Global Climate Oscillations Research Articles

Nonstationary warm spell frequency analysis integrating climate variability and change with application to the Middle East

The Middle East can experience extended wintertime spells of exceptionally hot weather, which can result in prolonged droughts and have major impacts on the already scarce water resources of the region. Recent observational studies point at increasing trends in mean and extreme temperatures in the Middle East, while climate projections seem to indicate that, in a warming weather scenario, the frequency, intensity and duration of warm spells will increase. The nonstationary warm spell frequency analysis approach proposed herein allows considering both climate variability through global climatic oscillations and climate change signals. In this study, statistical distributions with parameters conditional on covariates representing time, to account for temporal trend, and climate indices are used to predict the frequency, duration and intensity of wintertime warm spells in the Middle East. Such models could find a large applicability in various fields of climate research, and in particular in the seasonal prediction of warm spell severity. Based on previous studies linking atmospheric circulation patterns in the Atlantic to extreme temperatures in the Middle East, we use as covariates two classic modes of ‘fast’ and ‘slow’ climatic variability in the Atlantic Ocean (i.e., the Northern Atlantic Oscillation and the Atlantic Multidecadal Oscillation respectively). Results indicate that the use of covariates improves the goodness-of-fit of models for all warm spell characteristics.

Karst dolines provide diverse microhabitats for different functional groups in multiple phyla

Fine-scale topographic complexity creates important microclimates that can facilitate species to grow outside their main distributional range and increase biodiversity locally. Enclosed depressions in karst landscapes (‘dolines’) are topographically complex environments which produce microclimates that are drier and warmer (equator-facing slopes) and cooler and moister (pole-facing slopes and depression bottoms) than the surrounding climate. We show that the distribution patterns of functional groups for organisms in two different phyla, Arthropoda (ants) and Tracheophyta (vascular plants), mirror this variation of microclimate. We found that north-facing slopes and bottoms of solution dolines in northern Hungary provided key habitats for ant and plant species associated with cooler and/or moister conditions. Contrarily, south-facing slopes of dolines provided key habitats for species associated with warmer and/or drier conditions. Species occurring on the surrounding plateau were associated with intermediate conditions. We conclude that karst dolines provide a diversity of microclimatic habitats that may facilitate the persistence of taxa with diverse environmental preferences, indicating these dolines to be potential safe havens for multiple phyla under local and global climate oscillations.

Radial growth of Picea glauca and Picea engelmannii across Canada and USA: monthly climate, decadal oscillations, and climate change

ABSTRACTWe employ a dendrochronological approach to examine spatial variation in radial tree growth-climate relationships and responses to global climate oscillations across the geographic ranges of Picea glauca and Picea engelmannii. Tree-ring chronologies were constructed for 77 sites and analyzed using correlation coefficients for monthly climatic variables. In general, for Picea glauca, stands in the western portion of its range had significant negative correlations with temperature during fall, winter, and spring; only summer temperature was positively correlated with tree growth. In eastern North America, Picea glauca growth was negatively correlated with winter and spring temperature. Across the north-south range of Picea engelmannii, growth of northern populations was positively correlated with temperature in most seasons except spring, which had negative correlations, and response to winter precipitation differed between northern and southern populations. However, some monthly values for both species correlations were altered due to decadal oscillation phase, especially for the Pacific Decadal Oscillation.

Teleconnection between phytoplankton dynamics in north temperate lakes and global climatic oscillation by time-frequency analysis

We are still facing the knowledge gap of how the water-quality extremes (i.e. phytoplankton blooms), their causes, severity or occurrence could be directly related to the climatic oscillation. Considering that the climatic and phytoplankton concentration time series are highly non-stationary, we applied the advanced time-frequency analysis - Ensemble Empirical Mode Decomposition (EEMD), Hilbert-Huang Spectrum (HHS) and Wavelet Analysis (WA) - to examine the variability of long term phytoplankton dynamics from 1986 to 2014 in five North Temperate Lakes (NTLs). These analysis techniques isolated five separate time series for the surface Chlorophyll a concentrations (CHL) of the five NTLs and a time series for the global climate oscillation (denoted by multivariate ENSO index, MEI), and showed that these time series generally operated at similar time scales. The long-term residual trends of decreasing were found in three lakes (i.e., BM, SP and TR lakes), which are the same to global climate dynamics (MEI). The wavelet analysis reveals strong coherency between MEI and CHL data sets for all lakes, with a periodicity of 64-months. Intuitive associations between the CHL and MEI data set showed that two types of ENSO (El Nino and La Nina) differ in their influences to CHL. Potential mechanisms relating the phytoplankton dynamics in NTLs to climatic oscillation (ENSO) were also discussed.

