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Advances in understanding of the multi-scale and multi-disciplinary dynamics of the Southern European Seas (Mediterranean and Black Sea)

The Mediterranean and Black Seas have recently shown clear signs of climate change, including an increase in sea surface temperature for boths basins, salinization of the intermediate and deep waters and a rise in sea level over the last century for the Mediterranean seas and deoxygenation trends for the Black Sea. These trends stress the vulnerability of these environments given their particularities as semi enclosed densely populated basins.

Urgent social and economic drivers need targeted improvements in weather, climate, water, oceans, and relevant environmental information and services. Risks associated with climate variability and extreme environmental events may create social and economic stress which would require new meteorological, hydrological, oceanographic, and climate services in order to ensure the safety and security of populations and the development of adaptive economic strategies.

This session is devoted to scientific advances in multidisciplinary studies at several spatial and temporal scales in the Mediterranean and Black Seas. We seek for new approaches and methods in physical and biogeochemical observations and models as well as in developments in operational oceanography (e.g. the fusion of observations and modelling products as well as downstream product development).

Convener: Vanessa Cardin | Co-conveners: Arthur CapetECSECS, Alejandro Orfila, Katrin Schroeder
Presentations
| Thu, 26 May, 17:00–18:21 (CEST)
 
Room 1.34

Thu, 26 May, 17:00–18:30

Chairperson: Emil Stanev

17:00–17:03
Introduction

17:03–17:09
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EGU22-505
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ECS
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Virtual presentation
Joelle Habib et al.

The Levantine basin is the area of formation of the Levantine Intermediate Water. In this study, a 3D hydrodynamic-biogeochemical model (Symphonie/Eco3MS) was used to gain understanding in the dynamics of dissolved oxygen in the Levantine basin and estimate its annual budget and its interannual variability over the period of 2012-2020. Comparisons of model results with compiled in situ data from cruises and Argo floats showed that the model was able to reproduce well the seasonal variability of the dissolved oxygen. They also show that during winter, surface temperature decreased, generating  oxygen  undersaturation in the Levantine basin that absorbed atmospheric oxygen. From March to September, due to the increase of surface temperature the basin became oversaturated and released oxygen into the atmosphere. The estimate of the annual oxygen budget revealed that the Levantine basin acted as a sink of atmospheric oxygen. Gain of oxygen in the upper layer through air-sea exchanges and biogeochemical processes were counterbalanced by the loss of oxygen through physical processes via downward export into  intermediate depths and lateral transport towards the western regions. At the annual scale, the air-sea oxygen exchange term dominated the biogeochemical process term in the budget. Regarding the spatial distribution, maximum annual atmospheric oxygen uptake and biogeochemical fluxes were found in the Levantine Intermediate Water formation area of the Rhodes gyre where oxygen-poor and nutrient-rich waters were supplied in the upper layer and surface temperature was minimum. The current study revealed high interannual variability with large oxygen uptakes and physical exports during winters marked by intense heat losses.

How to cite: Habib, J., Ulses, C., Estournel, C., Marsaleix, P., Coppola, L., and Fakhri, M.: Dissolved oxygen budget in the eastern Mediterranean over the period of 2012 - 2020 using a 3D physical-biogeochemical model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-505, https://doi.org/10.5194/egusphere-egu22-505, 2022.

17:09–17:15
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EGU22-11207
Gianpiero Cossarini et al.

Ocean reanalyses integrate models and observations to provide a continuous and consistent reconstruction of the past physical and biogeochemical ocean state and variability. We present a reanalysis of the Mediterranean Sea biogeochemistry at a 1/24o resolution developed within the Copernicus Marine Service framework. The reanalysis is based on the Biogeochemical Flux Model (BFM) coupled with a variational data assimilation scheme (3DVarBio) and forced by the NEMO–OceanVar Mediterranean reanalysis and the ERA5 atmospheric reanalysis. Covering the 1999–2021 period, the reanalysis assimilates ESA-CCI satellite chlorophyll data and integrates EMODnet data as initial conditions, in addition to considering World Ocean Atlas data at the Atlantic boundary, CO2 atmospheric observations, and yearly estimates of riverine nutrient inputs.

