scholarly journals Pollen-based temperature and precipitation changes in the Ohrid Basin (western Balkans) between 160 and 70 ka

2018 ◽  
Author(s):  
Gaia Sinopoli ◽  
Odile Peyron ◽  
Alessia Masi ◽  
Jens Holtvoeth ◽  
Alexander Francke ◽  
...  
Keyword(s):  
Weighted Averaging ◽  
Stable Phase ◽  
Time Interval ◽  
Least Squares Regression ◽  
Last Interglacial ◽  
Lake Ohrid ◽  
The Balkans ◽  
Climate Reconstructions ◽  
Dry Conditions ◽  
Mis 5

Abstract. Our study aims to reconstruct climate changes that occurred at Lake Ohrid (south-western Balkan Peninsula), the oldest extant lake in Europe, between 160 and 70 ka (covering part of Marine Isotope Stage – "MIS" - 6 and all of MIS 5). A multi-method approach, including the "Modern Analogues Technique" and the "Weighted Averaging Partial Least-Squares Regression", is applied to the high-resolution pollen sequence of the DEEP site, collected from the central part of Lake Ohrid, to provide quantitative estimates of climate and bioclimate parameters. This allows us to document climatic change during the key periods of MIS 6 and MIS 5 in South Europe, a region where accurate climate reconstructions are still lacking for this time interval. Our results for the penultimate glacial show cold and dry conditions, while the onset of the Last Interglacial is characterized by wet and warm conditions, with temperatures higher than today (by ca. 2 °C). The Eemian in the Balkans was not a stable phase and a climatic tri-partition, with an initial phase of abrupt warming (128–121 ka), a central phase with decreasing temperatures associated to wet conditions (121–118 ka), followed by a phase of progressive change towards cold and dry conditions (118–112 ka), is evident. After the Eemian, an alternation of four warm/wet periods with cold/dry ones, likely related to the succession of Greenland stadials and cold events known from the North Atlantic, occurred. The observed pattern is also consistent with hydrological and isotopic data from the central Mediterranean. The Lake Ohrid climate reconstruction shows greater similarity with climate patterns inferred from northern European pollen records than with southern European ones, which is probably due to its intermediate position and the mountainous setting. However, this hypothesis needs further testing as very few climate reconstructions are available for southern Europe for this key time period.

scholarly journals Pollen-based temperature and precipitation changes in the Ohrid Basin (western Balkans) between 160 and 70 ka

2019 ◽  
Vol 15 (1) ◽  
pp. 53-71 ◽  
Author(s):  
Gaia Sinopoli ◽  
Odile Peyron ◽  
Alessia Masi ◽  
Jens Holtvoeth ◽  
Alexander Francke ◽  
...  
Keyword(s):  
Weighted Averaging ◽  
Time Interval ◽  
Southern Europe ◽  
Least Squares Regression ◽  
Last Interglacial ◽  
Lake Ohrid ◽  
The Balkans ◽  
Climate Reconstructions ◽  
Dry Conditions ◽  
Mis 5

Abstract. Our study aims to reconstruct climate changes that occurred at Lake Ohrid (south-western Balkan Peninsula), the oldest extant lake in Europe, between 160 and 70 ka (covering part of marine isotope stage 6, MIS 6; all of MIS 5; and the beginning of MIS 4). A multi-method approach, including the “Modern Analog Technique” and the “Weighted Averaging Partial Least-Squares Regression”, is applied to the high-resolution pollen sequence of the DEEP site, collected from the central part of Lake Ohrid, to provide quantitative estimates of climate and bioclimate parameters. This allows us to document climatic change during the key periods of MIS 6 and MIS 5 in southern Europe, a region where accurate climate reconstructions are still lacking for this time interval. Our results for the penultimate glacial show cold and dry conditions, while the onset of the “last interglacial” is characterized by wet and warm conditions, with temperatures higher than today (by ca. 2 ∘C). The Eemian also shows the well-known climatic tri-partition in the Balkans, with an initial pre-temperate phase of abrupt warming (128–121 ka), a central temperate phase with decreasing temperatures associated with wet conditions (121–118 ka), followed by a post-temperate phase of progressive change towards cold and dry conditions (118–112 ka). After the Eemian, an alternation of four warm/wet periods with cold/dry ones, likely related to the succession of Greenland stadials and cold events known from the North Atlantic, occurred. The observed pattern is also consistent with hydrological and isotopic data from the central Mediterranean. The Lake Ohrid climate reconstruction shows greater similarity with climate patterns inferred from northern European pollen records than with southern European ones, which is probably due to its intermediate position and the mountainous setting. However, this hypothesis needs further testing as very few climate reconstructions are available for southern Europe for this key time period.

