Introduction to "Sixty Years of Modern Tsunami Science, Volume 2: Challenges".

Fifteen papers are included in this PAGEOPH topical issue "Sixty Years of Modern Tsunami Science, Volume 2: Challenges." The issue starts with a general introduction, and then briefly summarizes all contributions, first papers addressing general topics, and then articles grouped on a regional basis: Northern Pacific, Southeast Pacific, Southwest Pacific and Indonesia, and Mediterranean regions.

Destructive coastal sea level oscillations generated by Typhoon Maysak in the Sea of Japan in September 2020.

Typhoon Maysak (Julian in the Philippines) was a powerful tropical cyclone that strongly impacted coastal regions of the Sea of Japan on 2-4 September 2020. Destructive winds, violent storm waves, and intense rainfall occurred in Japan, on the Korean Peninsula, and in Far-Eastern Russia. Devastating coastal floods caused severe damage to coastal infrastructure and to ships and boats anchored in harbours and were responsible for numerous deaths. Our study indicates that the main reason for the destructive floods was the superposition of storm surge, extreme seiches (meteorological tsunamis), and surf beats. At various sites, different types of sea level oscillations prevailed depending on the atmospheric forcing, local topographic properties, and resonant shelf/coastal zone features. The principal forcing factors of these oscillations were atmospheric pressure and wind stress, but the exact generation mechanism of each specific type of oscillation was strongly site dependent. The uniqueness of the sea level response at each site is the main challenge in our understanding of the generation process and to the mitigation of the hazardous consequences of possible future events.

Constrained circulation at Endeavour ridge facilitates colonization by vent larvae.

Understanding how larvae from extant hydrothermal vent fields colonize neighbouring regions of the mid-ocean ridge system remains a major challenge in oceanic research. Among the factors considered important in the recruitment of deep-sea larvae are metabolic lifespan, the connectivity of the seafloor topography, and the characteristics of the currents. Here we use current velocity measurements from Endeavour ridge to examine the role of topographically constrained circulation on larval transport along-ridge. We show that the dominant tidal and wind-generated currents in the region are strongly attenuated within the rift valley that splits the ridge crest, and that hydrothermal plumes rising from vent fields in the valley drive a steady near-bottom inflow within the valley. Extrapolation of these findings suggests that the suppression of oscillatory currents within rift valleys of mid-ocean ridges shields larvae from cross-axis dispersal into the inhospitable deep ocean. This effect, augmented by plume-driven circulation within rift valleys having active hydrothermal venting, helps retain larvae near their source. Larvae are then exported preferentially down-ridge during regional flow events that intermittently over-ride the currents within the valley.

Meteotsunamis in the Laurentian Great Lakes.

The generation mechanism of meteotsunamis, which are meteorologically induced water waves with spatial/temporal characteristics and behavior similar to seismic tsunamis, is poorly understood. We quantify meteotsunamis in terms of seasonality, causes, and occurrence frequency through the analysis of long-term water level records in the Laurentian Great Lakes. The majority of the observed meteotsunamis happen from late-spring to mid-summer and are associated primarily with convective storms. Meteotsunami events of potentially dangerous magnitude (height > 0.3 m) occur an average of 106 times per year throughout the region. These results reveal that meteotsunamis are much more frequent than follow from historic anecdotal reports. Future climate scenarios over the United States show a likely increase in the number of days favorable to severe convective storm formation over the Great Lakes, particularly in the spring season. This would suggest that the convectively associated meteotsunamis in these regions may experience an increase in occurrence frequency or a temporal shift in occurrence to earlier in the warm season. To date, meteotsunamis in the area of the Great Lakes have been an overlooked hazard.

Widespread tsunami-like waves of 23-27 June in the Mediterranean and Black Seas generated by high-altitude atmospheric forcing.

A series of tsunami-like waves of non-seismic origin struck several southern European countries during the period of 23 to 27 June 2014. The event caused considerable damage from Spain to Ukraine. Here, we show that these waves were long-period ocean oscillations known as meteorological tsunamis which are generated by intense small-scale air pressure disturbances. An unique atmospheric synoptic pattern was tracked propagating eastward over the Mediterranean and the Black seas in synchrony with onset times of observed tsunami waves. This pattern favoured generation and propagation of atmospheric gravity waves that induced pronounced tsunami-like waves through the Proudman resonance mechanism. This is the first documented case of a chain of destructive meteorological tsunamis occurring over a distance of thousands of kilometres. Our findings further demonstrate that these events represent potentially dangerous regional phenomena and should be included in tsunami warning systems.

The global reach of the 26 December 2004 Sumatra tsunami.

Numerical model simulations, combined with tide-gauge and satellite altimetry data, reveal that wave amplitudes, directionality, and global propagation patterns of the 26 December 2004 Sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid-ocean ridge topographic waveguides.

Phase diagrams of adsorption systems and calibration functions in the lattice-gas model.

Using the calibration function is suggested to increase the accuracy of approximate equations in the lattice-gas model at calculating various concentration dependences of equilibrium characteristics for nonideal adsorption systems in the vicinity of the critical point. This function should provide a shift of the approximate result to the exact one, when the lattice-gas model equations are used in the quality of the interpolation tool between the exact solutions. A comparison of approximate equations with Onsager's exact solution preferrably allows a use of the quasi-chemical approximation as the interpolation procedure and the exact information on the critical point. The modified lattice-gas model takes into account next the molecular properties of the Lennard-Jones fluid: the long-range potential of adsorbate-adsorbate, an excluded volume of the adsorption site, and a contribution of the triple interactions, as well as a softness of the lattice structure. The modified lattice-gas model with the calibration function is used for the phase diagram descriptions for argon adsorption on the homogeneous (111) CdCl2 face (two-dimensional systems) and for methane adsorption in carbon slitlike pores (three-dimensional system) as well as the other equilibrium characteristics of mentioned systems.