62 research outputs found

    3D crustal structure of the Ligurian Basin revealed by surface wave tomography using ocean bottom seismometer data

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    The Liguro-Provençal basin was formed as a back-arc basin of the retreating Calabrian–Apennines subduction zone during the Oligocene and Miocene. The resulting rotation of the Corsica–Sardinia block is associated with rifting, shaping the Ligurian Basin. It is still debated whether oceanic or atypical oceanic crust was formed or if the crust is continental and experienced extreme thinning during the opening of the basin. We perform ambient noise tomography, also taking into account teleseismic events, using an amphibious network of seismic stations, including 22 broadband ocean bottom seismometers (OBSs), to investigate the lithospheric structure of the Ligurian Basin. The instruments were installed in the Ligurian Basin for 8 months between June 2017 and February 2018 as part of the AlpArray seismic network. Because of additional noise sources in the ocean, OBS data are rarely used for ambient noise studies. However, we carefully pre-processed the data, including corrections for instrument tilt and seafloor compliance and excluding higher modes of the ambient-noise Rayleigh waves. We calculate daily cross-correlation functions for the AlpArray OBS array and surrounding land stations. We also correlate short time windows that include teleseismic earthquakes, allowing us to derive surface wave group velocities for longer periods than using ambient noise only. We obtain group velocity maps by inverting Green's functions derived from the cross-correlation of ambient noise and teleseismic events. We then used the resulting 3D group velocity information to calculate 1D depth inversions for S-wave velocities. The group velocity and shear-wave velocity results compare well to existing large-scale studies that partly include the study area. We observe a high-velocity area beneath the Argentera Massif in onshore France, roughly 10 km below sea level. We interpret this as the root of the Argentera Massif. Our results add spatial resolution to known seismic velocities in the Ligurian Basin, thereby augmenting existing seismic profiles. The velocity model indicates that the southwestern and north-eastern Ligurian Basin are structurally separate (Figure 1, panel a). In agreement with existing seismic studies, our shear-wave velocity maps indicate a deepening of the Moho from 12 km at the south-western basin centre to 20–25 km at the Ligurian coast in the north-east and over 30 km at the Provençal coast. The lack of high crustal vp/vs ratios beneath the southwestern part of the Ligurian Basin precludes mantle serpentinisation there. The poster summarises the findings published in Solid Earth (Wolf et al. (2021)

    Climate Response of Larch and Birch Forests across an Elevational Transect and Hemisphere-Wide Comparisons, Kamchatka Peninsula, Russian Far East

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    Kamchatka’s forests span across the peninsula’s diverse topography and provide a wide range of physiographic and elevational settings that can be used to investigate how forests are responding to climate change and to anticipate future response. Birch (Betula ermanii Cham.) and larch (Larix gmelinii (Rupr.) Kuzen) were sampled at eight new sites and together with previous collections were compared with monthly temperature and precipitation records to identify their climate response. Comparisons show that tree-ring widths in both species are primarily influenced by May through August temperatures of the current growth year, and that there is a general increase in temperature sensitivity with altitude. The ring-width data for each species were also combined into regional chronologies. The resulting composite larch chronology shows a strong resemblance to a Northern Hemisphere (NH) tree-ring based temperature reconstruction with the larch series tracking NH temperatures closely through the past 300 years. The composite birch ring-width series more closely reflects the Pacific regional coastal late summer temperatures. These new data improve our understanding of the response of forests to climate and show the low frequency warming noted in other, more continental records from high latitudes of the Northern Hemisphere. Also evident in the ring-width record is that the larch and birch forests continue to track the strong warming of interior Kamchatka

    Diverse soil carbon dynamics expressed at the molecular level

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    The stability and potential vulnerability of soil organic matter (SOM) to global change remains incompletely understood due to the complex processes involved in its formation and turnover. Here we combine compound-specific radiocarbon analysis with fraction-specific and bulk-level radiocarbon measurements in order to further elucidate controls on SOM dynamics in a temperate and sub-alpine forested ecosystem. Radiocarbon contents of individual organic compounds isolated from the same soil interval generally exhibit greater variation than those among corresponding operationally-defined fractions. Notably, markedly older ages of long-chain plant leaf wax lipids (n-alkanoic acids) imply that they reflect a highly stable carbon pool. Furthermore, marked 14C variations among shorter- and longer-chain n-alkanoic acid homologues suggest that they track different SOM pools. Extremes in SOM dynamics thus manifest themselves within a single compound class. This exploratory study highlights the potential of compound-specific radiocarbon analysis for understanding SOM dynamics in ecosystems potentially vulnerable to global change

