Tidal forcing was not included in a large proportion of numerical models of the ocean from the past but is known to be necessary to forecast the ocean accurately, since tides dissipate around 3.5TW of energy in the global ocean, and are an important driver of mixing. The inclusion of tides in models affects not only the near-field dynamics such as local temperature and salinity, but also large-scale circulations that influence the entire global ocean. In the Mediterranean Sea, amplitudes of tides are typically low, but are known to have effects both at local scales where tidal amplitude is larger, and across the entire basin. However, their impact on processes such as circulation, vertical mixing, and internal tides at the basin scale are not well known. 

In this work, the characteristics of tides in the Mediterranean Sea were investigated using the hydrodynamic model NEMO (Nucleus for European Modelling of the Ocean) version 3.6, corresponding to the Copernicus Monitoring Environment Marine Service (CMEMS) system, a baroclinic forecasting model for the Mediterranean Sea, integrated over five years. 

Analysis of potential and kinetic energy due to tides showed that tides have impacts across a wide variety of spatial and temporal scales in the basin, both at the surface and at deeper levels. Increased kinetic energy at depth in the basin led to an exploration of internal tides, which have not been previously studied at the scale of the Mediterranean Sea using a numerical approach. Additionally, the effects of tides on salt transport through the Gibraltar Strait were analysed, and numerical results were compared to a two-layer box model of the Gibraltar Strait and Mediterranean Sea. This demonstrated the utility of simple theoretical frameworks to understand dynamics in the region, while highlighting the impact of increased vertical mixing in the Gibraltar Strait due to internal tides.

Our improved understanding of the impacts of tides across temporal and spatial scales lays out an argument for the inclusion of tides in ocean models ranging from local to global, and from short timescales to long term climate modelling. Our analysis also provides a novel understanding of dynamics such as internal tides and transport of salinity in the Mediterranean region.

How to cite: McDonagh, B., Clementi, E., and Pinardi, N.: The characteristics and effects of tides on the general circulation of the Mediterranean Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14117, https://doi.org/10.5194/egusphere-egu23-14117, 2023.

Marine Heat Waves (MHWs) are events of prolonged anomalously warm water, in portions of the oceans, which may have severe impacts on the local marine ecosystems.  In a climate change scenario, with increasing temperatures and more frequent atmospheric extreme events, the frequency and intensity of the MHWs are expected to increase. However, in a warming ocean, the choice of the long-term baseline used to compute SST anomalies becomes a critical issue, since it can significantly affect the frequency and intensity of the events. It may be argued that this climate change signal should be removed, in some way, to allow for a correct detection of MHWs.

Here, we critically address the problem of how to characterize and define MHWs in the present warming climate scenario by evaluating the impact of different SST climatic baselines, and the effects of removing climate trends from the original SST time series. We focus on the Mediterranean Sea, a hot spot region for climate change, where a strong mean SST increasing trend (about 0.045 °C/year) has been observed in the last 40 years.  Specifically, we use the Mediterranean SSTs, a satellite-based daily gap-free (level-4) SST provided in near real time at 1 km grid resolution and distributed through the Copernicus Marine Service (https://doi.org/10.48670/moi-00172 ).

We then examine the strong Mediterranean MHW of 2022, which started in May and is not yet extinguished at the time of this writing (December 2022). The MHW extended its presence through the summer and autumn seasons, with a sequence of intense events that interested between 30% to 60% of the Mediterranean area. The intensity of the 2022 MHW was comparable to that of the famous 2003 event, but the durations of the two MHWs have been quite different: in 2003 the areal threshold of 30% was exceeded from May to August (4 months) while in 2022 that threshold was exceeded from May to December and continues in January 2023. The evolution of the 2022 MHW is also discussed in relation to the corresponding atmospheric events occurred over the western portion of Europe and of the Mediterranean Sea and complemented with in situ data acquired at the ENEA station for climate observation of Lampedusa.

This work is funded in the framework of project “Detection and threats of marine heat waves -CAREHeat” of the European Space Agency - ESA – OCEAN HEALTH  program.