An Overview of the Impact of Climate Change on Pathogens, Pest of Crops on Sustainable Food Biosecurity

Anthropogenic activities on the environment have intensified in the last century resulting in a devastating increase in greenhouse gases and triggering global climate oscillation. Global food productions have increase significantly by 50% in order to meet the anticipated demand of the world’s population by 2050. The challenges of food production increases are high and even harder if climate change as a global threat is not addressed. In the coming years, there could be more changes in the biosecurity of food crops due to escalating global climate change. The effects of climate change on plant pathogens and the diseases they cause have been reported in some pathosystems. Climatic changes have been predicted to affect pathogen development and survival rates with possible modification of host susceptibility, host-pathogen-vector interaction that could lead to changes in the impact of diseases on food crops. The climate change may affect not only the optimal conditions for infection but also host specificity and mechanisms of plant infection. Changes in the abiotic conditions are known to affect the microclimate surrounding plants and the susceptibility of plants to disease. These changing conditions are expected to affect microbial communities in the soil and canopy pathosystems, with the possibility of altering the beneficial effects of these communities. Since both the pathogens and host plants could be affected by the dramatic changes in the magnitude of disease expression in a given pathosystem, the geographical distribution of particular plant diseases, their economic importance in a given location, and the set of diseases that infect each crop are crucial to understand their etiology and level of virulence. These changes could affect the measures farmers take to efficiently manage these diseases, as well as the feasibility of cropping systems in particular regions. This review examines the effects of changes in temperature, CO2 and ozone concentrations, precipitation, and drought on the biology of pathogens and their ability to infect plants and survival in natural and agricultural environments. We also underpin the multiple aspects linked to the effects of climate change on crop plant diseases, including the impact of increasing concentrations of atmospheric CO2 and other gases, and how diseases can change under the alteration of atmospheric gases conditions in the future.

Long-term responses of mountain forests to environmental change in West-Central Mexico

This study is an important contribution to the International Long-term Ecological Research Network (ILTER), because it presents the local responses of soil and plant composition to global and regional climatic oscillations of the last millennia in Mexico. Mountain forests are ecosystems that have been constantly threatened by both anthropogenic and climate disturbances, mainly over the Late Holocene. By using palaeoecological techniques with fossil pollen and geochemical elements as proxies, this study incorporates the relationship of trees, herbs and epiphytes with dry and humid climate events. High-temporal resolution in the chronologies allowed the assessment of vegetation changes (every ~ 30 years) and soil geochemical elements in three forests located close (< 8 km) to each other. Our results showed that pine forest contracted along the dry periods of the Little Ice Age (AD 1350–1850), the Medieval Climate Anomaly (AD 800 to 1200) and the Late Classic Drought (AD 600 to 800). However, it expanded in the humid period (AD 1200 to 1350). Cloud forest was the most susceptible ecosystem to the above climate anomalies; trees contracted in periods of aridity and expanded in humid periods. The signature for the transitional forest was confounding: trees increased partially in both dry and humid periods with a well-correlated decrease in epiphytes. Soil losses were common in dry periods while fires increased along the last ~ 300 years.