With the use of multiple observation sources (remote, in situ, and BGC-Argo), the quality of the biogeochemical reanalysis is qualitatively and quantitatively assessed at three validation levels. Results of the first validation-level indicate an overall pretty good reanalysis skill in simulating basin-wide values and variability in the biogeochemical variables, such as phytoplankton biomass, net primary production and CO2 air-sea flux. Then, chlorophyll, nutrients, oxygen, and carbonate system variables show also satisfactory uncertainty in reproducing in situ observations at the mesoscale and weekly temporal scale. The uncertainty increases for a few variables (i.e., oxygen and ammonium) in the mesopelagic layers. Finally, using specific and process-oriented skill metrics based on BGC-Argo data, the vertical dynamics of phytoplankton and nitrate are positively assessed.

As a consequence of the continuous increases in temperature, salinity and atmospheric CO2 in the Mediterranean Sea over the last 20 years, the reanalysis results indicate basin-wide biogeochemical signals of surface deoxygenation, increase in alkalinity and dissolved inorganic carbon concentrations, and decrease in pH at the surface. The new, high-resolution reanalysis, open and freely available from the Copernicus Marine Service, allows users from different communities to investigate the spatial and temporal variability in 12 biogeochemical variables and fluxes at different scales (from the mesoscale to the basin-wide scale and from daily to multiyear scales) and the interaction between physical and biogeochemical processes shaping Mediterranean marine ecosystem functioning.

How to cite: Cossarini, G., Salon, S., Feudalel, L., Bolzon, G., Coidessa, G., Solidoro, C., Di Biagio, V., Amadio, C., Lazzari, P., and Brosich, A.: High-Resolution Reanalysis of the Mediterranean Sea Biogeochemistry , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11207, https://doi.org/10.5194/egusphere-egu22-11207, 2022.

17:15–17:21
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EGU22-9624
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ECS
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Virtual presentation
Valeria Di Biagio et al.

Extreme events can have great impacts on the functioning of marine ecosystems. In this work we describe a novel method that identifies and characterises extreme events in marine ecosystems at the basin scale, by accounting for the persistence of the events within a certain impacted area and over a specific time duration. Extreme events are firstly identified as peaks over a predefined threshold (i.e. the 99th percentile) computed from a local timeseries. Then, a series of extreme events that are connected over space and time is defined as an extreme event wave (EEW) and characterised by a set of indexes describing their initiation, extent, duration and strength.  
We applied the method to surface chlorophyll concentration, that is an essential ocean variable representative of the marine ecosystem state and evolution. Since high frequency and seamless data in time and space are mandatory to properly detect extreme events on the basin scale, we used daily data provided by a numerical model. In particular, we employed data of winter-spring surface chlorophyll concentration provided by the coupled hydrodynamic-biogeochemical model MITgcm-BFM at 1/12° horizontal resolution, validated in the Mediterranean Sea in the 1994-2012 period. Our method allowed us to identify and characterise surface chlorophyll EEWs occurring in the considered period and also to provide a bio-regionalisation of the Mediterranean Sea associated to different regimes of chlorophyll dynamics, by means of a fuzzy classification of EEW indexes.

How to cite: Di Biagio, V., Cossarini, G., Salon, S., and Solidoro, C.: Extreme event waves in marine ecosystems: method and application to the surface chlorophyll in Mediterranean Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9624, https://doi.org/10.5194/egusphere-egu22-9624, 2022.

17:21–17:27
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EGU22-8686
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On-site presentation
David Garcia-Garcia et al.

