Multiple drivers of extreme sea levels in the northern Adriatic Sea

2021 ◽  
Author(s):  
Christian Ferrarin ◽  
Piero Lionello ◽  
Mirko Orlic ◽  
Fabio Raicich ◽  
Gianfausto Salvadori
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Adriatic Sea ◽  
Driving Factors ◽  
Northern Adriatic Sea ◽  
Relative Sea Level ◽  
Northern Adriatic ◽  
Sea Levels ◽  
Extreme Sea Levels ◽  
Relative Sea Level Rise

<p><span><span>Extreme sea levels at the coast result from the combination of astronomical tides with atmospherically forced fluctuations at multiple time scales. Seiches, river floods, waves, inter-annual and inter-decad</span></span><span><span>al dynamics and relative sea-level rise can also contribute to the total sea level. While tides are usually well described and predicted, the effect of the different atmospheric contributions to the sea level and their trends are still not well understood. Meso-scale atmospheric disturbances, synoptic-scale phenomena and planetary atmospheric waves (PAW) act at different temporal and spatial scales and thus generate sea-level disturbances at different frequencies. In this study, we analyze the 1872-2019 sea-level time series in Venice (northern Adriatic Sea, Italy) to investigate the relative role of the different driving factors in the extreme sea levels distribution. The adopted approach consists in 1) isolating the different contributions to the sea level by applying least-squares fitting and Fourier decomposition; 2) performing a multivariate statistical analysis which enables the dependencies among driving factors and their joint probability of occurrence to be described; 3) analyzing temporal changes in extreme sea levels and extrapolating possible future tendencies. The results highlight the fact that the most extreme sea levels are mainly dominated by the non-tidal residual, while the tide plays a secondary role. The non-tidal residual of the extreme sea levels is attributed mostly to PAW surge and storm surge, with the latter component becoming dominant for the most extreme events. The results of temporal evolution analysis confirm previous studies according to which the relative sea-level rise is the major driver of the increase in the frequency of floods in Venice over the last century. However, also long term variability in the storm activity impacted the frequency and intensity of extreme sea levels and have contributed to an increase of floods in Venice during the fall and winter months of the last three decades.</span></span></p>

scholarly journals Historical and recent sea level rise and land subsidence in Marina di Ravenna, northern Italy

2016 ◽  
Vol 59 (5) ◽  
Author(s):  
Ines Cerenzia ◽  
Davide Putero ◽  
Flavio Bonsignore ◽  
Gaia Galassi ◽  
Marco Olivieri ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Land Subsidence ◽  
Adriatic Sea ◽  
Sea Level Change ◽  
Northern Adriatic Sea ◽  
Relative Sea Level ◽  
Northern Adriatic ◽  
Level Change ◽  
Rate Of Increase

The regions facing the northern Adriatic Sea are particularly vulnerable to sea-level rise. Several trade ports are located there, and the area is important from social and economical viewpoints. Since tourism and cultural heritage are a significant source of income, an increase in sea-level could hinder the development of these regions. One of the longest sea-level time series in the northern Adriatic, which goes back to the late 1880s, has been recorded at Marina di Ravenna, in Emilia-Romagna region. The record is anomalous, showing a rate of increase that largely exceeds that observed in nearby stations. During the last few decades, geodetic campaigns based on geometric high precision leveling, SAR interferometry, and GPS have monitored the Ravenna area. In this work, tide gauge observations are merged with yet unpublished geodetic data, aiming at a coherent interpretation of vertical land movements. We confirm that land subsidence is the major cause of relative sea-level change at Marina di Ravenna, at least during the period allowing  for a quantitative analysis (1990-2011). The rate of absolute sea-level change (2.2±1.3 mm yr−1 during the same time period), given by the difference between the rate of relative sea-level change and the rate of subsidence, is consistent with the rate of absolute sea-level change observed by altimetry in the northern Adriatic Sea.

scholarly journals A global analysis of subsidence, relative sea-level change and coastal flood exposure

2021 ◽  
Author(s):  
Daniel Lincke ◽  
Robert J. Nicholls ◽  
Jochen Hinkel ◽  
Sally Brown ◽  
Athanasios T. Vafeidis ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Global Analysis ◽  
Relative Sea Level ◽  
Sea Levels ◽  
Coastal Flood ◽  
Global Issue ◽  
Flood Exposure ◽  
Relative Sea Level Rise ◽  
Global Sea Level