scholarly journals Seasonal temperature and moisture changes in interior semi‐arid Spain from the last interglacial to the Late Holocene

2021 ◽  
pp. 1-13
Author(s):  
Dongyang Wei ◽  
Penélope González-Sampériz ◽  
Graciela Gil-Romera ◽  
Sandy P. Harrison ◽  
I. Colin Prentice
Keyword(s):  
Late Holocene ◽  
Potential Evapotranspiration ◽  
Weighted Averaging ◽  
Pollen Record ◽  
Seasonal Temperature ◽  
Last Interglacial ◽  
Mis 3 ◽  
Summer Warming ◽  
Temperature Seasonality ◽  
Mis 5

Abstract The El Cañizar de Villarquemado pollen record covers the last part of MIS 6 to the Late Holocene. We use Tolerance-Weighted Averaging Partial Least Squares (TWA-PLS) to reconstruct mean temperature of the coldest month (MTCO) and growing degree days above 0°C (GDD0) and the ratio of annual precipitation to annual potential evapotranspiration (MI), accounting for the ecophysiological effect of changing CO2 on water-use efficiency. Rapid summer warming occurred during the Zeifen-Kattegat Oscillation at the transition to MIS 5. Summers were cold during MIS 4 and MIS 2, but some intervals of MIS 3 had summers as warm as the warmest phases of MIS 5 or the Holocene. Winter temperatures declined from MIS 4 to MIS 2. Changes in temperature seasonality within MIS 5 and MIS 1 are consistent with insolation seasonality changes. Conditions became progressively more humid during MIS 5, and MIS 4 was also humid, although MIS 3 was more arid. Changes in MI and GDD0 are anti-correlated, with increased MI during summer warming intervals. Comparison with other records shows glacial-interglacial changes were not unform across the circum-Mediterranean region, but available quantitative reconstructions are insufficient to determine if east-west differences reflect the circulation-driven precipitation dipole seen in recent decades.

scholarly journals Excursions to C<sub>4</sub> vegetation recorded in the Upper Pleistocene loess of Surduk (Northern Serbia): an organic isotope geochemistry study

2013 ◽  
Vol 9 (3) ◽  
pp. 1001-1014 ◽  
Author(s):  
C. Hatté ◽  
C. Gauthier ◽  
D.-D. Rousseau ◽  
P. Antoine ◽  
M. Fuchs ◽  
...  
Keyword(s):  
General Pattern ◽  
Free Water ◽  
Circulation Pattern ◽  
Water Evaporation ◽  
C3 Plants ◽  
Mean Annual Precipitation ◽  
Glacial Cycle ◽  
Last Interglacial ◽  
The Balkans ◽  
The Mediterranean

Abstract. Loess sequences have been intensively studied to characterize past glacial climates of the 40–50° north and south latitude zones. Combining different approaches of sedimentology, magnetism, geochemistry, geochronology and malacology allows the general pattern of the climate and environment of the last interglacial–glacial cycle in Eurasia and America to be characterized. Previous studies performed in Europe have highlighted the predominance (if not the sole occurrence) of C3 vegetation. The presence of C3 plants suggests a regular distribution of precipitation along the year. Therefore, even if the mean annual precipitation remained very low during the most extensive glacial times, free water was available for more than 2 months per year. Contrarily, the δ13C record of Surduk (Serbia) clearly shows the occurrence and dominance of C4 plants during at least 4 episodes of the last glacial times at 28.0–26.0 kyr cal BP, 31.4–30.0 kyr cal BP, 53.4–44.5 kyr cal BP and 86.8–66.1 kyr. The C4 plant development is interpreted as a specific atmospheric circulation pattern that induces short and dry summer conditions. As possible explanation, we propose that during "C4 episodes", the Mediterranean Sea would have been under the combined influence of the following: (i) a strong meridional circulation unfavorable to water evaporation that reduced the Mediterranean precipitation on the Balkans; and (ii) a high positive North Atlantic Western Russian (NA/WR)-like atmospheric pattern that favored northerlies over westerlies and reduced Atlantic precipitation over the Balkans. This configuration would imply very dry summers that did not allow C3 plants to grow, thus supporting C4 development. The intra-"C4 episode" periods would have occurred under less drastic oceanic and atmospheric patterns that made the influence of westerlies on the Balkans possible.