The Mediterranean is connected to the Black Sea through the Turkish Straits, and to the Atlantic Ocean through the Strait of Gibraltar. The hydrological cycle of the Mediterranean-Black Sea system is driven by fresh water exchanges between the atmosphere, continents and oceans, and by salty water mass exchange among the ocean basins. In this study, we estimate the water-mass fluxes through these straits as  residuals in the water balance equation. To do so, the freshwater fluxes are estimated from the time-variable gravity fields inferred from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On satellites, and precipitation and evaporation data from ERA5 atmospheric reanalysis products. This study covers the 18 years period from 2002 to 2020. In the Black Sea, rivers introduce an average water volume of 391 ± 12 km3/year, one third of which escape through the atmosphere and two thirds go to the Mediterranean Sea. In the latter, 1787 ± 23 km3/year are lost via net evaporation. The rivers runoff (502 ± 27 km3/year), and the inflow of Atlantic waters (1020 ± 56 km3/year; 0.0323 ± 0.0018 Sv), finally restore the Mediterranean water budget. The balance is not reached instantaneously, and this delay introduces a seasonal variability in all the fluxes. In particular, the net water flux from the Atlantic Ocean increases up to 2660 ± 111 km3/year in August/September, and reverses to –407 ± 140 km3/year in April/May. On top of the climatology, the mean annual Atlantic water flux varies significantly in time ranging from 706 to 1262 km3/year.

The work of DGG, IV, MT and JV was partially supported by Spanish Project RTI2018-093874-B-100 funded by MCIN/AEI/10.13039/501100011033,  DGG and IV were partially supported by Grant PROMETEO/2021/030 (Generalitat Valenciana) and JMS was supported by the Generalitat Valenciana  and the European Social Fund under Grant APOSTD/2020/254.

How to cite: Garcia-Garcia, D., Vigo, I., Trottini, M., Vargas, J., and Sayol, J. M.: Net water-mass transport through the Strait of Gibraltar and the Turkish Strait , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8686, https://doi.org/10.5194/egusphere-egu22-8686, 2022.

17:27–17:33
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EGU22-12873
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ECS
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Virtual presentation
Maria Emanuela Mihailov et al.

We used monthly means by Copernicus Marine Services for the Black Sea basin to calculate a series of metrics related to wind-driven upwelling dynamics (Upwelling Index) and examine the relationship with nutrient and plankton environment. We then use these to objectively describe upwelling signals in terms of their frequency, intensity and duration during summer months over 26 years (1993 - 2019). We found that an increase or a decrease in the sea surface temperature is associated with a reduction (or increase) in upwelling events, a decrease/increase in the intensity of upwelling, and a decrease/increase in the cumulative upwelling intensity, with differences between Romanian Black sea areas. Nitrate supply by coastal upwelling has been estimated by combining sea surface temperature and salinity for the in-situ data for the North-Western Black Sea shallow waters. The seasonal vertical transport induced by wind forcing was assessed by daily wind data retrieved from the Copernicus Marine Service data was used. 

How to cite: Mihailov, M. E., Lazar, L., Chirosca, G., Popov, P., Pantea, E. D., Vatu, N., Andrescu, D., and Chirosca, A. V.: Climatological analysis on the North-Western Black Sea upwelling phenomena, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12873, https://doi.org/10.5194/egusphere-egu22-12873, 2022.

17:33–17:39
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EGU22-13265
Arthur Capet et al.

Mesoscale eddies are ubiquitous energetic features that alter the biogeochemical regimes of the oceans by blending large-scale gradients, isolating and transporting water masses over large distances, and by locally shallowing or deepening isopycnals [1]. While several studies highlighted mesoscale biogeochemical mechanisms in the open ocean, the difficulties affecting altimetry products in nearshore regions constitute a strong barrier to the observation-based characterization of nearshore biogeochemical eddy dynamics.

Because of their transitional nature, capturing observational snapshots of eddies with satisfactory coverage is challenging. To overcome this difficulty, composite analyses consist of gathering a large number of near-eddy data instances (from observation or model results) and analyzing their variations according to their relative position to nearby eddies. The method thus aims at characterizing average eddy-induced perturbations and provided the basis for many of the recent advances in the field [2].

The BGC-Argo program provides a powerful asset for eddy composite studies, resulting from 1) the large availability of data provided under the hood of common technical protocols, 2) the richness of characterized biogeochemical variables, and 3) the continuity of data acquisition which facilitates the characterization of local anomalies.

