Assessment of long-term structural movements in a historic cliffside construction through Lomb-Scargle spectral analysis of unevenly spaced time records: the Punta Begona Galleries (Getxo, Spain)

Long-term monitoring of structural movements in historic buildings and heritage sites allows assessing their stability and recognizing damages that require intervention. The Punta Begona Galleries, built in the earlier part of the twentieth century, present pioneering techniques in the use of reinforced concrete in building construction. They stand directly over a coastal cliff, and their recovery requires first to guarantee their stability, while maintaining their historic and patrimonial values. Thus, with the goal of analyzing their global stability, as well as the extent of the observed damages, we implemented a motion monitoring network that includes three boreholes for extensometric control, an inclinometer, and five crack gauges (crackmeters). This monitoring was complemented with the recording of hydrometeorological variables at the surface and in four piezometers. The spectral analysis of the signals of movements was performed by introducing the use of the Lomb-Scargle (LS) periodogram, which is particularly well-suited for the analysis of unevenly spaced time series. This analysis allowed us to differentiate the reversible seasonal elastic components of the records and to recognize the irreversible long-term plastic displacements, which highlight the sectors with active instability. In our case, the identified damages are related to two local problems of building support. Even though the irreversible component of the displacement after seasonal sinusoidal detrending is small (with maximums up to 0.12 mm/year), it does imply a dynamic plastic deformation, which calls for the need to adopt structural stabilization measures.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

Saturn’s Northern Hemisphere Ribbon: Simulations and Comparison with the Meandering Gulf Stream

Voyager observations of Saturn in 1980–81 discovered a wavy feature engirdling the planet at 47°N planetographic latitude. Its latitude coincides with that of an eastward jet stream, which is the second fastest on Saturn after the equatorial jet. The 47°N jet’s wavy morphology is unique among the known atmospheric jets on the gas giant planets. Since the Voyagers, it has been seen in every high-resolution image of this latitude for over 25 years and has been termed the Ribbon. The Ribbon has been interpreted as a dynamic instability in the jet stream. This study tests this interpretation and uses forward modeling to explore the observed zonal wind profile’s stability properties. Unforced, initial-value numerical experiments are performed to examine the nonlinear evolution of the jet stream. Parameter variations show that an instability occurs when the 47°N jet causes reversals in the potential vorticity (PV) gradient, which constitutes a violation of the Charney–Stern stability criterion. After the initial instability development, the simulations demonstrate that the instability’s amplitude nonlinearly saturates to a constant when the eddy generation by the instability is balanced by the destruction of the eddies. When the instability saturates, the zonal wind profile approaches neutral stability according to Arnol’d’s second criterion, and the jet’s path meanders in a Ribbon-like manner. It is demonstrated that the meandering of the 47°N jet occurs over a range of tropospheric static stability and background wind speed. The results here show that a nonlinearly saturated shear instability in the 47°N jet is a viable mechanism to produce the Ribbon morphology. Observations do not yet have the temporal coverage to confirm the creation and destruction of eddies, but these simulations predict that this is actively occurring in the Ribbon region. Similarities exist between the behaviors found in this model and the dynamics of PV fronts studied in the context of meandering western boundary currents in Earth’s oceans. In addition, the simulations capture the nonlinear aspects of a new feature discovered by the Cassini Visual and Infrared Mapping Spectrometer (VIMS), the String of Pearls, which resides in the equatorward tip of the 47°N jet. The Explicit Planetary Isentropic Coordinate (EPIC) model is used herein

Rockfall hazard mitigation in coastal environments using dune protection: A nature-based solution case on Barinatxe beach (Basque Coast, northern Spain)

