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This review first pays tribute to the famous Croatian oceanographer, Mira Zore-Armanda, and her seminal work on the Adriatic water masses in 1963, and emphasises the importance of the densest Mediterranean water mass: North Adriatic Dense Water (NAddW). This water mass is generated through substantial wintertime surface cooling and evaporation over the wide northern Adriatic and is known to (1) influence the Adriatic-Ionian thermohaline circulation, (2) bring oxygen and carbon to the deep Adriatic layers and, (3) more generally, have a substantial impact on the physics and biogeochemistry of the whole Adriatic. Second, the NAddW physics, from preconditioning, through generation and spreading, to accumulation in Adriatic depressions, is reviewed. Then, the temporal evolution of the NAddW properties influenced and connected to (1) basin-wide interannual and decadal variability and (2) trends towards warmer and saltier source characteristic due to ongoing climate change, is discussed. The importance of long-term observations and atmosphere-ocean modelling in event, decadal and climate studies is then presented. Finally, a review of the identified gaps and perspectives for future research is concluding this article. [ABSTRACT FROM AUTHOR]

Four chronologies of the bivalve species Glycymeris pilosa have been constructed along a 300 km gradient of the eastern coastal Adriatic Sea, all of which span the common period of 1982–2015. The chronologies are compared to local and remote environmental drivers suspected to influence the biology of the system, including air and seawater temperature, precipitation and freshwater discharge. The Adriatic-Ionian Bimodal Oscillating System (BiOS), a key oceanographic feature quantified by satellite-derived absolute dynamic topography, is also compared to the chronologies. The chronologies at the two southern sites are more strongly influenced by local river discharge, while the two northern chronologies are more strongly influenced by BiOS. These results highlight the broadscale importance of BiOS to the Adriatic system as well as the heterogeneity of nearshore environmental and drivers of growth. These G. pilosa chronologies provide unique multidecadal, continuous, biological time series to better understand the ecology and fine-scale variability of the Adriatic with potential for other shallow, semi-enclosed seas. [ABSTRACT FROM AUTHOR]

Highlights • Seven multi-decadal ocean simulations have been assessed for the Adriatic Sea. • Analysed simulations differ in resolution, forcing and coupling strategies. • Thermohaline properties and dynamic processes of the Adriatic Sea are better reproduced by coupled models. • All analysed models underrepresent dense water formation on the shelf. • Ocean model resolution and river forcing play a second-order role. Abstract A performance study of seven regional ocean configurations based on NEMO has been carried out for the Adriatic Sea over a common period (1980–2012). Assessed models differ in resolution, model physics, atmospheric forcing (forced vs. coupled models) and river discharges imposed within the Adriatic Sea. Models have been evaluated on the long-term temperature and salinity measurements in all of the Adriatic sub-basins, in particular within dense water collectors (Jabuka Pit and South Adriatic Pit) and dense water formation sites (northern and southern Adriatic). Adriatic-wide salinity content is mostly linked to the proper introduction of the overall water budget, rather than to the local river forcing. Forced models mostly overestimate temperature and salinity values. On average, coupled models better reproduce the thermohaline properties and processes, in particular the Adriatic-Ionian Bimodal Oscillating System (BiOS) reversals and its decadal variability. Wintertime heat losses are playing major role in defining the Adriatic Deep Water (ADW) transport rates in coupled models, while in forced models preconditioning in salinity is the most important factor. Further on, increase of resolution of the atmospheric forcing results in more realistic ocean behaviour, including dense water formation (DWF) in the complex coastal northern Adriatic. However, all models have large temperature biases and lower deep stratification at the dense water collector sites, indicating overall underrepresentation of the Adriatic DWF. Consequently, mixed-layer depth in the southern Adriatic is overestimated, reaching the bottom during some years. Ocean model resolution and river forcing seem to play a second-order role in defining the overall Adriatic-Ionian thermohaline properties, while inclusion of aerosol trend only slightly modified the BiOS reproduction. [ABSTRACT FROM AUTHOR]

The topical issue includes 22 papers on different aspects of meteorology and climatology of the Mediterranean and Black Seas. The papers are grouped into three categories, based on scale analysis of processes, and whether the study is dominantly related to the atmospheric or oceanic phenomenon. The category “Storms, Extremes and Mesoscale Processes” encompasses seven papers, ranging from observation and modelling data analysis of extreme atmospheric (severe winds, hailstorms, waterspout, cyclones) and oceanic (meteotsunamis, surface waves) events, occurring locally, but being connected to wider patterns and processes. The six papers in category “Atmospheric Climate, Variability and Climate Change” contain analyses of long-term observations and climate projection outputs, but also assess atmosphere-ocean-land interactions and cycles, that are important in a climate perspective. The category “Ocean Climate and Variability” includes nine papers, which map ocean processes (sea level variability, circulation, sea surface temperatures, vertical thermal structure, water masses and dense water formation) on a climate timescale, both, in the Mediterranean and Black Sea sub-basins, or taking them as a whole. [ABSTRACT FROM AUTHOR]

A performance analysis of the NEMOMED8 ocean regional circulation model was undertaken for the Adriatic Sea during the period of 1961-2012, focusing on two mechanisms, dense water formation (DWF) and the Adriatic-Ionian Bimodal Oscillating System (BiOS), which drive interannual and decadal variability in the basin. The model was verified based on sea surface temperature and sea surface height satellite measurements and long-term in situ observations from several key areas. The model qualitatively reproduces basin-scale processes: thermohaline-driven cyclonic circulation and freshwater surface outflow along the western Adriatic coast, dense water dynamics, and the inflow of Ionian and Levantine waters to the Adriatic. Positive temperature and salinity biases are reported; the latter are particularly large along the eastern part of the basin, presumably because of the inappropriate introduction of eastern Adriatic rivers into the model. The highest warm temperature biases in the vertical direction were found in dense-water-collecting depressions in the Adriatic, indicating either an inappropriate quantification of DWF processes or temperature overestimation of modelled dense water. The decadal variability in the thermohaline properties is reproduced better than interannual variability, which is considerably underestimated. The DWF rates are qualitatively well reproduced by the model, being larger when preconditioned by higher basin-wide salinities. Anticyclonic circulation in the northern Ionian Sea was modelled only during the Eastern Mediterranean Transient. No other reversals of circulation that could be linked to BiOS-driven changes were modelled. [ABSTRACT FROM AUTHOR]

A major tsunami-like event, locally known as ‘marrobbio’, impacted the southwestern coast of Sicily on 25-26 June 2014. The event was part of a chain of hazardous episodes in the Mediterranean and Black seas during the last week of June 2014 resulting from an anomalous atmospheric system (“tumultuous atmosphere”) propagating eastward over the region. The synoptic patterns and vertical structure of the atmosphere over Sicily at the time of the event indicate that atmospheric wave ducting was responsible for the generation of tsunamigenic air pressure disturbances that produced especially high sea level responses (“meteotsunamis”) at certain sites along the Sicilian coast. The strongest sea level oscillations were observed at Mazara del Vallo, where a 1-m meteotsunami bore, propagating upstream in the Mazaro River, was generated. The combined effects of external resonance (Proudman resonance on the western Sicilian shelf) and internal resonant conditions (bathymetric and topographic characteristics of specific sites) were found to be the key factors that caused the meteotsunami (marrobbio phenomenon) on the coast of Sicily and the meteobore at Mazara del Vallo. [ABSTRACT FROM AUTHOR]

