scholarly journals Spatiotemporal variability of alkalinity in the Mediterranean Sea

2015 ◽  
Vol 12 (6) ◽  
pp. 1647-1658 ◽  
Author(s):  
G. Cossarini ◽  
P. Lazzari ◽  
C. Solidoro
Keyword(s):  
Mediterranean Sea ◽  
Seasonal Cycle ◽  
Sea Water ◽  
Eastern Mediterranean ◽  
Surface Flux ◽  
Spatiotemporal Variability ◽  
The Black Sea ◽  
Biogeochemical Model ◽  
Basin Scale ◽  
The Mediterranean

Abstract. The paper provides a basin-scale assessment of the spatiotemporal distribution of alkalinity in the Mediterranean Sea. The assessment is made by integrating the available observations into a 3-D transport–biogeochemical model. The results indicate the presence of complex spatial patterns: a marked west-to-east surface gradient of alkalinity is coupled to secondary negative gradients: (1) from marginal seas (Adriatic and Aegean Sea) to the eastern Mediterranean Sea and (2) from north to south in the western region. The west–east gradient is related to the mixing of Atlantic water entering from the Strait of Gibraltar with the high-alkaline water of the eastern sub-basins, which is correlated to the positive surface flux of evaporation minus precipitation. The north-to-south gradients are related to the terrestrial input and to the input of the Black Sea water through the Dardanelles. In the surface layers, alkalinity has a relevant seasonal cycle (up to 40 μmol kg−1) that is driven by physical processes (seasonal cycle of evaporation and vertical mixing) and, to a minor extent, by biological processes. A comparison of alkalinity vs. salinity indicates that different regions present different relationships: in regions of freshwater influence, the two quantities are negatively correlated due to riverine alkalinity input, whereas they are positively correlated in open sea areas of the Mediterranean Sea.

scholarly journals CDOM Spatiotemporal Variability in the Mediterranean Sea: A Modelling Study

2021 ◽  
Vol 9 (2) ◽  
pp. 176
Author(s):  
Paolo Lazzari ◽  
Eva Álvarez ◽  
Elena Terzić ◽  
Gianpiero Cossarini ◽  
Ilya Chernov ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Optical Model ◽  
Eastern Mediterranean ◽  
Spatiotemporal Variability ◽  
Radiative Transfer Model ◽  
Biogeochemical Model ◽  
Transfer Model ◽  
Spatial And Temporal Variability ◽  
Limiting Nutrients ◽  
The Mediterranean

This study investigates the spatial and temporal variability of chromophoric-dissolved organic matter (CDOM) in the Mediterranean Sea. The analysis is carried out using a state-of-the-art 3D biogeochemical model. The model describes the plankton dynamics, the cycles of the most important limiting nutrients, and the particulate and dissolved pools of carbon. The source of CDOM is directly correlated to the dynamics of dissolved organic carbon (DOC) by a fixed production quota. Then CDOM degrades by photobleaching and remineralization. The main innovation of the system is the inclusion of a bio-optical radiative transfer model that computes surface upwelling irradiance, and therefore simulates remotely sensed reflectance (Rrs). Simulation results of three model configurations are evaluated using satellite Rrs, particularly at 412 nm, 443 nm, and 490 nm. All simulations show a winter minimum in Rrs for the considered bands. However, different parameterizations of DOC-release induce a different accumulation of CDOM, especially in the eastern Mediterranean, and a different Rrs signature: a more active microbial loop during summer implies a decrease of Rrs at 412 nm. We demonstrate how the usage of a bio-optical model allows us to corroborate hypotheses on CDOM-cycling based on blue–violet Rrs data, supporting the importance of this complementary data stream with respect to satellite-derived chlorophyll.

scholarly journals Seasonal and inter-annual variability of plankton chlorophyll and primary production in the Mediterranean Sea: a modelling approach

