Short period sea level oscillations at Strait of Gibraltar: Observations versus model results

Extreme sea levels are known to hit the Adriatic Sea and to occasionally cause floods that produce severe material damage. Whereas the contribution of longer-period (T > 2 h) sea-level oscillations to the phenomena has been well researched, the contribution of the shorter period (T <&#160;2 h) oscillations is yet to be determined. With this aim, data of 1-min sampling resolution were collected for 20 tide gauges, 10 located at the Italian (north and west) and 10 at the Croatian (east) Adriatic coast. Analyses were done on time series of 3 to 15 years length, with the latest data coming from 2020, and with longer data series available for the Croatian coast. Sea level data were thoroughly checked, and spurious data were removed.&#160;For each station, extreme sea levels were defined as events during which sea level surpasses its 99.9 percentile value. The contribution of short-period oscillations to extremes was then estimated from corresponding high-frequency (T < 2 h) series. Additionally, for four Croatian tide gauge stations (Rovinj, Bakar, Split, and Dubrovnik), for period of 1956-2004, extreme sea levels were also determined from the hourly sea level time series, with the contribution of short-period oscillations visually estimated from the original tide gauge charts.&#160;&#160;Spatial and temporal distribution of contribution of short-period sea-level oscillations to the extreme sea level in the Adriatic were estimated. It was shown that short-period sea-level oscillation can significantly contribute to the overall extremes and should be considered when estimating flooding levels.&#160;

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Analysis of the eastern Adriatic sea-level extremes

10.5194/egusphere-egu21-5676 ◽

2021 ◽

Author(s):

Marija Pervan ◽

Jadranka Šepić

Keyword(s):

Sea Level ◽

Adriatic Sea ◽

Hot Spot ◽

Storm Surges ◽

Low Pressure ◽

Long Period ◽

Short Period ◽

Sea Level Oscillations ◽

Low Pass ◽

Level Height

The Adriatic Sea is known to be under a high flooding risk due to both storm surges and meteorological tsunamis, with the latter defined as short-period sea-level oscillations alike to tsunamis but generated by atmospheric processes. In June 2017, a tide-gauge station with a 1-min sampling resolution has been installed at Stari Grad (middle Adriatic Sea), the well-known meteotsunami hot-spot, which is, also, often hit by storm surges.&#160;Three years of corresponding sea-level measurements were analyzed, and 10 strongest episodes of each of the following extreme types were extracted from the residual series: (1) positive long-period (T > 210 min) extremes; (2) negative long-period (T > 210 min) extremes; (3) short-period (T < 210) extremes. Long-period extremes were defined as situations during which sea level surpasses (is lower than) 99.7 (i.e. 2) percentile of sea level height, and short-period extremes as situations during which variance of short-period sea-level oscillations is higher than 99.4 percentile of total variance[J1]&#160; of short-period series. A strong seasonal signal was detected for all extremes, with most of the positive long-period extremes appearing during November to February, and most of the negative long-period extremes during January to February. As for the short-period extremes, these appear evenly throughout the year, but strongest events seem to appear during May to July.All events were associated to characteristic atmospheric situations, using both local measurements of the atmospheric variables, and ERA5 Reanalysis dataset. It was shown that positive low-pass extremes commonly appear during presence of low pressure over the Adriatic associated with strong SE winds (&#8220;sirocco&#8221;), and negative low-pass extremes are associated to the high atmospheric pressure over the area associated with either strong NE winds (&#8220;bora&#8221;), or no winds at all. On the other hand, high-pass sea level extremes are noticed during two distinct types of atmospheric situations corresponding to both &#8220;bad&#8221; (low pressure, strong SE wind) and &#8220;nice&#8221; (high pressure, no wind) weather.It is particularly interesting that short-period extremes, of which strongest are meteotsunamis, are occasionally coincident with positive long-period extremes contributing with up to 50 percent to total sea level height &#8211; thus implying existence of a double danger phenomena (meteotsunami + storm surge).&#160;

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Detection of short-period sea level oscillations in the Gulf of Genoa

OCEANS 2017 - Aberdeen ◽

10.1109/oceanse.2017.8084614 ◽

2017 ◽

Author(s):

Paola Picco ◽

Maurizio Demarte ◽

Riccardo D'Epifanio ◽

Matteo Guideri ◽

Luca Repetti ◽

...

