Unprecedented warming and salinization observed in the deep Adriatic

The deep Southern Adriatic Pit (dSAP) is a Mediterranean region highly sensitive to climate change, influenced by dense water cascading from the northern Adriatic and heat/salt transport from the Eastern Mediterranean. Historical (since 1957) and modern (permanent and opportunistic CTD sampling, Argo floats, fixed moorings) measurements reveal a mid-2000s transition in dSAP thermohaline properties. Previously marked by steady increases in temperature, salinity, and density, with substantial saw-tooth decadal variability, the dSAP has experienced unprecedented warming (0.8°C) and salinization (0.2) over the past decade, accelerating in time and reversing density trends. The inflow of much more saline waters reduced SAP stratification and altered dense water properties at its source in the northern Adriatic. This at least fivefold acceleration of the high-emission regional climate projections may have substantial effects on the Adriatic biogeochemistry and living organisms, increasing sea level rise trends and more.

Performance of multi-decadal ocean simulations in the Adriatic Sea

Dense water flow and carbonate system in the southern Adriatic: A focus on the 2012 event

While statistical analyses and observations show that severe bora with maximum gusts exceeding 40 m s−1 can occur in all parts of the Adriatic, the bora research to date has been mainly focused on the dynamics and structure of severe bora in the northern Adriatic. Examined to a significantly lesser degree is a less predictable counterpart in the southern Adriatic, where the Dinaric Alps are higher, broader, and steeper, and where the upwind bora layer is generally less well defined. Identification of the main differences in the sequence of mesoscale and macroscale events leading to the onset of bora in the northern and southern parts of the eastern Adriatic is of fundamental importance for its forecasting. To this end, presented here is a comparative analysis of the evolution and structure of two typical severe cyclonic bora events—one “northern” (7–8 November 1999) and one “southern” (6–7 May 2005) event. The analysis utilizes airborne, radiosonde, and ground-based observations, as well as the hydrostatic Aire Limitée Adaptation Dynamique Developement International (ALADIN/HR) mesoscale model simulations. It is shown that the development of a severe bora in both the northern and southern Adriatic is critically dependent on the synoptic setting to create an optimal set of environmental conditions. For severe bora in the northern Adriatic, these conditions include a strong forcing of the northeasterly low-level jet and pronounced discontinuities in the upstreamflow structure that promote layering, such as lower- to midtropospheric inversions and environmental critical levels. The development of severe bora in the southern Adriatic is crucially dependent on the establishment of a considerably deeper upstream layer that is able to overcome the strong blocking potential of the southern Dinaric Alps. While the upstream layering is less pronounced, it is closely tied to the presence of a cyclone in the southern Adriatic or over the southern Balkan peninsula. The upstream atmospheric layering is shown to strongly modulate bora behavior, and different phases of severe bora, related to the presence or absence of upstream layering, are shown to occur within a single bora episode. Furthermore, the presence of a mountain-parallel upper-level jet aloft appears to impede severe bora development in both the northern and southern Adriatic.

Calculations of the Adriatic heat fluxes have been carried out. The most appropriate expressions were used assuming that the Adriatic Sea on average loses heat, as shown by some previous studies. Interannual variations of the heat fluxes were analyzed for the period 1989–1999 using the European Centre for Medium‐Range Weather Forecasts ERA‐40 Reanalysis data set. One of the most relevant issues resulting from the climatological analysis is the presence of an interannual signal and a significant intra‐annual variability during the whole period considered. Large year‐to‐year changes were evidenced, including a net heat gain in some years like in 1994. Interannual yearly heat flux variations largely depend on winter heat losses. Winter convection and dense water formation in the southern Adriatic are directly linked to winter heat loss, although the extent of the vertical mixing is also dependent on the characteristics of the preconditioning period, more specifically of December. Because of mild winter climatic conditions, in some years, winter convection was shown to be completely absent. Separate analyses of the southern and northern Adriatic heat fluxes were carried out as well to see whether the two subbasin fluxes change independently on an interannual timescale. This is especially important considering that the ventilation of the Southern Adriatic Bottom Water takes place through the combined influence of the Northern Adriatic Dense Water and a local vertical convection.

