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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]

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]

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 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]

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]

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]

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]

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]

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]

In this study the impact of the Adriatic-Ionian Bimodal Oscillating System (BiOS) on the interannual to decadal variability of the Adriatic Sea thermohaline circulation is quantified during the 1987–2017 period with the numerical results of the Adriatic Sea and Coast (AdriSC) historical kilometer-scale climate simulation. The time series associated with the first five Empirical Orthogonal Functions (EOFs) computed from the salinity, temperature and current speed monthly detrended anomalies at 1-km resolution are correlated to the BiOS signal. First, it is found that the AdriSC climate model is capable to reproduce the BiOS-driven phases derived from in-situ observations along a long-term monitoring transect in the middle Adriatic. Then, for the entire Adriatic basin, high correlations to the 2-year delayed BiOS signal are obtained for the salinity and current speed first two EOF time series at 100 m depth and the sea-bottom. Finally, the physical interpretation of the EOF spatial patterns reveals that Adriatic bottom temperatures are more influenced by the dense water circulation than the BiOS. These findings confirmed and generalized the known dynamics derived previously from observations, and the AdriSC climate model can thus be used to better understand the past and future BiOS-driven physical processes in the Adriatic Sea. [ABSTRACT FROM AUTHOR]

In this evaluation study, the coupled atmosphere–ocean Adriatic Sea and Coast (AdriSC) climate model, which was implemented to carry out 31-year evaluation and climate projection simulations in the Adriatic and northern Ionian seas, is briefly presented. The kilometre-scale AdriSC atmospheric results, derived with the Weather Research and Forecasting (WRF) 3 km model for the 1987–2017 period, are then thoroughly compared to a comprehensive publicly and freely available observational dataset. The evaluation shows that overall, except for the summer surface temperatures, which are systematically underestimated, the AdriSC WRF 3 km model has a far better capacity to reproduce surface climate variables (and particularly the rain) than the WRF regional climate models at 0.11 ∘ resolution. In addition, several spurious data have been found in both gridded products and in situ measurements, which thus should be used with care in the Adriatic region for climate studies at local and regional scales. Long-term simulations with the AdriSC climate model, which couples the WRF 3 km model with a 1 km ocean model, might thus be a new avenue to substantially improve the reproduction, at the climate scale, of the Adriatic Sea dynamics driving the Eastern Mediterranean thermohaline circulation. As such it may also provide new standards for climate studies of orographically developed coastal regions in general. [ABSTRACT FROM AUTHOR]

In this evaluation study, the coupled atmosphere-ocean Adriatic Sea and Coast (AdriSC) climate model, which was implemented to carry out 31-year long evaluation and climate projection simulations in the Adriatic and northern Ionian seas, is briefly presented. The kilometre-scale AdriSC atmospheric results, derived with the Weather Research and Forecasting (WRF) 3-km model for the 1987-2017 period, are then thoroughly compared to a comprehensive publicly and freely available observational dataset. The evaluation shows that overall, except for the summer surface temperatures which are systematically underestimated, the AdriSC WRF 3-km model has a far better capacity to reproduce the surface climate variables (and particularly the rain) than the WRF regional climate models at 0.11° of resolution. In addition, several spurious data have been found in both gridded products and in situ measurements which thus should be used with care in the Adriatic region for climate studies at local and regional scales. Long-term simulations with the AdriSC climate model, which couples the WRF 3-km model with a 1-km ocean model, might thus be a new avenue to substantially improve the reproduction, at the climate scale, of the Adriatic Sea dynamics driving the Eastern Mediterranean thermohaline circulation. As such it may also provide new standards for climate studies of orographically-developed coastal regions in general. [ABSTRACT FROM AUTHOR]

• Contribution of seven sea level components to the Adriatic sea level extremes was studied for 1956–2019/2020 period. • Positive extremes dominantly occur due to superposition of tide , 6 h -10 d , and 10–100 d components. • Negative extremes dominantly occur due to superposition of tide and 10–100 d component. • Trends point to shortening of negative and prolonging and strengthening of positive extremes. The strongest episodes of extremely high sea levels in the Mediterranean are regularly observed in the Adriatic Sea, where they can cause substantial damage and loss of human lives. In this study, episodes of positive and negative sea level extremes were extracted from hourly series measured at six tide gauge stations located along the Adriatic coast (Venice, Trieste, Rovinj, Bakar, Split, Dubrovnik) between 1956 and 2019/2020. The time series were first checked for spurious data and then decomposed using tidal analysis, least-squares fitting and filtering procedures into (1) trend ; (2) seasonal ; (3) tide , (4) longer than 100 d (> 100 d), (5) 10–100 d , (6) 6 h -10 d , and (7) < 6 h components. These components correspond to sea level oscillations dominantly (but not exclusively) forced by (1) climate and isostatic change; (2) seasonal changes in thermohaline properties and circulation patterns, (3) tidal forcing, (4) quasi-stationary atmospheric and ocean circulation and climate variability patterns, (5) planetary atmospheric waves, (6) synoptic, and (7) mesoscale atmospheric processes. Significant differences exist between (1) the northern and middle/southern Adriatic extremes and (2) positive and negative extremes. The heights and return levels of positive (negative) extremes are 50–100% higher (lower) in the northern than in the middle/southern Adriatic. The northern Adriatic positive sea level extremes dominantly occur due to the superposition of the 6 h -10 d component and tide (contributing jointly to ∼70% of the total extreme height), whereas the middle/southern Adriatic positive extremes mostly occur due to the superposition of the 10–100 d component , 6 h -10 d component , and tide (each contributing ∼25% on average). The negative sea level extremes are explained as a combination of the 10–100 d component and tide: in the northern Adriatic tide provides the largest contribution (∼60%), while in the middle/southern Adriatic, the impacts of the two processes are similar (each contributing an average of ∼30%). Over the entire Adriatic, the < 6 h and seasonal components contribute the least to both positive and negative extremes. Sea level trends at all stations are positive; however, the observed sea level rise did not contribute significantly to the total height of extremes. Extreme episodes tend to occur simultaneously over larger parts of the coast and are often clustered within a few days. Both positive and negative extremes have a strong decadal variability, whereas trends of their number, duration and intensity point to shortening of negative extremes and prolonging and strengthening of positive extremes. [ABSTRACT FROM AUTHOR]