How to cite: Marullo, S., De Toma, V., di Sarra, A., Iacono, R., Landolfi, A., Leonelli, F., Napolitano, E., Meloni, D., Organelli, E., Pisano, A., Santoleri, R., and Sferlazzo, D.: Has the frequency of Mediterranean Marine Heatwaves really increased in the last decades?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4429, https://doi.org/10.5194/egusphere-egu23-4429, 2023.

Over the past 70 years, a major change in winter air-sea heat loss between the North-west Mediterranean (NWMed) and the Aegean Sea,  is revealed using the ERA5 amd 20CRv3 atmospheric reanalyses. The NWMed heat loss weakens from -154 Wm^-2 in 1951-1985 to -137 Wm^-2 in 1986-2020 as a results of weaker latent heat loss. This long-term weakening threatens continued dense water formation, and we show by evaluation of historical observations that winter-time ocean convection in the NWMed has declined by 40% from 1969 to 2018. Extension of the heat flux analysis reveals changes at other key dense water formation sites that favour an eastward shift in the locus of Mediterranean convection towards the Aegean Sea (where heat loss has remained unchanged at -172 Wm^-2). The contrasting behaviour is due to differing time evolution of sea-air humidity and temperature gradients. These gradients have weakened in the NWMed due to more rapid warming of the air than the sea surface but remain near-constant in the Aegean. The different time evolution reflects the combined effects of global heating and atmospheric circulation changes which tend to offset heating in the Aegean but not the NWMed. The shift in heat loss has potentially significant consequences for dense water formation at these two sites and outflow to the Atlantic. The process of differential heat loss change in the Mediterranean Sea has implications for temporal variations in the balance of convection elsewhere e.g., the  high latitude Atlantic/Arctic margin dense water formation sites (Labrador-Irminger-Nordic Seas).

How to cite: Josey, S. and Schroeder, K.: Reduction in Winter Surface Heat Loss over the Past 70 Years Threatens North-West Mediterranean Convection, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5884, https://doi.org/10.5194/egusphere-egu23-5884, 2023.

The Mediterranean Sea (MS) has been experiencing significant surface warming over the past decades, greater than the global ocean and particularly higher during summers. The present study proposes the concept of Extreme Marine Summers (EMS) and investigates their characteristics in the MS in a climatological framework, based on ECMWF ERA5 daily sea surface temperature (SST) data for the period 1950-2020. Main objectives are to explore the SST substructures within EMSs, the contribution of Marine Heatwaves (MHW) during EMSs and the driving role of air-sea heat fluxes in the EMS formation.

EMSs are defined as the summers (July-August-September) exhibiting a mean SST greater than the 95^th percentile of the mean summer SST values within the study period. A marine summer may evolve as extreme under different SST substructures within the season, e.g., due to uniformly increased SST values throughout the summer or due to higher than usual SSTs of a specific part of the SST distribution during the season. Results suggest that EMSs identified in the greatest part of the basin are formed due to the warmest part of the ranked daily SST distribution being warmer than normal. SSTs within EMSs are organised under high dependency on the climatological SST variability: locations where the warmest (coldest) part of the ranked daily SST distribution is more variable climatologically, experience EMSs primarily due to the contribution of the warmest (coldest) part of the SST distribution.

MHWs in EMSs present greater intensity, duration and occurrence frequency with respect to mean MHW conditions, in the northern flanks of the Mediterranean basin and particularly in the Aegean and Adriatic Seas. Although the north-western part of the basin experiences the most intense EMSs and summer MHWs, the role of MHWs in the formation of EMSs appears more pronounced in the central and eastern MS. In the rest of the basin, and particularly in southern MS regions, MHWs in EMSs are less intense but longer lasting and more frequent than usual.

To quantify the driving role of the net surface heat flux (Q_net) in the EMS formation, a metric is proposed based on the surface heat budget equation. The proposed metric represents the mean contribution of Q_net during summer sub-periods within which SST is kept above climatology via a) faster warming or b) slower cooling compared to the corresponding climatological period. Results show that EMSs are largely driven by Q_net in the northern MS regions: a latitudinal gradient is generally observed in the basin with increasing contribution percentages while moving northerly. In areas where the observed SST anomalies are not entirely explained by surface heat fluxes, negative wind speed and mixed layer depth seasonal anomalies relative to climatology are commonly observed, suggesting that wind-induced mixed layer shoaling is a complementary EMS contributing mechanism. Moreover, results reveal a strong link between MHW properties and surface heat fluxes during EMSs, suggesting that Q_net modulates particularly the intensity of MHWs.