2012 ◽  
Vol 9 (1) ◽  
pp. 217-233 ◽  
Author(s):  
P. Lazzari ◽  
C. Solidoro ◽  
V. Ibello ◽  
S. Salon ◽  
A. Teruzzi ◽  
...  
Keyword(s):  
Primary Production ◽  
Mediterranean Sea ◽  
Net Primary Production ◽  
Eastern Mediterranean ◽  
Light Extinction ◽  
Biogeochemical Model ◽  
Spatial And Temporal Variability ◽  
Nutrient Loads ◽  
Basin Scale ◽  
The Mediterranean

Abstract. This study presents a model of chlorophyll and primary production in the pelagic Mediterranean Sea. A 3-D-biogeochemical model (OPATM-BFM) was adopted to explore specific system characteristics and quantify dynamics of key biogeochemical variables over a 6 yr period, from 1999 to 2004. We show that, on a basin scale, the Mediterranean Sea is characterised by a high degree of spatial and temporal variability in terms of primary production and chlorophyll concentrations. On a spatial scale, important horizontal and vertical gradients have been observed. According to the simulations over a 6 yr period, the developed model correctly simulated the climatological features of deep chlorophyll maxima and chlorophyll west-east gradients, as well as the seasonal variability in the main offshore regions that were studied. The integrated net primary production highlights north-south gradients that differ from surface net primary production gradients and illustrates the importance of resolving spatial and temporal variations to calculate basin-wide budgets and their variability. According to the model, the western Mediterranean, in particular the Alboran Sea, can be considered mesotrophic, whereas the eastern Mediterranean is oligotrophic. During summer stratified period, notable differences between surface net primary production variability and the corresponding vertically integrated production rates have been identified, suggesting that care must be taken when inferring productivity in such systems from satellite observations alone. Finally, specific simulations that were designed to explore the role of external fluxes and light penetration were performed. The subsequent results show that the effects of atmospheric and terrestrial nutrient loads on the total integrated net primary production account for less than 5 % of the its annual value, whereas an increase of 30 % in the light extinction factor impacts primary production by approximately 10 %.

scholarly journals Space-time variability of alkalinity in the Mediterranean Sea

2014 ◽  
Vol 11 (9) ◽  
pp. 12871-12893 ◽  
Author(s):  
G. Cossarini ◽  
P. Lazzari ◽  
C. Solidoro
Keyword(s):  
Mediterranean Sea ◽  
Thermohaline Circulation ◽  
Sea Water ◽  
Dissolved Inorganic Carbon ◽  
Surface Flux ◽  
Atlantic Water ◽  
The Black Sea ◽  
Time Variability ◽  
Marginal Seas ◽  
The Mediterranean

Abstract. The paper provides a basin assessment of the spatial distribution of ocean alkalinity in the Mediterranean Sea. The assessment is made using a 3-D transport-biogeochemical-carbonate model to integrate the available experimental findings, which also constrains model output. The results indicate that the Mediterranean Sea shows alkalinity values that are much higher than those observed in the Atlantic Ocean on a basin-wide scale. A marked west-to-east surface gradient of alkalinity is reproduced as a response to the terrestrial discharges, the mixing effect with the Atlantic water entering from the Gibraltar Strait and the Black Sea water from Dardanelles, and the surface flux of evaporation minus precipitation. Dense water production in marginal seas (Adriatic and Aegean Seas), where alkaline inputs are relevant, and the Mediterranean thermohaline circulation sustains the west-to-east gradient along the entire water column. In the surface layers, alkalinity has a relevant seasonal cycle (up to 40 μmol kg−1) that is driven both by physical and biological processes. A comparison of alkalinity vs. salinity indicates that different regions present different relationships. In regions of freshwater influence, the two measures are negatively correlated due to riverine alkalinity input, whereas they are positively correlated in open seas. Alkalinity always is much higher than in the Atlantic waters, which might indicate a higher than usual buffering capacity towards ocean acidification, even at high concentrations of dissolved inorganic carbon.