Large scale climate oscillation impacts on temperature, precipitation and land surface phenology in Central Asia

Central Asia has been rapidly changing in multiple ways over the past few decades. Increases in temperature and likely decreases in precipitation in Central Asia as the result of global climate change are making one of the most arid regions in the world even more susceptible to large-scale droughts. Global climate oscillations, such as the El Niño–Southern Oscillation, have previously been linked to observed weather patterns in Central Asia. However, until now it has been unclear how the different climate oscillations act simultaneously to affect the weather and subsequently the vegetated land surface in Central Asia. We fit well-established land surface phenology models to two versions of MODIS data to identify the land surface phenology of Central Asia between 2001 and 2016. We then combine five climate oscillation indices into one regression model and identify the relative importance of each of these indices on precipitation, temperature, and land surface phenology, to learn where each climate index has the strongest influence. Our analyses illustrate that the North Atlantic Oscillation, the East Atlantic/West Russia pattern, and the Atlantic Multi-Decadal Oscillation predominantly influence temperature in the northern part of Central Asia. We also show that the Scandinavia index and the Multivariate ENSO index both reveal significant impacts on the precipitation in this region. Thus, we conclude that the land surface phenology across Central Asia is affected by several climate modes, both those that are strongly linked to far northern weather patterns and those that are forced by southern weather patterns, making this region a ‘climate change hotspot’ with strong spatial variations in weather patterns. We also show that regional climate patterns play a significant role in Central Asia, indicating that global climate patterns alone might not be sufficient to project weather patterns and subsequent land surface changes in this region.

Bottom-water oxygenation and environmental change in Santa Monica Basin, Southern California during the last 23 kyr

The Southern California Borderland is a region that experiences strong natural variations in bottom water oxygen and pH. We use marine sediments from Santa Monica Basin to reconstruct environmental conditions in the basin's bottom water from the Last Glacial Maximum (LGM) to present. We then compare the records to the adjacent Santa Barbara Basin and Santa Lucia Slope. High-resolution records of benthic foraminiferal oxygen and carbon isotopes (δ18O and δ13C), benthic foraminiferal assemblages, and bulk sedimentary organic matter geochemistry records exhibit major changes associated with late Quaternary millennial-scale global climate oscillations. Our data show the dominance of low‑oxygen benthic foraminiferal assemblages during warm intervals, and assemblages representing higher dissolved oxygen during cooler intervals, as also seen in Santa Barbara Basin and Santa Lucia Slope. However, our record shows a stronger and longer-lasting oxygen minimum zone (OMZ) between the mid Younger Dryas (YD) and the Early Holocene than at neighboring sites, indicated by dominance of Bolivina tumida (characteristic of major hypoxia) in the assemblage. The middle to late Holocene (from ~9 to 0kyr) had weaker hypoxia than the early Holocene, with assemblages mainly composed of Bolivina argentea and Uvigerina peregrina. Santa Monica Basin remained slightly hypoxic throughout the past 23kyr, however, differences in the degree of hypoxia from Santa Barbara Basin and Santa Lucia Slope (especially from the B-A to the Early Holocene) are seen. The Santa Monica Basin bottom water is affected by regional processes, such as changes in the source of intermediate water and/or changing ventilation (oxygenation) of the intermediate water source. This is due to the greater depth and the more southern geographic position of the Basin, which reduces exposure to the oxygenated North Pacific Intermediate Water current. Additional local processes also affect the basin, such as the effects of sediment influx from submarine canyons. This analysis utilizing parallel geochemical and micropaleontological records brings new insights into bottom water and climate conditions in Santa Monica Basin, indicating regional similarities and differences from adjacent basins, and provides insight into the causes for changes in bottom water oxygenation.

Does climate variability influence the demography of wild primates? Evidence from long-term life-history data in seven species.

Earth's rapidly changing climate creates a growing need to understand how demographic processes in natural populations are affected by climate variability, particularly among organisms threatened by extinction. Long-term, large-scale, and cross-taxon studies of vital rate variation in relation to climate variability can be particularly valuable because they can reveal environmental drivers that affect multiple species over extensive regions. Few such data exist for animals with slow life histories, particularly in the tropics, where climate variation over large-scale space is asynchronous. As our closest relatives, nonhuman primates are especially valuable as a resource to understand the roles of climate variability and climate change in human evolutionary history. Here, we provide the first comprehensive investigation of vital rate variation in relation to climate variability among wild primates. We ask whether primates are sensitive to global changes that are universal (e.g., higher temperature, large-scale climate oscillations) or whether they are more sensitive to global change effects that are local (e.g., more rain in some places), which would complicate predictions of how primates in general will respond to climate change. To address these questions, we use a database of long-term life-history data for natural populations of seven primate species that have been studied for 29-52years to investigate associations between vital rate variation, local climate variability, and global climate oscillations. Associations between vital rates and climate variability varied among species and depended on the time windows considered, highlighting the importance of temporal scale in detection of such effects. We found strong climate signals in the fertility rates of three species. However, survival, which has a greater impact on population growth, was little affected by climate variability. Thus, we found evidence for demographic buffering of life histories, but also evidence of mechanisms by which climate change could affect the fates of wild primates.