How to cite: Denaxa, D., Flaounas, E., Hatzaki, M., and Korres, G.: Extreme marine summers in the Mediterranean Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6923, https://doi.org/10.5194/egusphere-egu23-6923, 2023.

Using a suite of initial-condition (IC) ensemble forecasting experiments for the Mediterranean Sea, we assess the relative contribution of initial conditions versus atmospheric forcing in 10-day forecasts. Each ensemble member is forced at the surface by ECMWF fields and forecasts the same 10-day period starting from a different initial condition, which is taken from an ocean analysis estimate of the preceding 10-day period. This IC-time-shifted ensemble scheme allows us to explore the forecast dependency from both the IC and the atmospheric forcing (i.e., ECMWF).  Generally, the surface forcing dominates the forecast trajectory at the surface, leading to an inter-member spread that decreases with time. There are also cases in which the initial spread at the surface increases with time, indicating the dominant role of the uncertainty in the IC. While much less common, there are specific times and regions in which the initial condition determines the forecast trajectory during multiple days, indicating that certain oceanic structures are intrinsically more predictable. The identification of these highly-predictable oceanic states might prove extremely valuable in predicting the uncertainty in the forecast.

How to cite: Liguori, G., Nadia, P., and Hasan Ghani, M.: The relative contribution of initial condition versus atmospheric forcing in 10-day forecasts of the Mediterranean Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16588, https://doi.org/10.5194/egusphere-egu23-16588, 2023.

In a semi-enclosed sea basin, like in the Mediterranean, determining the heat flux components of the heat budget is crucial for better understanding of the water budget and the regional climate. Due to its relatively small sea basin and existence of many islands, it’s always a complex and uncertain to settle with an accurate net heat balance. The variation in the net heat budget is referred as a heat budget “closure” problem, which has referred by many authors for the Mediterranean Sea. The value of net heat flux under this closure hypothesis should be negative, but there is a considerable range of variation for net heat budget in published literatures. In that context, we have computed the heat fluxes for in the Mediterranean Sea using a higher resolution atmospheric model analysis dataset (ECMWF) along with heat fluxes using a lower resolution dataset (ERA5) to compare. The computation of heat fluxes using high resolution ECMWF analysis dataset is a newer one for the Mediterranean Sea. The resulted long-term climatology of heat flux components (between ECMWF & ERA5) has shown a close agreement except a variation is observed in the Long Wave (LW) flux which matches a similar finding from Marullo et al. (2020). In addition to the net heat budget, this study aims to provide a newer aspect with the analysis of probability distributions of air-sea fluxes and uncertainty in those distributions. We have investigated the probability distributions of heat fluxes on the base of computed air-sea fluxes time series. We have analysed the probability distributions of air-sea fluxes using atmospheric analysis and reanalysis datasets and fitted with three parameters Probability Density Function (PDF). Then, we have evaluated the applied theoretical PDF fits with observed heat fluxes that have indicated areas with uncertainty through our statistical modelling approach for the turbulent heat flux distributions. The statistical analysis of air-sea fluxes is not a usual one for the Mediterranean Sea but an important one to obtain the statistical inference of air-sea flux distributions in relation to the probable uncertainty arises in the ocean forecasts. 

How to cite: Ghani, M. H. and Ligouri, G.: Reassessment of heat budget in the Mediterranean Seaand uncertainty in the probability distributions of heat fluxes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16776, https://doi.org/10.5194/egusphere-egu23-16776, 2023.

Floating marine litter (FML) is a global problem because of the risk it poses to marine life and human health. In a semi-enclosed basin such as the Black Sea, the slow replenishment of water and the strong input from European rivers potentially favoured the increasing accumulation of FML. In this sense, it is absolutely necessary to generate strategies in the Black Sea to mitigate the impacts on the marine ecosystem and human populations. This is one focus of the DOORS European Union Project (Developing Optimal and Open Research Support for the Black Sea) within which this work is framed.