The paper provides a comprehensive review of all aspects of Adriatic Sea level research covered by the literature. It discusses changes occurring over millennial timescales and documented by a variety of natural and man-made proxies and post-glacial rebound models; mean sea level changes occurring over centennial to annual timescales and measured by modern instruments; and daily and higher-frequency changes (with periods ranging from minutes to a day) that are contributing to sea level extremes and are relevant for present-day flooding of coastal areas. Special tribute is paid to the historic sea level studies that shaped modern sea level research in the Adriatic, followed by a discussion of existing in situ and remote sensing observing systems operating in the Adriatic area, operational forecasting systems for Adriatic storm surges, as well as warning systems for tsunamis and meteotsunamis. Projections and predictions of sea level and related hazards are also included in the review. Based on this review, open issues and research gaps in the Adriatic Sea level studies are identified, as well as the additional research efforts needed to fill the gaps. The Adriatic Sea, thus, remains a laboratory for coastal sea level studies for semi-enclosed, coastal and marginal seas in the world ocean. [ABSTRACT FROM AUTHOR]

We present the Adriatic atmosphere–ocean trends and variability simulated by the kilometer-scale Adriatic Sea and Coast (AdriSC) climate model during the 1987–2017 period. As the AdriSC model has been successfully validated over the entire basin against an extensive dataset of in situ measurements and remote sensing products, the reliability of the presented results at the regional (basin-wide) and local (sub-domains) scales is high. We found that trends and variability in the atmosphere reveal strong land-sea contrasts with (1) stronger temperature trends associated with lower, mostly seasonal, variability over the Adriatic Sea than over the land and (2) positive trends of wind speed and negative trends of relative humidity associated with high, mostly seasonal, variability over the sea and vice versa over the land. While, in the ocean, the analysis highlights several processes: (1) extensive warming by the atmosphere at the surface during summer, affecting both temperature and salinity, (2) shallowing of the advection of the saline Levantine Intermediate Water inflow into the Adriatic, (3) decrease of the Adriatic deep water outflow and therefore the Adriatic-Ionian thermohaline circulation, (4) warming of near-bottom waters, in particular in the middle and northern Adriatic, and (5) shrinking and weakening of the Southern Adriatic Gyre, in particular at its center. We thus demonstrate that kilometer-scale coupled atmosphere–ocean modelling is an indispensable tool for proper quantification of climate change in complex coastal basins, as it captures local characteristics not properly reproduced by present state-of-the-art regional climate models with an order of magnitude coarser resolutions. [ABSTRACT FROM AUTHOR]

The article aims to quantify a multiyear ocean temperature change at a shallow (5 m) coastal site in the northeastern Adriatic. Measurements were taken between May 2014 and May 2021 with an hourly resolution, allowing for an extraction of temperature variations over longer-term, seasonal, synoptic, quasi-diurnal and hourly timescales. As expected for shallow waters, the seasonal influence is prevalent, while diurnal changes are quasi-persistent throughout the year. Marine heat waves and cold spells are the strongest during spring and summer months. Non-seasonal changes mostly guide longer-term (>10 days) variability, yet rapid temperature changes reach 2 °C/h during stratified seasons. Such rapid changes may impact benthic communities and the physiology of marine species, including bivalves. This is especially important in the era of global warming, in which environmental conditions are already pushed towards their thresholds, and where high-frequency variability analyses can be useful in introducing a precautionary approach for local climate change adaptation. • Multi-year hourly coastal temperature data has been analyzed in the Adriatic. • Near-surface temperature variability across timescales has been documented. • Seasonal variability is prevalent, yet the temperature may change rapidly. • The temperature changes may strongly impact the benthic organisms, like bivalve. [ABSTRACT FROM AUTHOR]

This study aims to document the effects of imposing different river runoff forcing and tidal forcing to the dense water formation (DWF) rates and dynamics in a semi-enclosed sea. An extreme DWF episode that occurred in the winter of 2012 in the shallow northern Adriatic Sea during a prolonged cold bora wind outbreak event has been reproduced using a one-way coupled atmosphere-ocean modelling system comprised of the atmospheric Aladin/HR mesoscale model and ocean ROMS model. Three different river runoff forcing and tides/no tides scenarios were imposed on the model. The introduction of tides and river climatology instead of real rivers did not substantially change the modelled DWF transports and volumes, whereas the simulation using the old Raicich climatology resulted in a substantial freshening of the entire Adriatic that reduced or prevented the DWF at sites in the northern and northeastern Adriatic. The necessity of using an up-to-date river runoff climatology to properly reproduce the DWF in semi-enclosed seas is emphasised. [ABSTRACT FROM AUTHOR]

We performed a number of sensitivity experiments by applying a mapping technique, self-organizing maps (SOM) method, to the surface current data measured by high-frequency (HF) radars in the northern Adriatic and surface winds modelled by two state-of-the-art mesoscale meteorological models, the Aladin (Aire Limitée Adaptation Dynamique Développement InterNational) and the Weather and Research Forecasting models. Surface current data used for the SOM training were collected during a period in which radar coverage was the highest: between February and November 2008. Different pre-processing techniques, such as removal of tides and low-pass filtering, were applied to the data in order to test the sensitivity of characteristic patterns and the connectivity between different SOM solutions. Topographic error did not exceed 15 %, indicating the applicability of the SOM method to the data. The largest difference has been obtained when comparing SOM patterns originating from unprocessed and low-pass filtered data. Introduction of modelled winds in joint SOM analyses stabilized the solutions, while sensitivity to wind forcing coming from the two different meteorological models was found to be small. Such a low sensitivity is considered to be favourable for creation of an operational ocean forecasting system based on neural networks, HF radar measurements and numerical weather prediction mesoscale models. [ABSTRACT FROM AUTHOR]

This paper examines oceanographic properties along the northern portion of the Palagruža Sill, middle Adriatic Sea, from 1998 to 2011. Temperature, salinity, dissolved oxygen (DO), total inorganic nitrogen (TIN) and orthophosphate concentrations were collected at four stations on a seasonal basis and monthly basis, spanning from coastal waters to the deepest part of the sill. Seasonal profiles and variances were computed, exhibiting no strong seasonal variability in either coastal or open Adriatic waters, except for temperature. The transect profiles were analysed using the Self-Organising Maps (SOM) method, which extracted two regimes with several transitional patterns characterized by an anomaly in one or more variables. These regimes match the Bimodal Adriatic-Ionian Oscillation (BiOS) regimes in the northern Ionian Sea, which are found to drive decadal oscillations in oceanographic parameters in the Adriatic. As the transect mainly encompasses the euphotic zone, no strong connection was found between BiOS regimes and DO, TIN and orthophosphate concentrations. This suggests that, in addition to basin-wide circulation, other physical and biogeochemical processes are more important for nutrient dynamics in the euphotic zone. The use of the SOM method in ocean coastal studies is discussed. [ABSTRACT FROM AUTHOR]