<p>Climate-induced sea-level rise and vertical land movements, including natural and human-induced subsidence in sedimentary coastal lowlands, combine to change relative sea levels around the world's coast. Global-average coastal relative sea-level rise was 2.5 mm/yr over the last two decades. However, as coastal inhabitants are preferentially located in subsiding locations, they experience an average relative sea-level rise up to four times faster at 7.8 to 9.9 mm/yr. This first global quantification of relative sea-level rise shows that the resulting impacts, and adaptation needs are much higher than reported global sea-level rise measurements would suggest. Hence, coastal subsidence is an important global issue that needs more assessment and action. In particular, human-induced subsidence in and surrounding coastal cities can be rapidly reduced with appropriate policy measures for groundwater utilization and drainage. This offers substantial and rapid benefits in terms of reducing growth of coastal flood exposure due to relative sea-level rise.</p>

Coastal landforms evolution during the Holocene marine transgression: a witness from the past to understand the future

2020 ◽  
Author(s):  
Livio Ronchi ◽  
Alessandro Fontana ◽  
Annamaria Correggiari
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Plain ◽  
Adriatic Sea ◽  
Tidal Inlets ◽  
Northern Adriatic Sea ◽  
Northern Adriatic ◽  
Marine Transgression ◽  
Coastal Landforms ◽  
Lagoon Systems

<p>The continental shelves submerged during the last marine transgression could constitute a unique laboratory to analyse how coastal landforms developed and evolved within the framework of a rising sea level. Such features therefore represent precious witnesses in the light of the high rates of sea-level rise predicted for the end of the century. Unfortunately, the majority of the coastal landforms have been wiped away during and soon after their submersion as a consequence of the pervasive wave and tidal action. Therefore, only few examples of well-preserved submerged coastal landforms are available.</p><p>In this study we focused our attention on the Italian side of northern Adriatic Sea, where a wide, low-gradient continental shelf, coupled to a very rapid marine ingression, allowed the partial conservation of the transgressive coastal landforms. Such study was carried out through the analysis of almost 10,000 km of high-resolution geophysical surveys (CHIRP-sonar profiles) and tens of stratigraphic cores carried out in the area during the last 30 years.</p><p>We recognized a series of almost 100 remnants of paleo tidal inlets which formed during the post-LGM transgression that led to the submersion of the Adriatic shelf. Despite paleo tidal inlets are often almost completely erased by the wave ravinement processes, when preserved they represent ideal markers for reconstructing the timing and impact of sea-level rise on the transgressed coastal plain. A wealth of information can be obtained by their analysis, such as the paleo coastlines locations, the dimensions of the paleo lagoon systems and, in particular conditions, the relative paleo sea-level. Such features therefore represent valid means to reconstruct the impact of the transgressive sea on the coastal area.</p><p>In particular, the paleo tidal inlets recognized in the northern Adriatic Sea suggest the recurrent formation followed by rapid overstepping of large lagoon systems during the early Holocene. Moreover, these features can be subdivided into clusters based on the depth of their top, thus allowing to infer the position of a series of paleo coastlines and suggesting the occurrence of periods of stasis of the relative sea-level rise, which allowed the formation of such inlets.</p><p>Although remnants of paleo tidal inlets are common on the northern Adriatic Shelf, they are almost absent in the northernmost portion of the basin (i.e. the Gulf of Trieste), where a series of paleo fluvial systems have been identified, thus providing a direct witness on the evolution of the coastal plain during a transgressive phase and right before its rapid submersion.</p><p>This research provides new insights on two main topics: i) it improves our knowledge on the post-LGM marine transgression, therefore contributing to reconstruct the history of sea-level rise and to constrain the modelling of future behaviour; ii) it contributes to understand the evolution of tidal inlets and lagoon-barrier island systems under the forcing of high rates of sea-level rise.</p>

A trail of crumbs: ancient geomorphological indicators of past sea-level rise in the Northern Adriatic Sea (Italy)

