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  • 1
    Publication Date: 2016-05-14
    Description: Time-series of varve properties and geochemistry were established from varved sediments of Lake Woserin (north-eastern Germany) covering the recent period AD 2010–1923 and the mid-Holocene time-window 6400–4950 varve years before present (vyr BP) using microfacies analyses, x-ray fluorescence (µ-XRF) scanning, microscopic varve chronology, and 14 C dating. The microscopic varve chronology was compared with a macroscopic varve chronology for the same sediment interval. Calcite layer thickness during the recent period is significantly correlated to increases in local annual precipitation ( r = 0.46, p = 0.03) and reduced air-pressure ( r = –0.72, p 〈 0.0001). Meteorologically consistent with enhanced precipitation at Lake Woserin, a composite 500 hPa anomaly map for years with 〉1 standard deviation calcite layer thickness depicts a negative wave train air-pressure anomaly centered over southern Europe, with north-eastern Germany at its northern frontal zone. Three centennial-scale intervals of thicker calcite layers around the mid-Holocene periods 6200–5900, 5750–5400, and 5300–4950 vyr BP might reflect humid conditions favoring calcite precipitation through the transport of Ca 2+ ions into Lake Woserin, synchronous to wetter conditions in Europe. Calcite layer thickness oscillations of about 88 and 208 years resemble the solar Gleissberg and Suess cycles suggesting that the recorded hydroclimate changes in north-eastern Germany are modified by solar influences on synoptic-scale atmospheric circulation. However, parts of the periods of thicker calcite layers around 5750–5400 and 5200 vyr BP also coincide with enhanced human catchment activity at Lake Woserin. Therefore, calcite precipitation during these time-windows might have further been favored by anthropogenic deforestation mobilizing Ca 2+ ions and/or lake eutrophication.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 2
    Publication Date: 2016-05-14
    Description: Annually laminated sediments of Lake Woserin in north-eastern Germany are investigated using sedimentological and palynological methods. They facilitate high-resolution reconstruction of environmental and land-use change during ca. 7000–4000 cal. BP. Between 6100 and 5800 cal. BP, changes in woodland composition and structure are evident which coincide with a change in subsistence strategy, that is, the adoption of animal husbandry. For the remaining period, eight phases of enhanced human impact (5750–5390, 5270–5150, 4890–4750, 4670–4600, 4520–4450, 4390–4350, 4250–4170 and 4070–3930 cal. BP) are identified. Hereby, the first phase relates to an opening of the landscape in connection with the adoption of large-scale, extensive cereal cultivation. Phases of decreased human impact are generally characterised by woodland regeneration. Over-regional comparison of the results reveals similar and synchronous fluctuation of human impact in the young moraine area of the south-western Baltic region and hints at a large-scale driver. In order to evaluate the role of environmental change for human activity, evidence for coinciding shifts in palaeoclimate records and their potential implication for human–environment interactions are discussed and generally support the idea that environmental changes played an important role for the cultural development during the Neolithic in Northern Germany. Hereby, climate change probably favoured the adoption of new subsistence strategies during the early Neolithic (6100–5350 cal. BP). Furthermore, the fluctuating human impact during Middle and Younger Neolithic (5350–4100 cal. BP) could indicate a socio-economic system susceptible for short-termed climatic fluctuation.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 3
    Publication Date: 2020-07-12
    Print ISSN: 0899-8418
    Electronic ISSN: 1097-0088
    Topics: Geosciences , Physics
    Published by Wiley
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  • 4
    Publication Date: 2015-10-13
    Description: Solar influences on climate variability are one of the most controversially discussed topics in climate research. We analyze solar forcing of flood frequency in Central Europe on inter-annual to millennial time-scales using daily discharge data of River Ammer (southern Germany) back to AD 1926 and revisiting the 5500 year flood layer time-series from varved sediments of the downstream Lake Ammersee. Flood frequency in the discharge record is significantly correlated to changes in solar activity during solar cycles 16–23 (r = −0.47, p 〈 0.0001, n = 73). Flood layer frequency (n = 1501) in the sediment record depicts distinct multi-decadal variability and significant correlations to 10Be fluxes from a Greenland ice core (r = 0.45, p 〈 0.0001) and 14C production rates (r =0.36, p 〈 0.0001), proxy records of solar activity. Flood frequency is higher when solar activity is reduced. These correlations between flood frequency and solar activity might provide empirical support for the solar top-down mechanism expected to modify the mid-latitude storm tracks over Europe by model studies. A lag of flood frequency responses in the Ammer discharge record to changes in solar activity of about one to three years could be explained by a modelled ocean–atmosphere feedback delaying the atmospheric reaction to solar activity variations up to a few years.
    Print ISSN: 1814-9340
    Electronic ISSN: 1814-9359
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 5
    Publication Date: 2015-09-21
    Description: The relationship between the frequency of River Ammer floods (southern Germany) and atmospheric circulation variability is investigated based on observational Ammer discharge data back to 1926 and a flood layer time series from varved sediments of the downstream Lake Ammersee for the pre-instrumental period back to 1766. A composite analysis reveals that, at synoptic time scales, observed River Ammer floods are associated with enhanced moisture transport from the Atlantic Ocean and the Mediterranean towards the Ammer region, a pronounced trough over Western Europe as well as enhanced potential vorticity at upper levels. We argue that this synoptic scale configuration can trigger heavy precipitation and floods in the Ammer region. Interannual to multidecadal increases in flood frequency as recorded in the instrumental discharge record are associated to a wave-train pattern extending from the North Atlantic to western Asia with a prominent negative center over western Europe. A similar atmospheric circulation pattern is associated to increases in flood layer frequency in the Lake Ammersee sediment record during the pre-instrumental period. We argue that the complete flood layer time-series from Lake Ammersee sediments covering the last 5500 years, contains information about atmospheric circulation variability on inter-annual to millennial time-scales.