This paper contains a basin-wide assessment of high-frequency sea level oscillations in the Mediterranean Sea for the period from 2010 to 2014. Sea level series with temporal resolutions of 1 min were taken from 29 tide gauges that had been operational for at least 4 years with high-quality time series. The contribution of high-frequency sea level variance (2 min–6 h) to the total and residual sea level variance was estimated to vary between 0.4% and 9.5% and between 0.6% and 12.1%, respectively, but to become dominant at some stations during extreme high-frequency events. A total of 36 high-frequency sea level events were extracted from the series, with some occurring locally in one of the four selected regions of Spain, Sardinia, Sicily and the Greece–Ionian Sea (6 events), some occurring over two or three regions (19 events), and some occurring in all of the selected regions within a period of 1–3 days (11 events). The basin-wide events normally propagate from the western to the eastern parts of the basin, with an average velocity of approximately 30 km/h. Synoptic patterns associated with high-frequency events were analysed, and a high resemblance to patterns associated with meteotsunamis was observed: (i) a cyclone with a centre W-NW from the affected area, (ii) a strong thermal front in the lower troposphere, and (iii) a forefront of an unstable strong mid-tropospheric jet placed over the affected area. The strong coherence between high-frequency sea level events and synoptic patterns introduces the possibility of a timely forecast of these events. [ABSTRACT FROM AUTHOR]

The paper documents dynamics of the middle Adriatic region, and is based on computation of relative geostrophic currents from temperature and salinity data taken along the Palagruža Sill transect between 1957 and 2010. The strongest westward current is found in the central part of the sill, corresponding to the offshore deflected Eastern Adriatic Current (EAC). The Western Adriatic Current (WAC) is, as expected, found in the southern part of the measured transect. The WAC is most significant during the summer season and exhibits stronger variability than the EAC due to the frequent growth of eddies within it. Long-term trends in both the central and southern parts of the sill oppose mean currents, indicating the weakening of the EAC and WAC and therefore of the entire Adriatic thermohaline cell. These opposing trends have not been reproduced by a climate model. [ABSTRACT FROM AUTHOR]

Global long-term sea-level variability trends and regional coherence patterns were mapped based on hourly sea-level time series data from the 29 longest operating tide gauge stations distributed worldwide. We split sea-level variability into three frequency bands: (1) small-scale synoptic bands (1-3 d), (2) large-scale synoptic bands (3-10 d) and (3) planetary-scale bands (10-100 d). We then calculated seasonal and annual trends. The most coherent result obtained involved a significant decrease in sea-level variability over the tropical and subtropical Pacific, particularly at the synoptic scale frequencies. Several other coherent regions were found and linked to changes in the global atmosphere. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The goal of this paper is to investigate the relationship between environmental variables and the occurrence of anchovy ( Engraulis encrasicolus) spawning over a year, in order to enable the timing and strength of high spawning activity to be predicted. Biological sampling of anchovy was conducted on the fishing grounds of the eastern Adriatic (the northernmost semi-enclosed basin in the Mediterranean) on a monthly basis from January 1999 to December 2010, while data on environmental parameters were taken from in situ measurements at the most representative and best surveyed eastern Adriatic hydrographic station and from I-COADS monthly surface fields. Anchovy spawning seasonality was defined by monthly changes of the maturity stages and the gonadosomatic index. Fluctuations of the gonadosomatic index revealed that spawning begins in March and lasts until September, with reproductive activity peaking from April to July. A significant correlation was found between the gonadosomatic index and upper layer salinity in the two preceding months, while the lagged wind-mixing index and surface temperature are barely correlated to the gonadosomatic index. An enhanced input of nutrient-rich freshwater of river origin, which reduces upper layer salinity and enhances primary production up to 2 months before anchovy spawning, seems to be correlated with the anchovy fertility, especially for a late spawning maximum (in July). [ABSTRACT FROM AUTHOR]

Abstract: This paper documents the present climate and future climate projections of sea-level variability (SLV) induced by atmospheric pressure and wind for period bands ranging from 1 to 100days in the Mediterranean Sea. The results are based on output from a regional barotropic numerical ocean model. Present climate SLV was simulated using air pressure and wind fields from a dynamical downscaling of the ERA40 reanalysis for 1958–2008 (hindcast) and validated with long-term tide gauge records. Climate projections for the 21st century were forced with output from the atmospheric ARPEGE model using scenarios B1, A1B and A2. Additionally, we performed a control simulation forced by observed SSTs, GHGs and aerosol concentrations for the period 1950–2000. SLV has been assessed over three different period bands (1–3, 3–10 and 10–100days) that were obtained by applying digital band-pass filtering procedures to both the present day and climate projections. Of the three time periods, the 1–3-day SLV had the worst comparability between the hindcast and the observations. We found that most of the SLV trends were insignificant in the present climate but were negative in the projections over all of the periods, especially for the medium- (A1B) and high-emission (A2) scenarios. Projections of 3–10- and 10–100-day extreme SLV, estimated from high-order percentiles, indicate increases in extreme SLV events versus the average. This result does not apply to the 1–3-day extreme SLV. The largest negative SLV trends were projected for autumn and for the 1–3-day period band, except for the low-emission (B1) scenario. However, the 1–3-day period band contributed less than 12% to the overall SLV, while the largest variance (55–75%) was present in the 10–100-day period band, indicating the importance of correct simulation of planetary-scale atmospheric processes with long temporal scales for the reliability of the climate projections. [Copyright &y& Elsevier]

Abstract: The paper attempts to document long-term changes in deep Adriatic water patterns by applying the Self-Organising Maps (SOM) method to temperature, salinity, dissolved-oxygen content, orthophosphate and total inorganic nitrogen profiles sampled at a single deep station in the South Adriatic Pit (SAP) over a half century (1957–2009). Seasonality observed in upper layers has been removed by the least-squares fitting of the annual and semi-annual sinusoidal functions. The sensitivity of the SOM to various parameter combinations reveals the importance of temperature, salinity and dissolved oxygen for mapping different water patterns, while nutrients have less influence on quality and applicability of SOM solutions to the extraction of characteristic SAP water profiles. The quality of fit obtained for different combination of the measured parameters introduced to a SOM suggests that the incomplete combinations of input parameters increase an imperfection in the applicability of SOMs to the dataset. Two modes of long-term changes in the SAP obtained by the SOM analyses are discussed with respect to the processes that drive the variability in the area, e.g., the Adriatic-Ionian Bimodal Oscillation: where the first mode is characterised by rapid changes in the transition of SAP water masses, observed before 1980s (less adoptable by the SOMs), and the second mode is characterised by steady transitions (better adoptable by the SOMs), observed in the 1990s and the 2000s. The SOM method is found to have certain advantages when compared to other methods that have previously been used to distinguish the Adriatic water masses, as it does not depend on predefinition of water mass sources and allows for gaps in series. [Copyright &y& Elsevier]