In recent years, scientific studies on marine litter in the Black Sea have increased at regional and coastal scales. Such works include counting, analysis of distribution, estimation of riverine input and the use of numerical models to identify circulation and accumulation patterns (Bouzaiene et al., 2021; González-Fernández et al., 2022). Using Lagrangian models has opened the door to the discussion of how such models should be configured and the importance of whether to include phenomena such as stokes drift. In addition, some areas have been suggested as high accumulation areas but these results diverge between authors and available data. 

LOCATE is a tool built with the Lagrangian solver OceanParcels and developed for the prediction of areas of high FML accumulation, which has been adapted and validated for the Black Sea. The experiments were performed using surface current velocity and Stokes drift data taken from the Copernicus Marine Service with items of FML represented by Lagrangian particles in the model. Two simulations were run with a homogeneous particle release over the whole basin, every month during one year. The first one with only the surface currents and the second one adding Stokes drift, in order to evaluate the contribution of including the Stokes drift taken from the wave data. A third simulation was carried out with both drivers and releasing particles daily during one year according to the estimated amount of waste transported at the mouths of the nine main contributing rivers, to identify the trends of particle movement from these discharge points.

The results indicate the south-western area as an area of high coastal accumulation in all three simulated cases. The mainly cyclonic circulation, the large input of FML from the Danube River and other northern rivers including a relevant fraction of the outflow from the Kerch Strait probably explained this. In addition, the percentage of particles beached on shore and the residence time in offshore waters were strongly influenced by including Stokes drift, moving from a percentage of 45.5% to 75.5% and from an average residence time of 99 to 63 days. These values are in agreement with recent literature supporting an overestimation of residence times by omitting Stokes drift. Finally, this is only the beginning of a forecasting tool for FML in the Black Sea that is expected to be further improved by using coupled hydrodynamic models, extending the resolution with nested areas and incorporating higher accuracy in coastal processes including beaching.

How to cite: Castro Rosero, L. M., Hernandez, I., Espino Infantes, M., and Alsina Torrent, J. M.: Numerical analysis of transport and accumulation of floating marine litter in the Black Sea., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2073, https://doi.org/10.5194/egusphere-egu23-2073, 2023.

Biogeochemical seasonal cycle in the Mediterranean Sea is characterized by late-winter early-
spring phytoplankton blooms driven by vertical mixing events that bring nutrients to surface
layers. Relatively intense bloom events are usually observed in areas where mixing is strong and
persistent enough to significantly impact concentration of nutrients in surface layers.
A markerlymarkedly intense bloom was forecasted in spring 2022 by the Med-MFC system, the
production center of the Copernicus Marine Service for the Mediterranean Sea, in the
southeastern basin (in the Cretan area). Thanks to the three-dimensional description of ocean
physical and biogeochemical dynamics at relatively high resolution (1/24°) provided by the
Med-MFC system, it has been possible to investigate various elements of the spring 2022 events.
In particular chlorophyll was 50% higher than usual, and patches of high chlorophyll
concentration lasted for 3/4 weeks. Comparison with satellite observations confirmed the notable
event and its anomaly with respect to past bloom events in the area. In this work, we investigate
the processes occurring in the area in spring 2022 using physical and biogeochemical Med-MFC
products as well as available observations. Results show that the spring 2022 event is particularly
strong with respect to climatology of the area and provide indications on the relationship
between the bloom and the forcing physical processes, e.g., water mass formation and mixing.
Moreover, it has been demonstrated the Med-MFC system capability to monitor in a real time
framework ocean health conditions and extreme marine events in the southeastern
Mediterranean.

How to cite: Teruzzi, A., Aydogdu, A., Amadio, C., Cossarini, G., Feudale, L., Grandi, A., Miraglio, P., Pistoia, J., and Salon, S.: Anomalous 2022 deep water formation and intense bloom event in the southeastern Mediterranean Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5442, https://doi.org/10.5194/egusphere-egu23-5442, 2023.

