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The north Adriatic basin experiences notable sea level variability induced by the atmospheric forcing on different time scales. The occurrence of sea level extreme events has increased over the last decades in connection with the mean sea level rising trend, and the coastal communities are becoming more and more sensitive to sea level changes.The observed sea level is the result of the superposition of contributions connected with different forcing factors. The sea level extreme events can be determined mainly by one of such components or by the interaction of some of them. On the basis of characteristic time scales, we identify and extract the sea level components connected with: the astronomical tide; the meteorological forcing, that is synoptic-scale atmospheric variations, mesoscale atmospheric disturbances, meteotsunamis, and planetary atmospheric waves; seasonal to inter-decadal variability, that is changes of large-scale atmospheric and oceanic circulations. The main Adriatic seiches, generally triggered by storm surges, and the long-term sea level variations, related to climate change, are also taken into account.Recent sea level archaeology activity has allowed to extend and revise the sea level time series of the tide-gauge station of Trieste, Molo Sartorio. As a result, hourly sea level elevations for the 1905-2022 period are now available.Thanks to this long time series, we study the variability of the sea level extreme events and their components during more than a century, with focus on the time variability and the relative importance of the components during major events., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

While confidence in estimating air-sea CO? fluxes in open sea environments is increasing, a large uncertainty remains in defining the role played by coastal ecosystems as CO? sinks or sources. This is due to their highly variable oceanographic and climatic characteristics and to the effects of continental inputs. Within ICOS-OTC network, the PALOMA station, (Northern Adriatic Sea), is continuously collecting sea surface pCO? data since 2012. In the framework of JERICO-NEXT project, PALOMA is working together with several stations located in European coastal seas to explore the role of biological and atmospheric drivers in determining the observed pCO? variability. In this work, we present and discuss the effects of meteorological conditions on CO? air-sea fluxes, using the data collected in four wintry seasons from 2012 to 2016. In winter 2012-2013, the presence of lower temperatures and the occurrence of several events of Bora (wind speed > 15 ms?¹) produced a decrease of the SST down to 8.3 C leading to more favorable conditions for CO? absorption. The following winter was characterized by a higher air temperature, weaker winds, intense precipitation and river discharges larger than the average of the previous decade. These distinct hydrological and meteorological conditions significantly affected the sea surface pCO? that was lower in 2012-2013 (median pCO? ? 324 ± 8.9 ?atm) than in 2013-2014 (median pCO? ? 343 ± 9.0 ?atm). Sea always absorbed CO? from the atmosphere, but average daily fluxes were almost doubled during the colder winter 2012-2013 (F ? - 6.4 mmol-CO? m²d?¹) than in the milder winter 2013-2014 (F ? -3.7 mmol-CO? m²d?¹). Our results highlight the sensitivity of the CO? sink in the northern Adriatic to changes in the meteorological conditions and suggest that its capability of sequestering CO? could dramatically decrease in the next decades under a climate change scenario.

The Northern Adriatic is a shallow, semi-enclosed sub-basin surrounded by an industrialized area in the northernmost part of the Mediterranean. The basin can be affected by intense air sea fluxes (gas, heat and water) and significant ecosystem changes. Dense water may form during winter (Northern Adriatic Dense Water, density anomalies > 29.2 kg m?³) and spread to the South along the Italian coast. Consequently the North Adriatic Sea seems interesting to the ICOS targets and the site in Gulf of Trieste, equipped for marine CO? measurements, was included in the ICOS Italy network. In the last few decades, ocean acidification of locally formed dense waters was estimated by non continuous data, spanning 25 years (Luchetta et al. 2010), thus indicating the area is prone to absorb CO? during winter. Then (2008), time series of the main physical and biogeochemical parameters (T, S, DO, nutrients, pH, TA, TOC) started being collected once per month by the fixed station (PALOMA) in the centre of the Gulf of Trieste. Gathered data indicate that dissolved CO? is driven by the sea temperature, the Gulf of Trieste is under saturated (290

Summary In Northern Italy, natural subsidence affects the Po and Veneto-Friuli Plains. Anthropogenic activities which started during the 1930s enhanced the natural rates considerably. Information on land lowering can be obtained not only by geodetic or geological data, but also analyzing and comparing sea-level time series of neighboring tide gauges. In the Northern Adriatic, several tide gauge stations were operational before the onset of the anthropogenic activities. We analyzed data spanning the period 1873–1922 from Marina di Ravenna, Venice and Trieste, in Italy. The 1897–1922 data of Pula, Croatia, were also considered for the analysis, but this time series was finally discarded because too short. Trieste, located in a relatively stable area, is characterized by a sea-level rate of 1.21 ± 0.35 mm/yr (1875–1922) that can be assumed to be a reliable estimate of the local sea-level rise during the period of interest. We compared the rate observed at Trieste with those obtained at Marina di Ravenna, 3.09 ± 0.31 mm/yr (1873–1922), and Venice, 2.05 ± 0.22 mm/yr (1873–1922). This comparison shows that the natural subsidence rate decreases from Marina di Ravenna to Venice and Trieste, turning out to be 1.88 ± 0.47 mm/yr and 0.84 ± 0.41 mm/yr at Marina di Ravenna and Venice, respectively.