Abstract: This paper documents the variability and trends of mean storminess and extreme sea level amplitudes at selected long-term operating tide gauge stations located in the European Seas over different frequency bands, seasons and months. Six stations have been chosen for the analyses–Antalya, Ceuta, Rovinj, Newlyn, Wladyslawowo and Lerwick–which possess at least a half-centurial record of hourly or higher frequency sea level data. The data have been carefully inspected for time shifts and drifts in the record. The analyses included the extraction of sea level amplitudes (envelopes) over four frequency bands: super-diurnal frequencies (0–1days), small-scale synoptic disturbances (1–3days), large-scale synoptic disturbances (3–10days) and planetary-scale disturbances (10–100days). Interannual variability in sea level amplitudes is occasionally found to coincide with some known variability in the atmosphere. For example, the northern European stations have overall positive sea level storminess and extreme trends, which is opposite from the southern stations, confirming a northward shift in atmosphere storm tracks. Redistribution of sea level amplitudes between different seasons and different frequency bands has been observed at some stations in both variability and trends. The latter may be important for the assessment of a region''s total hazard risks and vulnerability, as maximum storminess and extremes may or may not coincide with maximum mean sea level. [Copyright &y& Elsevier]

This paper documents the occurrence of strong fortnightly oscillations in the Adriatic Sea frequently observed in the current measurements. For that purpose, we analyzed half-decadal sea level series and long-term currents collected within different parts and layers of the Adriatic Sea. Harmonic analysis and band-pass filter with cutoff periods at 10 and 20 days have been applied to the series. The sea level Mf tide is found to be the only significant tidal constituent over periods between the diurnal and semi-annual ones, having no significant phase variations in the Adriatic Sea. Moreover, the currents on periods between 10 and 20 days could only partially be explained by atmospheric forcing. The fact that they are in-phase with the Mf tide gives a hint on a possible mechanism responsible for the generation of these oscillations. Additionally, these currents are usually strongly amplified during a weakly stratified season, indicating a baroclinic mechanism responsible for the multiplication of the fortnightly currents. [ABSTRACT FROM AUTHOR]

This paper aims to quantify the productivity of research concerning the Adriatic Sea, with a focus on oceanography and meteorology. Productivity and impact were measured by analysing articles and citations from the Thomson Reuters Web of Science database, spanning the period 1994-2008. The most productive country was Italy but the highest number of citations was achieved by articles from Germany (all Adriatic publications) and Spain ("Oceanography" and "Meteorology and atmospheric sciences", only). By contrast, the second-most productive country, Croatia, had the lowest citation rate. Collaborations between Adriatic researchers were driven not only by the geographical position of a country (e.g., Italy vs. Croatia), but also by investment rates in Adriatic research (e.g., Italy vs. USA and Croatia vs. USA). Such collaborations substantially improved the impact of the research, especially from transitional countries such as Croatia. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates whether concurrent or subsequent meteotsunamis could happen at both the Balearic Islands and the Adriatic Sea as a consequence of either the simultaneous presence of the favourable synoptic pattern above both areas, or propagation of the pattern from one area to another. Meteotsunami events in sea level records from Dubrovnik (chosen to be the proxy for the occurrence of meteotsunami events in the Adriatic Sea) are compared to 32 known Ciutadella (the Balearic Islands) events. The analysis shows that a meteotsunami at the Adriatic Sea is likely to happen if the favourable synoptic pattern propagates or spreads from the Balearic Islands to the Adriatic Sea, causing meteotsunamis in both places. Upper level instabilities are recognized as the most important synoptic feature for the occurrence of meteotsunamis, as these instabilities can generate the atmospheric gravity waves which provoke meteotsunamis and also help to trap the atmospheric energy at lower levels. [Copyright &y& Elsevier]

Abstract: The paper overviews meteotsunami events documented in the Adriatic Sea in the last several decades, by using available eyewitness reports, documented literature, and atmospheric sounding and meteorological reanalysis data available on the web. The source of all documented Adriatic meteotsunamis was examined by assessing the underlying synoptic conditions. It is found that travelling atmospheric disturbances which generate the Adriatic meteotsunamis generally appear under atmospheric conditions documented also for the Balearic meteotsunamis (rissagas). These atmospheric disturbances are commonly generated by a flow over the mountain ridges (Apennines), and keep their energy through the wave-duct mechanism while propagating over a long distance below the unstable layer in the mid-troposphere. However, the Adriatic meteotsunamis may also be generated by a moving convective storm or gravity wave system coupled in the wave-CISK (Conditional Instability of the Second Kind) manner, not documented at other world meteotsunami hot spots. The travelling atmospheric disturbance is resonantly pumping the energy through the Proudman resonance over the wide Adriatic shelf, but other resonances (Greenspan, shelf) are also presumably influencing the strength of the meteotsunami waves, especially in the middle Adriatic, full of elongated islands and with a sloping bathymetry. The generated long ocean waves are hitting funnel-shaped bays or harbours of large amplification factors, resulting in meteotsunami waves with heights up to 6m at the very end of bays or harbours. Within models the mechanism is fairly well understood, but it is extremely difficult to reproduce these events (and presently almost impossible to forecast) as the meteotsunami generating process is highly variable at both temporal and spatial scales. The final part of the paper discusses the possibilities for further research of the Adriatic meteotsunamis, and meteotsunamis in general, including the basis of a meteotsunami warning system which should be able to capture potentially dangerous travelling atmospheric disturbances in real-time. [Copyright &y& Elsevier]

Abstract: This paper describes an extraordinary tsunami-like event that occurred on 21 June 1978 that encompassed the middle and south Adriatic Sea. The flood had its culmination in Vela Luka, where a maximum wave height of 6m was reported. This paper contains a detailed description of the event as seen by eyewitnesses, its outreach along both the eastern and western coasts, and the aftermath and recovery activities in Vela Luka. All available records have been collected and analysed to detect the source and the generating mechanism of the long ocean waves. Seismic generation is fully excluded from the consideration, while a submarine landslide seems rather unrealistic as it does not explain the characteristics of the measured ocean waves. Therefore, the source of the event was presumably in the atmosphere, where a travelling disturbance was detected that had the capability to resonantly transfer energy to the ocean via the Proudman resonance mechanism. Although these data prove the proposed mechanism, the final confirmation for such a scenario should come from a process-oriented numerical modelling study. [Copyright &y& Elsevier]

A destructive tsunami-like event (locally known as “rissaga” waves) occurring on 15 June, 2006 in Ciutadella Harbour (Menorca, Balearic Islands) is reproduced by a numerical model forced by a travelling atmospheric disturbance. The disturbance is reconstructed from microbarograph measurements, being the only available instrumental data at the time of the event. The model is verified based on two weaker 1997 events, which were recorded by a number of bottom pressure recorders operating at that time on the Menorca shelf, in Ciutadella Inlet and adjacent Platja Gran Inlet. Both 1997 events are numerically simulated and good agreement is achieved with observations in time, frequency (including eigenfrequencies of the affected inlets) and wave heights. Subsequently the same model is applied to simulate the 2006 event. The vigorous currents with speeds up to 400 cm/s are found to occur specifically at those areas of the harbour where the most severe damage and sinking of boats had been reported. Maximum simulated sea-level heights of 2.5 m were about one half of those reported by eyewitnesses. This difference is apparently caused by quality and spatial resolution of bathymetry data. However, in general, the model is capable of reproducing the event fairly well and can probably be used for future assessment and mitigation activities on the coasts of the Balearic Islands. [ABSTRACT FROM AUTHOR]

