From natural hazard to environmental catastrophe: Past and present

The number of environmental catastrophes is rising, mostly owing to an increase in hydrometeorological hazards. The number of disasters is escalating as the world population grows and people settle in marginal areas. In order to improve preparedness, the geological and archaeological records must be investigated as they hold a wider range of possible events than the much shorter instrumental record. Catastrophes will gain amplitude with rapid onset, long duration, larger affected area, inflexible society and, of cause, convergence of threats. Too often, it seems that today’s societies resist learning from the past and therefore tend to repeat errors. A new field of science is emerging: the science of environmental catastrophes, which requires not only robust chronologies to firmly link cause and effect, but also bridges the crossing between the geosciences and social sciences

Vegetation cycles in a disturbed sequence around the Cobb-Mountain subchron in Catalonia

A 52 m-long lacustrine sequence has been recovered from the basin of Bòbila-Ordis, near Banyoles (N-E Spain). The presence of Early Biharian rodent teeth (Early Pleistocene) and of a c. 9 ka-long palaeomagnetic reversal (Cobb-Mountain subchron) suggests an age centred on 1.2 Ma, making this sequence one of the very few well-dated terrestrial sequences of that age in Europe. The first 22.5 m (with an interglacial character) are very homogenous owing to sedimentation affected by underwater springs. In the middle part of the sequence, palynological analyses, supported by sediment visual description, ostracod and mollusc assemblages, allow the reconstruction of one glacial-interglacial cycle, with vegetation succession. A second incomplete climatic cycle is recorded in the top part, within a shallower lake. These brief interruptions in the two climatic cycles are possibly linked to lake bank collapse caused by Hippopotamus amphibius or faulting linked to karst. The succession is likely to correlate to MIS 36-33. The Bòbila-Ordis lacustrine series (including two other nested lakes) covers altogether some sections of four glacial and four interglacial periods, not all contiguous

Pollen analysis of core DS7-1SC (Dead Sea) showing intertwined effects of climatic change and human activities in the Late Holocene

The Dead Sea sediment holds the archives of a complex relationship between ever-changing nature and ancient civilisations. Here the detailed pollen analyses of core DS7-1SC (off-Ein-Gedi) are presented for the first time. The record covers the last 2500 years. The facies changes from halite (when no freshwater flows in the Dead Sea) to laminites (when rainfall provides sufficient inflow for the Jordan and subsidiary rivers) a couple of times through the record. The pollen diagram (supported by the facies change) shows a wetter Roman-Byzantine period, which allowed intensive arboriculture and a wetter period at the end of the XIXth and beginning of the XXth centuries, the latter in good relation with historical and instrumental data. Based on radiocarbon chronologies on several pollen diagrams along the western Dead Sea shore, the transition to drier climates and the transition to pastoralism are suggested to take place between a few decades before the Islamic period and close to this transition. A high-resolution palynological study of the individual laminae forming the laminites (aragonite and gypsum in the summer versus detritics in winter) confirms the seasonal character of the laminae, but throws a note of caution as for their regular annual character

Progress in palynology of the Gelasian–Calabrian Stages in Europe: Ten messages

Europe has at present the most extensive network of palynological sites covering the Late Pliocene and the Early Pleistocene or roughly the Gelasian-Calabrian Stages. This paper covers ten points of recent progress in the palynology of this time period: 1) the contribution of palynology to truly global stratigraphy, 2) the existence and steps of vegetation succession after a glacial period, 3) the causes for the disappearance from Europe of some taxa, 4) the location and the types of vegetation refugia, 5) the causes of the low arboreal pollen representation in glacial times, 6) the extent of extreme glacial conditions, 7) the input of long marine records to short terrestrial ones, 8-9) cyclopalynostratigraphy for wiggle matching dating and duration estimations and, finally, 10) short glacial periods and long interglacial ones in an obliquity-forced climate

Impacts from SSTs, ENSO, stratospheric QBO and global warming on Hurricanes over the North Atlantic

Processes affecting hurricane development over the North Atlantic like the El Niño Southern Oscillation (ENSO), the stratospheric Quasi-Biennial Oscillation (QBO) and Sea Surface Temperatures (SSTs) are discussed. Global coupled climate model simulations cannot answer directly the question on enhancement of hurricane activities (or its absence) under increased greenhouse gas concentrations because of their too coarse resolution. Therefore large-scale quantities that affect hurricane formation are investigated in a future warmer climate. More frequent or more intense hurricanes are expected from an increase in the local SST, from more latent heat flux from the ocean to the atmosphere, from more westerly winds in the tropical stratosphere that reduces the occurrence of strong easterly phases of the QBO and from a more moist-unstable stratification of the atmosphere. However, a stronger vertical wind shear similar to the difference between El Niño and La Niña events suggests fewer hurricanes in the northern Atlantic. Also a more dry-stable atmosphere would lead to fewer hurricanes. Of the various forcing factors, the impact of wind shear appears to be more decisive, i.e. with a strong wind shear over the tropical Atlantic like during El Niño events strong hurricanes hardly happen while impacts from SSTs over the tropical Atlantic are less significant. As there are some factors favouring an increase of hurricane activity in a future climate and others favouring a decrease, it remains so far difficult to estimate their joint effect and to suggest any decisive trend. The area of hurricane development is limited among others by an increase of vertical wind shear towards the north and south from a minimum at 5-10˚N. This wind shear pattern does not change in a future climate and has the potential of superseding impacts from ocean warming. A need for very long time series for obtaining robust results becomes obvious. Here at least 50 years of data were used

