Short-term Climatic Oscillations Research Articles

Short-Term Climatic Oscillations in the Central Region of the East-European Plain at the Beginning of the Holocene Based on Palynological Studies of Lacustrine Deposits

The Preboreal (11.75–10.70 ka BP) is still the least paleogeographically studied time interval in the central part of the East European Plain. High-resolution multi-proxy studies of lacustrine sediments at the Seltso site located in the Desna River floodplain (Dnieper River basin) were conducted. Radiocarbon dating, loss-on-ignition determination, sedimentological and palynological studies and identification of Non-Pollen Palynomorphs in lacustrine sediments allow us to reconstruct changes in vegetation caused by rapid warming at the Younger Dryas–Holocene boundary, short-term climatic fluctuations within the Preboreal and subsequent resumption of warming. Initial Preboreal warming reached its maximum at about 11.5 ka BP when a relatively dry continental climate existed. Between 11.4 and 11.2 ka BP, a short-term cooling corresponding to the Preboreal Oscillation in Greenland occurred, as indicated by a significant reduction of woody vegetation and expansion of open plant communities. In the Late Preboreal, approximately 11.2–10.7 ka BP, warming resumed, which was accompanied by a decrease in the climate continentality. Comparison with high-resolution lithological and palynological data from eight reliably dated sections of the central East European Plain indicates that in northwestern and central Europe, the impact of the Preboreal Oscillation cooling on the vegetation and the lake ecosystems’ development was probably somewhat stronger.

An Impact of Short-Term Climate Oscillations in the Late Pleniglacial and Lateglacial Interstadial on Sedimentary Processes and the Pedogenic Record in Central Poland

Environmental studies based on analyses of fluvio-aeolian successions with paleosols in central Poland, forming the central part of the European Sand Belt, are presented. Paleogeographic reconstruction was based on high-resolution analyses of four sites using sedimentological and paleopedological methods as well as forty-four optically stimulated luminescence and fourteen radiocarbon dating measurements. Age-identified individual lithological and soil units were first correlated between sites, emphasizing the differences between them. The results were then correlated with Greenland ice-core stratigraphic units reflecting global environmental changes in the Late Pleniglacial and Lateglacial interstadial, thus ranging from GS-2.1a, through the GI-1 complex (seven subunits), to GS-1. Studies revealed considerable sensitivity of fluvio-aeolian succession to climate changes and oscillations. Climate ameliorations are recorded in fossil soil horizons developed beneath different types of vegetation cover. We detected that the climate cooling GI-1d (the Older Dryas) was not the main phase of dune formation as had been claimed earlier. It is postulated that dunes in the extraglacial zone were formed mainly in GI-1c2 (the Early Allerød). Preexisting dunes were transformed in GS-1 (the Younger Dryas) and in the Early Holocene, locally interrupted by soil formation.

Long-Term Changes in the Land–Ocean Ecological Environment in Small Island Countries in the South Pacific: A Fiji Vision

Small island countries in the South Pacific are ecologically fragile areas, vulnerable to climate change, and the long-term ecological changes in the sea and land have an important impact on their sustainable development. This study takes Fiji, a typical small island country in the South Pacific, as an example, to analyze the change and connection of marine and terrestrial ecosystem environments based on 30 years of multi-source, satellite, remote-sensing data. From 1991 to 2019, according to the change in forest area in Fiji, three stages were delineated: first was a period of stability, then a decrease, and then a recovery in recent years. From 1991 to 2002, Fiji’s vegetation accounted for 73% of the total area; sea environment surrounding the islands, such as sea level height and sea surface temperature, were relatively low, with high water transparency. From 2002 to 2014, with the development of forestry and tourism, vegetation decreased by 6.89% and bare land increased, which changes the runoff erosion in the drainage basin; correspondingly, the chlorophyll a concentration in three major estuaries was found to be slightly increased with low water transparency. Meanwhile, coupled with the rising sea temperature, the area of Fiji’s coral reefs shrank significantly, with 51.13% of the total loss of coral reefs occurring in the Vanua Levu, where bare land and runoff were more distributed in its drainage basin. From 2014 to 2019, Fiji’s vegetation and coral reef areas recovered from the former stage; affected by short-term climate oscillations such as El Niño-Southern Oscillation (ENSO), the sea surface temperature showed a significant abnormal drop and the water transparency decreased. In the past 30 years (1993–2018), the sea level rise rate around Fiji reached 4 mm/year, and the temperature increased by 0.3 °C, which threatens the coastal ecosystem environment, including coral reefs and mangrove; inappropriate land-use change would worsen the situation in these ecologically fragile areas.