Linking environmental changes with human occupations between 900 and 400 ka in Western Europe

Human occupation in Europe strongly fluctuated over the Quaternary. Archaeological records suggest an intermittent human occupation in Western Europe between 900 and 500 ka, especially in the north of Europe at latitude higher than 45°N. On the opposite, southern Europe, more stable from a palaeoenvironmental point of view, was occupied continuously. This period is followed by a more widespread and dense occupation over the last 450 ka. In parallel, the last 900 ka are characterized by global climatic oscillations and display shifts between glacial/drier and interglacial/wetter periods that modulate the general repartition of fauna and flora. The pacing of these climatic periods is well recorded in numerous palaeoclimatic archives that provide global as well as regional information concerning past climatic and environmental changes. A transition is observed from 1.25 Ma until up to 450 ka (Mid-Pleistocene Revolution) with a change of the dominant periodicity of climate cycles from 41ka to 100 ka in the absence of substantial change in orbital forcing. After 450 ka, the amplitude between glacials and interglacials increases. The change in periodicity since 450 ka corresponds to a change in the density of human occupations as well as the Acheulean technoculture expansion in Europe. There is a general perception that these climatic and environmental oscillations have played a role in human occupation and his morphological evolution. For instance, temperate environments might have favored permanent occupations or occupations over larger territories with long periods dominated by dry meadows and steppes and followed by the expansion of broadleaf deciduous and confireous forests. Testing this hypothesis for the period encompassing 900 to 500 ka is a challenge because of the lack of a common chronological framework between climatic/environmental archives and sites of human occupation, but also because archaeological records are only snapshots of cultural and morphological changes of hominins.

Late Early Miocene palaeoenvironmental changes in the North Alpine Foreland Basin

The North Alpine Foreland Basin (NAFB) experienced rapidly changing palaeoenvironmental conditions at the end of the Early Miocene (middle-to-late Burdigalian, Paratethys stages Ottnangian and Karpatian), with transformation of fully marine settings into brackish and eventually freshwater environments. These changes were related to global sea-level fluctuations, climate oscillations, and tectonic processes associated with the uplift of the Alps. This study presents a new and comprehensive data set, derived from 13 boreholes and 491 core samples from the Molasse Basin of southwest Germany, that provides a significantly better understanding of late Early Miocene palaeoenvironments in the NAFB. Based on lithostratigraphy, biostratigraphy, and palaeoecological interpretation of rich fauna and flora assemblages, we show that the upper Burdigalian sediments comprise a regressive lower segment (Grimmelfingen Formation and equivalents), as indicated by the occurrence of the bivalve Rzehakia, and a transgressive upper component (Kirchberg Formation and equivalents) characterized by the advent of new fish and mollusc assemblages. Furthermore, we present a new lithostratigraphic concept for the Kirchberg Formation, which forms an important part of the Upper Brackish Molasse (OBM). Based on biostratigraphic constraints and recently published magnetostratigraphic data, it appears that the regressive segment of the upper Burdigalian OBM sediments correlates with the end of the global third-order sea-level cycle Bur 3, while the transgressive component reflects the Karpatian transgression at the beginning of sea-level cycle Bur 4. This implies that the Karpatian transgression actually affected the Molasse Basin of southern Germany and Upper Austria, whereas previous studies had considered this part of the NAFB as terrestrial during that time span. The new results are depicted in three palaeogeographic maps for the NAFB at 18Ma, 17.5–17.1Ma and 17Ma, respectively.