scholarly journals Sediment core fossils in ancient Lake Ohrid: testing for faunal change in molluscs since the Last Interglacial period

2010 ◽  
Vol 7 (3) ◽  
pp. 3969-3999 ◽  
Author(s):  
C. Albrecht ◽  
H. Vogel ◽  
T. Hauffe ◽  
T. Wilke
Keyword(s):  
Sediment Core ◽  
Fossil Record ◽  
Interglacial Period ◽  
Ancient Lake ◽  
Last Interglacial ◽  
Lake Ohrid ◽  
Last Interglacial Period ◽  
History Of ◽  
Extinction Events ◽  
Mollusc Shells

Abstract. Ancient Lake Ohrid is probably of early Pleistocene or Pliocene origin and amongst the few lakes in the world harboring an outstanding degree of endemic biodiversity. Although there is a long history of evolutionary research in Lake Ohrid, particularly on molluscs, a mollusc fossil record has been missing up to date. For the first time, gastropod and bivalve fossils are reported from the basal, calcareous part of a 2.6 m long sediment succession (core Co1200) from the north-eastern part of Lake Ohrid. Electron spin resonance (ESR) dating of mollusc shells from the same stratigraphic level yielded an age of 130±28 ka. Lithofacies III sediments, i.e. a subdivision of the stratigraphic unit comprising the basal succession of core Co1200 between 181.5–263 cm appeared solid, grayish-white, and consisted almost entirely of silt-sized endogenic calcite (CaCO3>70%) and intact and broken mollusc shells. Here we compare the faunal composition of the thanatocoenosis with recent mollusc associations in Lake Ohrid. A total of 13 mollusc species (9 gastropod and 4 bivalve species) could be identified within Lithofacies III sediments. The value of sediment core fossils for reconstructing palaeoenvironmental settings was evaluated. The agreement between sediment and palaeontological proxies was tested. The combined findings of the ecological study and the sediment characteristics suggest deposition in a shallow water environment during the Last Interglacial period. We tested for major faunal changes since the Last Interglacial period and searched for signs of extinction events. The fossil fauna exclusively included species also found in the present fauna, i.e. no extinction events are evident for this site since the Last Interglacial. The thanatocoenosis showed the highest similarity with recent Intermediate Layer (5–25 m) mollusc assemblages. The demonstrated existence of a mollusc fossil record in Lake Ohrid sediment cores also has great significance for future deep drilling projects. It can be hoped that a more far reaching mollusc fossil record will then be obtained, enabling insight into the early evolutionary history of Lake Ohrid.

scholarly journals Sensitivity of Red Sea circulation to sea level and insolation forcing during the last interglacial

2011 ◽  
Vol 7 (2) ◽  
pp. 1195-1233 ◽  
Author(s):  
G. Trommer ◽  
M. Siccha ◽  
E. J. Rohling ◽  
K. Grant ◽  
M. T. J. van der Meer ◽  
...  
Keyword(s):  
Sea Level ◽  
Red Sea ◽  
Planktonic Foraminifera ◽  
Gulf Of Aden ◽  
Last Interglacial ◽  
The Holocene ◽  
Circulation Mode ◽  
Monsoon Strength ◽  
Mis 5E ◽  
Mis 5