Keyword(s):

Sea Level ◽

Short Period ◽

Sea Level Oscillations

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Relative Sea Level Variations and Climatic Evolutuion in Southeastern and Southern Brazil During the Late Holocene

Pesquisas em Geociências ◽

10.22456/1807-9806.20270 ◽

2001 ◽

Vol 28 (2) ◽

pp. 75 ◽

Cited By ~ 7

Author(s):

JEAN-PIERRE YBERT ◽

WALTER MARESCHI BISSA ◽

MIRYAN KUTNER

Keyword(s):

Sea Level ◽

Late Holocene ◽

Southeastern Brazil ◽

Relative Sea Level ◽

Swamp Forest ◽

Central Brazil ◽

Open Forest ◽

Short Period ◽

Sea Level Oscillations ◽

Sea Level Trend

Analysis of organic sediments from a swamp forest on the coastal plain of São Paulo State (southeastern Brazil) has been carried out. Diatom and pollen contents from the same samples were analysed. This study allowed reconstruction of the regional paleoenvironment during the Late Holocene. From at least 4400 to 3250 yr BP the site was a lagoon surrounded by a relatively open forest. At ca. 3250 yr BP, after the retreat of the sea, a swamp forest occupied the area. This swamp forest remains until the present day. It was locally altered during a short period between ca. 1400 and 775 yr BP when, due to a rise in groundwater, a fresh water lake or marsh was formed. The climate was similar to the present during the whole Late Holocene, except for three slightly more humid episodes: 3250-2600, around 2000, and 1400-775 yr BP. No human impact on the vegetation was recorded during the Late Holocene. Our results show that sea level was higher than the present zero level from 4400 to 3250 yr BP, contradicting a widely accepted relative sea level trend that suggests that at least two important negative sea level oscillations occurred during the Holocene (4100-3800 and 3000-2700 yr BP). Conversely, these results tend to confirm more recent studies that propose a continuously declining relative sea level trend. Comparison of our data with those from 24 sites situated in southeastern, southern and central Brazil show that the more humid episodes recorded at Cananéia-Iguape might be correlated with El Niño like events. Trends in climatic evolution during the Late Holocene are opposite at north and south of 20ºS latitude.

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NUMERICAL MODELING OF STORM SURGES, WIND WAVES AND FLOODING IN THE TAGANROG BAY

Proceedings of International Conference "Managinag risks to coastal regions and communities in a changinag world" (EMECS'11 - SeaCoasts XXVI) ◽

10.21610/conferencearticle_58b43153f04bb ◽

2017 ◽

Author(s):

Vladimir Fomin ◽

Dmitrii Alekseev ◽

Dmitrii Lazorenko ◽

...

Keyword(s):

Sea Level ◽

Wind Waves ◽

Storm Surges ◽

Atmospheric Model ◽

Extreme Storm ◽

Regional Atmospheric Model ◽

Sea Level Oscillations ◽

Flooding And Drying ◽

Flooded Area ◽

Taganrog Bay

Storm surges and wind waves are ones of the most important hydrological characteristics, which determine dynamics of the Sea of Azov. Extreme storm surges in Taganrog Bay and flooding in the Don Delta can be formed under the effect of strong western winds. In this work the sea level oscillations and wind waves in the Taganrog Bay were simulated by means of the coupled SWAN+ADCIRC numerical model, taking into account the flooding and drying mechanisms. The calculations were carried out on an unstructured mesh with high resolution. The wind and atmospheric pressure fields for the extreme storm from 20 to 28 of September, 2014 obtained from WRF regional atmospheric model were used as forcing. The analysis of simulation results showed the following. The western and northern parts of the Don Delta were the most flood-prone during the storm. The size of the flooded area of the Don Delta exceeded 50%. Interaction of storm surge and wind wave accelerated the flooding process, increased the size of the flooded area and led to the intensification of wind waves in the upper of Taganrog Bay due to the general rise of the sea level.

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Spatial distribution of water level impact to back-barrier bays

10.5194/nhess-2018-320 ◽

2018 ◽

Author(s):

Alfredo L. Aretxabaleta ◽

Neil K. Ganju ◽

Zafer Defne ◽

Richard P. Signell

Keyword(s):