Long-term variability of the multiannual circulation inversions of the North Ionian Gyre (Bimodal Oscillating System - BiOS) was analyzed using the surface geostrophic vorticity time-series. The vorticity evolution within the period 1992-2021 in the South Adriatic Pit (SAP) area was compared to the North Ionian one to look for their possible relationship. In parallel, variations in the thermohaline properties from Argo float data in the SAP were analyzed to search for the role of baroclinic forcing in generating the vorticity variability. The long-term variations of the North Ionian vorticity show a clear BiOS signal with prevalently constant amplitude of the cyclonic mode. On the other hand, the anticyclonic mode displays a maximum in the early 1990s and then it decreases in amplitude. The maximum anticyclonic amplitude during this period is associated with the Eastern Mediterranean Transient. The vorticity curve of the SAP shows positive values (cyclonic curl) over the entire period with amplitude which changes rather weakly in the first part of the record up to 2006, while after 2006 it displays large multiannual oscillations showing also a higher long-term average value.  A comparison between the vorticity time-series and the salinity in the SAP shows that large amplitude variations in the second part of the vorticity record are in counterphase with respect to the average 0-150m salinity. This suggests that these large amplitude vorticity variations after the end of the EMT are driven by the horizontal density gradient, which is largely associated with the salinity variations, i.e., baroclinic in origin. As for the long-term trend in salinity over the 30-year time-series, the increase is quite significant.

How to cite: Menna, M., Martellucci, R., Gačić, M., Pirro, A., Civitarese, G., Mauri, E., and Cardin, V.: Long-term variability of the North Ionian Gyre (BiOS); characteristics and causes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6475, https://doi.org/10.5194/egusphere-egu23-6475, 2023.

The deepwater formation in the northern part of the South Adriatic Pit (Mediterranean Sea) during winter 2018 is investigated using in-situ glider data. After a period of about 2 weeks from the beginning of the mixing phase, a homogeneous convective area ∼110-km-wide and ∼300-m deep, breaks up due to the baroclinic instability process in cyclonic cones made of geostrophically adjusted fluid. The base of these cones is located at the bottom of the mixed layer, and they extend up to the theoretical critical depth Z_c. These cones, with a diameter on the order of internal Rossby radius of deformation (∼6 km), populate the convective site, develop beneath it, and have a short lifetime of weeks. Later on, they extend deeper and intrusion from deep layers makes their inner core denser and colder. The breaking mechanism of these cyclonic spinning features occurring during the spreading phase and some bio-geochemical aspects associated to their evolution are also addressed. The observed cones differ from the long-lived cyclonic eddies sampled in other ocean sites and formed at the periphery of the convective area in a postconvection period. In-situ data are also corroborated by theoretical studies, laboratory experiments and model simulations.

How to cite: Pirro, A., Mauri, E., Gerin, R., Martellucci, R., Zuppelli, P., and Marie Poulain, P.: New Insights on the Formation and Breaking Mechanism of Convective Cyclonic Cones in the South Adriatic Pit during Winter 2018, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12054, https://doi.org/10.5194/egusphere-egu23-12054, 2023.

Dense water formation in the Eastern Mediterranean (EMed) is essential in sustaining the Mediterranean overturning circulation. Changes in the sources of dense water in the EMed point to changes in the circulation and the water properties of the Mediterranean Sea. Here we examine with a regional climate system model the changes in the dense water formation in the EMed through the twenty-first century under the RCP8.5 emission scenario. Our results show a shift in the dominant source of Eastern Mediterranean Deep Water (EMDW) from the Adriatic Sea to the Aegean Sea at the first half of twenty-first century. The projected dense water formation reduces by 75% for the Adriatic Sea, 84% for the Aegean Sea and 83% for the Levantine Sea by the end of the century. The reduction in the intensity of deep water formation is related to hydrographic changes of surface and intermediate water, that strengthen the vertical stratification hampering the vertical mixing and thus the convection. Those changes have an impact on the water that flows through the Sicilian Strait to the Western Mediterranean and therefore on the whole Mediterranean system.

How to cite: Parras Berrocal, I. M., Vázquez, R., Cabos, W., Sein, D. V., Álvarez, O., Bruno, M., and Izquierdo, A.: Dense water formation in the Eastern Mediterranean under global warming scenario, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13187, https://doi.org/10.5194/egusphere-egu23-13187, 2023.