Abstract. This study investigates the response of Red Sea circulation to sea level and insolation changes during termination II and across the last interglacial, in comparison with termination I and the Holocene. Sediment cores from the central and northern part of the Red Sea were investigated by micropaleontological and geochemical proxies. The recovery of the planktonic foraminiferal fauna following high salinities during MIS 6 took place at similar sea-level stand (~50 m below present day), and with a similar species succession, as during termination I. This indicates a consistent sensitivity of the basin oceanography and the plankton ecology to sea-level forcing. Based on planktonic foraminifera, we find that increased water exchange with the Gulf of Aden especially occurred during the sea-level highstand of interglacial MIS 5e. From MIS 6 to the peak of MIS 5e, northern Red Sea SST increased from 21 °C to 25 °C, with about 3 °C of this increase taking place during termination II. Changes in planktonic foraminiferal assemblages indicate that the development of the Red Sea oceanography during MIS 5 was strongly determined by insolation and monsoon strength. The SW Monsoon summer circulation mode was enhanced during the termination, causing low productivity in northern central Red Sea core KL9, marked by high abundance of G. sacculifer, which – as in the Holocene – followed summer insolation. Core KL11 records the northern tip of the intruding intermediate water layer from the Gulf of Aden and its planktonic foraminifera fauna shows evidence for elevated productivity during the sea-level highstand in the southern central Red Sea. By the time of MIS 5 sea-level regression, elevated organic biomarker BIT values suggest denudation of soil organic matter into the Red Sea and high abundances of G. glutinata, and high reconstructed chlorophyll-a values, indicate an intensified NE Monsoon winter circulation mode. Our results imply that the amplitude of insolation fluctuations, and the resulting monsoon strength, strongly influence the Red Sea oceanography during sea-level highstands by regulating the intensity of water exchange with the Gulf of Aden. These processes are responsible for the observation that MIS 5e/d is characterized by higher primary productivity than the Holocene.

scholarly journals Exceptional warmth and climate instability occurred in the European Alps during the Last Interglacial period

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Paul S. Wilcox ◽  
Charlotte Honiat ◽  
Martin Trüssel ◽  
R. Lawrence Edwards ◽  
Christoph Spötl
Keyword(s):  
Greenhouse Gases ◽  
Fluid Inclusions ◽  
Future Climate ◽  
Swiss Alps ◽  
Interglacial Period ◽  
Time Interval ◽  
European Alps ◽  
Reference Period ◽  
Last Interglacial ◽  
Last Interglacial Period

AbstractWarmer temperatures than today, over a period spanning millennia, most recently occurred in the Last Interglacial period, about 129,000 to 116,000 years ago. Yet, the timing and magnitude of warmth during this time interval are uncertain. Here we present a reconstruction of temperatures in the Swiss Alps over the full duration of the Last Interglacial period based on hydrogen isotopes from fluid inclusions in precisely dated speleothems. We find that temperatures were up to 4.0 °C warmer during the Last Interglacial period than in our present-day reference period 1971 to 1990. Climate instability, including an abrupt cooling event about 125,500 years ago, interrupted this thermal optimum but temperatures remained up to 2.0 °C warmer than the present day. We suggest that higher-elevation areas may be more susceptible to warming relative to lowland areas, and that this may hold also for a future climate forced by increasing levels of greenhouse gases.

QUANTIFICATION OF SYNCHRONIZATION PROCESSES BY COHERENCE AND PHASE AND ITS APPLICATION IN ANALYSIS OF ELECTROPHYSIOLOGICAL SIGNALS

2000 ◽  
Vol 10 (11) ◽  
pp. 2565-2586 ◽  
Author(s):  
BÄRBEL SCHACK ◽  
PETER RAPPELSBERGER ◽  
CHRISTOPH ANDERS ◽  
SABINE WEISS ◽  
EVA MÖLLER
Keyword(s):  
Muscle Activity ◽  
Information Transfer ◽  
Word Processing ◽  
Auditory Presentation ◽  
Stable Phase ◽  
Motor Unit Action Potential ◽  
Time Interval ◽  
Frequency Bands ◽  
Functional Relationships ◽  
Electrophysiological Signals