The Caspian Sea level forced by the atmospheric circulation, as observed and modelled

The Caspian Sea Level (CSL) has experienced large fluctuations with wide-reaching impacts on the population on the coastal regions and on the economy. The CSL variability is dominated by the variability of precipitation over the Volga River basin. The precipitation during summer plays a dominant role and can explain the two major events that happened in the 1930s (drop) and after 1977 (rise). Impacts are expected from global warming due to enhanced greenhouse gas concentrations; especially the precipitation over the Volga River basin is expected to increase. It is, however, compensated more or less by increased evaporation over the Caspian Sea (CS) itself. It is shown that the Max Planck Institute for Meteorology (Hamburg) models are able to simulate most processes relevant for the CSL variability quite realistically, i.e., within the uncertainty of observational data. The simulations suggest a slight increase of the CSL in the 21st century; but due to a large variability of precipitation over the Volga River basin a statement concerning the future development of the CSL cannot be made with confidence at the moment. r 2007 Elsevier Ltd and INQUA. All rights reserved

The tectonic influence on the last 1500-year infill history of a deep lake located on the North Anatolian Fault: Lake Sapanca (N-W Turkey)

Lake Sapanca on the North Anatolian Fault zone (NW Turkey) is a pull-apart basin at the junction between the İzmit-Sapanca fault segment, the Sakarya segment and the westernmost end of the Mudurnu Valley fault. Multiproxy analyses of a 586-cm-long sediment core taken in the lake centre have revealed a complex history of earthquake events. The radiocarbon chronology, affected by reworking of plant remains, suggests that the sediment sequence retrieved from the centre of the lake covers approximately the last 1500 years. The bottom metre of the sequence is a gley soil indicating that at least the eastern half of the lake was a wetland, a prolongation of the floodplain between the lake and River Sakarya, that has collapsed to form the modern deep lake. A series of sedimentological and palynological indicators have been used to highlight four major episodes of mass movements linked to earthquakes. The short existence of the eastern part of the lake highlights the complexity of the morphology of the Sakarya Straight, a possible past connection between the Gulf of İzmit and the Black Sea

High-resolution palynological analysis in Lake Sapanca as a tool to detect recent earthquakes on the North Anatolian Fault

High-resolution palynological analysis of a 38-cm-long core collected from Lake Sapanca, northwest Turkey, reveals large earthquakes that occurred during the second half of the 20th century along the North Anatolian Fault Zone. Four events have disturbed the lacustrine sedimentary sequence. Three of the four events are historical earthquakes in 1999 in Izmit, 1967 in Mudurnu and 1957 in Abant. These events are recorded in the core by turbiditic deposits and reworked sediment and by low overall palynomorph concentrations but high values of thick-exined pollen, fern spores and fungal spores. Palynomorphs in the event beds have been grouped based on their associations in modern moss, river and lake samples. The inferred mechanisms of transport and sources for the palynomorphs are: 1- lake sediment displaced by slump, 2- collapsed shoreline sediment owing to seiche, waves and sudden lake level changes, 3- subsidence of deltas and 4- river-transported soil and sediment from upland areas. The 1999 Izmit earthquake is only weakly recorded by palynomorphs, probably due to recent engineering control on the rivers. The 1967 Mudurnu earthquake had the strongest effect on the lake, introducing successive packages of sediment to the centre of the lake from underwater slopes, the lakeshore and rivers

A comparison of climate simulations for the last glacial maximum with three different versions of the ECHAM model and implications for summer-green tree refugia