The paper describes a finding of photoautotroph cyanobacteria Synechococcus in deep Adriatic waters during the spring of 2006. The maximum abundance in early May was positioned at 800 m, being of order of the values referred for the surface waters in the Adriatic Sea. The deep abundance maximum has been associated to the fast ventilation of deep Adriatic waters, usually occurring during wintertime strong cooling events. Two processes were detected: (1) deep convection in the South Adriatic Pit (SAP) and (2) density current going downslope. The first process was responsible for bringing the cyanobacteria down to 600-m depth in the area of convection, and the second one triggered the downslope transport of the cyanobacteria to the SAP very bottom. The depletion rate of Synechoccocus cyanobacteria in an extremely hostile environment has been computed to equal about 1 month. [ABSTRACT FROM AUTHOR]

This paper analyzes potential recruitment effect of endangered bivalve Pinna nobilis in a small marine protected area-Little Lake (Adriatic Sea). A box model has been applied for the estimation of residence time of the lake, forced by tides only at the open end of the lake system. The residence time of Little Lake was estimated to be 54 days. In our approach we assumed that P. nobilis larvae may be found in the surface waters only during the night, thus restricting their outgoing from the lake to about 7-8 hours per day in the June-August period, as the larvae need some time to reach surface waters. Therefore, the equivalent residence time of the larvae in Little Lake is estimated to be about 160-185 days. Knowing that the bivalve larva phase lasts between 3 and 5 weeks, one may estimate that only 11 to 22% of the larvae, respectively, leave Little Lake. From a conservation standpoint these low values imply a special level of protection within Mljet National Park In addition, future climatic changes will affect the recruitment of P. nobilis, not only due to sea level rise but also with temperature and other changes which may influence its reproduction phase and larvae transport. [ABSTRACT FROM AUTHOR]

Abstract: The paper documents numerical modelling exercises designed to reproduce the Proudman resonance on a shelf. Various sinusoidal air pressure disturbances were simulated to travel over the homogeneous waters on a flat or slope bathymetry, qualifying and quantifying the strength of resonance and near-resonance processes in the sea. The results were discussed in light of the worldwide documented destructive meteotsunami events, putting the attention particularly on the effects of the disturbance wavelength, on the weakening of the resonance in near-resonant conditions and on the effect of a slope to the resonance strength. [Copyright &y& Elsevier]

Abstract: The paper documents characteristics of the fundamental Adriatic seiche (period of 21.5h) by analysing hourly sea level data at Split and Rovinj in 1957–2002 interval. The seiche is extracted by digital filter from residual (detided) sea level series. Basic statistics, both on seasonal and interannual scale, as well as flood (threshold-exceeding) analysis has been performed in order to visualise the importance of the seiche. Although mean seiche variance is as small as 2–3%, seiche energy can be much larger than tidal energy during extreme events. The largest seiche amplitudes occur in February and March, being almost two times smaller in summer season. A decrease of seiche flood amplitudes in time has been documented, coinciding with a decrease in the storm surge height. This is presumably due to weakening of atmospheric activity during investigated period. However, a reversal in that trend may result in disastrous and exceptionally high floods in the future, due to coupling with the global sea level rise and its regional (Adriatic) manifestation. [Copyright &y& Elsevier]

Abstract: Winter thermohaline properties of the northern Adriatic are analysed here with the aim of getting a better insight into dense water formation on the shelf. The hydrographic parameters collected in February in the 1967–2000 interval at two stations, the first located close to the eastern shore (station 1), and the second positioned near the Po river mouth (station 2), are compared. Two types of winter hydrographic conditions are distinguished: type A when bottom salinity and density are higher at station 1 than at station 2 and type B when these parameters are higher at station 2 than at station 1. Type A is more likely to occur in warmer and type B in colder winters. Both A and B distribution types can occur in periods when the Adriatic is under the influence of very saline waters of Mediterranean origin. Interannual changes in density are, at both stations, more dependant on haline than on thermal variations. At both stations temperature was somewhat higher in the early seventies than during the eighties and nineties, while salinity and density were lower in the early seventies and early nineties than in other years of the analysed period. By comparing the 1967–2000 changes in hydrographic conditions in February to monthly values of northern Adriatic surface fluxes and Po river discharge rates, it is shown that winter thermohaline characteristics in the region depend on processes which occur much earlier, i.e. during the previous autumn and late in spring of the preceding year, and even during the previous winter, 12 months before. [Copyright &y& Elsevier]

The paper overviews recent and past studies of preconditioning, generation and spreading of North Adriatic Dense Water (NAdDW), by analysing both transient episodes and climatological data. The importance of wind stress, heat and water fluxes, and particularly river discharges during the preconditioning and generative period is emphasized, as well as the advection of saline levantine intermediate water from the southeast. After the generation, NAdDW affects deep and bottom layers of the middle and south Adriatic Sea, flowing as a dense current and mixing with the adjacent waters; it can be traced even in the Otranto Strait, contributing to the formation of deep water in the Eastern Mediterranean. Objective shortcomings and the projections in NAdDW investigations are also discussed, due to their high importance in the circulation of the Adriatic Sea, which may relate other similar basins around the world. [ABSTRACT FROM AUTHOR]

Abstract: Strong air pressure and sea level oscillations, which occurred in the Middle Adriatic region during the storm passage on 21 August 2004, were recorded at a number of meteorological and tide gauge stations. Large sea levels measured were related to the Proudman and harbour resonances, being also observed during the past event on 27 June 2003. Both cases were characterized by a travelling air pressure disturbance, but a part of the oscillations in August 2004 case were a result of short-lasting strong winds which were absent during the event in June 2003. Occurrence of a strong 4-h fundamental oscillation of the whole region versus weak harbour seiches was a result of the shape of travelling air pressure disturbance: it looked like a box-function containing large energies in a low frequency domain, whereas the event in June 2003 was characterized by a cosine-like disturbance, redistributing the energy towards higher frequencies. Using a numerical model it is shown that the strength of 4-h oscillation is sensitive to the speed of travelling atmospheric disturbance and to its incoming direction. The largest amplitudes were modelled for a speed of 13 m/s, indicating that inner part of the region is possibly the best place for occurrence of the Proudman resonance. [Copyright &y& Elsevier]

Abstract: The paper documents the occurrence of long-period internal Kelvin waves in Split Channel in spring 2002. The analyses were performed on thermohaline and current data measured at three moorings and one hydrographic section. The internal oscillation had a period of 5–6 days, being larger just after the generation which was probably excited by the alongshore Sirocco wind. The recorded current amplitude was up to 0.3ms-1 in the surface layer, while the observed pycnocline displacement was 10–15m. The oscillation was reproduced by one-dimensional two-layered model of a channel, imposing nodal lines at its entrances. Cross-shore properties of the oscillation, such as observed offshore decrease in pycnocline amplitude, are explained by the dynamics of an internal Kelvin wave propagating along channel boundaries, because the internal Rossby radius is smaller than the width of the channel. Conclusively, the observed oscillation probably represents the fundamental mode of internal waves trapped in the channel complex off Split. [Copyright &y& Elsevier]

