Effect of Subsurface Mediterranean Water Eddies on Sound Propagation Using ROMS Output and the Bellhop Model

Ocean processes can locally modify the upper ocean density structure, leading to an attenuation or a deflection of sound signals. Among these phenomena, eddies cause significant changes in acoustic properties of the ocean; this suggests a possible characterization of eddies via acoustics. Here, we investigate the propagation of sound signals in the Northeastern Atlantic Ocean in the presence of eddies of Mediterranean Water (Meddies). Relying on a high-resolution simulation of the Atlantic Ocean in which Meddies were identified and using the Bellhop acoustic model, we investigated the differences in sound propagation in the presence and absence of Meddies. Meddies create sound channels in which the signals travel with large acoustic energy. The transmission loss decreases to 80 or 90 dB; more signals reach the synthetic receivers. Outside of these channels, the sound signals are deflected from their normal paths. Using receivers at different locations, the acoustic impact of different Meddies, or of the same Meddy at different stages of its life, are characterized in terms of angular distributions of times of arrivals and of energy at reception. Determining the influence of Meddies on acoustic wave characteristics at reception is the first step to inverting the acoustic signals received and retrieving the Meddy hydrological characteristics.

Matched Field Processing for complex Earth structure

Matched Field Processing (MFP) is a technique to locate the source of a recorded wave field. It is the generalization of beamforming, allowing for curved wavefronts. In the standard approach to MFP, simple analytical Green's functions are used as synthetic wave fields that the recorded wave fields are matched against. We introduce an advancement of MFP by utilizing Green's functions computed numerically for real Earth structure as synthetic wave fields. This allows in principle to incorporate the full complexity of elastic wave propagation, and through that provide more precise estimates of the recorded wave field's origin. This approach also further emphasizes the deep connection between MFP and the recently introduced interferometry-based source localisation strategy for the ambient seismic field. We explore this connection further by demonstrating that both approaches are based on the same idea: both are measuring the (mis-)match of correlation wave fields. To demonstrate the applicability and potential of our approach, we present two real data examples, one for an earthquake in Southern California, and one for secondary microseism activity in the Northeastern Atlantic and Mediterranean Sea. Tutorial code is provided to make MFP more approachable for the broader seismological community.

Planktonic Ctenophora of the Madeira archipelago (Northeastern Atlantic)

Ctenophores are fragile gelatinous organisms whose diversity and distribution are relatively unknown. For the first time, the occurrence of four planktonic species, namely Ocyropsis crystallina, Eurhamphaea vexilligera, Cestum veneris, and Beroe sp., was reported from Madeira archipelago waters (NE subtropical Atlantic). This report represents the northernmost records in the Eastern Atlantic Ocean for O. crystallina and E. vexilligera.

Identification key for anuran amphibians in a protected area in the northeastern Atlantic Forest

The identification of anuran amphibians is still a challenge in megadiverse assemblages. In the Neotropics, the Atlantic Forest harbors more than 600 anuran species, and many studies in this ecoregion report anuran assemblages surpassing 30 species. Taxonomic keys facilitate the identification of biological diversity, however only a few are available for anuran assemblages in the Atlantic Forest. Herein we present an identification key for 40 anuran species distributed across 20 genera and nine families, occurring in the Environmental Protection Area of Catolé and Fernão Velho, northeastern Atlantic Forest. Thirty-five morphological characteristics were used in the key, all of which can be easily observed in living and museum specimens. This pioneer study provides the first identification key for an amphibian assemblage in the northeastern Atlantic Forest and this baseline information acts as the starting point for the development of evolutionary and ecological research in this conservation unit.