Here, we evaluate three Black Sea altimetry data sets (2011-2019) and compare their adequacy to characterize eddy-induced subsurface oxygen and salinity signatures by applying a common composite analysis framework exploiting in-situ data acquired by BGC-Argo profilers.

The locations, contours, and properties of eddies are obtained by applying the py-eddy-tracker procedure [3] to three altimetric sets, that differ in terms of along-track and gridding processing, and spatial resolution. For comparison, we consider equivalent CMEMS BS-MFC model products [4]. Oxygen and salinity subsurface anomalies are then obtained from BGC-Argo profiles and relocated in eddy-centric coordinates specifically for each altimetric product.

The most recent altimetric data set, issued from the ESA EO4SIBS project, provides eddy properties that are closer to model simulations, in particular for coastal anticyclones. More importantly, subsurface signatures reconstructed from BGC-Argo are more consistent when EO4SIBS is used to express eddy-centric coordinates.

We propose that the estimated error on the reconstructed mean anomaly may serve to qualify the accuracy of gridded altimetry products and that BGC-Argo data provide a strong asset in that regard.

Besides, we reveal intense subsurface oxygen anomalies whose structure supports the hypothesis that the mesoscale contribution to Black Sea oxygen dynamics extends beyond transport and involves net biogeochemical processes.

 

[1] D. J. McGillicuddy, (2016), Ann. Rev. Mar. Sci., 8, 125–159.

[2] P. Gaube, D. J. McGillicuddy, Jr, D. B. Chelton, M. J. Behrenfeld, P. G. Strutton, (2014), J. Geophys. Res. C: Oceans, 119, 8195–8220.

[3] E. Mason, A. Pascual, J. C. McWilliams, (2014), J. Atmos. Ocean. Technol., 31, 1181–1188.

[4] Ciliberti, S. A., et al. (2021), Journal of Marine Science and Engineering, 9(10), 1146.

How to cite: Capet, A., Taburet, G., Mason, E., Pujol, M.-I., D'Ortenzio, F., Grégoire, M., and Rio, M.-H.: Using Argo to characterize altimetric products: a study of eddy-induced subsurface oxygen anomalies in the Black Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13265, https://doi.org/10.5194/egusphere-egu22-13265, 2022.

17:39–17:45
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EGU22-7197
Emil Stanev et al.

Data from profiling floats in the Black Sea revealed complex temporal and spatial relationships between physical variables on the one hand and oxygen, chlorophyll (Chl-a) and the backscattering coefficient at 700 nm (bbp) on the other. It was demonstrated that the temperature-stratified upper layer and salinity-stratified layers below 50 m provide the ecological niche responsible for the major variability of the BGC system in the euphotic layer. There, around the depth of the minimum potential vorticity, the subsurface chlorophyll maximum presents a major BGC characteristics. Data analysis revealed some limits in understanding the details of BGC dynamics, as well as their dependence on physical drivers. One example is the fact that while bbp and Chl-a weakly follow the long-term changes in temperature and salinity, their responses to individual cooling events appear much stronger than what is observed in the physical fields. To fully account for different interdependences, a feedforward backpropagation neural network (NN) was used. The NN learnes from data recorded by profiling floats and predicts BGC states using physical measurements only. The skill was very high, particularly for oxygen, but it reduced when the NN was applied to older data because the interrelationships between the physical and BGC properties have changed recently. One indication of such change is the missing overshooting of either Chl-a or bbp penetration depth in winter reported in earlier studies. The BGC states reconstructed by the NN from physical data produced by a coupled physical-BGC operational model outperform the BGC output of the same coupled model. Therefore, the use of data from profiling floats, physical properties from numerical models and NN appeared a powerful tool to reconstruct the 4D dynamics of euphotic zone. Basin wide patterns and temporal variabilities of oxygen, bbp and Chl-a are also analyzed. Of particular interest is the reconstruction of short-living BGC features, particularly in the area of coastal anticyclones, which are difficult to observe basin-wide with available floats.