This paper describes thermohaline properties in the north and middle Adriatic Sea in 1999 based on temperature and salinity data collected along the Po-Rovinj, Jabuka Pit and Palagruǽa Sill profiles. The preconditioning, generation and spread of North Adriatic Dense Water (NAdDW), as well as their relationship to surface fluxes and river discharge are analyzed in detail. A strong Bora wind event in November 1998 resulted in heat loss exceeding 800W/m2, homogenizing and cooling the whole water column by 2.4°C, while another similar Bora episode in January/February with a cooling rate of 1.4°C ended with NAdDW generation. River discharge was low during the preconditioning and generation phases. Following its generation, the NAdDW flowed southeastward as a density current along the western Adriatic slope. Its northeastern part reached the steep edge of the Jabuka Pit and sank rapidly to the bottom, where it was observed a month after its generation. However, the core of the NAdDW current continued to follow the western slope as a density current, taking a detour around the pit on its southeastern side, and sinking to the bottom in the eastern segment of the pit. The detour and sinking at the Jabuka Pit slope was estimated with an analytical model to be 1.1m/km. Finally, the upper lighter part of the NAdDW current crossed the Palagruǽa Sill and followed the western slope entering the South Adriatic Pit and contributing to the water mass dynamics there. Another NAdDW branch was found at the very bottom of the middle of the Palagruǽa Sill, although being less pronounced than the one that moved over the western slope. [Copyright &y& Elsevier]

The study examines the occurrence of Proudman resonance in front of the Split harbour (Adriatic Sea). The dataset comprises air and sea pressure (sea level) data collected at the harbour entrance during August to October 2000 and is characterized by rather strong synoptic disturbances that took place over the harbour. The analyses encompass empirical tools, such as time-series analysis, high- and band-pass filtering, spectral and wavelet analyses, while the theoretical approach includes the conceptual model of the resonance. Resonance appears in front of the harbour and then propagates inward, covering periods between 7.7 and 28.5 min as a result of complex atmospheric gravity wave structure. Gain between sea level and air pressure equals 0.05–0.40 dbar/hPa (5–40 cm/hPa). [Copyright &y& Elsevier]

The paper examines dense water formation in the South Adriatic by analysing temperature, salinity and dissolved oxygen data collected during six along-Adriatic cruises carried out from the Jabuka Pit to the Otranto Strait. The leastsquares tracer analysis method is applied to distinguish the fractions of the four characteristic deep, dense water masses of the Adriatic Sea. Two types of dense water generation are considered: (1) shelf type occurring during cold and dry winters in the North Adriatic and resulting in the North Adriatic dense water (NAdDW) which partially transforms to the Middle Adriatic dense water (MAdDW) on its way along the Italian shelf to the Bari Canyon, where it interacts with topography, violently mixes and sinks; and (2) deep-convection type occurring in the centre of the South Adriatic Pit, generating dense water which reaches down to 800m, fills the bottom and enters the Ionian Sea through the Otranto Strait. Both processes are visible in the July 1976 data, as the previous winter was cold (February) and relatively dry over the whole Adriatic basin. Both types of processes can influence the bottom layer of the Otranto Strait, where the fraction of shelf-type dense water generated in the North and Middle Adriatic was occasionally observed along with the fraction of water generated by deep convection in the South Adriatic. During the nongenerative period, the cyclonic South Adriatic Gyre moved more to the northwest in general, as the Levantine intermediate water (LIW) occupied southeastern part of the South Adriatic Pit. However, such behaviour was not observed in January 1980, when LIW filled much of the Adriatic, thus diminishing density gradients in the South Adriatic. By applying a simple box model of water masses, it is estimated that the decay time of the Adriatic water masses equals 26 months, whereas transport of the Adriatic deep water (ADW) in the Otranto Strait amounted to 0.34 Sv during summer 1975. In the winter 1974/75 the... [ABSTRACT FROM AUTHOR]

The paper presents a unique time series of organic matter content (dissolved organic carbon, DOC, and its surface active substances fraction, SAS) collected in the northern Adriatic along the Po-Rovinj transect between 1998 and 2017. The data were collected on a monthly or bimonthly basis. Seasonal variance of organic matter content does not exceed 30% of its total variance, while the DOC and the SAS trends are significantly negative and positive, respectively, over the whole transect. The organic matter content, however, exhibits pronounced interannual and decadal changes, with periods of high and low carbon content and evident changes in composition of the SAS content. The changes indicate altering episodes between eutrophication and oligotrophication, embedded in the overall oligotrophication trend in the considered period. Both series were correlated with the potential local and regional yearly-averaged drivers in both atmosphere and sea. DOC is most strongly (significant at 99%) correlated with the Po River discharges, at the phase lag of −1 to −2 years. For the SAS, the largest correlations (significant at 99%) are obtained with the Adriatic-Ionian Bimodal Oscillating System index (BiOS index), at the phase lag of −3 to −4 years. Correlations between the organic matter content and the hemispheric or the regional climate indices (North Atlantic Oscillation, East Atlantic/West Russia, East Atlantic, Scandinavian, and Mediterranean Oscillation) are much lower and only sparsely significant at 95% at some phase lags. The same was found for the other local drivers (precipitation and net heat flux). Our analysis highlights the importance of remote processes, like the BiOS, that weren't previously considered to shape the biogeochemical properties of such shallow coastal region impacted by freshwater load. To properly assess such impacts, long-term ecological monitoring and homogenized data series are required. Unlabelled Image • Long-term study of temporal and spatial distribution of OM in the Adriatic Sea • Alternating episodes of eutrophication and oligotrophication in the northern Adriatic • Seawater OM as a complex mixture of organic material with surface active properties • Decreasing DOC and increasing SAS trend in the northern Adriatic over last 20 years • NAd OM quality and quantity controlled by variable Po water discharge and BiOS [ABSTRACT FROM AUTHOR]

In situ thermohaline variables measured monthly or bimonthly in the shallow northern Adriatic at prescribed stations between 1979 and 2017 were correlated with the local (river runoff, precipitation, net heat flux) and remote atmospheric (various hemispheric and regional indices) and oceanic (the Adriatic-Ionian Bimodal Oscillating System, BiOS) drivers acting on monthly to annual timescales. The highest correlation between the temperature and the local drivers was obtained in winter along the western part of the study area, while the rivers and precipitation mostly shaped the summer and December salinity values. The net heat fluxes and river discharges preceding the dense water formation (DWF) by 1–2 months and up to 3 months were found to be important for the February temperature and salinity variability, respectively. No significant correlations were found between the February thermohaline variables and the monthly BiOS index for the phase lags up to −11 months, while the correlation was the largest between the yearly averaged BiOS index and the yearly averaged salinity at phase lags of −2 to −4 years. The bottom yearly averaged salinity has also been highly correlated with the Mediterranean Oscillation index at phase lags of −1 and −3 years, while the yearly averaged surface temperature was influenced by the East Atlantic and East Atlantic/West Russia patterns. Acting independently on different timescales, both the local and remote processes were found to drive the thermohaline variability in the northern Adriatic, thus providing an option for a forecast of the DWF and the thermohaline circulation in the Adriatic-Ionian basin. • Thermohaline observations have been correlated with atmospheric and oceanic drivers. • Local drivers shape the thermohaline variability at monthly timescales. • Remote drivers were correlated with temperature and salinity at yearly timescale. • The BiOS is a key driver for the northern Adriatic decadal thermohaline variability. [ABSTRACT FROM AUTHOR]

