Twenty years of progresses in oceanic rogue waves: the role played by weakly nonlinear models

Here we discuss some of the progresses that have been made in the last 20 years in the field of oceanic rogue waves, focusing on the role played by leading order equations such as the nonlinear Schrödinger and the Korteweg-De Vries equations. For such equations, it is possible, as shown in Onorato et al. (Origin of heavy tail statistics in equations of the nonlinear Schrödinger type: an exact result, 2016. arXiv:1601.04317), to derive a very simple relation in which the variation of the third (for the KdV) and fourth (for the NLS) moment of the probability density function of the wave field can be related to the variation of the spectral bandwidth. These relations give some new perspectives on the formation of rogue waves in a random sea state.     

Strategically Locating Wildlife Crossing Structures for Florida Panthers Using Maximal Covering Approaches

Crossing structures are an effective method for mitigating habitat fragmentation and reducing wildlife‐vehicle collisions, although high construction costs limit the number that can be implemented in practice. Therefore, optimizing the placement of crossing structures in road networks is suggested as a strategic conservation planning method. This research explores two approaches for using the maximal covering location problem (MCLP) to determine optimal sites to install new wildlife crossing structures. The first approach is based on records of traffic mortality, while the second uses animal tracking data for the species of interest. The objective of the first is to cover the maximum number of collision sites, given a specified number of proposed structures to build, while the second covers as many animal tracking locations as possible under a similar scenario. These two approaches were used to locate potential wildlife crossing structures for endangered Florida panthers (Puma concolor coryi) in Collier, Lee, and Hendry Counties, Florida, a population whose survival is threatened by excessive traffic mortality. Historical traffic mortality records and an extensive radio‐tracking dataset were used in the analyses. Although the two approaches largely select different sites for crossing structures, both models highlight key locations in the landscape where these structures can remedy traffic mortality and habitat fragmentation. These applications demonstrate how the MCLP can serve as a useful conservation planning tool when traffic mortality or animal tracking data are available to researchers.     

Surface gravity waves from direct numerical simulations of the Euler equations: A comparison with second-order theory

When the wave spectrum is sufficiently narrow-banded and the wave steepness is sufficiently high, the modulational instability can take place and waves can be higher than expected from second-order wave theory. In order to investigate these effects on the statistical distribution of long-crested, deep water waves, direct numerical simulations of the Euler equations have been performed. Results show that, for a typical design spectral shape, both the upper and lower tails of the probability density function for the surface elevation significantly deviate from the commonly used second-order wave theory. In this respect, the crest elevation is observed to increase up to 18% at low probability levels. It would furthermore be expected that wave troughs become shallower due to nonlinear effects. Nonetheless, the numerical simulations show that the trough depressions tend to be deeper than in second-order theory.     

Wave modelling - The state of the art

This paper is the product of the wave modelling community and it tries to make a picture of the present situation in this branch of science, exploring the previous and the most recent results and looking ahead towards the solution of the problems we presently face. Both theory and applications are considered.The many faces of the subject imply separate discussions. This is reflected into the single sections, seven of them, each dealing with a specific topic, the whole providing a broad and solid overview of the present state of the art. After an introduction framing the problem and the approach we followed, we deal in sequence with the following subjects: (Section) 2, generation by wind; 3, nonlinear interactions in deep water; 4, white-capping dissipation; 5, nonlinear interactions in shallow water; 6, dissipation at the sea bottom; 7, wave propagation; 8, numerics. The two final sections, 9 and 10, summarize the present situation from a general point of view and try to look at the future developments.     

Wave crest and trough distributions in a broad-banded directional wave field

It is well established that the modulational instability enhances the probability of occurrence for extreme events in long crested wave fields. Recent studies, however, have shown that the coexistence of directional wave components can reduce the effects related to the modulational instability. Here, numerical simulations of the Euler equations are used to investigate whether the modulational instability may produce significant deviations from second-order statistical properties of surface gravity waves when short crestness (i.e., directionality) is accounted for. The case of a broad-banded directional wave field (i.e. wind sea) is investigated. The analysis is concentrated on the wave crest and trough distribution. For completeness a comparison with a unidirectional wave field is presented also. Results will show that the distributions based on second-order theory provide a good estimate for the simulated crest and trough height also at low probability levels.     

Biogenic stalactites in submarine caves at the Cape of Otranto (SE Italy): dating and hypothesis on their formation

Submarine caves at the Cape of Otranto (SE, Italy) host pseudostalactites. Only recently have they been recognised as originating mainly from the marine tube worm Protula tubularia (Serpulidae, Polychaeta). Their formation depends on the adaptability, life history and behaviour of that species in the cave habitat. The dating of calcareous tubes in the pseudostalactite core represents the first attempt to describe the formation of such bio-construction, and the gregarious behaviour of the species. Calcareous tubes along the core axis of three pseudostalactites removed from the cave lu Lampiùne (Otranto, South East Italy) have been dated using the ¹⁴C method. Measures established ages from 2600 to 5000 years for the three structures. This extremely long period (when compared with the life span of each worm) suggests that each tube aggregation is the result of punctuated growth periods alternated with long standstill phases. At the end of a growth period, each tube aggregation was covered with a brownish concretion, completing the pseudostalactite.     

Mercury concentrations in red drum, Sciaenops ocellatus, from estuarine and offshore waters of Florida

Dorsal muscle tissue from 712 red drum, Sciaenops ocellatus, from Florida waters were analyzed for total mercury content. Mercury levels detected in these red drum varied but in most study areas were usually lower than regulatory threshold guidelines. Total mercury levels in individual fish from all study areas ranged from 0.020 to 3.6 ppm (wet weight). Total mercury levels detected in red drum from the Florida Keys-Florida Bay area were often higher than those in fish from all other estuarine study areas. Positive relationships between total mercury levels and fish size (length and weight) and fish age were observed in most Florida study areas, indicating that mercury levels tend to increase over time as red drum grow. The majority of large, mature red drum examined contained mercury levels greater than the 0.5-ppm threshold level set by the Florida Department of Health (DOH). Approximately 94% of all adult red drum from offshore waters adjacent to Tampa Bay contained mercury levels greater than or equal to the 0.5-ppm threshold level, and 64% contained levels greater than or equal to the DOH 1.5-ppm "no consumption" level. All fish from this area with mercury levels greater than 1.5 ppm were large individuals (670 mm SL). Eight percent of legal-size red drum from Florida waters contained total mercury levels greater than or equal to the 0.5-ppm threshold level. The majority (52%) of these legal-size fish greater than or equal to 0.5 ppm were from the Florida Keys-Florida Bay area. In the Florida recreational fishery, the current maximum size limit for this species is an effective filter that prevents humans from consuming those red drum with the greatest likelihood of containing high mercury levels.