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 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 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 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.

Vertical distribution of dissolved organic carbon (DOC) in the Mediterranean Sea

2006 ◽  
Vol 31 ◽  
pp. 205-216 ◽  
Author(s):  
C Santinelli ◽  
BB Manca ◽  
GP Gasparini ◽  
L Nannicini ◽  
A Seritti
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Vertical Distribution ◽  
Mediterranean Sea ◽  
The Mediterranean

DOM DYNAMICS IN THE MEDITERRANEAN SEA. Can a new fluorescence SENSOR contribute to its understanding?

2020 ◽  
Author(s):  
Simona Retelletti Brogi ◽  
Marta Furia ◽  
Giancarlo Bachi ◽  
Vanessa Cardin ◽  
Giuseppe Civitarese ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Mediterranean Sea ◽  
Water Column ◽  
Fluorescence Sensor ◽  
Global Ocean ◽  
Intermediate Water ◽  
Physical Processes ◽  
Open Sea ◽  
The Mediterranean

<p>The Mediterranean Sea (Med Sea) can be considered as a natural laboratory for the study of dissolved organic matter (DOM) dynamics. Despite its small size, it is characterized by the same physical processes and dissolved organic carbon (DOC) concentration and distribution as the global ocean. The Med Sea deep water DOC pool is however older than the Atlantic one and differences in the microbial loop and in DOM dynamics have been observed between the eastern (EMED) and western (WMED) basins. Fluorescence is a fast, cheap and highly sensitive tool to study DOM dynamics, it can therefor give useful information about the main processes affecting DOM distribution.</p><p>The main aims of this study were: (i) to investigate DOM dynamics in both Med Sea basins, in relation to the physical processes (e.g. vertical stratification, irradiation); and (ii) to validate the use of a new fluorescence sensor, developed in the framework of the SENSOR project (POR FESR, Tuscany Region), for the rapid, in-situ measurements of open-sea fluorescent DOM (FDOM). DOM dynamics was investigated by measuring dissolved organic carbon (DOC) and the fluorescence of FDOM. Samples were collected from surface to bottom in 26 stations during the trans-Mediterranean cruise “MSM72”, carried out on board the R/V MARIA S.MERIAN (Institut für Meereskunde der Universität Hamburg). The stations cover both the EMED and the WMED, from Gibraltar to the Crete Island.</p><p>Six fluorescent components were identified by applying the parallel factorial analysis (PARAFAC) to the measured excitation-emission matrices (EEMs). Two components were identified as marine humic-like, two as terrestrial humic-like, one as protein-like and one as polycyclic aromatic hydrocarbon-like (PAH-like).</p><p>Temperature and salinity increased moving from the WMED to the EMED. A surface minimum in salinity, was observed in the WMED, indicating the occurrence of the Atlantic Water (AW), whereas the presence of the Levantine Intermediate Water (LIW) was observed south of Crete. The vertical distribution of both DOC and humic-like FDOM was strongly affected by the water masses circulation and water column stratification. In the upper 200 m, DOC markedly increased from 50 to 80 μM moving eastward, likewise the protein-like component dominates the upper layer and increased moving from Gibraltar to Crete. In contrast, the humic-like components showed a minimum in the surface layer, and a decreasing moving eastward, probably due to photobleaching. The PAH-like component showed its maximum in correspondence with the areas characterized by intensive naval traffic. The accumulation of DOC, observed in the EMED, could be explained by a change in DOM quality, supported by the differences in FDOM.</p><p>In 2 selected stations, the fluorescence of humic-like and protein-like compounds was also measured along the water column by using the new fluorescence sensor and compared with PARAFAC results, in order to evaluate its performance for open sea waters.</p>

scholarly journals Pre-operational short-term forecasts for the Mediterranean Sea biogeochemistry

2009 ◽  
Vol 6 (2) ◽  
pp. 1223-1259 ◽  
Author(s):  
P. Lazzari ◽  
A. Teruzzi ◽  
S. Salon ◽  
S. Campagna ◽  
C. Calonaci ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Coupled Model ◽  
Biogeochemical Model ◽  
Short Term ◽  
Future Studies ◽  
Successful Execution ◽  
Fundamental Research ◽  
Fully Automatic ◽  
The Mediterranean ◽  
Assimilation Scheme

Abstract. Operational prediction of the marine environment is recognised as a fundamental research issue for Europe. We present a pre-operational implementation of a biogeochemical model for pelagic waters of the Mediterranean Sea, as developed within the framework of the MERSEA-IP European project. The OPATM-BFM coupled model is the core of a fully automatic system that weekly delivers analysis and forecast maps for the Mediterranean Sea biogeochemistry. The system in the present configuration has been working since April 2007 with successful execution of the fully automatic operational chain in the 87% of the cases, and in the remaining cases the runs were successfully accomplished after operator intervention. A description of the system developed and a comparison of the model results with satellite data are also presented, with Spearman correlation on surface chlorophyll temporal evolution equal to 0.71. Future studies will be addressed to the implementations of a data assimilation scheme for the biogeochemical compartment in order to increase the skill of the model performances.

scholarly journals Towards an assessment of riverine dissolved organic carbon in surface waters of the western Arctic Ocean based on remote sensing and biogeochemical modeling

2018 ◽  
Vol 15 (5) ◽  
pp. 1335-1346 ◽  
Author(s):  
Vincent Le Fouest ◽  
Atsushi Matsuoka ◽  
Manfredi Manizza ◽  
Mona Shernetsky ◽  
Bruno Tremblay ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Arctic Ocean ◽  
Coupled Model ◽  
The Arctic ◽  
In Situ Data ◽  
Basin Scale ◽  
Western Arctic ◽  
Potential Impact

Abstract. Future climate warming of the Arctic could potentially enhance the load of terrigenous dissolved organic carbon (tDOC) of Arctic rivers due to increased carbon mobilization within watersheds. A greater flux of tDOC might impact the biogeochemical processes of the coastal Arctic Ocean (AO) and ultimately its capacity to absorb atmospheric CO2. In this study, we show that sea-surface tDOC concentrations simulated by a physical–biogeochemical coupled model in the Canadian Beaufort Sea for 2003–2011 compare favorably with estimates retrieved by satellite imagery. Our results suggest that, over spring–summer, tDOC of riverine origin contributes to 35 % of primary production and that an equivalent of ∼ 10 % of tDOC is exported westwards with the potential of fueling the biological production of the eastern Alaskan nearshore waters. The combination of model and satellite data provides promising results to extend this work to the entire AO so as to quantify, in conjunction with in situ data, the expected changes in tDOC fluxes and their potential impact on the AO biogeochemistry at basin scale.

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.

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