Dense water formation in the Southern Adriatic Sea and spreading into the Ionian Sea in the period 1997–1999

Dynamics of particles along the western margin of the Southern Adriatic: Processes involved in transferring particulate matter to the deep basin

Off-shelf fluxes across the southern Adriatic margin: Factors controlling dense-water-driven transport phenomena

Detection of diarrhoetic shellfish toxins in mussels from Italy by ionspray liquid chromatography-mass spectrometry

The phenology of phytoplankton blooms holds significant implications for marine ecosystems as it shapes pelagic food webs. The onset, intensity, and duration of phytoplankton blooms, along with their synchronization with zooplankton cycles, can impact the survival rates of these species and overall community production. In this study, we employ a combination of in situ and satellite-derived chlorophyll concentrations, utilizing various statistical methods to discern the presence and timing of spring and autumn blooms in different regions of the Adriatic Sea. The northern Adriatic (NA) represents a coastal, river-dominated ecosystem influenced by anthropogenic nutrient enrichment, with a recent decline observed in chlorophyll concentration and primary production. Conversely, the southern Adriatic (SA) is characterized as a true pelagic ecosystem with minimal influence from coastal waters on nutrient levels. Here, primary production is primarily controlled by meteorological conditions that dictate convective mixing and nutrient availability for autotrophic uptake. Our analysis reveals that the northern Adriatic predominantly experiences both spring and autumn blooms, whereas the southern Adriatic witnesses only autumn blooms, peaking in late autumn or winter. We investigate trends in the timing of the onset and peak of phytoplankton blooms, searching for environmental factors influencing these shifts. As anticipated, the onset of the autumn bloom is found to be delayed, with statistically significant trends observed in specific areas. It is worth noting that the lack of statistical significance in some instances may be attributed, at least in part, to the relatively short period of available satellite data (from 1997 onwards).

Dense-water bottom currents in the Southern Adriatic Sea in spring 2012

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.

Dense shelf water production and the deep convection process in the Adriatic Sea are investigated, considering two case studies: the first is representative of the present climatic situation, whereas the second may be expected in a scenario characterized by mild winter conditions over the basin. Dense water production and spreading are studied using a high‐resolution implementation of the Massachusetts Institute of Technology general circulation model that is initialized and forced with realistic conditions. This paper provides qualitative and quantitative information on mass transport, dense water pathways, thermohaline structures, and the mixing properties of the basin. In the northern Adriatic shelf, seawater temperature is the key element for winter dense water production because it contributes more relevantly than salinity in determining density. In the southern Adriatic Sea, a small amount of dense water that cascades directly into the pit can be formed on the narrow western shelf only during cold winter conditions. Moreover, open ocean deepwater formation occurs in the middle of the southern basin. In late winter and spring, although only when winter conditions have been sufficiently cold, northern Adriatic dense shelf water forms a subsurface stream of which the densest part rapidly sinks in the southern pit along the shelf break, whereas its lighter part flows southward and reaches the Otranto Strait. The frequent occurrence of mild winter conditions could lead to lower dense water production, with a reduced dense water flow from the Adriatic Sea to the Ionian Sea and a potential great impact on the eastern Mediterranean thermohaline circulation.

Plankton diversity in Anthropocene: Shipping vs. aquaculture along the eastern Adriatic coast assessed through DNA metabarcoding

The checklist of polychaetes of the Adriatic Sea (Mediterranean) based on bibliographic sources published from 1840 to 2014, as well as on novel data, with 49 new records for the area, is herein presented. The Adriatic Sea polychaete fauna comprises at present of 764 species in 360 genera and 62 families. The richest family is the Syllidae, with 112 species (c.a. 15% of the all taxa). Eight families account for as much as 50% of the diversity (Syllidae, Serpulidae, Sabellidae, Phyllodocidae, Spionidae, Polynoidae, Terebellidae and Nereididae). Among the three Adriatic sectors (Northern, Central and Southern Adriatic), the Northern Adriatic is the richest one, whereas the composition of the most diverse families is very similar in all sectors. Data on endemisms (6), aliens (29) and valid species with the type locality in the Adriatic Sea (90) are also discussed. The list of all relevant papers citing each species in the Adriatic is included, allowing future detailed information retrievals for distinct purposes. Results suggest that the number of species will keep increasing in the future, as new surveys will be undertaken, so regular updates of the present list will be necessary.