A 211‐year growing season temperature reconstruction using tree‐ring width in Zhangguangcai Mountains, Northeast China: linkages to the Pacific and Atlantic Oceans

ABSTRACTNortheast China is one of the most vulnerable areas to climate change in high latitude regions of the Northern Hemisphere. The past temperature variations are critical to reveal the driving mechanism of climate change and to reduce the uncertainty in predicting future climates. Pre‐instrument climatic variability is poorly understood, because of the scarcity of centuries‐long climatic data. Here, we present a 211‐year (1803–2013) growing season (May–July) temperature reconstruction based on tree‐ring width chronology of Korean pine (Pinus koraiensis) from Zhangguangcai Mountains in Northeast China. The reconstruction accounted for 41.3% of the temperature variance during the calibration period from 1959 to 2013. The temperature reconstruction was similar to other nearby temperature reconstructions and correlated well spatially to gridded land and ocean surface temperature data. We identified four major cold periods (1839–1846, 1884–1901, 1906–1908 and 1941–1958) and three major warm periods (1855–1880, 1918–1932 and 1998–2013) in the past 211 years. The multi‐taper method spectral analysis revealed significant cycles at 48.8, 11.5, 8.9, 3.9, 3.5 and 2–3 years, which might be associated with global climate oscillations and land‐sea thermal contrasts, such as the sea surface temperatures, El Niño‐Southern Oscillation, Atlantic Multidecadal Oscillation and solar activity.

Method for reconstructing the monthly mean water transparencies for the northwestern part of the Black Sea as an example

A model based on neural networks with a teacher is suggested to reconstruct the data of observations of hydrophysical parameters. The indices of global climate oscillations in the ocean–atmosphere system were used as input signals for the model. The processes of model training and adaptation, permitting the most accurate solution of the modeling problem, is described. A comparison of model-predicted monthly mean of the Danube runoff volumes with observational data showed their good agreement. Gaps in data of observations of the water transparency (visibility depth of a white disk) in different years are filled by reconstructed data. A close correspondence in absolute value between reconstructed and measured visibility depths of the white disk is reported. Some features of interannual variations in reconstructed data on water transparency, caused by both climatic factors during 1950–1962 and changes in the chlorophyll а concentration during 1998–2010, were revealed.

Reflection of global late glacial and Holocene paleoclimate oscillations in the palynological record from bottom sediments of Tavatui Lake (Middle Urals)

The palynological analysis of the reliably dated core section of bottom sediments from Tavatui Lake revealed consistency between the chronology and succession of Late Pleistocene and Early Pliocene events (GI-a/b, CS-1, GH-11.2) in the Middle Urals and the North Atlantic region. It is established that the Holocene thermal maximum (5.3–8.0 cal. ka ago) in the Middle Urals was characterized by high temperatures and humidity. The initial stage of the Subboreal cooling was reffered to the interval of 4.5–5.3 cal. ka ago. The data obtained provided grounds for the conclusion that the palynological record in the Tavatui Lake section reflects in detail global and regional climate oscillations, which allows it to be used as a Holocene and late glacial reference section, as well as for predicting the behavior of the natural system of the Middle Urals in response to future climate change.

Environmental and climate changes reflected in the Domuraty 2 section (NE Poland) based on analysis of plant macroremains

Abstract Research in the Domuraty 2 section was focused on a series of lacustrine-river-swamp deposits in which the full spectrum of vegetation and climate changes was recognised in a detailed analysis of plant macroremains and a comparison with the results of pollen analysis. Based on plant macrofossil data, two (Dom II, Dom III) of three palynologically documented warm units were distinguished in the Domuraty succession. The palaeobotanical data from the Domuraty succession document several successive local vegetation changes in both interglacial and glacial periods, which can be related to global climate oscillations. The succession of local vegetation stands and changes in the vegetation, climate, water level, and trophy during the period of the Domuraty succession were analysed and compared with corresponding parameters of the Augustovian and Ferdynandovian interglacials. The taxonomically most diverse unit is Warm unit Dom II, with the highest share of taxa with high thermal requirements, which was compared to the older Augustovian (A II) and younger Ferdynandovian (F II) units. The comparison of the Domuratovian interglacial flora to that of the Korchevian interglacial in Belarus shows high similarity; most of the extinct taxa or taxa unknown in the present-day flora are common to the Korchevian and Domuratovian floras, suggesting similar age for these two communities. However, the Domuratovian flora lacks a few species important to the Korchevian flora, such as Stratiotes goretskyi, Carex rostrata-pliocenica, Brasenia sp., Caulinia antiqua, Aldrovanda borysthenica, and A. zusii.

