The characteristics of acoustic-gravity waves (waveforms, time durations, amplitudes, azimuths and horizontal phase speeds) from the eruption of the Hunga-Tonga-Hunga-Hapai volcano detected at ...different infrasound stations of the Infrasound Monitoring System and at a network of low-frequency microbarographs in the Moscow region are studied. Using the correlation analysis of the signals at different locations, six arrivals of signals from the volcano, which made up to two revolutions around the Earth, were detected. The Lamb mode of acoustic gravity waves from the volcano eruption is identified and the effect of this mode on generation of tsunami waves and variation of aerosol concentration is studied. The energy released from an underwater volcano into the atmosphere is estimated from the parameters of the Lamb wave and compared with the energy released from the most powerful nuclear bomb of 58 Mt TNT.
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.
Long-term time series of physical and chemical parameters collected between 1960 and 2010 along the Palagruza Sill transect, Middle Adriatic Sea, have been investigated in terms of average water ...properties and their variability. Nutrients, especially orthophosphates, reached rather high levels of concentration below the euphotic zone between 1991 and 1998, the highest levels in the investigated period. Simultaneously, the N:P ratio, which is normally higher than 25:1, decreased to values less than 16:1 in the euphotic zone, indicating a switch from typical phosphorus to nitrogen- limited preconditioning for the primary production. Higher-than-usual nutrient levels peaking in the mid-1990s, coupled with lower-than-usual temperature, salinity, dissolved oxygen and pH values, are presumably related to the flow of the nutrient richer Western Mediterranean waters to the Adriatic below the euphotic layer. These waters, which keep their footprint in the N:P ratio, enter the Adriatic during the anticyclonic phase of the Bimodal Adriatic-Ionian Oscillation (BiOS), which has been uniquely strengthened by the Eastern Mediterranean Transient occurring in the early 1990s. This hypothesis should be confirmed through targeted research and modelling exercises, as it is highly relevant for the biogeochemistry of the Adriatic Sea.
A systematic survey of high-frequency sea level oscillations (<6 h) measured between 2006 and 2011 along the US East Coast is performed. Raw 1-min resolution sea level data is used. After performing ...a data quality check, the nine most intense events, with maximum recorded wave heights ranging from 40 to 100 cm, are identified. Focusing on three of these events enables us to recognize two different generation mechanisms: (i) topographically-trapped edge waves which are found to be a significant contributor to the strongest observed oscillations, and (ii) standing waves, which occur over enclosed shallow waters and may result in significant wave heights of up to 100 cm. A reproduction of the observed oscillations is a part of a future work, which will include an assessment of a generating force in the atmosphere, allowing for a better prevention of potential flooding along the US East Coast.
In this paper, we document observational support for the long-term weakening of the northwestern part of the Adriatic−Ionian thermohaline cell (AITHC), one of the 3 cells that drive the deep ...Mediterranean thermohaline circulation. The AITHC weakening is detected from long-term temperature, salinity and dissolved oxygen trends estimated from data measured between 1952 and 2010 along the Palagruža Sill, Adriatic Sea. We assumed that the weakening of the AITHC may be deduced from long-term changes in the dense water outflow characteristics across the sill, which are characterized by a strong decrease in dissolved oxygen content, slight warming and shallowing of the outflow and by lower advection of saline and warmer Levantine Intermediate Water (LIW) toward the northwestern Adriatic. The latter was deduced from the negative temperature trends and the lowest salinity trends estimated for the area of LIW inflow. Further weakening of the AITHC may have a noteworthy impact on deep aquatic systems and should therefore be monitored and assessed regularly.
The paper overviews meteotsunami events documented in the Adriatic Sea in the last several decades, by using available eyewitness reports, documented literature, and atmospheric sounding and ...meteorological reanalysis data available on the web. The source of all documented Adriatic meteotsunamis was examined by assessing the underlying synoptic conditions. It is found that travelling atmospheric disturbances which generate the Adriatic meteotsunamis generally appear under atmospheric conditions documented also for the Balearic meteotsunamis (rissagas). These atmospheric disturbances are commonly generated by a flow over the mountain ridges (Apennines), and keep their energy through the wave-duct mechanism while propagating over a long distance below the unstable layer in the mid-troposphere. However, the Adriatic meteotsunamis may also be generated by a moving convective storm or gravity wave system coupled in the wave-CISK (Conditional Instability of the Second Kind) manner, not documented at other world meteotsunami hot spots. The travelling atmospheric disturbance is resonantly pumping the energy through the Proudman resonance over the wide Adriatic shelf, but other resonances (Greenspan, shelf) are also presumably influencing the strength of the meteotsunami waves, especially in the middle Adriatic, full of elongated islands and with a sloping bathymetry. The generated long ocean waves are hitting funnel-shaped bays or harbours of large amplification factors, resulting in meteotsunami waves with heights up to 6
m at the very end of bays or harbours. Within models the mechanism is fairly well understood, but it is extremely difficult to reproduce these events (and presently almost impossible to forecast) as the meteotsunami generating process is highly variable at both temporal and spatial scales. The final part of the paper discusses the possibilities for further research of the Adriatic meteotsunamis, and meteotsunamis in general, including the basis of a meteotsunami warning system which should be able to capture potentially dangerous travelling atmospheric disturbances in real-time.
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.
This paper investigates whether concurrent or subsequent meteotsunamis could happen at both the Balearic Islands and the Adriatic Sea as a consequence of either the simultaneous presence of the ...favourable synoptic pattern above both areas, or propagation of the pattern from one area to another. Meteotsunami events in sea level records from Dubrovnik (chosen to be the proxy for the occurrence of meteotsunami events in the Adriatic Sea) are compared to 32 known Ciutadella (the Balearic Islands) events. The analysis shows that a meteotsunami at the Adriatic Sea is likely to happen if the favourable synoptic pattern propagates or spreads from the Balearic Islands to the Adriatic Sea, causing meteotsunamis in both places. Upper level instabilities are recognized as the most important synoptic feature for the occurrence of meteotsunamis, as these instabilities can generate the atmospheric gravity waves which provoke meteotsunamis and also help to trap the atmospheric energy at lower levels.
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