The genus Sveltia (Gastropoda, Cancellariidae) in the Atlantic Pliocene of Iberia with a new species from the Cenozoic Mondego Basin of Portugal

The cancellarid genus Sveltia Jousseaume, 1887, is widespread in western European and North African Neogene marine fossil assemblages. In Pliocene deposits it is commonly represented by Sveltia varicosa (Brocchi, 1814), which until recently was considered a widely distributed taxon in the Mediterranean Sea and adjacent Atlantic faunas. A recent review of the species from the Pliocene of Italy and Spain (Guadalquivir Basin), leading to the erection of S. confusa, prompted the reassessment of the Sveltia material from the Atlantic Pliocene of the Portuguese Mondego Basin and the subsequent description of Sveltia sofiae n. sp. Consequently, a mosaic of species has emerged from what was previously viewed as the broad Atlanto-Mediterranean range of the widespread and quite variable S. varicosa. From a biogeographic standpoint, it is now clear that S. varicosa was a Mediterranean species, occurring east of the Alboran Sea. Sveltia confusa had a mainly Atlantic distribution, from the French Pliocene Ligerian Gulf to the Gulf of Cadiz, at least, and straddling the Strait of Gibraltar into the Alboran Sea. Sveltia sofiae n. sp. was endemic to western Iberia, represented today only in the western Portuguese Mondego Basin. Sveltia is a thermophilic genus. Since early Pliocene times, because of northeastern Atlantic sea surface temperature decline, it underwent a southward range contraction, occurring today—in the eastern Atlantic—from Cape Blanc, Mauritania, south. This range reduction was coupled with the post mid-Piacenzian southward contraction of the Pliocene Mediterranean-West African tropical molluscan province and the consequent rise of the present-day Mediterranean-Moroccan subtropical province. UUID: http://zoobank.org/0cf3c73a-8d57-472e-87e4-f1ad065e5fb6.

Genetic hypervariability of a Northeastern Atlantic venomous rockfish

Background Understanding the interplay between climate and current and historical factors shaping genetic diversity is pivotal to infer changes in marine species range and communities’ composition. A phylogeographical break between the Atlantic and the Mediterranean has been documented for several marine organisms, translating into limited dispersal between the two basins. Methods In this study, we screened the intraspecific diversity of 150 individuals of the Madeira rockfish (Scorpaena maderensis) across its distributional range (seven sampling locations in the Atlantic and Mediterranean basins) using the mitochondrial control region and the nuclear S7 first intron. Results The present work is the most comprehensive study done for this species, yielding no genetic structure across sampled locations and no detectable Atlantic-Mediterranean break in connectivity. Our results reveal deep and hyper-diverse bush-like genealogies with large numbers of singletons and very few shared haplotypes. The genetic hyper-diversity found for the Madeira rockfish is relatively uncommon in rocky coastal species, whose dispersal capability is limited by local oceanographic patterns. The effect of climate warming on the distribution of the species is discussed.

Tropopause Folding Events to the East of Tibetan Plateau in Boreal Summer and their Remote Relation to the Circulation Anomalies over Northeastern Atlantic

This study investigates the occurrence of tropopause folding (TF) events to the east of Tibetan Plateau (ETP) (TF–ETP) in boreal summer. Firstly, it is revealed that, anomalously frequent TF–ETP occurrence in summer, always corresponds to a significant dipole rainfall anomaly pattern over China, with negative rainfall anomalies over the upper and middle reaches of the Yangtze and Yellow river valleys, and positive rainfall anomalies over eastern China. Secondly, the South Asian High (SAH) center over Tibetan Plateau (TP) is found to be anomalously stronger when occurrence of TF–ETP events is frequent. Further diagnosis indicates that, the TF–ETP occurrence is related to an eastward propagating Rossby wave train (RWT) that originates from a barotropic low anomaly center over the northeastern Atlantic (NEA) about one–week before. The RWT propagates downstream via Western Europe, the west of Baikal and down to East Asia along the mid-latitude westerlies, and is connected to a high anomaly center over the north rim of TP, which enhances the SAH center over TP. The enhanced SAH in turn favors the southward and downward PV intrusion and the subsequent occurrence of TF–ETP. Furthermore, the low anomaly center that initiates the RWT is related to dynamical forcing of transient eddy activity over the NEA, which induces the low via eddy-forced upper divergence and its pumping. Finally, such local and remote processes are confirmed in a typical TF–ETP case. The ERA–Interim daily fields during 1979–2018 is used.