Across the world, coastal environments of great landscape, recreational and environmental value are coming under increasing pressure. Within such environments, cliffs are particularly characteristic and unique elements, in which processes of instability develop. Their management requires a transdisciplinary approach ensuring protection of the natural condition of the environment, while at the same time allowing for their continued use and enjoyment. In the case of Barinatxe (Basque Coast), the beach has evolved into a system of foredunes, flanked by cliffs with frequent rockfall processes. This research analyzes the effect of coastal dunes as an element of natural protection. To this end, based on a Digital Terrain Model developed by Terrestrial Laser Scanning (TLS) and in situ geological characterization, 3D modeling has been used to analyze rockfall trajectories and evaluate their runout and energy. These models confirm the protective role of coastal dunes, which act as efficient natural barriers against rock blocks that become detached from cliffs. This is particularly important in areas where the use of tools based on Nature-Based Solutions (NBSs) guidelines is recommended.This study has been carried out by the UPV/EHU Research Group IT1678-22 (Government of the Basque Country) in the framework of the strategic project “Analysis of instabilities in coastal environments of the Basque Country” PES-18/97 (University of the Basque Country)

Landforms of the lower Hushe Valley (Central Karakoram, Pakistan)

This paper presents a new geomorphological map for the lower Hushe Valley (below 3400 m asl), located to the SE of the Central Karakoram in Baltistan (North Pakistan). Fieldwork and remote sensing were combined to improve understanding of the most recent surface landforms to produce a 1:50,000 scale map. Thirteen landform types associated with glacial, fluvial, gravitational and mass wasting processes were identified and mapped. Particular emphasis was made on currently dynamic processes that could pose a threat to the population. The distribution of the landforms on the valley (reworked tills, alluvial fans, rockfalls, among others) differs between the eastern and the western hillslopes, and from north to south, mainly due to bedrock types, location of geological structures and distribution of lateral tributaries. This map is the first and necessary step towards a deep assessment on geological risk related to external processes in the area.This research was funded by the Basque Government (Eusko Jaurlaritza) through the Humanitarian Action 2018 fund (PRE2018EH/0004) and the Consolidated Research Group IT1029-16. We also thank the University of the Basque Country UPV/EHU for the suppor

Rockfall susceptibility analysis through 3D simulations in marine protected areas of the Portofino coastline: case studies of San Fruttuoso and Paraggi bays

The research focuses on the assessment of the potential geomorphological hazards affecting the stability of the Promontory of Portofino (Regional Natural Park of Portofino, Northern Italy), mainly on the bays of San Fruttuoso and Paraggi. The study area constitutes one of the most representative and most populated environments, both by locals and tourists, of the entire Liguria area. For this reason, there is a growing need for investigation on the natural dynamics of these landscapes, based on detailed topographic information. The research starts from a regional geological and geomorphological analysis specific to the study area, combined with a multi-model comparison algorithm (M3C2), which allows comparing two LiDAR datasets acquired in 2008 and 2020, respectively, to assess the overall dynamics of the promontory development. Then, a detailed study of San Fruttuoso and Paraggi bays, two key points for visitors and therefore for management, is performed. Three-dimensional modeling of rockfalls is carried out, which allows the development of a specific management oriented to the use of nature-based solutions (NBSs) strategies, respecting the environment and increasing safety against instability processes in these areas.This study has been carried out in the framework of a collaboration among ISPRA, GISIG, Universita di Genova, and Universidad del Pais Vasco (UPV/EHU, IT1678-22 Research Group, PES-18/92 Project) within the RECONECT Project (Regenerating ECOsystems with Nature-based solutions for hydro-meteorological risk rEduCTion)

Spectral determination of the colour and vertical structure of dark spots in Neptune’s atmosphere

Previous observations of dark vortices in Neptune’s atmosphere, such as Voyager 2’s Great Dark Spot (1989), have been made in only a few broad-wavelength channels, hampering efforts to determine these vortices’ pressure levels and darkening processes. We analyse spectroscopic observations of a dark spot on Neptune identified by the Hubble Space Telescope as NDS-2018; the spectral observations were made in 2019 by the Multi Unit Spectroscopic Explorer (MUSE) of the Very Large Telescope (Chile). The MUSE medium-resolution 475–933 nm reflection spectra allow us to show that dark spots are caused by darkening at short wavelengths (700 nm). This bright feature is much deeper than previously studied dark-spot companion clouds and may be connected with the circulation that generates and sustains such spots