The Mediterranean is a climate change hot spot: it is warming 20% faster than the rest of the globe's oceans. Despite the importance of monitoring such dramatic changes and their consequences, the processes and the mechanisms involved in deep-sea variability are still unclear, due to a lack of long-term observations above 2000 m of depth. The availability of seafloor time series data and full-depth CTD profiles collected in the Ionian Sea allowed studying processes connecting the deep variability with the whole water column. The analysis of the in-situ seafloor time series showed a near-inertial peak in the current kinetic energy spectrum in the bottom layer, which hints at the presence of local vorticity. Moreover, the analysis of the CTD profiles revealed for the first time in this area the presence of variability at tidal periodicity in the deep layers (below 2000m), suggesting a connection with what was observed in the surface and subsurface layers. A unique opportunity to study and validate this mechanism was offered by the adjustment of the water stratification before and after the Eastern Mediterranean Transient, the major climate event occurred at the beginning of the 90s when warmer and saltier Aegean waters replaced colder and fresher Adriatic deep waters in the bottom layers of the Ionian basin. Data collected between 1999 and 2003 depict a stable water mass in the Ionian deep layers, identified as the Ionian Abyssal Water (IAW). The presence of the IAW layer could be a key condition for catching such variability in the deep. This allows studying the role that the stratification can have on the rapid propagation of the perturbation in depth, and also how the relative layer thicknesses and different densities can trigger the instability transport throughout the water column. The observed mean structure of the Ionian Sea stratification suggests that a 4-layer scheme should be enough to have a realistic yet straightforward theoretical representation. To study how much and under which conditions a potential vorticity input can propagate, a quasi-geostrophic equation has been considered, with 4 coupled layers of arbitrary thickness and density, simulated with a custom-designed algorithm. The relative stability of the coupled layers, and their response to external forcing, is crucial to understand how vorticity can propagate through the water column down/up and to/from the deepest layers. This case study aims to give more insight into how energy stored by the deep-sea layers can be released along the entire water column. This will enable a better parametrization of the deep processes also contributing to future Mediterranean climate numerical models.

How to cite: Giambenedetti, B., Lo Bue, N., Artale, V., and Falcini, F.: Role of stratification in vorticity propagation throughout the entire water column: a Mediterranean example (Ionian Sea), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13857, https://doi.org/10.5194/egusphere-egu23-13857, 2023.

An analysis of in-situ data gathered over the two decade post POEM period in the South-Eastern Levantine Basin from extensive hydrographic (CTD) campaigns and VOS XBT transects, along with data provided by the latest SeaDataCloud Mediterranean Sea Temperature and Salinity climatology (http://dx.doi.org/10.12770/3f8eaace-9f9b-4b1b-a7a4-9c55270e205a) and the Mediterranean Sea Physics Reanalysis from the Copernicus Marine Service (CMS; https://data.marine.copernicus.eu/product/MEDSEA_MULTIYEAR_PHY_006_004), have all provided insight on the dominant, coherent, meso-scale, circulation features as well as the evolution and variability of the thermohaline properties of the main water masses in this sub-basin. The most pronounced feature, the warm core Cyprus Eddy, migrates over the broad region of the Eratosthenes seamount and exhibits significant seasonal and inter-annual spatio-temporal variability. Another prominent structure is the anticyclonic Shikmona Eddy generated periodically due to instabilities of the strong northward flowing jet along the south-easternmost shelf and slope of the Levantine basin. Its evolution and co-existence with the Cyprus Eddy for periods of a few months, affects the temporal re-establishment of the Shikmona Gyre, which was first observed during the POEM cruises in the mid 1980s. The eastward flowing Mid Mediterranean Jet (MMJ) defines the northern flanks of these sub-basin scale eddies and transports the lower salinity Modified Atlantic Water (MAW) through the warmest and most saline region of the Mediterranean. Periodically the MMJ bifurcates and/or is diverted northward, along the western coast of Cyprus due to spatial fluctuations of the Cyprus Eddy. Four active periods were identified with either a dominant Cyprus Eddy only or coexisting Cyprus and Shikmona Eddies. This long term in-situ monitoring also provides an overview of the extent of the main water masses and characterizes their variability throughout the period considered. The temperature and salinity of the Levantine Surface Water (LSW) and of the subsurface MAW have increased. The Eastern Mediterranean Transient Water (EMTW) is shown to occupy the deep cavities, below the Eastern Mediterranean Deep Water (EMDW), in the vicinity of the Eratosthenes seamount while its upper boundary was lifted to shallower depths over the same period.