GEOMORPHOLOGICAL DYNAMICS OF THE ELEVATED GEOSYSTEMS OF THE BORBOREMA HIGHLANDS, NORTHEAST OF BRAZIL, FROM OPTICALLY STIMULATED LUMINESCENCE DATING OF HILLSLOPE SEDIMENTS

The geomorphological dynamics of the elevated compartments of the Borborema Highlands, northeastern Brazil, were assessed through the analysis of hillslope sediments. The chosen study area was the Baixa Verde massif, in the State of Pernambuco. The main morphostratigraphic features were identified on the basis of their relevance to the reconstruction of the geomorphological dynamics. First hillslope deposits in the shape of colluvial fans, or infills of hollows and zero order catchments were identified. Following field study of the stratigraphic interactions in four sampling areas within the massif, samples were collected for a number of laboratory tests: sedimentological analysis, soil micromorphology and Optically Stimulated Luminescence (OSL) dating. A fragment of charcoal found on the top of a gravel layer was radiocarbon- dated. The sampling procedures were aimed at the characterization of the several depositional units. The results of the dating of 14 sampling sites point to the occurrence of discrete events of hillslope material remobilization within the last 20,000 years as a dynamic response of the geomorphological systems to the following events: the Last Glacial Maximum (LGM), the Pleistocene/Holocene transition, the mid-Holocene climatic optimum and the recent anthropic period and its short term climatic oscillations.

Climatically-driven cyclicity and peat formation in fluvial setting of the Moscovian – Early Kasimovian Cracow Sandstone Series, Upper Silesia (Poland)

The approximately 1200 m thick Cracow Sandstone Series (Middle – early Late Pennsylvanian) in the Polish part of the Upper Silesian Coal Basin consists of 25–70 m thick fining up and laterally widespread fluvial cycles. The cycles are marked by alternating sheet-like sandstone bodies overlain by much thinner intervals dominated by mudstone and coal. These two-member cycles record the alternation of a sand-dominated fluvial braidplain and floodplain-dominated fluvial system with channels confined to narrow belts. The lateral persistence, internal architecture, and isochronous alternations suggest an allogenic origin for the cycles, possibly related to climate. This interpretation is supported by a three-stage evolution of pedogenic processes operating on floodplain deposits beginning with the formation of vertisols, followed later by gleying and, finally, termination by a Histosol (peat) formation. Such a succession of paleosols indicates a climatic shift from highly seasonal (Vertisol) to humid climate (coal) with the most seasonal part of the cycle likely represented by the sheet-like sandbody. The mechanistic link between climate and the cyclic pattern of strata is explained as climatically-driven variations in clastic supply, which was highest during periods of prominent seasonality. Short-term climatic oscillations generating cyclic patterns in the Cracow Sandstone Series are superimposed on a long-term climatic shift towards increased seasonality near the Middle – Late Pennsylvanian boundary. This is evidenced by the termination of peat formation in the Upper Silesian Basin as well as in some other coeval basins of the equatorial Pangea and is interpreted to represent a potentially regional climatic event.

Relationship between regional climate change and primary ecosystem characteristics in a lagoon undergoing anthropogenic eutrophication, Lake Mokoto, Japan

Annual-scale environmental and ecosystem changes since the mid-19th century were reconstructed in a seasonally frozen lagoon, Lake Mokoto, located along the Okhotsk Sea coast of Hokkaido, northern Japan. X-ray fluorescence (XRF) and diatom analyses of laminated sediment were conducted to determine the impact of short-term climate oscillations and anthropogenic eutrophication on the lagoon ecosystem. In this lagoon, eutrophication has progressed since the early 20th century due to deforestation and human activity in the catchment area, such as development of the cattle industry and field agriculture. In particular, the sedimentation rate of Lake Mokoto and potassium and phosphorus contents of lake sediment have increased rapidly since 1970, in association with an increase in the number of cattle. In addition, the Lake Mokoto ecosystem shows interannual and decadal cyclic fluctuations that are separate from the anthropogenic effects. Prior to anthropogenic eutrophication, the nutrient condition of Lake Mokoto showed a close relationship with the Pacific decadal oscillation (PDO). The growth of seagrass, inferred from epiphytic diatom abundance, showed a clear decadal cycle following variation in solar irradiance.