• Anomalous physical and microbial properties were detected in the middle Adriatic. • Local and remote drivers contributed to record-breaking salinities. • Picoplankton biomass and production sharply declined in high salinity conditions. • The documented conditions could be more frequent in the future climate. Oceanographic measurements carried out in the middle Adriatic during summer 2017 revealed anomalous conditions in both physical and microbial properties. High salinities were observed throughout the entire water column, with an 'inverse' salinity profile in August and a maximum in the surface layer, recorded for the first time in the middle Adriatic. Surface salinity of 39.02 recorded in August was 2.5 standard deviations above the long-term average (1961–2016). The observed salinity distributions are the result of both local and remote drivers, whereby the North Ionian cyclonic gyre controlled by the Adriatic-Ionian Bimodal Oscillating System has been responsible for the overall above-average salinities since 2011. Yet, local factors present in 2017, such as strong evaporation caused by extremely high air temperatures, lack of precipitation and low river discharges, combined with a decrease in horizontal transport estimated from the Regional Ocean Modeling System simulations, contributed substantially to the observed surface salinity anomaly. The decrease in horizontal advection was conjoined with high values of repelling barriers in the fields of the finite-time Lyapunov exponent. Documented physical conditions were synchronized with considerably lower bacterial production and abundance of the most studied picoplankton groups in comparison to values during the last decade. The exception was the euryhaline organism Synechococcus , whose abundance was 88% higher than the average in the study area. Nutrient content and chlorophyll-a concentrations followed regular seasonal cycles during 2017, with typical low values pointing to salinity as a possible driver of the observed changes in the microbial food web. Following ongoing climate change and future projections, these documented anomalous physical and microbiological conditions may become more frequent in the Adriatic Sea. [ABSTRACT FROM AUTHOR]

In this study, the Adriatic Sea and Coast (AdriSC) kilometre-scale atmosphere–ocean climate model covering the Adriatic Sea and northern Ionian Sea is presented. The AdriSC ocean results of a 31-year-long (i.e. 1987–2017) climate simulation, derived with the Regional Ocean Modeling System (ROMS) 3 km and 1 km models, are evaluated with respect to a comprehensive collection of remote sensing and in situ observational data. In general, it is found that the AdriSC model is capable of reproducing the observed sea surface properties, daily temperatures and salinities, and the hourly ocean currents with good accuracy. In particular, the AdriSC ROMS 3 km model demonstrates skill in reproducing the main variabilities of the sea surface height and the sea surface temperature, despite a persistent negative bias within the Adriatic Sea. Furthermore, the AdriSC ROMS 1 km model is found to be more capable of reproducing the observed thermohaline and dynamical properties than the AdriSC ROMS 3 km model. For the temperature and salinity, better results are obtained in the deeper parts than in the shallow shelf and coastal parts, particularly for the surface layer of the Adriatic Sea. The AdriSC ROMS 1 km model is also found to perform well in reproducing the seasonal thermohaline properties of the water masses over the entire Adriatic–Ionian domain. The evaluation of the modelled ocean currents revealed better results at locations along the eastern coast and especially the northeastern shelf than in the middle eastern coastal area and the deepest part of the Adriatic Sea. Finally, the AdriSC climate component is found to be a more suitable modelling framework to study the dense water formation and long-term thermohaline circulation of the Adriatic–Ionian basin than the available Mediterranean regional climate models. [ABSTRACT FROM AUTHOR]

In this study, the Adriatic Sea and Coast (AdriSC) kilometre-scale atmosphere-ocean climate model covering the Adriatic and northern Ionian Seas is presented. The AdriSC ocean results of a 31-year long (i.e. 1987-2017) climate simulation, derived with the Regional Ocean Modeling System (ROMS) 3-km and 1-km models, are evaluated with respect to a comprehensive collection of remote-sensing and in situ observational data. In general, it is found that the AdriSC model is capable to reproduce the observed sea-surface properties, daily temperatures and salinities and the hourly ocean currents with good accuracy. In particular, the AdriSC ROMS 3-km model demonstrates skill in reproducing the main variabilities of the sea-surface height as well as the sea-surface temperature, despite a persistent negative bias within the Adriatic Sea. Furthermore, the AdriSC ROMS 1-km model is found to be more capable to reproduce the observed thermohaline and dynamical properties than the AdriSC ROMS 3-km model. For the temperature and salinity, better results are obtained in the deeper parts than in the shallow shelf and coastal parts, particularly for the surface layer of the Adriatic Sea. The AdriSC ROMS 1-km model is also found to perform well in reproducing the seasonal thermohaline properties of the water masses over the entire Adriatic-Ionian domain. The evaluation of the modelled ocean currents revealed better results at locations along the eastern coast and especially the north-eastern shelf than in the middle-eastern coastal area and the deepest part of the Adriatic Sea. Finally, the AdriSC climate component is found to be a more suitable modelling framework to study the dense water formation and long-term thermohaline circulation of the Adriatic-Ionian basin than the available Mediterranean regional climate models. [ABSTRACT FROM AUTHOR]

A climate synoptic meteotsunami index has been constructed using synoptic variables for the Balearic Islands. The index allows for the very first assessment of atmospherically driven intense sea level oscillations at the tsunami timescale (<2 hr) in future climates. The index has been computed using outputs from evaluation, historical, and three scenario MED‐11_CNRM Med‐CORDEX regional atmospheric climate runs. The reliability of the index has been verified against reanalysis simulations and on documented meteotsunami events. No significant changes in the index are projected under RCP2.6 and RCP4.5 scenarios, while the yearly number of days with meteotsunamis is expected to increase by 34% under the RCP8.5 scenario by the year 2100. This increase will dominantly occur during the summer season (May–August), being contemporaneous with maximum index values. The presented results are relevant for assessment of sea level extremes worldwide, since high‐frequency sea level oscillations may contribute up to 40% of the total range. Plain Language Summary: The study aims to develop the proxy methodology to be used for assessment of meteotsunamis—atmospherically driven waves in a tsunami frequency band—in the future climate, as the present climate models are far from reproduction of processes on a minute and a kilometer scale. The proxy estimates are based on connecting synoptic parameters and patterns to the high‐frequency sea level observations. The methodology is successfully verified for Ciutadella harbor, a known hot spot for meteotsunamis, on state‐of‐the‐art reanalysis data. It seems that meteotsunamis are likely not to increase in all but business‐as‐usual (RCP8.5) climate scenarios, where the increase is matching the season when meteotsunami reach their maximum (spring–summer). The methodology might be useful for assessing meteotsunami hazard in future climates, while being applied at places where meteotsunamis are driven dominantly by a single atmospheric process. Global and regional analyses indicate that these might encompass the majority of midlatitudal regions. Key Points: A proxy‐based index has been developed for assessing meteotsunamigenic potential in future climateNo significant changes in the index have been found for the RCP2.6 and RCP4.5 scenariosThe number of days with meteotsunamis is expected to increase by 34% by the end of the century for the RCP8.5 scenario [ABSTRACT FROM AUTHOR]