How to cite: Stanev, E., Wahle, K., and Staneva, J.: Dynamics of the euphotic zone in the Black Sea: The synergy of data from profiling floats, machine learning and numerical modeling , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7197, https://doi.org/10.5194/egusphere-egu22-7197, 2022.

17:45–17:51
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EGU22-763
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Virtual presentation
Olga Dymova and Sergey Demyshev

The aim of this work is to study the seasonal variability of the mean current kinetic energy MKE, the eddy kinetic energy EKE, the mean available potential energy MPE, the eddy available potential energy EPE, and the rates of energy conversion for basin-scale and eddy circulation regimes in the Black Sea. The basin-scale circulation is a regime when the entire basin is covered by the cyclonic Main Black Sea Current (the Rim Current), which spread over the continental slope. The eddy circulation is a regime when the Rim Current is partially or completely destroyed and intense mesoscale eddies evolve in the abyssal part of the sea. Monthly energy characteristics are calculated based on eddy-resolving simulation data derived under atmospheric forcing SKIRON. Analysis of the reconstructed current fields showed that the basin-scale and the eddy circulation regime are realized in 2011 and in 2016, respectively.

Seasonal signal is weakly manifested in the variability of the MKE; its value depends on the wind forcing and current velocities, which are higher in the basin-scale circulation regime. The distribution of the MPE is predominantly seasonal; temporal variability is qualitatively similar for both regimes and is caused by increase in the density anomaly due to warming up of seawater. The energy transport MPE→MKE due to the buoyancy work is provided in the subsurface layer for all seasons and the Cold Intermediate Layer for the warm seasons in both regimes.

Seasonal variability of the EKE and the mechanisms of its intensification are different for two circulation regimes. The EKE is maximal in spring and summer in the basin-scale circulation regime, and in the cold season in the eddy circulation regime. In winter, when the Rim Current or its elements are most intense, irrespective of the circulation regime, the mesoscale eddies develop mainly due to energy transport MKE→EKE via barotropic instability mechanism. In summer, the mesoscale variability in the basin-scale circulation regime is due to commensurate contributions of barotropic and baroclinic instability, and in the eddy circulation regime only by the energy transport MPE→EKE due to baroclinic instability.

The reported study was funded by the Marine Hydrophysical Institute state task No. 0555-2021-0004.

How to cite: Dymova, O. and Demyshev, S.: Seasonal variability of energy transport in the Black Sea for the basin-scale and eddy circulation regimes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-763, https://doi.org/10.5194/egusphere-egu22-763, 2022.

17:51–17:57
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EGU22-3773
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ECS
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Virtual presentation
Vassiliki Metheniti et al.

The thermohaline and dynamic characteristics of the upper ocean can be affected by the way the sunlight is absorbed and scattered on the surface layer. Changes in light penetration can be investigated through the turbidity of the layer, which is determined by a synthesis of terrestrial inputs (atmospheric and riverine), and the biological activity in a region, of both natural and anthropogenic origin. To examine the effects that turbidity variability has on the surface-layer characteristics of the ocean, a twin modeling sensitivity experiment was performed, using as a case study the Aegean Sea, NE Mediterranean. The Aegean Sea is an oligotrophic region with most nutrient inputs located in the northern coasts of the basin, creating a north-to-south chlorophyll-a gradient, with the highest concentrations on the North and lowest on the South. The first experiment corresponds to a very clear ocean, and the second incorporates the turbidity field, varying according to chlorophyll-a concentration.
The experiments were implemented using the NEMO models' ocean component (v3.6) for the region (34.05-41.16 °N, 22.29-28.98 °E) and for the period 1997-2001, discretized on a 1/36° Arakawa-C grid, with 75 partial step vertical levels. Atmospheric inputs are ERA-5 reanalysis products of the ECMWF service, whereas inputs for initial and boundary values have been derived from the Copernicus database. First, a two-band light penetration scheme was applied, using a Jerlov Type-I extinction depth at 23.0 m, representing the constant-low turbidity field. An RGB scheme was applied for the second experiment, using the multiyear monthly mean of the chlorophyll-a concentration variable derived from the ESA-CCI service. The sea surface variables' response is examined for the final year of the experiment. The results indicate that the RGB-scheme experiment estimates elevated sea surface salinity and temperature values, with the most significant difference in salinity located in the northern part of the basin, where there is a strong influence of the inflow of Black Sea Water from the Dardanelles Straits. Elevated eddy kinetic energy is observed in the gyres formed in the Cretan Sea.

