Effects of solar activity and climate variability on large floods in Switzerland

The paper presents the variability of major floods in Switzerland for the period 1800-2008 from a summer index (INU). The index is constructed from the damage caused by flooding, with the aim of establishing the possible influence of the solar and climate variability on the major floods. The coincidence of flood-rich periods with those observed in other regions of different climate and fluvial regimes suggests that climate forcings and changes in the general circulation of the atmosphere are those who govern the appearance of these high-frequency temporal clusters

Pluridisciplinary analysis and multi-archive reconstruction of paleofloods: societal demand, challenges and progress

Floods are one of the gravest natural hazards for societies, worsened by population growth, unchecked development, and climate change. From a Global Change perspective, past extreme events merit particular interest because they can be linked to wider climate and environmental changes, introduce perturbations. During the last decade, knowledge of long-term flood frequency and magnitude has been improved by extracting data from different types of archive. But, despite advances in dating methods, proxies and statistical techniques and efforts to identify atmospheric drivers, some fundamental questions remain unresolved. The Special Issue entitled "Pluridisciplinary analysis and multi-archive reconstruction of paleofloods" in the journal Global and Planetary Change addresses these uncertainties and complexities by assembling a selection of studies, which were first presented at the Past Climate Changes (PAGES) Open Scientific Meeting held at Zaragoza in 2017. In this introductory paper, the guest editors outline the 17 research contributions and meta-data from the 17 paleoflood studies were systematically analyzed in terms of i) geographical distribution; ii) methodologies applied; iii) types of archives; iii) numbers of flood series compiled and iv) spatial and temporal resolution of paleoflood data. The data indicate that paleoflood studies focused on fluvial depositional environments show a higher rate of integration with other types of paleoflood archive (mean of 4.5 types of archive) than studies focused on documentary sources (mean of 3.5) and lake sediments (mean of 2.4). We suggest that this strategy of archive integration has been adapted to effectively compensate for the higher uncertainties of fluvial deposition in floodplains

Effects of solar activity and climate variability on large floods in Switzerland

Resume

Influencia de la actividad solar y de la variabilidad climática sobre las grandes crecidas en Suiza

Texto resumen

500-year flood history in the arid environments of southeastern Spain. The case of the Almanzora River

The study of flood events, especially analyses of flood magnitude and flood frequency, is crucial for the planning and management of settlements and infrastructure located near river channels. This work studies the historical floods of the Almanzora catchment, in southeastern Spain, one of the driest regions in Europe. We compile, describe and statistically process flood data that extend back to the year 1500 CE. The data were collected from historical sources held in both local and regional archives. The analysis of the flood record shows that the most destructive events occurred in 1550, 1729, 1879 and 1973, the last of these being the most catastrophic event on record. The synoptic configurations of the four most destructive floods in the time-series were explored and found to present the same type of pattern (cold drop). Historical flood discharges were estimated by calibrating historical flood magnitudes with instrumental data. This assessment was undertaken using a cumulative function applied to flood episodes that exceeded the threshold of magnitudes ≥3. The flood frequency analysis performed by combining instrumental and historical data shows that catastrophic events, such as the 1973 flood with a discharge of 5600 m3 s−1, occur with a return period of <100 years. We also estimate that high magnitude floods with a discharge between 684 and 3081 m3 s−1 can occur every 10-50 years. During recent decades, several municipalities and, above all, the coastal area of the Almanzora catchment have experienced significant urban growth and land use changes, as a result of the development of both tourism and extensive agriculture. This, in turn, has contributed to an increase in flood exposure

Perturbation theory for non-spherical fluids based on discretization of the interactions

7 páginas, 5 figuras; PACS: 65.20.De, 61.20.JaAn extension of the discrete perturbation theory [A. L. Benavides and A. Gil-Villegas, Mol. Phys. 97(12), 1225 (1999)10.1080/00268979909482924] accounting for non-spherical interactions is presented. An analytical expression for the Helmholtz free energy for an equivalent discrete potential is given as a function of density, temperature, and intermolecular parameters with implicit shape dependence. The presented procedure is suitable for the description of the thermodynamics of general intermolecular potential models of arbitrary shape. The overlap and dispersion forces are represented by a discrete potential formed by a sequence of square-well and square-shoulders potentials of shape-dependent widths. By varying the intermolecular parameters through their geometrical dependence, some illustrative cases of square-well spherocylinders and Kihara fluids are considered, and their vapor-liquid phase diagrams are tested against available simulation data. It is found that this theoretical approach is able to reproduce qualitatively and quantitatively well the Monte Carlo data for the selected potentials, except near the critical region.A.L.B. acknowledges funding received by Grant No. 152684 CONACYT (México). F.G. acknowledges funding through Project No. P07-FQM-02600 (Junta de Andalucía-FEDER) for his postdoctoral fellowship.Peer reviewe

Influence of solar forcing, climate variability and modes of low-frequency atmospheric variability on summer floods in Switzerland