    Velocity structure of the Ligurian Sea (Mediterranean Sea) revealed by ambient noise tomography using ocean bottom seismometer data

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    The Liguro-Provencal-basin was formed as a back-arc basin of the retreating Calabrian-Apennines subduction zone during the Oligocene and Miocene. The resulting rotation of the Corsica-Sardinia block at roughly 32–24 Ma is associated with rifting, shaping the Ligurian Sea. It is highly debated though, whether oceanic or atypical oceanic crust was formed or if the crust is of continental nature, which was extremely thinned during opening of the basin. In order to investigate the velocity structure of the Ligurian Sea a network (LOBSTER) of 29 broadband Ocean Bottom Seismometer (OBS) was installed jointly by GEOMAR (Germany) and ISTerre (France). The LOBSTER array measured continuously for eight months between June 2017 and February 2018 and is part of the AlpArray seismic network. AlpArray is a European initiative to further reveal the geophysical and geological properties of the greater Alpine area. We contribute to the debate by surveying the type of crust and lithosphere flooring the Ligurian Sea. Because of additional noise sources in the ocean, causing instrument tilt or seafloor compliance, OBS data are rarely used for ambient noise studies. However, we extensively pre-process the data to improve the signal-to-noise ratio. Then, we calculate daily cross-correlation functions for the LOBSTER array and surrounding land stations. We use teleseismic events by correlating short time windows that include strong events. Those cross-correlations are dominated by earthquake signals and allow to derive surface wave group velocities for longer periods than using AN. Finally, phase velocity maps are obtained by inverting Green’s functions derived from cross-correlation of ambient noise (AN) and teleseismic events. In the course of this ongoing project we target to derive 3D velocity models of the adjacent Alpine belt region and its complex subduction geometry contributing to questions like the prolongation of the Alpine from beneath the Ligurian Sea

    Control of Gene Expression by the Retinoic Acid-Related Orphan Receptor Alpha in HepG2 Human Hepatoma Cells

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    Retinoic acid-related Orphan Receptor alpha (RORα; NR1F1) is a widely distributed nuclear receptor involved in several (patho)physiological functions including lipid metabolism, inflammation, angiogenesis, and circadian rhythm. To better understand the role of this nuclear receptor in liver, we aimed at displaying genes controlled by RORα in liver cells by generating HepG2 human hepatoma cells stably over-expressing RORα. Genes whose expression was altered in these cells versus control cells were displayed using micro-arrays followed by qRT-PCR analysis. Expression of these genes was also altered in cells in which RORα was transiently over-expressed after adenoviral infection. A number of the genes found were involved in known pathways controlled by RORα, for instance LPA, NR1D2 and ADIPOQ in lipid metabolism, ADIPOQ and PLG in inflammation, PLG in fibrinolysis and NR1D2 and NR1D1 in circadian rhythm. This study also revealed that genes such as G6PC, involved in glucose homeostasis, and AGRP, involved in the control of body weight, are also controlled by RORα. Lastly, SPARC, involved in cell growth and adhesion, and associated with liver carcinogenesis, was up-regulated by RORα. SPARC was found to be a new putative RORα target gene since it possesses, in its promoter, a functional RORE as evidenced by EMSAs and transfection experiments. Most of the other genes that we found regulated by RORα also contained putative ROREs in their regulatory regions. Chromatin immunoprecipitation (ChIP) confirmed that the ROREs present in the SPARC, PLG, G6PC, NR1D2 and AGRP genes were occupied by RORα in HepG2 cells. Therefore these genes must now be considered as direct RORα targets. Our results open new routes on the roles of RORα in glucose metabolism and carcinogenesis within cells of hepatic origin

    Global wood anatomical perspective on the onset of the Late Antique Little Ice Age (LALIA) in the mid-6th century CE