Time–frequency characterization of sub-divisional scale seasonal rainfall in India using the Hilbert–Huang transform

Time–frequency characterization is useful in understanding the nonlinear and non-stationary signals of the hydro-climatic time series. The traditional Fourier transform, and wavelet transform approaches have certain limitations in analyzing non-linear and non-stationary hydro-climatic series. This paper presents an effective approach based on the Hilbert–Huang transform to investigate time–frequency characteristics, and the changing patterns of sub-divisional rainfall series in India, and explored the possible association of monsoon seasonal rainfall with different global climate oscillations. The proposed approach integrates the complete ensemble empirical mode decomposition with adaptive noise algorithm and normalized Hilbert transform method for analyzing the spectral characteristics of two principal seasonal rainfall series over four meteorological subdivisions namely Assam-Meghalaya, Kerala, Orissa and Telangana subdivisions in India. The Hilbert spectral analysis revealed the dynamic nature of dominant time scales for two principal seasonal rainfall time series. From the trend analysis of instantaneous amplitudes of multiscale components called intrinsic mode functions (IMFs), it is found that both intra and inter decadal modes are responsible for the changes in seasonal rainfall series of different subdivisions and significant changes are noticed in the amplitudes of inter decadal modes of two seasonal rainfalls in the four subdivisions since 1970s. Further, the study investigated the links between monsoon rainfall with the global climate oscillations such as Quasi Bienniel Oscillation (QBO), El Nino Southern Oscillation (ENSO), Sunspot Number (SN), Atlantic Multidecadal Oscillation (AMO) etc. The study noticed that the multiscale components of rainfall series IMF1, IMF2, IMF3, IMF4 and IMF5 have similar periodic structure of QBO, ENSO, SN, tidal forcing and AMO respectively. As per the seasonal rainfall patterns is concerned, the results of the study indicated that for Assam-Meghalaya subdivision, there is a likelihood of extreme rare events at ~0.2 cycles per year, and both monsoon and pre-monsoon rainfall series have decreasing trends; for Kerala subdivision, extreme events can be expected during monsoon season with shorter periodicity (~2.5 years), and monsoon rainfall has statistically significant decreasing trend and post-monsoon rainfall has a statistically significant increasing trend; and for Orissa subdivision, there are chances of extremes rainfall events in monsoon season and a relatively stable rainfall pattern during post-monsoon period, but both monsoon and post-monsoon rainfall series showed an overall decreasing trend; for Telangana subdivision, there is a likelihood of extreme events during monsoon season with a periodicity of ~4 years, but both monsoon and post-monsoon rainfall series showed increasing trends. The results of correlation analysis of IMF components of monsoon rainfall and five climate indices indicated that the association is expressed well only for low frequency modes with similar evolution of trend components.

Influence of climate oscillations on temperature and precipitation over the United Arab Emirates

In this study, we investigate the influence of global climate oscillations on the local temperature and precipitation over the United Arab Emirates (UAE), which is one of the driest regions in the world with very high temperatures and low precipitation. The identification and assessment of remote interactions (teleconnections) are carried out by using ground station and gridded data sets. Monthly rainfall data from six ground stations over the UAE for the period of 1982–2010 is used in this study along with the long-term gridded precipitation and temperature data from the Global Precipitation Climatology Center and Global Historic Climatic Network. Linear correlations, wavelet analysis, and cross-wavelet analysis have been applied to identify the relation between climate indices and precipitation (temperature). The analysis reveals that the strong variability in precipitation is closely associated with the Southern Oscillation Index (SOI) and the Indian Ocean Dipole Index (IOD) during the months of August–March, September–January, respectively. In case of temperature, the strong variability is associated with the North Atlantic Oscillation Index (NAO) and the East Atlantic Oscillation Index (EAO) during the months of April–October, July–December. Spatial analysis of cross-wavelet reveals that the winter precipitation is significantly influenced by SOI and temperature during summer by the NAO. This research concludes that the negative phases of SOI (NAO) play a significant role in the increase of precipitation (decrease in summer temperatures) over the UAE region.