Effects of inlet excavation and climate oscillation on the ecosystem of a fishery lagoon in northern Japan

The chemical components and benthic foraminiferal assemblages in core sediments from Notoro Lagoon in northern Japan revealed the effects of artificial inlet excavation and the role of regional climate cycles on the shift of oxygen conditions in the lagoon basin. The materials analyzed were four sediment cores obtained from three basins in Notoro Lagoon using pushing-piston corers. An artificial inlet was excavated at the lagoon in 1977. Immediately after excavation, CNS contents in the sediment began to decrease, and benthic foraminiferal assemblages shifted due to high-oxygen seawater inflow. There was a 7-year transition before the lagoon environment and ecosystem were stable. After inlet excavation, the bottom environment and benthic foraminiferal assemblage of Notoro Lagoon were strongly influenced by short-term climate oscillations such as the Pacific Decadal Oscillation and Arctic Oscillation. Frequent short-duration peaks of oxygen-proxy foraminifera taxa and decreases in total organic carbon in sediment were confirmed between 1986 and 1998. This transition occurred because the spring air temperature and pressure over Notoro Lagoon were affected by the short-term climate oscillations, which have determined the timing of lake ice melt and the volume of oxygen-rich seawater inflow. As a result, bottom conditions and the benthic ecosystem of the Notoro Lagoon have shifted along with these regional climate changes.

Obliquity pacing of the hydrological cycle during the Oceanic Anoxic Event 2

The Oceanic Anoxic Event 2 (OAE2, ca. ∼93.5 Ma) represents a major phase of environmental change during the Mesozoic, and is associated with a pronounced positive excursion in the carbon-isotope record. Short-term climate oscillations within the OAE2 are recorded as Milankovitch cycles, which have been used to establish a precise temporal framework for the OAE2. However, few studies discuss the sedimentary expression of Milankovitch cycles during the OAE2, and its paleoenvironmental implications. Here we present carbonate and organic-carbon isotope data from a biostratigraphically well-dated, organic-rich OAE2 interval in a sedimentary succession outcropping in the Briançonnais Domain at Roter Sattel (Fribourg Prealps, Switzerland). We sampled the OAE2 interval (4.28 m) for proxies of detrital sediment quantification (Al, Ti, magnetic susceptibility) at ultra-high resolution (1 cm). Time-series analysis of multiple detrital proxies permits the construction of an orbital timescale for the OAE2 based, for the first time, on the stable 173 kyr (s3–s6) obliquity modulation cycle. The resulting OAE2 orbital timescale at Roter Sattel is consistent with previous timescales obtained in the Western Interior Basin, and in southern Tibet (China). Our cyclostratigraphic results show an unusually strong obliquity signal during the initiation of OAE2. Previous studies have demonstrated that the onset of OAE2 was associated with magmatic pulses coupled with increases in atmospheric pCO2, followed by an overall, gradual drawdown of CO2. Accordingly, we suggest that detrital input during the OAE2 was the result of intensified continental weathering related to magmatic activity, the substantially release of greenhouse gases, and an accelerated hydrological cycle modulated by obliquity cycles.

Paleoclimatological and Geoarchaeological Significance of the Holocene Loess – Soil Successions of the Tien Shan Foothills of Uzbekistan

AbstractScenario of climate changes in the Late Pleistocene and Holocene in Central Asia is very fragmentary and inconsistent. Therefore, interaction between the development and decline of ancient cultures and the climate fluctuations are difficult to be traced. To resolve this problem, the key role can be played by multidisciplinary studies of unique Late Pleistocene and especially Holocene loess – soil succession of the Tien Shan foothills in Uzbekistan. This area yields unique successions of paleosols interbedded with loesses that are particularly useful for paleoclimate analysis. They are represented by continuous and uninterrupted sedimentary sequences with a highly varied record of magnetic susceptibility. As such, they contain a full sequence of short-term climatic oscillations of the Holocene in high resolution and therefore, in this case, they are exceptional on global scale. The correlation of Late Pleistocene and Holocene climate changes scenario with stages of development and collapse of the past human settlement in Central Asia seems at present one of the most promising research directions, in line with the substantial course of interdisciplinary research on the interaction between humans and the natural environment.