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    Linked to major volcanic eruptions around 536 and 540 CE, the onset of the Late Antique Little Ice Age has been described as the coldest period of the past two millennia. The exact timing and spatial extent of this exceptional cold phase are, however, still under debate because of the limited resolution and geographical distribution of the available proxy archives. Here, we use 106 wood anatomical thin sections from 23 forest sites and 20 tree species in both hemispheres to search for cell-level fingerprints of ephemeral summer cooling between 530 and 550 CE. After cross-dating and double-staining, we identified 89 Blue Rings (lack of cell wall lignification), nine Frost Rings (cell deformation and collapse), and 93 Light Rings (reduced cell wall thickening) in the Northern Hemisphere. Our network reveals evidence for the strongest temperature depression between mid-July and early-August 536 CE across North America and Eurasia, whereas more localised cold spells occurred in the summers of 532, 540–43, and 548 CE. The lack of anatomical signatures in the austral trees suggests limited incursion of stratospheric volcanic aerosol into the Southern Hemisphere extra-tropics, that any forcing was mitigated by atmosphere-ocean dynamical responses and/or concentrated outside the growing season, or a combination of factors. Our findings demonstrate the advantage of wood anatomical investigations over traditional dendrochronological measurements, provide a benchmark for Earth system models, support cross-disciplinary studies into the entanglements of climate and history, and question the relevance of global climate averages. © 2022 Science China PressFritz & Elisabeth Schweingruber FoundationNational Science Foundation, NSF, (1203749, 1902625, 2002454, 2112314, 2124885, RSF 18-14-00072P, RSF 21-14-00330)Engineering Research Centers, ERCEuropean Research Council, ERC, (AdG 882727, CZ.02.1.01/0.0/0.0/16_019/0000797)Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, SNF, (CRSII5 183571)Fondo Nacional de Desarrollo Científico y Tecnológico, FONDECYT, (1201411, 1221307)Vetenskapsrådet, VR, (2018-01272)Universität BielefeldRussian Science Foundation, RSF, (RSF 21-17-00006)Fondo de Financiamiento de Centros de Investigación en Áreas Prioritarias, FONDAP, (15110009, BASAL FB210018)Neurosciences Foundation, NSFAgencia Nacional de Investigación y Desarrollo, ANIDFunding text 1: Ulf Büntgen and Jan Esper received funding from the ERC Advanced Project MONOSTAR (AdG 882727). Ulf Büntgen, Jan Esper, and Mirek Trnka received funding from SustES: adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions (CZ.02.1.01/0.0/0.0/16_019/0000797). Ulf Büntgen, Jan Esper, and Clive Oppenheimer discussed many aspects of this study at the Center for Interdisciplinary Research (ZiF) at the University of Bielefeld, Germany. Alan Crivellaro received funding from the Fritz & Elisabeth Schweingruber Foundation. Duncan A. Christie and Carlos Le Quesne received funding from the ANID (FONDECYT 1201411, 1221307, FONDAP 15110009, BASAL FB210018). Olga V. Churakova (Sidorova) received funding from the Russian Science Foundation grant (RSF 21-17-00006). Rosanne D'Arrigo received funding from NSF Arctic Social Science 2112314 and NSF Arctic Natural Science 2124885, as well as the NSF P2C2 (Paleo Perspectives on Climatic Change) program (various grants). Rashit M. Hantemirov received funding from the Russian Science Foundation grant (RSF 21-14-00330). Alexander V. Kirdyanov received funding from the Russian Science Foundation grant (RSF 18-14-00072P). Fredrik C. Ljungqvist was supported by the Swedish Research Council (2018-01272). Patrick Fonti and Markus Stoffel received funding from the Swiss National Science Foundation through the SNSF Sinergia CALDERA project (CRSII5 183571). Matthew Salzer and Malcolm K. Hughes received funding from the National Science Foundation's P2C2 Program (1902625 and 1203749) and from the Malcolm H. Wiener Foundation. Greg Wiles was funded through NSF P2C2 Program (2002454). Ulf Büntgen designed the study and wrote the first draft of this manuscript with input from Jan Esper, Paul J. Krusic, and Clive Oppenheimer. Samples were processed and analysed by Alma Piermattei and Alan Crivellaro. All authors provided data and/or contributed to discussion and improving the article.Funding text 2: Ulf Büntgen and Jan Esper received funding from the ERC Advanced Project MONOSTAR (AdG 882727). Ulf Büntgen, Jan Esper, and Mirek Trnka received funding from SustES : adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions (CZ.02.1.01/0.0/0.0/16_019/0000797). Ulf Büntgen, Jan Esper, and Clive Oppenheimer discussed many aspects of this study at the Center for Interdisciplinary Research (ZiF) at the University of Bielefeld, Germany. Alan Crivellaro received funding from the Fritz & Elisabeth Schweingruber Foundation . Duncan A. Christie and Carlos Le Quesne received funding from the ANID ( FONDECYT 1201411 , 1221307, FONDAP 15110009 , BASAL FB210018). Olga V. Churakova (Sidorova) received funding from the Russian Science Foundation grant ( RSF 21-17-00006 ). Rosanne D’Arrigo received funding from NSF Arctic Social Science 2112314 and NSF Arctic Natural Science 2124885 , as well as the NSF P2C2 (Paleo Perspectives on Climatic Change) program (various grants). Rashit M. Hantemirov received funding from the Russian Science Foundation grant (RSF 21-14-00330). Alexander V. Kirdyanov received funding from the Russian Science Foundation grant (RSF 18-14-00072P). Fredrik C. Ljungqvist was supported by the Swedish Research Council (2018-01272). Patrick Fonti and Markus Stoffel received funding from the Swiss National Science Foundation through the SNSF Sinergia CALDERA project (CRSII5 183571). Matthew Salzer and Malcolm K. Hughes received funding from the National Science Foundation’s P2C2 Program (1902625 and 1203749) and from the Malcolm H. Wiener Foundation . Greg Wiles was funded through NSF P2C2 Program (2002454)

