K. Bertram ◽  
Jean-Pierre Blanchet ◽  
...  
Keyword(s):  
Long Range ◽  
Mineral Dust ◽  
Sea Surface ◽  
The Arctic ◽  
Long Range Transport ◽  
Surface Microlayer ◽  
Biogeochemical Models ◽  
Sea Surface Microlayer ◽  
Range Transport ◽  
Warming World

Abstract. Motivated by the need to predict how the Arctic atmosphere will change in a warming world, this article summarizes recent advances made by the research consortium NETCARE (Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments) that contribute to our fundamental understanding of Arctic aerosol particles as they relate to climate forcing. The overall goal of NETCARE research has been to use an interdisciplinary approach encompassing extensive field observations and a range of chemical transport, earth system, and biogeochemical models. Several major findings and advances have emerged from NETCARE since its formation in 2013 . (1) Unexpectedly high summertime dimethyl sulfide (DMS) levels were identified in ocean water and the overlying atmosphere in the Canadian Arctic Archipelago (CAA). Furthermore, melt ponds, which are widely prevalent, were identified as an important DMS source. (2) Evidence was found of widespread particle nucleation and growth in the marine boundary layer in the CAA in the summertime. DMS-oxidation-driven nucleation is facilitated by the presence of atmospheric ammonia arising from sea bird colony emissions, and potentially also from coastal regions, tundra, and biomass burning. Via accumulation of secondary organic material (SOA), a significant fraction of the new particles grow to sizes that are active in cloud droplet formation. Although the gaseous precursors to Arctic marine SOA remain poorly defined, the measured levels of common continental SOA precursors (isoprene and monoterpenes) were low, whereas elevated mixing ratios of oxygenated volatile organic compounds were inferred to arise via processes involving the sea surface microlayer. (3) The variability in the vertical distribution of black carbon (BC) under both springtime Arctic haze and more pristine summertime aerosol conditions was observed. Measured particle size distributions and mixing states were used to constrain, for the first time, calculations of aerosol–climate interactions under Arctic conditions. Aircraft- and ground-based measurements were used to better establish the BC source regions that supply the Arctic via long-range transport mechanisms. (4) Measurements of ice nucleating particles (INPs) in the Arctic indicate that a major source of these particles is mineral dust, likely derived from local sources in the summer and long-range transport in the spring. In addition, INPs are abundant in the sea surface microlayer in the Arctic, and possibly play a role in ice nucleation in the atmosphere when mineral dust concentrations are low. (5) Amongst multiple aerosol components, BC was observed to have the smallest effective deposition velocities to high Arctic snow.

Sign in / Sign up

Export Citation Format

Share Document