TY - JOUR A1 - Biskaborn, Boris K. A1 - Subetto, D. A. A1 - Savelieva, L. A. A1 - Vakhrameeva, P. S. A1 - Hansche, A. A1 - Herzschuh, Ulrike A1 - Klemm, J. A1 - Heinecke, L. A1 - Pestryakova, Luidmila Agafyevna A1 - Meyer, H. A1 - Kuhn, G. A1 - Diekmann, Bernhard T1 - Late Quaternary vegetation and lake system dynamics in north-eastern Siberia: Implications for seasonal climate variability JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Although the climate development over the Holocene in the Northern Hemisphere is well known, palaeolimnological climate reconstructions reveal spatiotemporal variability in northern Eurasia. Here we present a multi-proxy study from north-eastern Siberia combining sediment geochemistry, and diatom and pollen data from lake-sediment cores covering the last 38,000 cal. years. Our results show major changes in pyrite content and fragilarioid diatom species distributions, indicating prolonged seasonal lake-ice cover between similar to 13,500 and similar to 8900 cal. years BP and possibly during the 8200 cal. years BP cold event. A pollen-based climate reconstruction generated a mean July temperature of 17.8 degrees C during the Holocene Thermal Maximum (HTM) between similar to 8900 and similar to 4500 cal. years BP. Naviculoid diatoms appear in the late Holocene indicating a shortening of the seasonal ice cover that continues today. Our results reveal a strong correlation between the applied terrestrial and aquatic indicators and natural seasonal climate dynamics in the Holocene. Planktonic diatoms show a strong response to changes in the lake ecosystem due to recent climate warming in the Anthropocene. We assess other palaeolimnological studies to infer the spatiotemporal pattern of the HTM and affirm that the timing of its onset, a difference of up to 3000 years from north to south, can be well explained by climatic teleconnections. The westerlies brought cold air to this part of Siberia until the Laurentide ice sheet vanished 7000 years ago. The apparent delayed ending of the HTM in the central Siberian record can be ascribed to the exceedance of ecological thresholds trailing behind increases in winter temperatures and decreases in contrast in insolation between seasons during the mid to late Holocene as well as lacking differentiation between summer and winter trends in paleolimnological reconstructions. (C) 2015 Elsevier Ltd. All rights reserved. KW - Diatoms KW - Pollen KW - Summer and winter temperature KW - Holocene Thermal Maximum KW - Aquatic and terrestrial ecosystems KW - Lake-ice cover Y1 - 2016 U6 - https://doi.org/10.1016/j.quascirev.2015.08.014 SN - 0277-3791 VL - 147 SP - 406 EP - 421 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Fritz, Michael A1 - Opel, Thomas A1 - Tanski, George A1 - Herzschuh, Ulrike A1 - Meyer, H. A1 - Eulenburg, A. A1 - Lantuit, Hugues T1 - Dissolved organic carbon (DOC) in Arctic ground ice JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg L-1 (mean: 9.6 mg L-1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km(2). This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost car-bon pool for ecosystems and climate feedback upon mobilization. Y1 - 2015 U6 - https://doi.org/10.5194/tc-9-737-2015 SN - 1994-0416 SN - 1994-0424 VL - 9 IS - 2 SP - 737 EP - 752 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Koebnick, Corinna A1 - Wagner, K. A1 - Thielecke, F. A1 - Dieter, G. A1 - Hohne, A. A1 - Franke, A. A1 - Garcia, Ada A1 - Meyer, H. A1 - Hoffmann, I. A1 - Leitzmann, P. A1 - Trippo, U. A1 - Zunft, Hans-Joachim Franz T1 - An easy-to-use semiquantitative food record validated for energy intake by using doubly labelled water technique N2 - Background: Estimating dietary intake is important for both epidemiological and clinical studies, but often lacks accuracy. Objective: To investigate the accuracy and validity of energy intake estimated by an easy-to-use semiquantitative food record (EISQFR) compared to total energy expenditure ( TEE) estimated by doubly labelled water technique (EEDLW). Design: TEE was measured in 29 nonobese subjects using the doubly labelled water method over a period of 14 days. Within this period, subjects reported their food consumption by a newly developed semiquantitative food record for 4 consecutive days. Energy intake was calculated using the German Food Code and Nutrition Data Base BLS II.3. Results: A good correlation was observed between EISQFR and EEDLW (r = 0.685, P<0.001). The mean difference between EISQFR and EEDLW was - 1.7 +/- 2.6 MJ/ day ( - 14 +/- 21%, P = 0.002). An underestimation of EISQFR <10% was observed in nine subjects (31%), of 10 - 20% in six subjects (21%), and of >20% in nine subjects (31%). In five subjects (17%), an overestimation of EISQFR was observed. Conclusions: The easy-to-use semiquantitative food record provided good estimates of EI in free-living and nonobese adults without prior detailed verbal instructions. The presented food record has limitations regarding accuracy at the individual level Y1 - 2005 SN - 0954-3007 ER - TY - JOUR A1 - Koebnick, Corinna A1 - Wagner, K. A1 - Thielecke, F. A1 - Moeseneder, Jutta A1 - Hoehne, A. A1 - Franke, A. A1 - Meyer, H. A1 - Garcia, Ada A1 - Trippo, U. A1 - Zunft, Hans-Joachim Franz T1 - Validation of a simplified physical activity record by doubly labeled water technique N2 - INTRODUCTION: For obtaining reliable information about physical activity in epidemiological studies, validated and easy-to-use instruments are required. Therefore, a new simplified physical activity record based on 15-min recording intervals was developed and validated. SUBJECTS: Nonobese volunteers (n = 31). MEASUREMENTS: Physical activity was recorded over a 7-day period without detailed instructions. Energy expenditure was calculated (EEsPAR) and compared to energy expenditure measured by doubly labelled water technique (EEDLW). RESULTS: A good agreement between EEsPAR (12.1 +/ 3.0) and EEDLW (11.7 +/- 3.3) with a mean difference of 0.33 +/- 1.55 MJ (r = 0.880, P < 0.001) was observed. The absolute difference between EEsPAR and EEDLW was <10% in 65% of the subjects. The difference between EEsPAR and EEDLW was independent of gender, age, body weight, and body mass index. A weak positive association between the difference and total body fat was observed (r = 0.618, P < 0.001), suggesting a slight tendency to overestimate EEsPAR with increasing total body fat. CONCLUSION: The new simplified physical activity protocol needs no detailed instructions, provides valid estimates of physical activity in nonobese free-living adults and can be used in epidemiological studies to assess total daily energy expenditure and physical activity level Y1 - 2005 SN - 0307-0565 ER -