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

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.

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

Biogeosciences ◽

10.5194/bg-17-5967-2020 ◽

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

Biogeosciences ◽

10.5194/bg-12-7025-2015 ◽

2015 ◽

Vol 12 (23) ◽

pp. 7025-7046 ◽

Cited By ~ 21

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.

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Spatiotemporal variability of alkalinity in the Mediterranean Sea

Biogeosciences ◽

10.5194/bg-12-1647-2015 ◽

2015 ◽

Vol 12 (6) ◽

pp. 1647-1658 ◽

Cited By ~ 35

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.

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

Biogeosciences Discussions ◽

10.5194/bgd-12-6147-2015 ◽

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.

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Alkalinization Scenarios in the Mediterranean Sea for Efficient Removal of Atmospheric CO2 and the Mitigation of Ocean Acidification

Frontiers in Climate ◽

10.3389/fclim.2021.614537 ◽

2021 ◽

Vol 3 ◽

Author(s):

Momme Butenschön ◽

Tomas Lovato ◽

Simona Masina ◽

Stefano Caserini ◽

Mario Grosso

Keyword(s):

Carbon Dioxide ◽

Mediterranean Sea ◽

Implementation Strategies ◽

Horizontal Resolution ◽

Biogeochemical Model ◽

Baseline Scenario ◽

Surface Ph ◽

The Mean ◽

The Mediterranean ◽

Annual Discharge

It is now widely recognized that in order to reach the target of limiting global warming to well below 2°C above pre-industrial levels (as the objective of the Paris agreement), cutting the carbon emissions even at an unprecedented pace will not be sufficient, but there is the need for development and implementation of active Carbon Dioxide Removal (CDR) strategies. Among the CDR strategies that currently exist, relatively few studies have assessed the mitigation capacity of ocean-based Negative Emission Technologies (NET) and the feasibility of their implementation on a larger scale to support efficient implementation strategies of CDR. This study investigates the case of ocean alkalinization, which has the additional potential of contrasting the ongoing acidification resulting from increased uptake of atmospheric CO2 by the seas. More specifically, we present an analysis of marine alkalinization applied to the Mediterranean Sea taking into consideration the regional characteristics of the basin. Rather than using idealized spatially homogenous scenarios of alkalinization as done in previous studies, which are practically hard to implement, we use a set of numerical simulations of alkalinization based on current shipping routes to quantitatively assess the alkalinization efficiency via a coupled physical-biogeochemical model (NEMO-BFM) for the Mediterranean Sea at 1/16° horizontal resolution (~6 km) under an RCP4.5 scenario over the next decades. Simulations suggest the potential of nearly doubling the carbon-dioxide uptake rate of the Mediterranean Sea after 30 years of alkalinization, and of neutralizing the mean surface acidification trend of the baseline scenario without alkalinization over the same time span. These levels are achieved via two different alkalinization strategies that are technically feasible using the current network of cargo and tanker ships: a first approach applying annual discharge of 200 Mt Ca(OH)2 constant over the alkalinization period and a second approach with gradually increasing discharge proportional to the surface pH trend of the baseline scenario, reaching similar amounts of annual discharge by the end of the alkalinization period. We demonstrate that the latter approach allows to stabilize the mean surface pH at present day values and substantially increase the potential to counteract acidification relative to the alkalinity added, while the carbon uptake efficiency (mole of CO2 absorbed by the ocean per mole of alkalinity added) is only marginally reduced. Nevertheless, significant local alterations of the surface pH persist, calling for an investigation of the physiological and ecological implications of the extent of these alterations to the carbonate system in the short to medium term in order to support a safe, sustainable application of this CDR implementation.

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

Biogeosciences ◽

10.5194/bg-9-217-2012 ◽

2012 ◽

Vol 9 (1) ◽

pp. 217-233 ◽

Cited By ~ 97

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 %.

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Modeling the biogeochemical dynamics of the Northern Adriatic Sea with an explicit benthic-pelagic coupling

10.5194/egusphere-egu2020-13458 ◽

2020 ◽

Author(s):

Isabella Scroccaro ◽

Marco Zavatarelli ◽

Tomas Lovato

Keyword(s):