Spectral determination of the colour and vertical structure of dark spots in Neptune's atmosphere

Previous observations of dark vortices in Neptune's atmosphere, such as Voyager-2's Great Dark Spot, have been made in only a few, broad-wavelength channels, which has hampered efforts to pinpoint their pressure level and what makes them dark. Here, we present Very Large Telescope (Chile) MUSE spectrometer observations of Hubble Space Telescope's NDS-2018 dark spot, made in 2019. These medium-resolution 475 - 933 nm reflection spectra allow us to show that dark spots are caused by a darkening at short wavelengths (< 700 nm) of a deep ~5-bar aerosol layer, which we suggest is the H$_2$S condensation layer. A deep bright spot, named DBS-2019, is also visible on the edge of NDS-2018, whose spectral signature is consistent with a brightening of the same 5-bar layer at longer wavelengths (> 700 nm). This bright feature is much deeper than previously studied dark spot companion clouds and may be connected with the circulation that generates and sustains such spots.Comment: 1 table. 3 figures. Nature Astronomy (2023

Latitudinal Variations in Methane Abundance, Aerosol Opacity and Aerosol Scattering Efficiency in Neptune's Atmosphere Determined From VLT/MUSE

Spectral observations of Neptune made in 2019 with the Multi Unit Spectroscopic Explorer (MUSE) instrument at the Very Large Telescope (VLT) in Chile have been analyzed to determine the spatial variation of aerosol scattering properties and methane abundance in Neptune's atmosphere. The darkening of the South Polar Wave at ∼60°S, and dark spots such as the Voyager 2 Great Dark Spot is concluded to be due to a spectrally dependent darkening (λ 650 nm. We find the properties of an overlying methane/haze aerosol layer at ∼2 bar are, to first-order, invariant with latitude, while variations in the opacity of an upper tropospheric haze layer reproduce the observed reflectivity at methane-absorbing wavelengths, with higher abundances found at the equator and also in a narrow “zone” at 80°S. Finally, we find the mean abundance of methane below its condensation level to be 6%–7% at the equator reducing to ∼3% south of ∼25°S, although the absolute abundances are model dependent.We are grateful to the United Kingdom Science and Technology Facilities Council for funding this research (Irwin: ST/S000461/1, Teanby: ST/R000980/1). Glenn Orton was supported by funding to the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). Leigh Fletcher and Mike Roman were supported by a European Research Council Consolidator Grant (under the European Union's Horizon 2020 research and innovation programme, grant agreement no. 723890) at the University of Leicester. Santiago Pérez-Hoyos and Agustin Sánchez-Lavega are supported by the Spanish project PID2019-109467GB-I00 (MINECO/FEDER, UE), Elkartek21/87 KK-2021/00061 and Grupos Gobierno Vasco IT-1742-22

Strong Temporal Variation Over One Saturnian Year: From Voyager to Cassini

Here we report the combined spacecraft observations of Saturn acquired over one Saturnian year (~29.5 Earth years), from the Voyager encounters (1980–81) to the new Cassini reconnaissance (2009–10). The combined observations reveal a strong temporal increase of tropic temperature (~10 Kelvins) around the tropopause of Saturn (i.e., 50 mbar), which is stronger than the seasonal variability (~a few Kelvins). We also provide the first estimate of the zonal winds at 750 mbar, which is close to the zonal winds at 2000 mbar. The quasi-consistency of zonal winds between these two levels provides observational support to a numerical suggestion inferring that the zonal winds at pressures greater than 500 mbar do not vary significantly with depth. Furthermore, the temporal variation of zonal winds decreases its magnitude with depth, implying that the relatively deep zonal winds are stable with time