The northernmost part of the Mediterranean Sea, the northern Adriatic shelf, is a complex area where the intensity of dense water formation and the consequent Adriatic-Ionian thermohaline circulation are shaped by a combination of extreme wintertime bora winds and substantial freshwater loads. To better understand the impact of global warming on extreme bora dynamics and the associated sea surface cooling, this study applies the Adriatic Sea and Coast (AdriSC) kilometer-scale modelling suite to the far future climate (2060–2100) period. Under both Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 greenhouse emission scenarios, the AdriSC simulations are carried out via the combination of a statistical approach—consisting of an ensemble of 3-day simulations for 22 extreme bora events, and a pseudo-global warning (PGW) methodology—imposing a climatological change to the forcing used to produce the evaluation (present climate) runs. Despite a noteworthy decrease in intensity of the bora winds (by up to 3 m/s), the latent heat losses are simulated to increase (by up to 150 W/m2) due to the reduction in relative humidity in the northern Adriatic (by up to 3%). Consequently, the sea surface cooling associated with severe bora events and preconditioning the dense shelf water formation in the northern Adriatic is projected to not significantly change compared to present climate. Although these results need to be further confirmed, this study thus provides a new view on the future of processes driven by sea surface cooling, such as the dense shelf water formation or the Adriatic-Ionian thermohaline circulation, that were projected to decrease in the future climate by regional climate models an order of magnitude coarser than the AdriSC simulations. [ABSTRACT FROM AUTHOR]

Present investigations of sea level extremes are based on hourly data measured at coastal tide gauges. The use of hourly data restricts existing global and regional analyses to periods larger than 2 h. However, a number of processes occur at minute timescales, of which the most ruinous are tsunamis. Meteotsunamis, hazardous nonseismic waves that occur at tsunami timescales over limited regions, may also locally dominate sea level extremes. Here, we show that nonseismic sea level oscillations at tsunami timescales (<2 h) may substantially contribute to global sea level extremes, up to 50% in low-tidal basins. The intensity of these oscillations is zonally correlated with mid-tropospheric winds at the 99% significance level, with the variance doubling from the tropics and subtropics to the mid-latitudes. Specific atmospheric patterns are found during strong events at selected locations in the World Ocean, indicating a globally predominant generation mechanism. Our analysis suggests that these oscillations should be considered in sea level hazard assessment studies. Establishing a strong correlation between nonseismic sea level oscillations at tsunami timescales and atmospheric synoptic patterns would allow for forecasting of nonseismic sea level oscillations for operational use, as well as hindcasting and projection of their effects under past, present and future climates. [ABSTRACT FROM AUTHOR]

The paper aims to estimate wintertime thermohaline properties and dense water formation (DWF) dynamics, rates, and transports in the northern and middle Adriatic between 2008 and 2015. The focus has also been directed to the year-to-year differences between two known DWF sites located on the northern Adriatic shelf and in the eastern coastal region. The estimates are based on a high-resolution interannual simulation by Regional Ocean Modelling System, one-way forced by the meteorological Aladin/HR operational mesoscale model, with new river climatology imposed particularly at the eastern Adriatic coast. Substantial interannual variability in wintertime bottom densities has been found, varying for more than 1.0 kg m−3 among years. Such variations are largely associated with the January-February heat losses, while atmospheric preconditioning in November-December seems to have a little effect on the DWF rates. By contrast, salinity is preconditioning the DWF in the eastern coastal site. That has been found relevant for DWF rates during extraordinary winters, as in the case of 2012. Contribution of a coastal site to the overall DWF rates in other years has not been substantial. Finally, a saw-tooth-like pattern in thermohaline time series has been found in observations and reproduced by the numerical model at the bottom of the middle Adriatic depressions. [ABSTRACT FROM AUTHOR]

In engineering studies, harbor resonance, including quality and amplification factors, is typically computed for swell and waves with periods shorter than 10 min. However, in various locations around the world, such as Vela Luka Bay in Croatia, meteotsunami waves of periods greater than 10 min can excite the bay or harbor natural modes and produce substantial structural damages. In this theoretical study, the impact of some geomorphological changes of Vela Luka Bay—i.e. deepening of the bay, dredging the harbor, adding a pier or a marina—to the amplification of the meteotsunami waves are presented for a set of 6401 idealized pressure wave field forcing used to derive robust statistics. The most substantial increase in maximum elevation is found when the Vela Luka harbor is dredged to a 5 m depth, which is in contradiction with the calculation of the quality factor showing a decrease of the harbor natural resonance. It has been shown that the forcing energy content at different frequency bands should also be taken into account when estimating the quality and amplification factors, as their typical definitions derived from the peak frequency of the sea level spectrum fail to represent the harbor response during meteotsunami events. New definitions of these factors are proposed in this study and are shown to be in good agreement with the results of the statistical analysis of the Vela Luka Bay maximum elevation results. In addition, the presented methodology can easily be applicable to any other location in the world where meteotsunamis occur. [ABSTRACT FROM AUTHOR]

The paper aims to introduce quality measures that can evaluate how well the Self-organizing Maps method performs in transitional stages. The errors have been computed with respect to the spatial and temporal properties of the data and in relation to the data gap significance. Temperature and salinity data collected in the central Adriatic Sea at six stations during 196 field cruises carried out between 1963 and 2011 have been used for the mapping of ocean patterns and computation of the respective errors. The errors resemble both the stability of ocean regimes and variability of patterns that are documented in the investigated region. As the data collection methodology and approach have changed over time, the errors may be a good indication for the presence of bad data in a series, which may then be controlled by other quality-check techniques. [ABSTRACT FROM AUTHOR]

A series of tsunami-like waves of non-seismic origin struck several southern European countries during the period of 23 to 27 June 2014. The event caused considerable damage from Spain to Ukraine. Here, we show that these waves were long-period ocean oscillations known as meteorological tsunamis which are generated by intense small-scale air pressure disturbances. An unique atmospheric synoptic pattern was tracked propagating eastward over the Mediterranean and the Black seas in synchrony with onset times of observed tsunami waves. This pattern favoured generation and propagation of atmospheric gravity waves that induced pronounced tsunami-like waves through the Proudman resonance mechanism. This is the first documented case of a chain of destructive meteorological tsunamis occurring over a distance of thousands of kilometres. Our findings further demonstrate that these events represent potentially dangerous regional phenomena and should be included in tsunami warning systems. [ABSTRACT FROM AUTHOR]

This paper aims to document salinity and temperature regimes in the middle and south Adriatic Sea by applying the Self-Organizing Maps (SOM) method to the available long-term temperature and salinity series. The data were collected on a seasonal basis between 1963 and 2011 in two dense water collecting depressions, Jabuka Pit and Southern Adriatic Pit, and over the Palagruža Sill. Seasonality was removed prior to the analyses. Salinity regimes have been found to oscillate rapidly between low-salinity and high-salinity SOM solutions, ascribed to the advection of Western and Eastern Mediterranean waters, respectively. Transient salinity regimes normally lasted less than a season, while temperature transient regimes lasted longer. Salinity regimes prolonged their duration after the major basin-wide event, the Eastern Mediterranean Transient, in the early 1990s. A qualitative relationship between high-salinity regimes and dense water formation and dynamics has been documented. The SOM-based analyses have a large capacity for classifying the oscillating ocean regimes in a basin, which, in the case of the Adriatic Sea, beside climate forcing, is an important driver of biogeochemical changes that impacts trophic relations, appearance and abundance of alien organisms, and fisheries, etc. [ABSTRACT FROM AUTHOR]