Floods in the Venice city centre result from the superposition of several factors: astronomical tides; seiches; and atmospherically forced fluctuations, which include storm surges, meteotsunamis, and surges caused by atmospheric planetary waves. All these factors can contribute to positive water height anomalies individually and can increase the probability of extreme events when they act constructively. The largest extreme water heights are mostly caused by the storm surges produced by the sirocco winds, leading to a characteristic seasonal cycle, with the largest and most frequent events occurring from November to March. Storm surges can be produced by cyclones whose centres are located either north or south of the Alps. Historically, the most intense events have been produced by cyclogenesis in the western Mediterranean, to the west of the main cyclogenetic area of the Mediterranean region in the Gulf of Genoa. Only a small fraction of the inter-annual variability in extreme water heights is described by fluctuations in the dominant patterns of atmospheric circulation variability over the Euro-Atlantic sector. Therefore, decadal fluctuations in water height extremes remain largely unexplained. In particular, the effect of the 11-year solar cycle does not appear to be steadily present if more than 100 years of observations are considered. The historic increase in the frequency of floods since the mid-19th century is explained by relative mean sea level rise. Analogously, future regional relative mean sea level rise will be the most important driver of increasing duration and intensity of Venice floods through this century, overcompensating for the small projected decrease in marine storminess. The future increase in extreme water heights covers a wide range, largely reflecting the highly uncertain mass contributions to future mean sea level rise from the melting of Antarctica and Greenland ice sheets, especially towards the end of the century. For a high-emission scenario (RCP8.5), the magnitude of 1-in-100-year water height values at the northern Adriatic coast is projected to increase by 26–35 cm by 2050 and by 53–171 cm by 2100 with respect to the present value and is subject to continued increase thereafter. For a moderate-emission scenario (RCP4.5), these values are 12–17 cm by 2050 and 24–56 cm by 2100. Local subsidence (which is not included in these estimates) will further contribute to the future increase in extreme water heights. This analysis shows the need for adaptive long-term planning of coastal defences using flexible solutions that are appropriate across the large range of plausible future water height extremes.

The historical data corresponding to the period 1873–1922 of the Porto Corsini (northern Adriatic, Italy) tide gauge have been retrieved from the archive of the Italian Istituto Geografico Militare, in Florence ( http://www.igmi.org ). The data consist of daily high and low waters, which were recorded in six handwritten volumes. The 1873–1896 observations were, until now, totally unknown since they were never published, while, for the remaining years, only monthly mean values were available. We digitized and quality controlled the rescued data. Searching in different archives, we also found detailed information on the three sites occupied by the tide gauge within the Porto Corsini/Marina di Ravenna harbor. In addition, the rescue of the leveling data and of the datum definition made it possible to realize a homogeneous time series of monthly mean sea-level values, which now spans 144 years. Sea-level time series exceeding a century are rare, and they are most important because they provide key information for studying climate change-related processes. The Porto Corsini/Marina di Ravenna area is affected by natural subsidence, much enhanced by anthropogenic activities during the period 1940–1980, in particular. Using leveling, GPS and InSAR data we have modeled the subsidence behavior over the 1873–2016 period. After removing the subsidence from the series of monthly mean values, we estimated a long-period linear sea-level rise of + 1.25 ± 0.16 mm/year.

Vertical deformations of the Earth’s surface result from a host of geophysical and geological processes. Identification and assessment of the induced signals is key to addressing outstanding scientific questions, such as those related to the role played by the changing climate on height variations. This study, focused on the European and Mediterranean area, analyzed the GPS height time series of 114 well-distributed stations with the aim of identifying spatially coherent signals likely related to variations of environmental parameters, such as atmospheric surface pressure (SP) and terrestrial water storage (TWS). Linear trends and seasonality were removed from all the time series before applying the principal component analysis (PCA) to identify the main patterns of the space/time interannual variability. Coherent height variations on timescales of about 5 and 10 years were identified by the first and second mode, respectively. They were explained by invoking loading of the crust. Single-value decomposition (SVD) was used to study the coupled interannual space/time variability between the variable pairs GPS height–SP and GPS height–TWS. A decadal timescale was identified that related height and TWS variations. Features common to the height series and to those of a few climate indices—namely, the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), the East Atlantic (EA), and the multivariate El Niño Southern Oscillation (ENSO) index (MEI)—were also investigated. We found significant correlations only with the MEI. The first height PCA mode of variability, showing a nearly 5-year fluctuation, was anticorrelated (–0.23) with MEI. The second mode, characterized by a decadal fluctuation, was well correlated (+0.58) with MEI, the spatial distribution of the correlation revealed, for Europe and the Mediterranean area, height decrease till 2015, followed by increase, while Scandinavian and Baltic countries showed the opposite behavior.