Accounting for the Local Wave and Morphodynamic Processes in Coastal Hydraulic Engineering

Purpose. Estimates of wave parameters in the coastal waters are of great practical importance for designing and operating coastal infrastructure facilities. On the example of the Saki bay-bar region (Western Crimea), the experience of studying the wave and morphodynamic processes in the coastal zone is presented being applied to the tasks of designing and building protective hydraulic structures. Methods and Results. Mathematical modeling of the wave and morphodynamic processes in the area under study was done using the following: spectral model of the wind waves SWAN, hydrodynamic model SWASH, complex morphodynamic model XBeach and integral model of the coastal zone evolution GenCade. The wave regime was analyzed using the 41-year time series (1979–2019) of wave parameters resulted from the retrospective calculations of wind waves based on the SWAN model and the ERA atmospheric reanalysis data. The operational and extreme characteristics of wind waves were obtained. The spatial structure of the wave fields for different types of wind effects was modeled. The most intense waves are shown to occur during the southwest wind. The height and length of wave run-up on the coast and the coastal zone profile deformations for the storms of different durations were estimated. The values of the total annual along-coastal sediment flow in the design area were obtained for 1979–2019. In 70% of the cases, the sediment flow was established to be directed towards the Evpatoriya coast. Conclusions. The studies have shown that neglecting scientifically based recommendations when designing coastal infrastructure facilities can lead both to disruption of the existing system of the coastal zone natural formation, and to significant negative consequences for the coastline of almost 10 km length. These consequences can be manifested in a reduction of the beach zone width, a decrease in elevation marks, and replacement of sand with the pebble-gravel fractions in some areas that worsen recreational features of the beaches. Having been analyzed and taken into account, the planned location of the base of the enclosing wall shows that in some parts, the embankment wall can be possibly washed away and damaged. These conclusions were confirmed in practice already during the facility construction. Based on the results of the performed study, the constructions contributing significantly to the changes in the coastal zone morphodynamics were recommended for exclusion from the project

Local ecosystem feedbacks and critical transitions in the climate

Global and regional climate models, such as those used in IPCC assessments, are the best tools available for climate predictions. Such models typically account for large-scale land-atmosphere feedbacks. However, these models omit local vegetationenvironment 5 feedbacks that are crucial for critical transitions in ecosystems. Here, we reveal the hypothesis that, if the balance of feedbacks is positive at all scales, local vegetation-environment feedbacks may trigger a cascade of amplifying effects, propagating from local to large scale, possibly leading to critical transitions in the largescale climate. We call for linking local ecosystem feedbacks with large-scale land10 atmosphere feedbacks in global and regional climate models in order to yield climate predictions that we are more confident about

Chronosequenzielle Veränderungen post-agrarischer Böden in verschiedenen Klimazonen Russlands.

Chronosequenzielle Veränderungen der Vegetation und Böden wurden in der Taiga (Podzole und Albeluvisole), in der semihu-miden Steppe (Chernozeme) und in der semiariden Steppe (Solonetze und Calcisole) untersucht. Die Pflanzen-sukzession entwickelte sich in Richtung ihrer jeweiligen Klimax-Stadien. Die Böden, die vor Beginn der Selbstrestaurierung unabhängig von Klima- und Bodenzone ähnliche Eigenschaften zeigten, entwickelte sich in Richtung natürlicher Ausprägung. Als Resultat stieg die Pedodiversität. Selbstrestaurierung führte zur Zunahme der Kohlenstoffvorräte (C) in Richtung Wiederherstellung der natürlichen C-Vorräten in der Taiga nach ca. 150 Jahren (wie Vegetationssuksession), in der Steppe nach ca. 100 Jahren (langsamer als Vegetationssukzession). Die Zunahme des Gesamt-C verlief in signifikant positiven Korrelation mit der C-Akkumulation in aktiven (freie partikuläre organisches Material (POM); POM in Aggregaten; C in Sand, grob/mittel Schlufffraktion) und passiven (C in Feinschluff- und Tonfraktion) C-Pools (g kg-1). Während der chronosequentiellen Zeiträume (42 – 170 Jahre) war eine komplette Restaurierung aller Eigenschaften meistens nicht erreicht, was darauf hindeutet, dass Selbstrestaurierung sehr langwierig ist

Chronosequenzielle Dynamik sich selbst-restaurierender, post-agrarischer Calcisols und Solonetzs der trockenen Steppe Russlands.

In postagrarischen Calcisol- und Solonetz-Chronosequenzen wurden die Pflanzensukzession und die Veränderung der Bodeneigenschaften untersucht. Die Pflanzensukzession entwickelt sich in die Richtung Klimax – Steppe mit Dominanz von Artemisia L. und Stipa pennata. Die chronosequenzielle Entwicklung der Böden ist im Oberboden (0–0.2m) durch Wiederaufbau von natürlichen Gefüge und Aggregation und durch steigende Vorräte des organischen Kohlenstoffs (OC) gekennzeichnet. OC-Zunahme aller Fraktionen zeigt eine signifikant positive Korrelation zum Gesamt-OC. Eine relative Veränderung der Fraktionen war nur für Aggregaten-C bei der Solonetz Chronosequenz feststellbar

Optical, geochemical and mineralogical characteristics of light-absorbing impurities deposited on Djankuat Glacier in the Caucasus mountains

Supra-glacial material, including light-absorbing impurities (LAI) such as mineral dust of crustal and soil origin, black carbon, algae and cryoconite, reduce the reflectance of snow and glacier ice. The reduction depends on the amount of LAI and their physical and chemical properties, which vary spatially and temporally. Spectral reflectance data and snow and ice samples, containing LAI, were collected in the ablation zone of the Djankuat Glacier, Central Caucasus, Russia. The spectra of the samples containing mineral dust transported from deserts were characterized by negative visible near-infrared gradients and were different from the spectra of clean aged snow and exposed glacier ice and from the samples containing mineral dust produced locally. Geochemical and mineralogical analysis using X-ray diffraction and X-ray fluorescence spectrometry showed that samples containing desert dust were characterised by a high proportion of clay materials and such minerals as smectites, illite–smectites and palygorskite and by a smaller size of mineral particles. They were enriched in chromium, zinc and vanadium. The latter served as an indicator of dust transport over or origin from the oil-producing regions of the Middle East. There was a strong negative correlation between the amount of organic matter and mineral dust in the collected samples and the albedo of surfaces from which the samples were collected. The results suggested that organic matter reduced albedo more efficiently than mineral dust. The study highlighted the importance of supra-glacial material in changing the surface reflectivity of snow and glaciers in the Caucasus region

Chronosequenzielle Dynamik sich selbst-restaurierender, postagrarischer Stagnic Albeluvosols (Pseudogley-Fahlerde) der Taiga Russlands.

In einer postagrarischen Stagnic Albeluvisol-Chronosequenz mit Auflassungszeiten von 4, 12, 17, 68 Jahren sind die Pflanzensukzession und die Veränderung der Bodeneigenschaften untersucht. Die Pflanzensukzession entwickelt sich in die Richtung eines Fichtenwaldes mit Krautschicht. Die chronosequenzielle Entwicklung der Boden ist im Oberboden von 0–0.2m durch fortschreitende Versauerung, Abnahme der Vorräte an pflanzenverfügbarem Phosphor und Kalium und Zunahme der C-Vorräte gekennzeichnet