This is an open access article. The official link can be found below.Model simulations of the last glacial maximum (21 ± 2 ka) with the ECHAM3 T42 atmosphere-only, ECHAM5-MPIOM T31 atmosphere-ocean coupled and ECHAM5 T106 atmosphere-only models are compared. The topography, land-sea mask and glacier distribution for the ECHAM5 simulations were taken from the Paleoclimate Modelling Intercomparison Project Phase II (PMIP2) data set while for ECHAM3 they were taken from PMIP1. The ECHAM5-MPIOM T31 model produced its own sea surface temperatures (SST) while the ECHAM5 T106 simulations were forced at the boundaries by this coupled model SSTs corrected from their present-day biases and the ECHAM3 T42 model was forced with prescribed SSTs provided by Climate/Long-Range Investigation, Mapping, and Prediction project (CLIMAP). The SSTs in the ECHAM5-MPIOM simulation for the last glacial maximum (LGM) were much warmer in the northern Atlantic than those suggested by CLIMAP or Overview of Glacial Atlantic Ocean Mapping (GLAMAP) while the SSTs were cooler everywhere else. This had a clear effect on the temperatures over Europe, warmer for winters in western Europe and cooler for eastern Europe than the simulation with CLIMAP SSTs. Considerable differences in the general circulation patterns were found in the different simulations. A ridge over western Europe for the present climate during winter in the 500 hPa height field remains in both ECHAM5 simulations for the LGM, more so in the T106 version, while the ECHAM3 CLIMAP-SST simulation provided a trough which is consistent with cooler temperatures over western Europe. The zonal wind between 30° W and 10° E shows a southward shift of the polar and subtropical jets in the simulations for the LGM, least obvious in the ECHAM5 T31 one, and an extremely strong polar jet for the ECHAM3 CLIMAP-SST run. The latter can probably be assigned to the much stronger north-south gradient in the CLIMAP SSTs. The southward shift of the polar jet during the LGM is supported by palaeo-data. Cyclone tracks in winter represented by high precipitation are characterised over Europe for the present by a main branch from the British Isles to Norway and a secondary branch towards the Mediterranean Sea, observed and simulated. For the LGM the different models show very different solutions: the ECHAM3 CLIMAP-SST simulation shows just one track going eastward from the British Isles into central Europe, while the ECHAM5 T106 simulation still has two branches but during the LGM the main one goes to the Mediterranean Sea, with enhanced precipitation in the Levant. This agrees with an observed high stand of the Dead Sea during the LGM. For summer the ECHAM5 T106 simulation provides much more precipitation for the present over Europe than the other simulations, thus agreeing with estimates by the Global Precipitation Climatology Project (GPCP). Also during the LGM this model makes Europe less arid than the other simulations. In many respects the ECHAM5 T106 simulation for the present is more realistic than the ECHAM5 T31 coupled simulation and the older ECHAM3 T42 simulation, when comparing them with the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis or the GPCP precipitation data. For validating the model data for the LGM, pollen, wood and charcoal analyses were compared with possible summer-green tree growth from model estimates using summer precipitation, minimum winter temperatures and growing degree days (above 5 °C). The ECHAM5 T106 simulation suggests for more sites with findings of palaeo-data, likely tree growth during the LGM than the other simulations, especially over western Europe. The clear message especially from the ECHAM5 T106 simulation is that warm-loving summer-green trees could have survived mainly in Spain but also in Greece in agreement with findings of pollen or charcoal. Southern Italy is also suggested but this could not be validated because of absence of palaeo-data. Previous climate simulations of the LGM have suggested less cold and more humid climate than that reconstructed from pollen findings. Our model results do agree more or less with those of other models but we do not find a contradiction with palaeo-data because we use the pollen data directly without an intermediate reconstruction of temperatures and precipitation from the pollen spectra

Vegetation context and climatic limits of the Early Pleistocene hominin dispersal in Europe

The vegetation and the climatic context in which the first hominins entered and dispersed in Europe during the Early Pleistocene are reconstructed, using literature review and a new climatic simulation. Both in situ fauna and in situ pollen at the twelve early hominin sites under consideration indicate the occurrence of open landscapes: grasslands or forested steppes. The presence of ancient hominins (Homo of the erectus group) in Europe is only possible at the transition from glacial to interglacial periods, the full glacial being too cold for them and the transition interglacial to glacial too forested. Glacial–interglacial cycles forced by obliquity showed paralleled vegetation successions, which repeated c. 42 times during the course of the Early Pleistocene (2.58–0.78 Ma), providing 42 narrow windows of opportunity for hominins to disperse into Europe. The climatic conditions of this Early Pleistocene vegetation at glacial-interglacial transitions are compared with a climatic simulation for 9 ka ago without ice sheet, as this time period is so far the best analogue available. The climate at the beginning of the present interglacial displayed a stronger seasonality than now. Forest cover would not have been hampered though, clearly indicating that other factors linked to refugial location and soils leave this period relatively free of forests. Similar situations with an offset between climate and vegetation at the beginning of interglacials repeated themselves throughout the Quaternary and benefitted the early hominins when colonising Europe. The duration of this open phase of vegetation at the glacial–interglacial transition was long enough to allow colonisation from the Levant to the Atlantic. The twelve sites fall within rather narrow ranges of summer precipitation and temperature of the coldest month, suggesting the hominins had only a very low tolerance to climate variability