Understanding and Building on Indigenous Agro-Pastoral Adaptation strategies for Climate Change in Sub-Saharan Africa: Experiences from Rural Cameroon

Rural communities in the Sub-Sahara African region have become focal points for climate adaptation especially in the agricultural sector. This is due to their significant involvement in agro-pastoral activities which constitute the lifeblood of most of the economies of this region, with about 85% of the indigenous populations relying on it for their survival. Both long and short term climatic oscillations have succeeded, and will continue to disrupt crop and livestock output thus signaling threats to food security. Although the communities have either consciously or unconsciously made use of some indigenous adaptation strategies, they are judged to be weak at the moment. This requires the designation of context-specific agro-pastoral adaptation frameworks. Using focus group discussions (FGDs) of 6 agro-pastoral groups (10 representatives each) in this region, complemented by content analysis, field surveys and the extensive review of literature on case studies for other SSA communities, we analyze current indigenous adaptation mechanisms in the agro-pastoral sector and attempt to construct an indigenous adaptation framework for rural agro-pastoral communities in Cameroon. Our analysis of data leads us to conclude that current adaptation measures rely mainly on crop diversification and mixed farming. Although these methods are good, the scale of operation and the degree of diversification is still low to climate-proof the agro-pastoral sector. Furthermore, these changes are introduced in the midst of poor farming practices such as slash and burn and related systems. Current indigenous adaptation strategies are weak and are correlated with income levels, level of farmers involvement in organizations, knowledge and perception. We recommend the effective engagement of agro-pastoral stakeholders as key in developing an adaptable framework, based on their knowledge of current adaptation strategies.

Temporal Succession of Ancient Phytoplankton Community in Qinghai Lake and Implication for Paleo-environmental Change.

Tibetan lake sediments in NW China are sensitive recorders of climate change. However, many important plankton members do not leave any microscopic features in sedimentary records. Here we used ancient DNA preserved in Qinghai Lake sediments to reconstruct the temporal succession of plankton communities in the past 18,500 years. Our results showed that seven classes and sixteen genera of phytoplankton in the lake underwent major temporal changes, in correlation with known climatic events. Trebouxiophyceae and Eustigmatophyceae were predominant during the cold periods, whereas Chlorophyceae, Phaeophyceae, Xanthophyceae, Bacillariophyceae, and Cyanophyceae were abundant during the warm periods. The inferred changes in temperature, nutrients, precipitation, and salinity, as driven by the Westerlies and summer Monsoon strength, likely contributed to these observed temporal changes. Based on these correlations, we propose the phytoplankton index as a proxy to reconstruct the stadial versus interstadial climate change history in Qinghai Lake. This taxon-specific index is free of terrestrial contamination, sensitive to short-term climatic oscillations, and continuous in recording all climatic events in the lake. The validity of this index and its applicability to other lakes is demonstrated by its good correlations with multiple climate records of Qinghai Lake and another lake on the Tibetan Plateau, Kusai Lake.

Global Redox Carbon Cycle and Periodicity of Some Phenomena in Biosphere

The irregular periodicity of some biosphere phenomena, such as climatic cycles, mass extinctions, abrupt changes of biodiversity rate and others in the course of geological time is analyzed on the basis of a global redox carbon cycle model. It is shown that these differences by nature phenomena have a common cause for the periodicity. The cause is the periodic impact of moving lithospheric plates on photosynthesis via CO2 injections. The source of CO2 is the oxidation of sedimentary organic matter in thermochemical sulfate reduction from zones, where plates collide. The periodicity and the irregularity of lithospheric plates’ movement generate orogenic cycles, at the background of which biosphere events appear. The biosphere events are usually followed by a set of traits that are used to identify the events in the geological past. Orogenic cycles manifested till the moment when the carbon cycle didn’t reach the ecological compensation point, i.e., when the amount of photosynthetically produced carbon will become equal to the amount of the reduced carbon oxidized in the numerous oxidation processes in the Earth’s crust. After reaching this point long-term organic cycles were replaced by short-term climatic oscillations. The same set of traits characterizing the organic cycles and the climatic oscillations evidences for their same nature. The changes concern only duration of the event and the scale of its influence.