scholarly journals Characterisation of extreme events waves in marine ecosystems: the case of Mediterranean Sea

2020 ◽  
Author(s):  
Valeria Di Biagio ◽  
Gianpiero Cossarini ◽  
Stefano Salon ◽  
Cosimo Solidoro
Keyword(s):  
Cluster Analysis ◽  
Mediterranean Sea ◽  
Extreme Events ◽  
Marine Ecosystems ◽  
Horizontal Resolution ◽  
Ecosystem Functions ◽  
Biogeochemical Model ◽  
Open Sea ◽  
Basin Scale ◽  
The Mediterranean

Abstract. We propose a new method to identify and characterise the occurrence of prolonged extreme events in marine ecosystems on the basin scale. There is a growing interest about events that can affect ecosystem functions and services in a changing climate. Our method identifies extreme events as peak occurrences over 99th percentile thresholds computed from local time series and defines an Extreme Events Wave (EEW) as a connected region including these events. The EEWs are characterised by a set of novel indexes, referred to initiation, extent, duration and strength. The indexes, associated to the areas covered by each EEW, are then statistically analysed to highlight the main features of the EEWs on the considered domain. We applied the method to the winter-spring daily chlorophyll field of a validated multidecadal hindcast provided by a coupled hydrodynamic-biogeochemical model of the Mediterranean open-sea ecosystem, with 1/12° horizontal resolution. This allowed to identify the maxima of chlorophyll as exceptionally high and prolonged blooms and to characterise their phenomenology in the period 1994–2012. A fuzzy k-means cluster analysis on the EEWs indexes provided a bio-regionalisation of the Mediterranean Sea associated to the occurrence of chlorophyll EEWs with different regimes.

scholarly journals Investigation of the Inherent Variability of the Mediterranean Sea Under Contrasting Extreme Climatic Conditions

2021 ◽  
Vol 8 ◽  
Author(s):  
Angeliki Sampatakaki ◽  
Vassilis Zervakis ◽  
Ioannis Mamoutos ◽  
Elina Tragou ◽  
Alexandra Gogou ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Thermohaline Circulation ◽  
Eastern Mediterranean ◽  
Internal Variability ◽  
Climatic Conditions ◽  
Spatiotemporal Variability ◽  
Atmospheric Forcing ◽  
Buoyancy Forcing ◽  
Deep Layers ◽  
The Mediterranean

The internal variability of the thermohaline circulation of the Mediterranean Sea is examined under contrasting extreme thermal and mass atmospheric forcing conditions. Three millennium-long numerical simulation experiments were performed under: (a) the current climatology, (b) a strong buoyancy forcing (SBF) scenario due to cold and dry conditions resembling the Younger Dryas event, and (c) a weak buoyancy forcing (WBF) scenario due to S1a sapropel deposition-like conditions (warm and wet). To isolate the inherent variability of the system, independent of interannual atmospheric forcing variability, the latter was defined as a perpetual year pertinent to each experiment. Self-diagnosed heat and salt fluxes, consistent to sea-surface characteristics of the above periods, forced three millenium-long, relaxation-free numerical experiments. These simulations were preceded by initial spin-up periods. The inherent spatiotemporal variability of the Mediterranean Sea was analyzed using the empirical orthogonal function (EOF) and spectral analysis on the simulated density fields. Our results revealed that the Mediterranean Sea exhibits high sensitivity to climatic conditions, allowing its circulation to change from anti-estuarine (for the SBF scenario, leading to a buoyancy loss to the atmosphere) to estuarine (for the WBF scenario, corresponding to a buoyancy gain from the atmosphere). In all three experiments, the interannual and decennial variabilities dominate in upper layers, and the decennial variability dominates in the Gibraltar and Sicily Straits. Under current climatic conditions the first two EOF modes express only 60% of the density variability in the deep layers. This contribution exceeds 90% under more extreme conditions. Moreover, the first EOF modes correspond to a basin-wide in-phase variability of the deep layers under the reference and WBF conditions. During SBF conditions the first modes reveal a vertical buoyancy exchange between upper and deeper layers. The second EOF mode of deep waters under both extreme scenarios showed that the western and eastern basins exchange buoyancy in decennial (for the cold/dry) and interdecennial (for the warm/humid) timescales. The residence time of the Eastern Mediterranean deep water was diagnosed to be centennial, semicentennial, and intercentennial for the cases of current period, SBF, and WBF, respectively.