    Print ISSN: 1814-9340
    Electronic ISSN: 1814-9359
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
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    JOHN WILEY & SONS LTD
    In:  EPIC3International Journal of Climatology, JOHN WILEY & SONS LTD, 41(S1), pp. E644-E655, ISSN: 0899-8418
    Publication Date: 2021-02-15
    Description: The relationship between River Ammer flood frequency variability, extreme summer climate over Europe, and solar forcing is investigated. First, we used observational data to evaluate extreme weather and climate anomaly patterns associated with flood and solar forcing as well as the possible dynamical mechanisms behind them. Then, the annual resolution flood layer record from the Lake Ammer sediments is analysed to evaluate millennial‐scale variability of floods and possible related extreme climate patterns back to 5,500 years BP. A composite analysis reveals that observed River Ammer flood frequency variability at interannual to multidecadal time scales is connected to large‐scale extreme precipitation and temperature patterns. From a synoptic‐scale perspective, the extreme precipitation pattern associated with floods is related to an increase in the frequency of high upper‐level potential vorticity (PV) events over western Europe and a decrease over eastern Europe and western Russia. Increased (decreased) frequency of upper‐level high PV events is related to more (less) surface extreme precipitation occurrence. Furthermore, we show that increased frequency of upper‐level high PV events over western Europe is associated with enhanced blocking activity over eastern Europe. Therefore, the out of phase interannual to millennial‐scale variations of River Ammer flood frequency and solar irradiance, as presented in previous studies, can be explained by a solar modulation of eastern European‐western Russia summer blocking and associated upstream upper‐level wave breaking activity. In addition, we identify two distinct quasi‐periodic signals in both frequency of Lake Ammer flood layer and solar irradiance records with periods of ~900 years and ~2,300 years. We argue that similar cycles should dominate millennial‐scale variations of blocking activity in eastern Europe‐western Russia as well as extreme precipitation and flood frequency variability over central and western Europe during the last ~5,500 years.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
    Publication Date: 2021-10-26
    Description: The relationship between River Ammer flood frequency variability, extreme summer climate over Europe, and solar forcing is investigated. First, we used observational data to evaluate extreme weather and climate anomaly patterns associated with flood and solar forcing as well as the possible dynamical mechanisms behind them. Then, the annual resolution flood layer record from the Lake Ammer sediments is analysed to evaluate millennial-scale variability of floods and possible related extreme climate patterns back to 5,500 years BP. A composite analysis reveals that observed River Ammer flood frequency variability at interannual to multidecadal time scales is connected to large-scale extreme precipitation and temperature patterns. From a synoptic-scale perspective, the extreme precipitation pattern associated with floods is related to an increase in the frequency of high upper-level potential vorticity (PV) events over western Europe and a decrease over eastern Europe and western Russia. Increased (decreased) frequency of upper-level high PV events is related to more (less) surface extreme precipitation occurrence. Furthermore, we show that increased frequency of upper-level high PV events over western Europe is associated with enhanced blocking activity over eastern Europe. Therefore, the out of phase interannual to millennial-scale variations of River Ammer flood frequency and solar irradiance, as presented in previous studies, can be explained by a solar modulation of eastern European-western Russia summer blocking and associated upstream upper-level wave breaking activity. In addition, we identify two distinct quasi-periodic signals in both frequency of Lake Ammer flood layer and solar irradiance records with periods of ~900 years and ~2,300 years. We argue that similar cycles should dominate millennial-scale variations of blocking activity in eastern Europe-western Russia as well as extreme precipitation and flood frequency variability over central and western Europe during the last ~5,500 years.
    Keywords: 551.6 ; floods ; extreme precipitation ; potential vorticity ; solar forcing
    Language: English
    Type: map
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  • 8
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/conferenceObject
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  • 9
    Publication Date: 2020-02-12
    Description: Solar modulated variations in cosmogenic radionuclide production provide both information on past changes in the activity of the Sun and a global synchronization tool. However, to date the use of cosmogenic radionuclides for these applications is almost exclusively based on 10Be records from ice cores and 14C time-series from tree rings, all including archive-specific limitations. We present the first 10Be record from annually laminated (varved) lake sediments for the Lateglacial-Holocene transition from Meerfelder Maar. We quantify environmental influences on the catchment and, consequently, 10Be deposition using a new approach based on regression analyses between our 10Be record and environmental proxy time-series from the same archive. Our analyses suggest that environmental influences contribute to up to 37% of the variability in our 10Be record, but cannot be the main explanation for major 10Be excursions. Corrected for these environmental influences, our 10Be record is interpreted to dominantly reflect changes in solar modulated cosmogenic radionuclide production. The preservation of a solar production signal in 10Be from varved lake sediments highlights the largely unexplored potential of these archives for solar activity reconstruction, as global synchronization tool and, thus, for more robust paleoclimate studies.
    Type: info:eu-repo/semantics/article
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  • 10
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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