Search results for "geoscience"
showing 10 items of 58 documents
Abrupt Alnus population decline at the end of the first millennium CE in Europe - The event ecology, possible causes and implications
2019
The study, based on the examination of 70 published and unpublished pollen profiles from Poland and supplementary data from the surrounding regions, shows that an abrupt, episodic Alnus population decline at the end of the first millennium CE was a much more widespread event than has been previously reported, spanning large areas of the temperate and boreal zones in Europe. The data from Poland suggest that the decline was roughly synchronous and most likely occurred between the 9th and 10th centuries, with strong indications for the 10th century. The pollen data indicate that human impacts were not a major factor in the event. Instead, we hypothesize that one or a series of abrupt climatic…
A 5500-year oxygen isotope record of high arctic environmental change from southern Spitsbergen
2017
The oxygen isotope composition of chironomid head capsules in a sediment core spanning the past 5500 years from Lake Svartvatnet in southern Spitsbergen was used to reconstruct the oxygen isotope composition of lake water (δ18Olw) and local precipitation. The δ18Olw values display shifts from the baseline variability consistent with the timing of recognized historical climatic episodes, such as the Roman Warm Period, the Dark Ages Cold Period and the ‘Little Ice Age’. The highest values of the record, ca. 3‰ above modern δ18Olw values, occur at ca. 1900–1800 cal. yr BP. Three negative excursions increasing in intensity toward the present, at 3400–3200, 1250–1100, and 350–50 cal. yr BP, are…
Cyanophyte calcification morphotypes and depositional environments (Alenquer oncolite, upper Kimmeridgian?, Portugal)
1985
Terrigenous red siliciclastics of Upper Kimmeridgian(?) to Portlandian age around Alenguer, Portugal, comprise a narrow level of oncoid-bearing limestones. Oncoid cortices are composed of cyanophytes which appear in different calcification morphotypes according to changing physico-chemical parameters. Recent examples reveal that in most cases each calcification morphotype is related to one single species or one defined association. Hence, the characteristic calcification patterns are mostly biologically rather than abiogenetically controlled. Oncoid shapes, sizes and arrangement, on the other hand, are mainly determined by the hydraulic parameter within the depositional environment.
Establishing the representativeness of available surface water scenarios for plant protection products in environmental risk assessment Opinion of th…
2021
Methodology for the estimation of the increase in time loss due to future increase in tropical cyclone intensity in Japan
2009
Published version of an article from the journal: Climatic Change. The original publication is available at Spingerlink. http://dx.doi.org/10.1007/s10584-009-9725-9 The present paper develops a methodology for estimating the risks and consequences of possible future increases in tropical cyclone intensities that would allow policy makers to relatively quickly evaluate the cost of different mitigation strategies. The methodology simulates future tropical cyclones by modifying the intensity of historical tropical cyclones between the years 1978 and 2007. It then uses a Monte Carlo Simulation to obtain the expected number of hours that a certain area can expect to be affected by winds of a giv…
The Raunis section, central Latvia, revisited: first luminescence results and re-evaluation of a key Baltic States stratigraphic site
2020
This is an Accepted Manuscript version of the following article: Kalińska, E., Alexanderson, H. & Krievāns, M. (2020). The Raunis section, central Latvia, revisited: first luminescence results and re-evaluation of a key Baltic States stratigraphic site. Geografiska Annaler: Series A, Physical Geography, 102(4), 376-396. It is deposited under the terms of the Creative Commons Attribution-NonCommercial License, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. In interstadial deposits, sand interbeds gain limited consideration in comparison with organic sediments, and therefore tend to be underrepresented in paleoe…
Regional climate model simulations for Europe at 6 and 0.2 k BP: sensitivity to changes in anthropogenic deforestation
2014
International audience; This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climate at two contrasting periods in the Holocene, ∼ 6 and ∼ 0.2 k BP in Eu-rope. We apply the Rossby Centre regional climate model RCA3, a regional climate model with 50 km spatial resolution, for both time periods, considering three alternative descriptions of the past vegetation: (i) potential natural vegetation (V) simulated by the dynamic vegetation model LPJ-GUESS, (ii) potential vegetation with anthro-pogenic land use (deforestation) from the HYDE3.1 (History Database of the Global Environment) scenario (V + H3.1), and (iii) potential vegetation with anthropogenic land …
The Potsdam Open Source Radio Interferometry Tool (PORT)
2021
The Potsdam Open Source Radio Interferometry Tool (PORT) is the very long baseline interferometry (VLBI) analysis software developed and maintained at the GFZ German Research Centre for Geosciences. Chiefly, PORT is tasked with the timely processing of VLBI sessions and post-processing activities supporting the generation of celestial and terrestrial reference frames. In addition, it serves as a framework for research and development within the GFZ's VLBI working group and is part of the tool set employed in educating young researchers. Starting out from VLBI group delays, PORT estimates station and radio sources positions, as well as Earth orientation parameters, tropospheric parameters, a…
Seasonal and Inter-annual Variation of Evapotranspiration in Amazonia Based on Precipitation, River Discharge and Gravity Anomaly Data
2019
We analyzed seasonal and spatial variations of evapotranspiration (ET) for five Amazon sub-basins and their response to the 2015/16 El Nino episode using a recently developed water-budget approach. ET varied typically between similar to 7 and 10 cm/month with exception of the Xingu basin for which it varied between 10 and 15 cm/month. Outstanding features of ET seasonality are (i) generally weak seasonality, (ii) two ET peaks for the two very wet catchments Solimoes and Negro, with one occurring during the wet season and one during the drier season, and (iii) a steady increase of ET during the second half of the dry season for the three drier catchments (Madeira, Tapajos, Xingu). Peak ET oc…
Formation and significance of black pebbles from the ota limestone (Upper Jurassic, Portugal)
1987
Black pebbles are a characteristic facies element of the Upper Jurassic Ota carbonate bank (Portugal). They occur both scattered or concentrated in two horizons, the upper of which is very widespread and may serve as a lithostratigraphic correlation level.