    Complexity of soil organic matter: AMS 14C analysis of soil lipid fractions and individual compounds

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    From the 18th International Radiocarbon Conference held in Wellington, New Zealand, September 1-5, 2003.Radiocarbon measurements of different lipid fractions and individual compounds, isolated from soil samples collected on 2 different agricultural long-term study sites, located in the rural area of Rotthalmunster (Germany) and in the city of Halle/Saale (Germany), were analyzed to obtain information about sources and the stability of soil organic matter (SOM). Different lipid compound classes were isolated by automated solvent extraction and subsequent medium-pressure liquid chromatography. Generally, 14C contents of lipid compound classes from topsoil samples of maize plots at Rotthalmünster are close to the modern atmospheric 14C content. Lower 14C values of aliphatic and aromatic hydrocarbons isolated from neutral lipids suggest a contribution of old carbon to these fractions. In contrast, 14C values of bulk soil (52 pMC) as well as isolated lipid classes from Halle are highly depleted. This can be attributed to a significant contribution of fossil carbon at this site. Extremely low 14C contents of aromatic (7 pMC) and aliphatic hydrocarbons (19 pMC) reflect the admixture of fossil hydrocarbons at the Halle site. Individual phospholipid fatty acids (PLFA), which are used as a proxy for viable microbial biomass, were isolated by preparative capillary gas chromatography (PCGC) from topsoils at Rotthalmünster and Halle. PLFA 14C values are close to atmospheric 14C values and, thus, indicate a clear microbial preference for relatively young SOM. At Rotthalmünster, the 14C concentration of short-chain unsaturated PLFAs is not significantly different from that of the atmosphere, while the saturated PLFAs show a contribution of sub-recent SOM extending over the last decades. At Halle, up to 14% fossil carbon is incorporated in PLFAs n-C17:0 and cy-C18:0, which suggests the use of fossil carbon by soil microorganisms. Moreover, it can be concluded that the 14C age of soil carbon is not indicative of its stability.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

    Reconstructed summer temperatures over the last 400 years based on Larch ring widths: Sakhalin Island, Russian Far East

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    A new ring-width record from the eastern flanks of the Eastern Sakhalin Range, Sakhalin Island, Russian Federation is significantly correlated with summer temperatures and allows for the reconstruction of May–July average temperatures for the past 400 years. The reconstruction explains 37 % of the variance in May–July temperatures and shows a strong cooling between 1680 and 1710 CE coincident with the Maunder solar minimum and in agreement with other independent tree-ring reconstructions and glacier histories from sites along the margin of the Sea of Okhotsk. While recent decades are among the warmest in the record they are rivaled by periods centered on 1650 and 1850 CE. Warming in the observational record and the reconstruction is consistent with the influence of the declining strength of the Siberian High and loss of sea ice over the same interval. Decadal (17–25 year) variability persists throughout the reconstruction. At interannual timescales the Sakhalin reconstruction is most strongly correlated with local and central North Pacific sea surface temperatures over the past 120 years, whereas at decadal timescales there is an additional association with Asian land surface temperatures
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