scholarly journals New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

2015 ◽  
Vol 12 (23) ◽  
pp. 7025-7046 ◽  
Author(s):  
A. Guyennon ◽  
M. Baklouti ◽  
F. Diaz ◽  
J. Palmieri ◽  
J. Beuvier ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Mediterranean Sea ◽  
Coupled Model ◽  
Phosphate Limitation ◽  
Biogeochemical Model ◽  
Carbon Export ◽  
Western Basin ◽  
Eastern Basin ◽  
Basin Scale ◽  
The Mediterranean

Abstract. The Mediterranean Sea is one of the most oligotrophic regions of the oceans, and nutrients have been shown to limit both phytoplankton and bacterial activities, resulting in a potential major role of dissolved organic carbon (DOC) export in the biological pump. Strong DOC accumulation in surface waters is already well documented, though measurements of DOC stocks and export flux are still sparse and associated with major uncertainties. This study provides the first basin-scale overview and analysis of organic carbon stocks and export fluxes in the Mediterranean Sea through a modeling approach based on a coupled model combining a mechanistic biogeochemical model (Eco3M-MED) and a high-resolution (eddy-resolving) hydrodynamic simulation (NEMO-MED12). The model is shown to reproduce the main spatial and seasonal biogeochemical characteristics of the Mediterranean Sea. Model estimations of carbon export are also of the same order of magnitude as estimations from in situ observations, and their respective spatial patterns are mutually consistent. Strong differences between the western and eastern basins are evidenced by the model for organic carbon export. Though less oligotrophic than the eastern basin, the western basin only supports 39 % of organic carbon (particulate and dissolved) export. Another major result is that except for the Alboran Sea, the DOC contribution to organic carbon export is higher than that of particulate organic carbon (POC) throughout the Mediterranean Sea, especially in the eastern basin. This paper also investigates the seasonality of DOC and POC exports as well as the differences in the processes involved in DOC and POC exports in light of intracellular quotas. Finally, according to the model, strong phosphate limitation of both bacteria and phytoplankton growth is one of the main drivers of DOC accumulation and therefore of export.

scholarly journals New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

2015 ◽  
Vol 12 (8) ◽  
pp. 6147-6213
Author(s):  
A. Guyennon ◽  
M. Baklouti ◽  
F. Diaz ◽  
J. Palmieri ◽  
J. Beuvier ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Mediterranean Sea ◽  
Coupled Model ◽  
Nutrient Concentrations ◽  
Biogeochemical Model ◽  
Carbon Export ◽  
Western Basin ◽  
Basin Scale ◽  
The Mediterranean

Abstract. The Mediterranean Sea is one of the most oligotrophic regions of the oceans, and nutrients have been shown to limit both phytoplankton and bacterial activities. This has direct implications on the stock of dissolved organic carbon (DOC), whose high variability has already been well-documented even if measurements are still sparse and are associated with important uncertainties. We here propose a Mediterranean Basin-scale view of the export of organic carbon, under its dissolved and particulate forms. For this purpose, we have used a coupled model combining a mechanistic biogeochemical model (Eco3M-MED) and a high-resolution (eddy-resolving) hydrodynamic simulation (NEMO-MED12). This is the first Basin-scale application of the biogeochemical model Eco3M-MED and is shown to reproduce the main spatial and seasonal biogeochemical characteristics of the Mediterranean Sea. Model estimations of carbon export are of the same order of magnitude as estimations from in situ observations, and their respective spatial patterns are consistent with each other. As for surface chlorophyll, nutrient concentrations, and productivity, strong differences between the Western and Eastern Basins are evidenced by the model for organic carbon export, with only 39% of organic carbon (particulate and dissolved) export taking place in the Western Basin. The major result is that except for the Alboran Sea, dissolved organic carbon (DOC) contribution to organic carbon export is higher than that of particulate (POC) in the whole Basin, especially in the Eastern Basin. This paper also investigates the seasonality of DOC and POC exports as well as the differences in the processes involved in DOC and POC exports.