2021 ◽  
Author(s):  
Livio Ronchi ◽  
Alessandro Fontana ◽  
Annamaria Correggiari
Keyword(s):  
Sea Level ◽  
Adriatic Sea ◽  
Regional Scale ◽  
Seismic Profiles ◽  
Tidal Inlets ◽  
Northern Adriatic Sea ◽  
Northern Adriatic ◽  
Marine Transgression ◽  
Sea Levels ◽  
Sediment Dispersal

<p>The reconstruction of timing and modes of the last marine transgression is often hampered by the scarceness of available indicators, which is caused by bad preservation, lack of formation or difficult accessibility.</p><p>This is particularly true for the first period of the Holocene, between 7 ka and 11 ka cal, when the rate of transgression was high (hence little to absent formation of possible indicators) and the sea level was placed below ca. -20 m MSL (hence scarce accessibility).</p><p>Shoreline deposits and erosional landforms have long been recognized as geomorphological indicators of past sea levels. Such indicators (e.g. beach ridges, tidal notches) can be both submerged or exposed due to RSL variations of coastal progradation.</p><p>A major group of potential indicators which, up to date, is largely underrepresented, is constituted by paleo tidal inlets. Being excavated up to several meters below the surrounding lagoon and filled during the migration or deactivation of the inlet, such landforms may represent outstanding archives with a potentially high chance of preservation from erosion. Paleo tidal inlets can be easily recognized and cataloged through shallow sub-bottom profiling methods.</p><p>The analysis of almost 7000 km of high resolution seismic profiles collected in the northern Adriatic Sea allowed to recognized almost 100 paleo tidal inlets dating to the early Holocene, which constitute the only widespread witnesses of the post-LGM marine transgression in the area. Paleo tidal inlets are essential features to the paleo-geographic and -environmental reconstruction and provide new data to constrain the position of the transgressive coastlines. The presence of widespread lagoon environments during a phase of strong RSL rise comes from the interplay between sediment dispersal operated by the main fluvial actors of the area and phases of slowdown of the RSL rise. This study sheds light on the phenomena affecting coastal plains in response to RSL rise and constitutes the first report of an extensive distribution of paleo tidal inlets on a regional scale.</p>

Relative sea-level rise during the Main Postglacial Transgression in NE Scotland, U.K.

1999 ◽  
Vol 90 (1) ◽  
pp. 1-27 ◽  
Author(s):  
D. E. Smith ◽  
C. R. Firth ◽  
C. L. Brooks ◽  
M. Robinson ◽  
P. E. F. Collins
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Sea Levels ◽  
Relative Sea Level Rise ◽  
The Mean ◽  
Run Up ◽  
Storegga Slide

AbstractFlandrian (Holocene) relative sea level changes in the lower Ythan valley, NE Scotland, U.K., are inferred from detailed stratigraphical evidence including microfossil analysis and radiocarbon assay. The principal event recorded is the Main Postglacial Transgression, which was under way in the area by c. 8300 and had culminated before c. 4000 radiocarbon years BP. It is concluded that the rise in relative sea levels during the transgression in the area exceeded 12 m; that the mean rate of rise there was 8·05 mm a−1 between c. 8300 and c. 7100 radiocarbon years BP, or 7·09 mm a−1 based upon calibrated dates for the same period, before declining markedly to 1·75 mm a−1 (radiocarbon) or 1·86 mm a−1 (calibrated) to the culmination of the event. By comparison with other sites, the culmination appears to have been time-transgressive in eastern Scotland. Deposits of the Second Storegga Slide tsunami, which occurred during the Main Postglacial Transgression, are present in the Ythan valley, where the sediment run-up of the event at the sites studied is estimated to have been within the range 2·99–5·19 m.

scholarly journals Quantifying Thresholds of Barrier Geomorphic Change in a Cross-Shore Sediment Partitioning Model

2020 ◽  
Author(s):  
Daniel J. Ciarletta ◽  
Jennifer L. Miselis ◽  
Justin L. Shawler ◽  
Christopher J. Hein
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Cross Sections ◽  
Sediment Flux ◽  
State Transitions ◽  
Morphologic Change ◽  
Relative Sea Level ◽  
Coastal System ◽  
Sea Levels ◽  
Relative Sea Level Rise