Neuronal activity during information processing and muscle activity are generally characterized by oscillations. Mostly, widespread areas are involved and electrophysiological signals are measured on different sites of the cortex or of the muscle. In order to investigate functional relationships between different components of multidimensional electrophysiological signals, coherence and phase analyses turned out to be useful tools. These parameters allow the investigation of synchronization phenomena with regard to oscillations of defined frequencies or frequency bands. Coherence and phase are closely connected spectral parameters. Coherence may be understood as a measure of phase stability. Whereas coherence describes the amount of common information with regard to oscillations within certain frequency bands, the corresponding phase, from which time delays of these oscillations can be computed, hints at the direction of information transfer through oscillation. Coherence and phase analysis of surface EMG during continuous activity of deep and superficial muscles show distinct differences due to volume conduction properties of myoelectrical signals. Superficial activity therefore is characterized by significant coherence and stable phase relationships, which, additionally, can be used to determine motor unit action potential (MUAP) propagation velocity along the fibre direction without application of invasive methods. Deep muscle activity lacks significant coherence. Mental processes can be very brief and cooperation between different areas may be highly dynamic. For this reason in addition to usual Fourier estimation of coherence and phase, a two-dimensional approach of adaptive filtering was developed to estimate coherence and phase continuously in time. Statistical and dynamic properties of instantaneous phase are discussed. In order to demonstrate the value of this method for studying higher cognitive processes the method was applied to EEG recorded during word processing. During visual presentation of abstract nouns an information transfer through the propagation of oscillations from visual areas to frontal association areas in the α1-frequency band could be verified within the first 400 ms. In contrast, in case of auditory presentation positive phases from the temporal electrode locations T3 and T4 towards the occipital areas appear within the time interval of 300 ms–600 ms. The α1-band predominately seems to reflect sensory processing and attention processes.

Effects of the characteristics of online multimedia synergy on consumers’ message acceptance and message response

2017 ◽  
Vol 41 (5) ◽  
pp. 710-727 ◽  
Author(s):  
Xuebing Dong ◽  
Yaping Chang ◽  
Xiaojun Fan
Keyword(s):  
Information Seeking ◽  
Moderating Effect ◽  
Future Research ◽  
Online Media ◽  
Time Interval ◽  
Least Squares Regression ◽  
Sources Of Information ◽  
Content Type ◽  
Perceived Credibility ◽  
Message Acceptance

Purpose Marketers recognize that the internet is crucial in the lives of consumers; thus, they invest money on online advertisements. Using multiple online media primarily influences the message acceptance of consumers. The synergistic effect of online multimedia relies on form, content, and sources of information, and time. The paper aims to discuss these issues. Design/methodology/approach A model that reflects the influence of the characteristics of online multimedia on message response through message acceptance is established based on theories of information persuasion, encoding variability, and multiple-source assumption. Based on a survey of 411 online media users, the study applies partial least-squares regression to test the research model. Findings The results show that variety of forms, complementary of contents, diversity of sources, and time interval influence message response via message strength. Complementary of contents and diversity of sources affect message response via perceived credibility. Synergy type moderates the relationship between variety of forms and perceived credibility and between diversity of sources and perceived credibility. Research limitations/implications The current study mainly tests the effect of these characteristics on message response and the moderating effect of synergy type. Future research can examine the effect of these characteristics on information seeking and consumption behavior and the moderating effect of the cognitive mode of consumers. Practical implications This study provides insight into the characteristics of synergy and contributes to the literature on integrated marketing communication. The results provide guidance for practitioners to effectively plan online multimedia practices. Originality/value This study explored the influence of the characteristics of online media synergy on message response through message acceptance. The study also discussed the moderating effect of the type of online multimedia synergy.

scholarly journals Last Interglacial (MIS 5) ungulate assemblage from the Central Iberian Peninsula: The Camino Cave (Pinilla del Valle, Madrid, Spain)

2013 ◽  
Vol 374 ◽  
pp. 327-337 ◽  
Author(s):  
Diego J. Álvarez-Lao ◽  
Juan L. Arsuaga ◽  
Enrique Baquedano ◽  
Alfredo Pérez-González
Keyword(s):  
Iberian Peninsula ◽  
Last Interglacial ◽  
Mis 5

scholarly journals The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania): testing diatom response to climate

2010 ◽  
Vol 7 (3) ◽  
pp. 4689-4714 ◽  
Author(s):  
J. M. Reed ◽  
A. Cvetkoska ◽  
Z. Levkov ◽  
H. Vogel ◽  
B. Wagner
Keyword(s):  
Morphological Variability ◽  
Central Area ◽  
Early Holocene ◽  
Future Research ◽  
Lake Basin ◽  
Last Interglacial ◽  
Lake Ohrid ◽  
Concentration Data ◽  
Last Glacial ◽  
The Last Glacial

Abstract. Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacial-interglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 15–7.4 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, following by a post-Medieval cooling trend. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom concentration data in future studies.

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