The higher frequency of severe flood events in Switzerland in recent decades has given fresh impetus to the study of flood patterns and their possible forcing mechanisms, particularly in mountain environments. This paper presents a new index of summer flood damage that considers severe and catastrophic summer floods in Switzerland between 1800 and 2009, and explores the influence of external forcings on flood frequencies. In addition, links between floods and low-frequency atmospheric variability patterns are examined. The flood damage index provides evidence that the 1817-1851, 1881-1927, 1977-1990 and 2005-present flood clusters occur mostly in phase with palaeoclimate proxies. The cross-spectral analysis documents that the periodicities detected in the coherency and phase spectra of 11 (Schwabe cycle) and 104 years (Gleissberg cycle) are related to a high frequency of flooding and solar activity minima, whereas the 22-year cyclicity detected (Hale cycle) is associated with solar activity maxima and a decrease in flood frequency. The analysis of low-frequency atmospheric variability modes shows that Switzerland lies close to the border of the principal summer mode. The Swiss river catchments situated on the centre and southern flank of the Alps are affected by atmospherically unstable areas defined by the positive phase of the pattern, while those basins located in the northern slope of the Alps are predominantly associated with the negative phase of the pattern. Furthermore, a change in the low-frequency atmospheric variability pattern related to the major floods occurred over the period from 1800 to 2009; the summer principal mode persists in the negative phase during the last cool pulses of the Little Ice Age (1817-1851 and 1881-1927 flood clusters), whereas the positive phases of the mode prevail during the warmer climate of the last 4 decades (flood clusters from 1977 to present)

Evolución morfodinámica de un enclave montañoso recién deglaciado: El caso del Corral del Veleta (Sierra Nevada), ¿Consecuencia del cambio climático?

RESUMEN: El Corral del Veleta (Sierra Nevada. España) cobija en su seno y bajo manto detrítico hielo glaciar fósil y permafrost alpino, restos, como mínimo, de la Pequeña Edad del Hielo (siglos XV/XIX). En la actualidad, estas masas heladas se encuentran en proceso de degradación. Los análisis y controles que desde 2001 se vienen llevando a cabo en un glaciar rocoso incipiente instalado en el tercio oriental del Corral del Veleta muestran procesos continuados de subsidencia de su manto detrítico, apoyado sobre las masas heladas referidas. La merma del manto nival durante el verano, las aguas de fusión y el grado de penetración de la onda de radiación externa en el suelo, son parámetros clave que explican este mecanismo de subsidencia, que podría estar relacionado con variaciones climáticas que vienen detectándose desde hace décadas

What burned the forest? Wildfires, climate change and human activity in the Mesolithic – Neolithic transition in SE Iberian Peninsula

Climate variability such as higher or lower temperatures, changing precipitation patterns, shifts in plant communities and other climate-related changes have particularly affected areas with Mediterranean-type climates. A multi-proxy analysis including pollen, sedimentary charcoal, mineralogy and Summed Probability Distributions (SPD) of archaeological 14C dates, allowed the reconstruction of landscape change, geomorphological evolution and fire history at the Laguna de Villena, in the southeastern Iberian Peninsula, during the Mesolithic-Neolithic transition. The Villena paleolake was sensitive to Early Holocene and Middle Holocene regional climatic variability that included several arid phases (around 8.2 ka cal BP, 6.8 ka cal BP and 5.9 ka cal BP) according to geochemical and pollen data. During this period, landscape dynamics show the degradation of oak forests and expansion of pyrophytic pine forests and shrublands, as well as open spaces predominated by grasses. The charcoal record shows a decreasing trend of biomass burned from 8.5 ka cal BP onwards, although fire peaks occurred recurrently during the Early and Middle Holocene. The most intense phase of fire activity was experienced in the last millennia of the Early Holocene, with five fire episodes from 9.1 to 8.4 ka cal BP, coinciding with a phase of higher archaeological evidence in the area. A decrease in archaeological evidence coincides with a gap in fire episodes during the Early Holocene-Middle Holocene transition, suggesting an effect of the abrupt 8.2 ka cal BP event on human activity and on landscape dynamics. After 8.0 ka cal BP, lowerer biomass burned is explained by the configuration of a more open landscape due to the combination of climate (increasing aridity) and increasing human activities in the region. The mineralogical and palynological data highlighted the interaction between human activities, climate and fire dynamics. The sedimentary charcoal record evidenced how most of the fire peaks did not occur in the context of dry episodes, as often assumed, deriving on an anthropogenic explanation related to Early and Late Mesolithic burning practices during a phase of higher archaeological evidence in the Villena paleolake surroundings. Afterwards, combined agropastoral activities from the Early Neolithic onwards and increasing aridity during the Middle Holocene maintained the forest clearances, in the context of fire episodes characterised by decreased biomass burned. This study shows how Middle Holocene palaeoecological records reflect complex histories blending climate and anthropogenic processes that derived in major landscape changes explaining the origin of current landscapes.This research has received funding from the European Research Council (ERC) under the Horizon 2020 research and innovation programme (Grant agreement No. 683018) to JFLdP. Additional analyses on the pollen data sets have been produced in the context of the research project PID2020-113664RB-100 supported by the Spanish Ministry of Science and Innovation. JFLdP is additionally supported by the Plan Gen-T program (Ref. CIDEGENT-18/040) of the Generalitat Valenciana. CSG is currently supported by a Margarita Salas fellowship (ref. MARSALAS21-22) funded by the European Union-Next Generation EU, the Spanish Ministry of Universities and the University of Alicante. JR, IE and FB are members of the research group GAPS (2017 SGR 836). JR acknowledges postdoctoral fellowship support from the Spanish “Juan de la Cierva Incorporación (IJC2020)” program (MICINN, Spain). The Institut Català de Paleoecologia Humana I Evolució Social (IPHES-CERCA) has received financial support from the Spanish Ministry of Science and Innovation through the “María de Maeztu'' program for Units of Excellence (CEX2019-000945-M). LS is granted by the ICREA Academia Program