Globalni porast razine mora? Nove tehnike određivanja apsolutne razine mora

A brief review is given of recent papers on the relative mean sea level, global sea level rise effect, and the predictions to the year 2100. The influence of vertical crustal movements on the relative sea level is visible in the longest sea level records. Both modern space geodetic techniques and absolute gravity measurements have now achieved the accuracy within a centimetre that is comparable to the quality of mean sea level records. As the extraction of land movements from the tide gauge records is possible after about a decade of measurements, a number of international projects have been (e.g. SELF) and will be (e.g. MedGLOSS) launched with the aim of determining the absolute sea level.U radu je dan kratak pregled novijih radova koji analiziraju relativnu razinu mora, efekt globalnog porasta razine mora te predviđanja porasta do godine 2100. Utjecaj vertikalnih geotektonskih gibanja sadržanih u mjerenoj relativnoj razini mora se jasno vidi na podacima najdužih mareografskih nizova. Geodetska tehnika preciznog pozicioniranja i apsolutna gravimetrija danas postižu centimetarsku preciznost mjerenja vertikalnih pomaka, usporedivu s geološkim pomacima tla uključenim u registraciju relativne razine mora. Iz istih je moguće, kontinuirano mjereći poziciju i razinu mora oko desetak godina, izdvojiti pomake tla. Stoga je pokrenuto (npr. SELF) ili će se pokrenuti (npr. MedGLOSS) više međunarodnih projekata s ciljem određivanja apsolutne razine mora

Dense-water generation episodes in the Northern Adriatic

The generation of North Adriatic Dense Water (NAdDW) has been documented in the paper, by analysing three generation episodes occurred in winters of 1981, 1987 and 1989. Temperature, salinity and density collected at the Po Delta-Rovinj transect before, during and after NAdDW generation were analysed and discussed. Furthermore, monthly surface heat, water and buoyancy fluxes were computed for the respective time intervals, coupled with Po River discharge rates. The decrease in the Po River runoff in the preceding 4 months is common characteristics for all of three NAdDW generation episodes. Nevertheless, NAdDW generated in winter of 1989 was the result of extremely lowered water fluxes that preceded to the generation, producing extremely saline dense water. In contrary, winters of 1981 and 1987 were characterized by extensive heat losses in January/February therefore resulting in very cold NAdDW. NAdDW density in all of the cases surpassed 29.7, being dense enough to influence wider area and bottom layers of the whole Adriatic, changing a lot its physical and chemical properties

High-frequency atmospherically-induced oscillations in the middle Adriatic coastal area

Temporal and spatial characteristics of the resonant coupling between travelling air pressure disturbances and the middle Adriatic coastal waters are examined using a barotropic numerical model for a one year period (July 2000–July 2001). The model is forced by the travelling air pressure disturbances reconstructed from the 2-min resolution air pressure series measured at Split. Six experiments for the studied period are performed, in order to analyse the influence of the speed and disturbance direction on the resonant coupling. The first group of three experiments uses variable disturbance direction, whereas in the second three, a constant direction is employed during the whole experiment. Disturbance direction for the first group of experiments is computed from the 500-mb geopotential data provided by European Center for Medium Range Weather Forecast (ECMWF), as it is found that all of the past extreme events are correlated with them. Each experiment, with variable and constant disturbance direction, is repeated with three different constant values of 10, 20 and 30 m/s for the disturbance speed. The model verification on the Split sea level data reveals that the model reproduces most of the events but also overestimates/underestimates some of them and creates some false events due to the rigid assumption of a constant disturbance speed. The best agreement with data is obtained in the model runs assuming a disturbance speed of 20 m/s. A number of trapped and edge waves have been modelled at the constrictions and along the coast, in particular on a shoal that lies off Split perpendicular to the channel axis. The importance of the disturbance direction to the energy content is highlighted, particularly close to the shore, where the difference may be significant at 2–3 times on average, up to 30 cm in maximum amplitude

Long-term changes in hydrographic conditions in northern Adriatic and its relationship to hydrological and atmospheric processes

A very long data series (1921–2000) of hydrographic parameters (temperature, salinity and density) collected in surface and bottom layers at a station in the coastal zone in the northeastern Adriatic was analyzed. Seasonal and interannual variability of the three parameters is described on the basis of monthly and yearly averages. The seasonal cycles obtained were found to be typical for the northern Adriatic. Interannual analysis showed that there was no trend in temperature, salinity and density in the region during the interval analyzed. The long-term series of yearly means of hydrographic parameters were related to the long-term series of yearly means of several hydrological/atmospheric parameters using different time lags of between 0 and 4 years. These parameters are surface heat flux gained by insolation Qs computed for Trieste, precipitation P in Trieste, Po River discharge rate R and two atmospheric oscillation indexes, a Mediterranean Oscillation (MO) index and North Atlantic Oscillation (NAO) index. At zero time lag the interannual changes at the surface were found to be significantly related to changes in the Qs and NAO index (temperature) and R (salinity and density). At the same time lag the changes in the bottom were found to be related to the MO index (temperature, salinity and density). Additionally, bottom salinity and density were significantly related to R at a time lag of 1 year.<br><br> <b>Key words.</b> Oceanography: Physical (air-sea interactions; hydrography

Minute Sea-Level Analysis (MISELA): a high- frequency sea-level analysis global dataset

