Abstract. In light of the recent enhanced activity in the study of tsunami waves and their source mechanisms, we consider tsunami-like waves that are induced by atmospheric processes rather than by seismic sources. These waves are mainly associated with atmospheric gravity waves, pressure jumps, frontal passages, squalls and other types of atmospheric disturbances, which normally generate barotropic ocean waves in the open ocean and amplify them near the coast through specific resonance mechanisms (Proudman, Greenspan, shelf, harbour). The main purpose of the present study is to describe this hazardous phenomenon, to show similarities and differences between seismic and meteorological tsunamis and to provide an overview of meteorological tsunamis in the World Ocean. It is shown that tsunamis and meteotsunamis have the same periods, same spatial scales, similar physical properties and affect the coast in a comparably destructive way. Some specific features of meteotsunamis make them akin to landslide-generated tsunamis. The generation efficiency of both phenomena depend on the Froude number (Fr), with resonance taking place when Fr∼1.0. Meteotsunamis are much less energetic than seismic tsunamis and that is why they are always local, while seismic tsunamis can have globally destructive effects. Destructive meteotsunamis are always the result of a combination of several resonant factors; the low probability of such a combination is the main reason why major meteotsunamis are infrequent and observed only at some specific locations in the ocean.

Generation of dense waters in the Adriatic Sea during an extreme cooling event in the winter of 2012, including its preconditioning and spreading phases, have been investigated using the one-way coupled ROMS and the ALADIN/HR modeling system. Both climatological and real river fluxes are used in the simulations. Aside from the ''convenient'' dense water formation areas located at the northernmost Adriatic shelf, we found that a similar amount of dense water, with slightly lower density, was formed in the eastern and deeper Adriatic coastal area, which was subjected to extreme heat losses (up to 2000 W/m 2 ) during peak cooling periods. This part of the Adriatic has been known for extreme cooling during wintertime bora outbreaks; nevertheless, no ocean model study has previously reproduced dense water formation in this area. The most likely reason for that was an overestimate of river discharges introduced to ocean models. From newly available data, we estimated that the contribution of eastern Adriatic rivers between the Neretva River and Rijeka Bay is more than six times lower than what has been previously documented. Transport of dense water toward the middle Adriatic had a peak value of about 0.6 Sv, while the speed of initial bottom density current surpassed 40-50 cm/s, which is several times faster than past events. Different pathways of the dense water toward the middle and south Adriatic depressions have also been documented. The contribution of the eastern coastal Adriatic area to the overall north Adriatic dense water formation has been quantified and discussed for average and low freshwater load conditions, indicating that this part of the Adriatic is a common place for dense water generation.

Abstract. In this paper we document dense water formation throughout the Adriatic shelf and coastal area in January/February 2012, resulting in record-breaking densities observed during and after the event. The unprecedented dense water generation was preconditioned by a dry and warm year which resulted in a significant reduction of coastal freshwaters, superimposed on a long-term basin-wide salinity increase. The final event that triggered the dense water formation was an extended period of cold weather with strong and severe winds. Record-breaking potential density anomalies (above 30 kg m −3 ) were measured at several formation sites. Accumulated surface net heat and water losses in some coastal regions exceeded 1.5 GJ m −2 and 250 kg m −2 over 21 days, respectively. Excessiveness, importance of shelf-type dense water formation and effects on the thermohaline circulation and deep aquatic systems are discussed.

[1] Exceptional sea level oscillations and strong current reversals, observed in the east Adriatic on 27 June 2003, are analyzed using available meteorological and tide-gauge measurements and numerical model results. It is shown that the variability in the atmosphere-sea system was characterized by high frequencies (0.01-0.1 min À1 ) and sea level and current amplitudes surpassing 1 m and 1 m s À1 , respectively. The event was related to the occurrence of a gravity disturbance in the atmosphere above the Adriatic. The disturbance traveled toward the east-southeast at a speed of 22 m s À1 and was resonantly coupled with a wave in the sea 50 m deep. The resulting forced wave was further amplified when entering funnel-shaped bays opened to it. There are indications that the forcing disturbance and its counterpart in the sea excited normal modes of the bays and harbors in the area. Moreover, nonlinear steepening of the forced wave seemingly occurred, resulting in the formation of high-frequency wave trains. This process, along with the generation of coastal seiches, could explain the observed and modeled differences between the spectra of coastal variability and the spectrum of forcing wave.

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