scholarly journals Seasonal and inter-annual variability of plankton chlorophyll and primary production in the Mediterranean Sea: a modelling approach

2011 ◽  
Vol 8 (3) ◽  
pp. 5379-5422 ◽  
Author(s):  
P. Lazzari ◽  
C. Solidoro ◽  
V. Ibello ◽  
S. Salon ◽  
A. Teruzzi ◽  
...  
Keyword(s):  
Primary Production ◽  
Mediterranean Sea ◽  
Seasonal Variability ◽  
Net Primary Production ◽  
Eastern Mediterranean ◽  
Light Extinction ◽  
Spatial And Temporal Variability ◽  
Nutrient Loads ◽  
Basin Scale ◽  
The Mediterranean

Abstract. This study presents a model of chlorophyll and primary production in the pelagic Mediterranean Sea. A 3-D-ecosystem model (OPATM-BFM) was adopted to explore specific system characteristics and quantify key biogeochemical variables covering a 6-yr period, from 1999 to 2004. We show that, on a basin scale, the Mediterranean Sea is characterised by a high degree of spatial and temporal variability in terms of primary production and chlorophyll concentrations. On a spatial scale, important horizontal and vertical gradients have been observed. In particular, notable differences between surface net primary production variability and the corresponding vertically integrated production rates have been identified, suggesting that care must be taken when inferring productivity in such systems from satellite observations alone. The present study indicates that seasonal variability dominates inter-annual differences. According to the simulations over a 6-yr period, the developed model correctly simulated the climatological features of deep chlorophyll maxima and chlorophyll west-east gradients, as well as the seasonal variability in the primary offshore regions that were studied. The integrated net primary production highlights north-south gradients that differ from surface net primary production gradients and illustrates the importance of adopting a spatial and temporal description to calculate basin-wide budgets and their variabilities. According to the model, the western Mediterranean, in particular the Alboran Sea, can be considered mesotrophic, whereas the eastern Mediterranean is oligotrophic. Finally, specific simulations that were designed to explore the role of ecosystem boundary conditions were performed. The subsequent results show that the effects of atmospheric and terrestrial nutrient loads on the total integrated net primary production account for less than 5 % of the annual budget, whereas an increase of 30 % in the light extinction factor impacts primary production by approximately 10 %.

scholarly journals Extreme event waves in marine ecosystems: an application to Mediterranean Sea surface chlorophyll

2020 ◽  
Vol 17 (23) ◽  
pp. 5967-5988
Author(s):  
Valeria Di Biagio ◽  
Gianpiero Cossarini ◽  
Stefano Salon ◽  
Cosimo Solidoro
Keyword(s):  
Mediterranean Sea ◽  
Extreme Events ◽  
Extreme Event ◽  
Marine Ecosystems ◽  
Fuzzy Classification ◽  
Ecosystem Functions ◽  
Biogeochemical Model ◽  
Open Sea ◽  
Basin Scale ◽  
The Mediterranean