Global Redox Carbon Cycle and Photosynthesis Development

The principle of actualism and recent findings on carbon isotope fractionation in photosynthesis, combining with data on isotopic ratio of carbon in sedimentary rocks in form of carbonates and coeval organic matter allowed developing a new model of the redox carbon cycle. According to the model, carbon transfer between biosphere and geospheres is a conversion of the element from the oxidized state to the reduced one, and back. The transfer proceeds under the control of photosynthesis, which is an essential element of the carbon cycle. The lithospheric plates’ movement exerts impact on photosynthesis development via periodic injections of CO2 into “atmosphere – hydrosphere” system during plates’ collisions. Due to irregular lithospheric plates’ movement the orogenic cycle consists of a short-term orogenic period of active volcanism, magmatism and mountain building and a long-term geosynclynal period of low volcanic activity and quiet development of Earth crust processes. In short-term orogenic periods, when plates move fast and collide frequently, a great amount of CO2 evolves from the subduction zones of the Earth’s crust (where plates collide) and fills the “atmosphere – hydrosphere” system. It causes expansion of photosynthesis. At the same time oxygen concentration drops due to oxidation of reducing magmatic rocks. In longterm geosynclynal period, due to photosynthesis, the CO2 concentration gradually drops whereas O2 concentration increases and achieves the maximum by the end of the cycle. In the following relatively extended geosynclynal periods, the collisions of plates are seldom, and the rate of CO2 emission from subduction zones becomes weaker than the rate of CO2 assimilation. The pulsating movement of plates exerts an impact on dynamics and development of photosynthesis. It, in turn, determines periodicity of numerous processes, including climatic cycles, changes in the rate of biodiversity, irregular accumulation of organic matter in sediments, uneven stratigraphic oil distribution, sea level changes, etc. The redox carbon cycle is a self-organizing system due to negative feedback between CO2 assimilation and photorespiration in response to oxygen growth. It made carbon cycle to shift to ecological compensation point. In this point the system become sensitive to separate plates’ collisions what results in shortterm climatic oscillations.

Late Quaternary vegetation and climate dynamics at the northern limit of the East Asian summer monsoon and its regional and global-scale controls

A late Quaternary pollen record from northern Sakhalin Island (51.34°N, 142.14°E, 15 m a.s.l.) spanning the last 43.7 ka was used to reconstruct regional climate dynamics and vegetation distribution by using the modern analogue technique (MAT). The long-term trends of the reconstructed mean annual temperature (TANN) and precipitation (PANN), and total tree cover are generally in line with key palaeoclimate records from the North Atlantic region and the Asian monsoon domain. TANN largely follows the fluctuations in solar summer insolation at 55°N. During Marine Isotope Stage (MIS) 3, TANN and PANN were on average 0.2 °C and 700 mm, respectively, thus very similar to late Holocene/modern conditions. Full glacial climate deterioration (TANN = −3.3 °C, PANN = 550 mm) was relatively weak as suggested by the MAT-inferred average climate parameters and tree cover densities. However, error ranges of the climate reconstructions during this interval are relatively large and the last glacial environments in northern Sakhalin could be much colder and drier than suggested by the weighted average values. An anti-phase relationship between mean temperature of the coldest (MTCO) and warmest (MTWA) month is documented during the last glacial period, i.e. MIS 2 and 3, suggesting more continental climate due to sea levels that were lower than present. Warmest and wettest climate conditions have prevailed since the end of the last glaciation with an optimum (TANN = 1.5 °C, PANN = 800 mm) in the middle Holocene interval (ca 8.7–5.2 cal. ka BP). This lags behind the solar insolation peak during the early Holocene. We propose that this is due to continuous Holocene sea level transgression and regional influence of the Tsushima Warm Current, which reached maximum intensity during the middle Holocene. Several short-term climate oscillations are suggested by our reconstruction results and correspond to Northern Hemisphere Heinrich and Dansgaard–Oeschger events, the Bølling–Allerød and the Younger Dryas. The most prominent fluctuation is registered during Heinrich 4 event, which is marked by noticeably colder and drier conditions and the spread of herbaceous taxa.