How to cite: Metheniti, V., Vervatis, V., Karageorgis, A. P., Kampanis, N., and Sofianos, S.: Response of the Aegean Sea surface characteristics to turbidity variations, using numerical simulations., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3773, https://doi.org/10.5194/egusphere-egu22-3773, 2022.

17:57–18:03
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EGU22-7628
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ECS
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On-site presentation
Bethany McDonagh et al.

Tidal forcing in numerical models is necessary to correctly forecast the ocean, since tides are a significant source of energy and driver of mixing in the global ocean. In the Mediterranean Sea, the amplitude of tides is lower than in many other regions of the global ocean, with the exception of the Alboran Sea, North Adriatic, and Gulf of Gabes, but the effects of tides are not limited to parts of the basin with high tidal amplitude. Analysis of the relationship between tidal forcing and measures of vertical motion including mixed layer depth, vertical velocity, and vertical diffusivity have not previously been carried out throughout the Mediterranean Sea.

This work investigates the effects of tides on vertical motion in the Mediterranean Sea, using the hydrodynamic model corresponding to the Copernicus Monitoring Environment Marine Service (CMEMS) system, a baroclinic forecasting model for the Mediterranean Sea, integrated over 5 years. Several regions were selected for separate study, based on their tidal amplitude and the local importance of vertical dynamics, such as deep water formation. The inclusion of tides increased the mean mixed layer depth in winter in the Mediterranean Sea, as well as in most of the selected regions. The magnitude of vertical velocity was also increased by tides on a basin level, but did not increase consistently throughout the selected regions. Vertical diffusivity, Brunt-Väisälä frequency, and Richardson number results were also explored.

The relationship between tidal amplitude and vertical velocity was additionally studied from a theoretical perspective. This work developed a prognostic equation for vertical velocity which was then compared to model results.

Our improved understanding of the effects of tidal forcing on vertical motion in the Mediterranean Sea highlights the necessity of including tides in high resolution ocean models, and allows for the separation of their effects from the impact on vertical mixing due to other modelling choices such as the chosen parametrization of vertical diffusivity. 

How to cite: McDonagh, B., Clementi, E., Pinardi, N., Goglio, A. C., and Cessi, P.: The effects of tides on vertical motion in the Mediterranean Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7628, https://doi.org/10.5194/egusphere-egu22-7628, 2022.

18:03–18:09
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EGU22-9382
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Highlight
Melanie Juza et al.

In a warming world, society is facing major climate-related challenges and impacts, such as marine heat waves (MHW) that have devastating effects on ecosystems, threaten economies and strengthen severe storms. MHWs are substantially increasing in intensity, duration and frequency worldwide and particularly in the Mediterranean Sea. This semi-enclosed and relatively small basin responds rapidly to global warming experiencing strong spatial variations that require specific consideration, in particular to better understand the drivers, mechanisms and consequences of such extreme events on the physical, biogeochemical and biological components of the oceans.

This study proposes a comprehensive characterization of MHWs in the Mediterranean at sub-regional scale from surface to sub-surface and from open to coastal waters, using remote sensing and multi-platform in situ observations. First, the long-term evolution of MHW characteristics (mean and maximum intensities, mean duration and frequency) is analysed at sub-regional scale using the satellite observations of sea surface temperature over the last four decades. Then, the propagation of sub-regional MHWs into the ocean interior and the associated modified stratification are examined through the use of vertical hydrographic profiles from profiling floats. Finally, the ocean response to extreme temperature events is also investigated in the coastal ocean complementing the satellite observations with mooring data in the near-shore waters of the Balearic Islands.