Mediterranean Sea ◽

General Circulation ◽

Adriatic Sea ◽

Circulation Model ◽

Horizontal Resolution ◽

Open Boundary ◽

Biogeochemical Model ◽

Northern Adriatic Sea ◽

Northern Adriatic ◽

The Mediterranean

A high resolution three-dimensional (physical-biogeochemical) numerical model of the Northern Adriatic Sea has been implemented by coupling the European general circulation model - NEMO (Nucleus for European&#160;Modeling of the Ocean,&#160;https://www.nemo-ocean.eu/), with the marine biogeochemical model BFM (Biogeochemical Flux Model,&#160;bfm-community.eu/).The modeling system is implemented with a horizontal resolution of about 800 m and a vertical resolution of 2 m, in z coordinates. The NEMO model is off-line nested at its open boundary with the Mediterranean Sea physical model of the Copernicus Marine Environment Monitoring Service (CMEMS, http://marine.copernicus.eu/).The BFM component of the modeling system now includes a detailed and explicit representation of the benthic biogeochemical cycling (benthic fauna, organic matter, nutrients), as well as the dynamics of the benthic-pelagic processes.The inclusion of the benthic dynamics in the 3D biogeochemical modeling of a shallow coastal basin, such as the Northern Adriatic Sea, represents an innovative application in the field of coastal and shelf biogeochemistry, since benthic biogeochemical processes can significantly constrain the coastal environmental dynamics.Simulations have been performed in hindcasting mode with interannually varying physical (surface heat and water fluxes, including river runoff) and biogeochemical (river nutrient load) forcing. Results are validated against available observations from in situ and satellite platforms for sea surface temperatures, chlorophyll-a and dissolved inorganic nutrients, in order to explore the sensitivity of the pelagic environment to the inclusion of an explicit benthic dynamics and to evaluate issues related to model coupling and error/prediction limits.The study is carried out in the framework of the European Project H2020 "ODYSSEA" (Operating a network of integrated observatory systems in the Mediterranean SEA,&#160;http://odysseaplatform.eu/), with the final goal to build an on-line forecasting modeling system of the Northern Adriatic Sea.

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Mapping the impact of alien species on marine ecosystems: the Mediterranean Sea case study

Diversity and Distributions ◽

10.1111/ddi.12429 ◽

2016 ◽

Vol 22 (6) ◽

pp. 694-707 ◽

Cited By ~ 52

Author(s):

Stelios Katsanevakis ◽

Fernando Tempera ◽

Heliana Teixeira

Keyword(s):

Alien Species ◽

Mediterranean Sea ◽

Marine Ecosystems ◽

The Mediterranean ◽

The Impact

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A Synergetic Approach for the Space-Based Sea Surface Currents Retrieval in the Mediterranean Sea

Remote Sensing ◽

10.3390/rs11111285 ◽

2019 ◽

Vol 11 (11) ◽

pp. 1285 ◽

Cited By ~ 4

Author(s):

Daniele Ciani ◽

Marie-Hélène Rio ◽

Milena Menna ◽

Rosalia Santoleri

Keyword(s):

Numerical Model ◽

Mediterranean Sea ◽

Mediterranean Area ◽

Hf Radar ◽

Sea Surface ◽

Reconstruction Method ◽

Surface Currents ◽

Basin Scale ◽

The Mediterranean ◽

Sicily Channel

We present a method for the remote retrieval of the sea surface currents in the Mediterranean Sea. Combining the altimeter-derived currents with sea-surface temperature information, we created daily, gap-free high resolution maps of sea surface currents for the period 2012–2016. The quality of the new multi-sensor currents has been assessed through comparisons to other surface-currents estimates, as the ones obtained from drifting buoys trajectories (at the basin scale), or HF-Radar platforms and ocean numerical model outputs in the Malta–Sicily Channel. The study yielded that our synergetic approach can improve the present-day derivation of the surface currents in the Mediterranean area up to 30% locally, with better performances for the the meridional component of the motion and in the western section of the basin. The proposed reconstruction method also showed satisfying performances in the retrieval of the ageostrophic circulation in the Sicily Channel. In this area, assuming the High Frequency Radar-derived currents as reference, the merged multi-sensor currents exhibited improvements with respect to the altimeter estimates and numerical model outputs, mainly due to their enhanced spatial and temporal resolution.

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A high-resolution free-surface model of the Mediterranean Sea

Ocean Science ◽

10.5194/os-4-1-2008 ◽

2008 ◽

Vol 4 (1) ◽

pp. 1-14 ◽

Cited By ~ 144

Author(s):

M. Tonani ◽

N. Pinardi ◽

S. Dobricic ◽

I. Pujol ◽

C. Fratianni

Keyword(s):

Free Surface ◽

Mediterranean Sea ◽

General Circulation ◽

Forecast Model ◽

Surface Model ◽

Argo Data ◽

Basic Model ◽

Basin Scale ◽

Before And After ◽

The Mediterranean

Abstract. This study describes a new model implementation for the Mediterranean Sea with what is currently the highest vertical resolution over the Mediterranean basin. The resolution is of 1/16°×1/16° in the horizontal and has 72 unevenly spaced vertical levels. This model has been developed in the frame of the EU-MFSTEP project and is the operational forecast model currently used at the basin scale. The model considers an implicit free surface and this characteristic enhances the model's capability to simulate the sea surface height variability and the net transport at the Strait of Gibraltar. In this study we show the calibration/validation experiments performed before and after the model was used for forecasting. The first experiment consists of a six-year simulation forced by a perpetual year forcing, and the other experiment is a simulation from January 1997 to December 2004, forcing the model with 6-h atmospheric forcing fields from ECMWF. The model Sea Level Anomaly has been compared for the first time with satellite SLA and with ARGO data to provide evidence of the quality of the simulation. The results show that this model is capable of reproducing most of the variability of the general circulation in the Mediterranean Sea. However, some basic model inadequacies stand out and should be corrected in the near future.

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