Water Level ◽

Sea Level ◽

Water Levels ◽

Analytical Models ◽

Barnegat Bay ◽

Sea Level Fluctuations ◽

Flooding Hazard ◽

Short Period ◽

Inlet Geometry ◽

Spatial Estimates

Abstract. Water level in semi-enclosed bays, landward of barrier islands, is mainly driven by offshore sea level fluctuations that are modulated by bay geometry and bathymetry, causing spatial variability in the ensuing response (transfer). Local wind setup can have a secondary role that depends on wind speed, fetch, and relative orientation of the wind direction and the bay. Inlet geometry and bathymetry primarily regulate the magnitude of the transfer between open ocean and bay. Tides and short-period offshore oscillations are more damped in the bays than longer-lasting offshore fluctuations, such as storm surge and sea level rise. We compare observed and modeled water levels at stations in a mid-Atlantic bay (Barnegat Bay) with offshore water level proxies. Observed water levels in Barnegat Bay are compared and combined with model results from the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system to evaluate the spatial structure of the water level transfer. Analytical models based on the dimensional characteristics of the bay are used to combine the observed data and the numerical model results in a physically consistent approach. Model water level transfers match observed values at locations inside the Bay in the storm frequency band (transfers ranging from 70–100 %) and tidal frequencies (10–55 %). The contribution of frequency-dependent local setup caused by wind acting along the bay is also considered. The approach provides transfer estimates for locations inside the Bay where observations were not available resulting in a complete spatial characterization. The approach allows for the study of the Bay response to alternative forcing scenarios (landscape changes, future storms, and rising sea level). Detailed spatial estimates of water level transfer can inform decisions on inlet management and contribute to the assessment of current and future flooding hazard in back-barrier bays and along mainland shorelines.

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A Near-Uniform Basin-Wide Sea Level Fluctuation of the Mediterranean Sea

Journal of Physical Oceanography ◽

10.1175/jpo3016.1 ◽

2007 ◽

Vol 37 (2) ◽

pp. 338-358 ◽

Cited By ~ 56

Author(s):

Ichiro Fukumori ◽

Dimitris Menemenlis ◽

Tong Lee

Keyword(s):

Atlantic Ocean ◽

Mediterranean Sea ◽

Sea Level ◽

Ocean Circulation ◽

Large Scale ◽

Circulation Model ◽

Level Fluctuation ◽

Strait Of Gibraltar ◽

Sea Level Fluctuation ◽

The Mediterranean

Abstract A new basin-wide oscillation of the Mediterranean Sea is identified and analyzed using sea level observations from the Ocean Topography Experiment (TOPEX)/Poseidon satellite altimeter and a numerical ocean circulation model. More than 50% of the large-scale, nontidal, and non-pressure-driven variance of sea level can be attributed to this oscillation, which is nearly uniform in phase and amplitude across the entire basin. The oscillation has periods ranging from 10 days to several years and has a magnitude as large as 10 cm. The model suggests that the fluctuations are driven by winds at the Strait of Gibraltar and its neighboring region, including the Alboran Sea and a part of the Atlantic Ocean immediately to the west of the strait. Winds in this region force a net mass flux through the Strait of Gibraltar to which the Mediterranean Sea adjusts almost uniformly across its entire basin with depth-independent pressure perturbations. The wind-driven response can be explained in part by wind setup; a near-stationary balance is established between the along-strait wind in this forcing region and the sea level difference between the Mediterranean Sea and the Atlantic Ocean. The amplitude of this basin-wide wind-driven sea level fluctuation is inversely proportional to the setup region’s depth but is insensitive to its width including that of Gibraltar Strait. The wind-driven fluctuation is coherent with atmospheric pressure over the basin and contributes to the apparent deviation of the Mediterranean Sea from an inverse barometer response.

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Water circulation around Britomart Reef, Great Barrier Reef, during July 1979

Marine and Freshwater Research ◽

10.1071/mf9800415 ◽

1980 ◽

Vol 31 (4) ◽

pp. 415 ◽

Cited By ~ 13

Author(s):

E Wolanski ◽

M Jones

Keyword(s):

Great Barrier Reef ◽

Sea Level ◽

Central Region ◽

Reef Flat ◽

Water Circulation ◽

Barrier Reef ◽

Trade Winds ◽

Sea Breezes ◽

Coral Sea ◽

Sea Level Oscillations

Weather and currents at eight sites were measured and drogue trajectories obtained in July 1979 at Britomart Reef, a middle reef located at 18�16'S.,146� 38'E. in the central region of the Great Barrier Reef province. The longest current records (3 weeks) were obtained at two sites in passes between the Coral Sea and the Great Barrier Reef Lagoon where westerly currents modulated by tides were observed. Analysis of residuals also showed the importance of wind-driven secondary circulation. Non-tidal sea-level oscillations were very small. Shorter current records (1-10 days) at six sites in the lagoon and on the reef flat showed a predominant northerly flow, also modulated by tides and wind. A residual anticlockwise water circulation existed in the lagoon where flushing was controlled more by winds than by tides. The rise in sea level over the reef flat as a result of waves breaking was negligible. Temperature differences between air and water accounted for the cooling of the water column during the expedition. Constant south-east trade winds were experienced at the reef, while on land the wind was weaker. more variable, and often dominated by land-sea breezes.

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