A smart platform has been implemented to monitor, visualize and share timely information on sub-regional MHWs, from event detection in real-time to long-term variations in response to climate change, to diverse stakeholders (e.g., scientific community, educators in marine science, environmental agencies and policy decision-makers). The “Sub-regional Mediterranean Marine Heat Waves” visualization tool will help to implement adaptive management, to establish adaptation strategy and to support the marine conservation and sustainable management of the oceans in a warming world.

How to cite: Juza, M., Fernandez-Mora, A., and Tintore, J.: Sub-regional marine heat waves in the Mediterranean Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9382, https://doi.org/10.5194/egusphere-egu22-9382, 2022.

18:09–18:15
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EGU22-3942
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Virtual presentation
Giuseppe Aulicino et al.

Ocean biomass distribution has a growing importance in the world economy as a global strategic reserve, due to environmental and industrial applications and its variability related to climate change. Satellite imagery allows multi-resolution methodologies to obtain estimation, and hopefully classification, of biomass content over sea surface. This information is largely used in numerical simulations and nowadays represents an important contribute to future projections. Nevertheless, satellite, models and classical in situ monitoring resolution/accuracy sometimes cannot provide data at the finer spatial scales needed to describe the complex threedimensional water column system. On the other hand, glider surveys allow scientists to collect observations of ocean phenomena at very high resolution along the water column, to assess numerical simulations reliability and, eventually, to assimilate these data into ocean models. In this study, we present a quantitative comparison between the glider observations collected in the Algerian Basin (Western Mediterranean Sea) during the ABACUS surveys from 2014 to 2018, and the daily outputs of two co-located CMEMS model products (i.e., GLB and IBI).
The achieved results point out that model products are well correlated with glider potential temperature measurements but they still need improvements to provide a correct representation of the chlorophyll concentration variability in the study area. Generally, IBI daily simulations present higher linear correlation with concurrent glider in situ data than GLB ones. IBI products also reproduce better the pattern of the local maxima of chlorophyll concentration across the Algerian Basin. Nevertheless, they largely underestimate glider chlorophyll measurements and present significant differences that limit their capability to reproduce its upper ocean concentration that is needed for accomplishing advanced ecological studies.

How to cite: Aulicino, G., Cesarano, C., Zerrouki, M., Ruiz, S., Budillon, G., and Cotroneo, Y.: On the use of ABACUS high resolution glider observations for theassessment of phytoplankton ocean biomass from CMEMS model products, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3942, https://doi.org/10.5194/egusphere-egu22-3942, 2022.

18:15–18:21
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EGU22-2337
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ECS
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Highlight
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Virtual presentation
Nydia Catalina Reyes Suarez et al.

On 7 April 2021, an exceptional bloom of the scyphomedusa Rhizostoma pulmo was observed in the Gulf of Trieste (Italy). Blooms of these species in the northern Adriatic Sea have been reported since the late 1800s, however, the density of jellyfish observed in 2021 reached dozens of specimens per cubic meter. In this work, we analyze the bloom from a multi-platform approach using observation and model data at different time scales. This study aims to contextualize the oceanographic/environmental conditions that may have contributed to the exceptional aggregation of the scyphomedusa Rhizostoma pulmo along the northernmost coast of the Adriatic Sea. Our study shows that 1) the bloom was probably enabled by anomalous warm sea conditions during winter 2020, allowing specimens that reproduced in 2020 to survive and reach considerable abundance and sizes by early 2021; 2) strong wind events, such as the Bora wind for the Gulf of Trieste, enhanced upwelling and mixing processes in the gulf thus bringing the jellyfish present in deeper waters to the surface and clustering them along the coast.

How to cite: Reyes Suarez, N. C., Ursella, L., Tirelli, V., Ličer, M., Querin, S., and Cardin, V.: How physical properties can unveil the biological processes in the water column: a multi-platform study of the extreme bloom of Rhizostoma pulmo jellyfish in the Gulf of Trieste,  April 2021 case study., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2337, https://doi.org/10.5194/egusphere-egu22-2337, 2022.