Historical demography of southern African patellid limpets: congruence of population expansions, but not phylogeography

Global climatic oscillations have shaped the contemporary genetic structure of marine taxa in different ways. Previous demographic studies have indicated that various intertidal marine species display genetic signatures of demographic expansion that either pre- or postdate the Last Glacial Maximum. Such expansions and the ability of species to colonise new habitats will influence their genetic structure, but the link between scales of larval dispersal and the strength of phylogeographic structure is not always clear. We analysed a fragment of the mitochondrial COI gene of 11 sympatric species of intertidal southern African patellid limpets to investigate how ancient oceanographic dynamics have shaped and maintained their contemporary spatial genetic variation. Our data show that the patellid limpets investigated display congruent evidence of spatial expansion during the Late Pleistocene or Early Holocene, which corresponds with the establishment of the contemporary southern African shoreline. We argue that closely related and co-distributed southern African intertidal invertebrates responded to ancient climatic oscillations as a cohesive group. In contrast, contemporary oceanographic circulation has shaped the phylogeographic patterns of these limpets in different ways. We show close relationships between phylogeography and biogeography for some species, but not for others, despite the similarities in their life histories and exposure to the same climatic changes.

Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years

AbstractThe lithostratigraphic framework of Lake Van, eastern Turkey, has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years. The lithostratigraphy and chemostratigraphy of a 219 m long drill core from Lake Van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity. An age model was established based on the climatostratigraphic alignment of chemical and lithological signatures, validated by 40Ar/39Ar ages. The drilled sequence consists of ca 76% lacustrine carbonaceous clayey silt, ca 2% fluvial deposits, ca 17% volcaniclastic deposits and 5% gaps. Six lacustrine lithotypes were separated from the fluvial and event deposits, such as volcaniclastics (ca 300 layers) and graded beds (ca 375 layers), and their depositional environments are documented. These lithotypes are: (i) graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations; (ii) varved clayey silts reflecting strong seasonality and an intralake oxic–anoxic boundary, for example, lake‐level highstands during interglacials/interstadials; (iii) CaCO3‐rich banded sediments which are representative of a lowering of the oxic–anoxic boundary, for example, lake level decreases during glacial inceptions; (iv) CaCO3‐poor banded and mottled clayey silts reflecting an oxic–anoxic boundary close to the sediment–water interface, for example, lake‐level lowstands during glacials/stadials; (v) diatomaceous muds were deposited during the early beginning of the lake as a fresh water system; and (vi) fluvial sands and gravels indicating the initial flooding of the lake basin. The recurrence of lithologies (i) to (iv) follows the past five glacial/interglacial cycles. A 20 m thick disturbed unit reflects an interval of major tectonic activity in Lake Van at ca 414 ka bp. Although local environmental processes such as tectonic and volcanic activity influenced sedimentation, the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes, making Lake Van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years.

Texture contrast profile with stonelayer in the Cape Peninsula, South Africa: Autochthony and polygenesis

We studied a soil-geomorphic unit with a stonelayer at the Cape Peninsula, South Africa, for which there is no previous documented research, to characterize the soils and draw inferences regarding their pedogenesis and palaeoenvironment aspects. Mineralogy and element geochemistry were determined using XRD and XRF respectively; micromorphology by thin section description. Physicochemical properties were determined by routine procedures. The operational pedogenic process in the buried horizons include plinthization; and in the younger overlying soil, podzolization. Element abundance followed SiO2>Al2O3>Fe2O3>TiO2. Variations in climate and parent material are the principal causes of differences in the soil properties. The stonelayer appears to have been deposited as a lag by a palaeoriver as the energy decreased and the material was later mixed with the soil matrix by turbation. Two regional climate cycles are in evidence: a relatively warm and humid subtropical climate which gave rise to the formation of the buried palaeosol and a drier, more seasonal semi-arid Mediterranean climate under which the soils overlying the stone line are currently forming. Like many other places, the Cape Peninsula has also been subjected to global climate oscillations. Palaeosol-based proxies are capable of providing insights into palaeoenvironments.