Abstract. We propose a new method to identify and characterise the occurrence of prolonged extreme events in marine ecosystems at the basin scale. There is growing interest in events that can affect ecosystem functions and services in a changing climate. Our method identifies extreme events as the peak occurrences over a predefined threshold (i.e. the 99th percentile) computed from a local time series, and it defines a series of extreme events that are connected over space and time as an extreme event wave (EEW). The main features of EEWs are then characterised by a set of novel indexes, related to initiation, extent, duration and strength. The indexes associated with the areas covered by each EEW were then statistically analysed to highlight the main features of the EEWs in the considered domain. We applied the method to a multidecadal series of winter–spring daily chlorophyll fields that was produced by a validated coupled hydrodynamic–biogeochemical model of the Mediterranean open-sea ecosystem. This application allowed us to identify and characterise surface chlorophyll EEWs in the period from 1994 to 2012. Finally, a fuzzy classification of EEW indexes provided bio-regionalisation of the Mediterranean Sea based on the occurrence of chlorophyll EEWs with different regimes.

scholarly journals Sea Surface Salinity trends in the Mediterranean and Black Seas from 10 years of SMOS measurements

2020 ◽  
Author(s):  
Estrella Olmedo ◽  
Verónica González-Gambau ◽  
Antonio Turiel ◽  
Cristina González-Haro ◽  
Justino Martínez ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Black Sea ◽  
Eastern Mediterranean ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
The Black Sea ◽  
Surface Salinity ◽  
Run Off ◽  
The Mediterranean ◽  
Regional Product

<p>The monitoring of the sea surface salinity (SSS) in the semi-enclosed seas has a significant impact in the study of the climate change. In those basins the oceanographic processes occur at higher temporal scales than in the open ocean, and therefore, trends and anomalies can be detected before. The Mediterranean Sea is a strongly evaporative basin (evaporation exceeds the precipitation and river run-off). Converserly, in the Black Sea the river run-off and precipitation exceeds the evaporation. Based on a 4-year time series (2015-2019) of SMAP SSS, a recent study has shown that there is an increase of the salinity in the Eastern Mediterranean [Grodsky, et al. 2019]. On the other hand, the Black Sea exhibits a rich variability in space and time from (sub)mesoscale to larger scales (interannual and larger)  that needs to be appropriately taken into account when trying to identify long-term trends. <br><br>We present new estimates of SSS trends in the Mediterranean and Black Seas. These estimations are based on 10-year series obtained from the European Soil Moisture and Ocean Salinity (SMOS) mission. Two new SMOS SSS regional products have been generated. On the one hand, we have generated a new realease of SMOS SSS regional product for the Mediterranean Sea. The new release of SMOS SSS regional product for the Mediterranean Sea provides better coverage in the Eastern Mediterranean than the previous version of this product (see [Olmedo et al 2018]). The new dedicated SMOS SSS product for the Black Sea has been developed under the currently on-going ESA EO4BIS contract (An Earth Observation Data for Science and Innovation in the Black Sea). The Black Sea and the Eastern Mediterranean are strongly affected by Radio Frequency Interferences (RFI) sources, which hamper the salinity retrieval. We have applied specific methodologies to diminish the strong RFI effects in these two basins [González-Gambau et al 2017].  The new realase of these two SMOS SSS regional products will be available soon in the Barcelona Expert Center website (http://bec.icm.csic.es ). <br><br>At this conference we will present the methodologies that we have used for the generation of both regional SMOS SSS products. We will also present a quality assessment over the two regions consisting of comparing with in situ salinity measurements. Finally, we will show the SSS trends that are obtained in the different basin (and sub-basins) as well as the significance of the results with respect to the accuracy of the new SMOS SSS products. <br><br>[Grodsky, et al. 2019] Grodsky S., et al. (2019), “Eastern Mediterranean salinification observed in satellite salinity from SMAP mission”, Journal of Marine Systems,  198 <br>[Olmedo et al 2018] Olmedo, E, et al. , (2018) “Improving SMOS Sea Surface Salinity in the Western Mediterranean Sea through Multivariate and Multifractal Analysis,” Remote sensing,  10(3), 485. <br>[González-Gambau et al 2017] González-Gambau, V. et. al, (2017), "Improvements on calibration and image reconstruction of SMOS for salinity retrievals in coastal regions," in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 10, 7, 3064-3078</p>

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