Abstract. Barrier coasts, including barrier islands, beach-ridge plains, and associated landforms, can assume a broad spectrum of morphologies over decadal scales that reflect conditions of sediment availability, accommodation, and relative sea-level rise. However, the quantitative thresholds of these controls on barrier-system behavior remain largely unexplored, even as modern sea-level rise and anthropogenic modification of sediment availability increasingly reshape the world’s sandy coastlines. In this study, we conceptualize barrier coasts as sediment partitioning frameworks, distributing sand delivered from the shoreface to the subaqueous and subaerial components of the coastal system. Using an idealized morphodynamic model, we explore thresholds of behavioral/morphologic change over decadal to centennial timescales, simulating barrier evolution within quasi-stratigraphic morphological cross-sections. Our results indicate a wide diversity of barrier behaviors can be explained by the balance of fluxes delivered to the beach versus the dune/backbarrier, including previously understudied forms of transgression that allow the subaerial system to continue accumulating sediment during landward migration. Most importantly, our results show that barrier state transitions between progradation, cross-shore amalgamation, aggradation, and transgression are controlled largely through balances within a narrow range of relative sea-level rise and sediment flux. This suggests that, in the face of rising sea levels, subtle changes in sediment fluxes could result in significant changes in barrier morphology. We also demonstrate that modeled barriers with reduced vertical sediment accommodation are highly sensitive to the magnitude and direction of shoreface fluxes. Therefore, natural barriers with limited sediment accommodation could allow for exploration of the future effects of sea-level rise and changing flux magnitudes over a period of years as opposed to the decades required for similar responses in sediment-rich barrier systems. Finally, because our model creates stratigraphy generated under different input parameters, we propose it could be used in combination with stratigraphic data to hindcast the sensitivity of existing barriers and infer changes in pre-historic morphology, which we anticipate will provide a baseline to assess the reliability of forward modeling predictions.

scholarly journals Quantifying thresholds of barrier geomorphic change in a cross-shore sediment-partitioning model

2021 ◽  
Vol 9 (2) ◽  
pp. 183-203
Author(s):  
Daniel J. Ciarletta ◽  
Jennifer L. Miselis ◽  
Justin L. Shawler ◽  
Christopher J. Hein
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Cross Sections ◽  
Sediment Flux ◽  
State Transitions ◽  
Morphologic Change ◽  
Relative Sea Level ◽  
Coastal System ◽  
Sea Levels ◽  
Relative Sea Level Rise

Abstract. Barrier coasts, including barrier islands, beach-ridge plains, and associated landforms, can assume a broad spectrum of morphologies over multi-decadal scales that reflect conditions of sediment availability, accommodation, and relative sea-level rise. However, the quantitative thresholds of these controls on barrier-system behavior remain largely unexplored, even as modern sea-level rise and anthropogenic modification of sediment availability increasingly reshape the world's sandy coastlines. In this study, we conceptualize barrier coasts as sediment-partitioning frameworks, distributing sand delivered from the shoreface to the subaqueous and subaerial components of the coastal system. Using an idealized morphodynamic model, we explore thresholds of behavioral and morphologic change over decadal to centennial timescales, simulating barrier evolution within quasi-stratigraphic morphological cross sections. Our results indicate a wide diversity of barrier behaviors can be explained by the balance of fluxes delivered to the beach vs. the dune or backbarrier, including previously understudied forms of transgression that allow the subaerial system to continue accumulating sediment during landward migration. Most importantly, our results show that barrier state transitions between progradation, cross-shore amalgamation, aggradation, and transgression are controlled largely through balances within a narrow range of relative sea-level rise and sediment flux. This suggests that, in the face of rising sea levels, subtle changes in sediment fluxes could result in significant changes in barrier morphology. We also demonstrate that modeled barriers with reduced vertical sediment accommodation are highly sensitive to the magnitude and direction of shoreface fluxes. Therefore, natural barriers with limited sediment accommodation could allow for exploration of the future effects of sea-level rise and changing flux magnitudes over a period of years as opposed to the decades required for similar responses in sediment-rich barrier systems. Finally, because our model creates stratigraphy generated under different input parameters, we propose that it could be used in combination with stratigraphic data to hindcast the sensitivity of existing barriers and infer changes in prehistoric morphology, which we anticipate will provide a baseline to assess the reliability of forward modeling predictions.

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