The early Miocene paleolake Manuherikia: vegetation heterogeneity and warm-temperate to subtropical climate in southern New Zealand

The Manuherikia Group in southern New Zealand represents terrestrial sediments associated with a large paleolake, Lake Manuherikia, formed during a period of basin subsidence in the early Miocene, ca. 18.7–15.1 Ma. Micro- and macrofloral assemblages collected throughout the Manuherikia Group were studied to derive terrestrial climate proxies, relying on leaf physiognomy (CLAMP) and taxonomic affinity (bioclimatic analysis). The assemblages were also analyzed for the component loading of the relative abundances of different leaf morphotypes and the results were interpreted in light of stratigraphic and lateral ecological variation. Independent paleoclimate proxies from a variety of depositional environments consistently indicate warm-temperate to marginally subtropical mean annual temperatures (16.5–20 °C) and high annual precipitation (1,500–2,500 mm) during the Burdigalian–Langhian of mid-latitude New Zealand. Leaf physiognomy reveals an amplified seasonal contrast in both precipitation and temperature, possibly caused by seasonal shifts in the position of the subtropical high-pressure cells and westerly wind belts, causing overcast wet winters and dry summers. Regional and local vegetation variation was most likely caused by fluctuations in lake levels, which in turn may have been affected by enhanced seasonality from short-term climate oscillations.

Building an Indigenous Agro-pastoral Adaptation Framework to Climate Change in Sub-Saharan Africa: Experiences from the North West Region of Cameroon

Sub-Saharan Africa (SSA), among other regions of the world, stands today as one of the hardest hit areas as far as the concomitants of climate change is concerned. This is particularly the case with the agro-pastoral sector which is the lifeblood of most of the economies of this region with about 85% of the indigenous populations relying on agriculture for their survival. Both long and short term climatic oscillations have succeeded to disrupt crop and livestock output thus signaling threats to food security. Although the communities have either consciously or unconsciously made use of some indigenous adaptation strategies, they are judged to be weak at the moment. This requires the designation of context-specific agro-pastoral adaptation frameworks. Using focus group discussions (FGDs) of 6 agro-pastoral groups (10 representatives each) in this region, complemented by field surveys and the extensive review of literature on case studies for other SSA communities, we analyze the knowledge, perceptions and adaptation strategies for individual agro-pastoral households in rural Cameroon. Our analysis of data leads us to conclude that future climatic situation is characterized by increasing unpredictability, introducing shocks of varying degrees in the crop and livestock sector necessitating varying formal and informal mechanisms. Current adaptation measures rely mainly on crop diversification and mixed farming. Although these methods are good, the scale of operation and the degree of diversification is still low to climate-proof the agro-pastoral sector. Furthermore, these changes are introduced in the midst of poor farming practices such as slash and burn and ankara systems. Current indigenous adaptation strategies are weak and have a connection with income levels, level of farmers organizations, knowledge and perception.

Quantifying variable erosion rates to understand the coupling of surface processes in the Teton Range, Wyoming

Short-term geomorphic processes (fluvial, glacial, and hillslope erosion) and long-term exhumation control transient alpine landscapes. Long-term measurements of exhumation are not sufficient to capture the processes driving transient responses associated with short-term climatic oscillations, because of high variability of individual processes across space and time. This study compares the efficacy of different erosional agents to assess the importance of variability in tectonically active landscapes responding to fluctuations in Quaternary climate. We focus on the Teton Range, where erosional mechanisms include hillslope, glacial, and fluvial processes. Erosion rates were quantified using sediment accumulation and cosmogenic dating (bedrock and stream sediments). Results show that rates of erosion are highly variable, with average short-term rockfall rates (0.8mm/y) occurring faster than either apparent basin-averaged (0.2mm/y) and long-term ridge erosion rates (0.02mm/y). Examining erosion rates separately also demonstrates the coupling between glacial, fluvial, and hillslope processes. Apparent basin-averaged erosion rates amalgamate valley wall and ridge erosion with stream and glacial rates. Climate oscillations drive the short-term response of a single erosional process (e.g., rockfalls or other mass wasting) that may enhance or limit the erosional efficiency of other processes (glacial or fluvial). While the Teton landscape may approach long-term equilibrium, stochastic processes and rapid response to short-term climate change actively perpetuate the transient ruggedness of the topography.