Sea-level observations provide information on a variety of processes occurring over different temporal and spatial scales that may contribute to coastal flooding and hazards. However, global research on sea-level extremes is restricted to hourly datasets, which prevent the quantification and analyses of processes occurring at timescales between a few minutes and a few hours. These shorter-period processes, like seiches, meteotsunamis, infragravity and coastal waves, may even dominate in low tidal basins. Therefore, a new global 1 min sea-level dataset – MISELA (Minute Sea-Level Analysis) – has been developed, encompassing quality-checked records of nonseismic sea-level oscillations at tsunami timescales (T<2 h) obtained from 331 tide-gauge sites (https://doi.org/10.14284/456, Zemunik et al., 2021b). This paper describes data quality control procedures applied to the MISELA dataset, world and regional coverage of tide- gauge sites, and lengths of time series. The dataset is appropriate for global, regional or local research of atmospherically induced high-frequency sea-level oscillations, which should be included in the overall sea-level extremes assessments

The development and implementation of a real-time meteotsunami warning network for the Adriatic Sea

The Adriatic Sea meteotsunami research and warning network is described. The network is located in the middle Adriatic, an area where the most destructive of the Adriatic meteotsunamis (destructive tsunami-like sea level oscillations generated by air pressure oscillations) occur. The network consists of three microbarograph meteorological stations, and is supplemented by four permanent tide-gauge stations. The two strongest air pressure disturbances, detected in almost a year and a half of measurements, are examined in more detail and used to test functionality and applicability of the network. Both of these disturbances had a meteotsunami favourable velocity, however, only one generated a meteotsunami. It is discussed why this happened and additional information on creating a meteotsunami warning system are obtained. Methods to construct a simple low-cost meteotsunami warning network are given

Hydrographic conditions driving sardine and anchovy populations in a land-locked sea

The aim of this paper is to establish a relationship between long-term variability in sardine and anchovy populations in the Adriatic Sea and ocean dynamics and processes that occur over interannual and decadal timescales in the Adriatic-Ionian basin. Basis for such analysis are annual time series of sardine and anchovy landings and recruits at age 0 and annual time series of environmental parameters observed at a representative Adriatic station between 1975 and 2010. Pearson correlations and robust Dynamic Factor Analysis (DFA) were applied to quantify the connections between fisheries and environmental parameters. Variations and trends in fisheries series were best explained by changes in near-bottom temperature and salinity, being an appropriate proxy for tracking changes in water masses' dynamics and hydrographic conditions in the basin. It seems that a prolonged period of decreasing sardine population was characterized by low oxygen availability and environmental conditions in the deep Adriatic waters, triggered by an extraordinary basin-wide event called the Eastern Mediterranean Transient. A collapse in anchovy population has been observed after an exceptional cooling event followed by dense water formation

A framework for the probabilistic analysis of meteotsunamis

This paper is not subject to U.S. copyright. The definitive version was published in Natural Hazards 74 (2014): 123-142, doi:10.1007/s11069-014-1294-1.A probabilistic technique is developed to assess the hazard from meteotsunamis. Meteotsunamis are unusual sea-level events, generated when the speed of an atmospheric pressure or wind disturbance is comparable to the phase speed of long waves in the ocean. A general aggregation equation is proposed for the probabilistic analysis, based on previous frameworks established for both tsunamis and storm surges, incorporating different sources and source parameters of meteotsunamis. Parameterization of atmospheric disturbances and numerical modeling is performed for the computation of maximum meteotsunami wave amplitudes near the coast. A historical record of pressure disturbances is used to establish a continuous analytic distribution of each parameter as well as the overall Poisson rate of occurrence. A demonstration study is presented for the northeast U.S. in which only isolated atmospheric pressure disturbances from squall lines and derechos are considered. For this study, Automated Surface Observing System stations are used to determine the historical parameters of squall lines from 2000 to 2013. The probabilistic equations are implemented using a Monte Carlo scheme, where a synthetic catalog of squall lines is compiled by sampling the parameter distributions. For each entry in the catalog, ocean wave amplitudes are computed using a numerical hydrodynamic model. Aggregation of the results from the Monte Carlo scheme results in a meteotsunami hazard curve that plots the annualized rate of exceedance with respect to maximum event amplitude for a particular location along the coast. Results from using multiple synthetic catalogs, resampled from the parent parameter distributions, yield mean and quantile hazard curves. Further refinements and improvements for probabilistic analysis of meteotsunamis are discussed

Response of the Adriatic Sea to the atmospheric anomaly in 2003

Unusual weather conditions over the southern Europe and the Mediterranean area in 2003 significantly impacted the oceanographic properties of the Adriatic Sea. To document these changes, both in the atmosphere and the sea, anomalies from the normal climate were calculated. The winter 2003 was extremely cold, whereas the spring/summer period was extremely warm. The air temperature in June was more than 3 standard deviations above the average. On the other hand, precipitation and river runoff were extremely low between February and August. The response of the sea was remarkable, especially in surface salinity during spring and summer, with values at least one standard deviation above the average. Analysis of thermohaline properties in the middle Adriatic showed the importance of two phenomena responsible for the occurrence of exceptionally high salinity: (1) enhanced inflow of saline Levantine Intermediate Water (LIW) in the Adriatic, and (2) extremely low precipitation and river runoff, accompanied with strong evaporation. Two large-scale atmospheric indices: NAOI (North Atlantic Oscillation Index) and MOI (Mediterranean Oscillation Index), although generally correlated to the Adriatic climate, failed to describe anomalies in 2003. The air pressure gradients used for the definition of both indices significantly decreased in 2003 due to the presence of the high pressure areas over most of Europe and the northern Atlantic, and were actually responsible for the observed anomalies above and in the Adriatic