How to cite: Brenner, S., Gertman, I., Ozer, T., Simoncelli, S., and Zodiatis, G.: Dominant features and variability of the mesoscale circulation and thermohaline structure of the eastern Levantine during the post POEM period 1995-2015, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14768, https://doi.org/10.5194/egusphere-egu23-14768, 2023.

The more than 6000 submarine canyons worldwide constitute key oceanic morphologies incising continental slopes. They favor exchanges of organic matter, water masses, carbon, heat or pollutants between shallow and deep waters, driving ecosystems. They interact with the shelf and slope circulation generating local dynamics that have rarely been surveyed and observed.

Observations of currents, temperature and turbidity along the Cassidaigne canyon, in the Gulf of Lions, northwestern Mediterranean Sea, were carried out to understand the specific circulation patterns in submarine canyons and their transitions. Two oceanographic cruises led in 2017 and 2019 gathered data from the outer shelf and canyon head at 100-400 m to the base of the continental slope at 1900 m depth.

The Cassidaigne canyon is characterized by a steep and narrow morphology and is located in an active circulation area. Near the canyon head and on the shelf, the current is modulated by the stratification, the bottom morphology, the general circulation and the wind. Intermittent upwellings and consecutive relaxations lead to strong transient dynamics characterized by near inertial oscillations inside the canyon. The succession of upwellings induce a quasi-permanent residual up-canyon flow as observed in the narrow gorge area at 1700 m depth. Along-slope currents crossing the canyon during Northern Current intrusion events in the Gulf of Lions favor a temporary down-canyon circulation. Finally, turbidity currents were observed for the first time in connection with upwelling events, suggesting the triggering role of canyons’ internal hydrodynamics on shelf sedimentary processes.

How to cite: Brun, L., Pairaud, I., Silva Jacinto, R., Garreau, P., and Dennielou, B.: Hydrodynamics of the Mediterranean Cassidaigne submarine canyon from observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5490, https://doi.org/10.5194/egusphere-egu23-5490, 2023.

A submesoscale cyclonic eddy, less than 10 km in diameter, was observed in the Balearic Sea from inception to dissipation for more than a month in winter 2022 The feature was heavily sampled by freely-drifting (Lagrangian) instruments to study its kinematics, spatial structure and temporal evolution.  The Lagrangian sensors included drifters, wirewalkers and profiling floats. Additional shipboard data (underway CTD, ADCP) and remote sensing images revealed that the eddy was formed by doming isopycnals, extending more than 200 m in depth, with dense salty water at the center. The near-surface chlorophyll concentration was maximum in the eddy center, as clearly seen in ocean color satellite images.

The eddy formed in late February by pinching off from a larger cyclonic feature via the collapse of a sharp submesoscale ridge that connected it to a larger cyclone. Wavelet analysis of the drifter trajectories revealed that the submesoscale eddy had a maximum orbital speed of ~ 30 cm/s, at a radius of ~3 km. In its inner core, vorticity was as large as twice the local inertial frequency (Rossby number ~ 2). The surface drifters made looping tracks that were slightly elliptical. Tracked by the swarm of drifters until mid-March, the eddy remained surprisingly coherent as it moved to the South and then East with a drift speed between 2 and 5 cm/s. After a strong wind event, just a few drifters remained in the eddy until it weakened and dissipated in early April.

These observations were a part of the CALYPSO program, an ONR Departmental Research Initiative that addresses the challenge of observing, understanding and predicting the three-dimensional pathways by which water from the surface ocean makes its way into the deeper ocean. Vertical transports by submesoscale fronts and eddies can play an important role in ocean and climate dynamics.

How to cite: Poulain, P.-M., Centurioni, L., Ozgokmen, T., Rypina, I., Mahadevan, A., Middelton, L., Johnston, S., and D'Asaro, E.: Evolution of a submesoscale cyclone in the Balearic Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13547, https://doi.org/10.5194/egusphere-egu23-13547, 2023.