The last glacial maximum and late glacial environmental and climate dynamics in the Baikal region inferred from an oxygen isotope record of lacustrine diatom silica

The last glacial maximum and late glacial environmental and climatic variability in the Baikal region, southern Siberia, Russia has been studied in a sediment sequence from Lake Kotokel, located 2 km east of Lake Baikal, using the oxygen isotope composition of diatom silica (δ18Odiatom). The purification of diatom frustules involved the process of trimethylsilylation, which has been shown to be suitable for preparation of diatoms for oxygen isotope analysis. The Lake Kotokel δ18Odiatom record presented here spans intervals from about 24.6 to 22.9 ka BP (further referred to as ‘last glacial maximum’) and ∼16.7–11.5 ka BP (further referred to as ‘late glacial’) displaying variations in the oxygen isotope composition between +26.7 and +31.2‰. Overall high δ18Odiatom values of about +29 to +31‰ during the two investigated intervals characterize a strongly evaporative lake system in a dry environment and suggest a lower than present lake level due to enhanced evaporation. The Lake Kotokel diatom isotope record is roughly in line with the 60° N summer solar insolation, pointing to a linkage to broader-scale climate change, but displays weaker reaction to short-term climatic oscillations, i.e. Bølling-Allerød or Younger Dryas. The climate warming at ∼14.3 ka BP is marked by negative spikes in the δ18Odiatom record due to isotopically low melt water input from the mountainous hinterland.

A high-resolution Late Glacial to Holocene record of environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)

Abstract Lake Ohrid (Macedonia/Albania) is the oldest extant lake in Europe and exhibits an outstanding degree of endemic biodiversity. Here, we provide new high-resolution stable isotope and geochemical data from a 10 m core (Co1262) through the Late Glacial to Holocene and discuss past climate and lake hydrology (TIC, δ13Ccalcite, δ18Ocalcite) as well as the terrestrial and aquatic vegetation response to climate (TOC, TOC/N, δ13Corganic, Rock Eval pyrolysis). The data identifies 3 main zones: (1) the Late Glacial–Holocene transition represented by low TIC and TOC contents, (2) the early to mid-Holocene characterised by high TOC and increasing TOC/N and (3) the Late Holocene–Present which shows a marked decrease in TIC and TOC. In general, an overall trend of increasing δ18Ocalcite from 9 ka to present suggests progressive aridification through the Holocene, consistent with previous records from Lake Ohrid and the wider Mediterranean region. Several proxies show commensurate excursions that imply the impact of short-term climate oscillations, such as the 8.2 ka event and the Little Ice Age. This is the best-dated and highest resolution archive of past Late Glacial and Holocene climate from Lake Ohrid and confirms the overriding influence of the North Atlantic in the north-eastern Mediterranean. The data presented set the context for the International Continental scientific Drilling Program Scientific Collaboration On Past Speciation Conditions in Lake Ohrid project cores recovered in spring–summer 2013, potentially dating back into the Lower Pleistocene, and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history.

Late Pleistocene Aeolian Dust Dynamics in Central Asia and their Teleconnection with Short-term Climate Oscillations and Abrupt Climate Events in the Northern Hemisphere

(1) Aberystwyth University, Institute of Geography and Earth Sciences, Aberystwyth, Wales, UK , (2) Humboldt-Universitat zu Berlin, Institute of Geography, Department of Climatology, Unter den Linden 6, D-10099 Berlin, Germany, (b.machalett@nakula.de), (3) Bentley University, Department of Natural and Applied Sciences, Waltham, Massachusetts, USA, (4) Harvard University, Applied Mathematics, Cambridge, Massachusetts, USA, (5) Chinese Academy of Science (CAS), Qinghai Institute of Salt Lakes, Xining, China