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  • Dynamic interplay between climate and marine biodiversity upheavals during the early Triassic Smithian -Spathian biotic crisis
    Earth Sci. Rev. (IF 7.491) Pub Date : 2019-01-17
    Nicolas Goudemand, Carlo Romano, Marc Leu, Hugo Bucher, Julie A. Trotter, Ian S. Williams

    In the aftermath of the Permian-Triassic boundary mass extinction (~252 Ma) ― the most dramatic biotic crisis of the Phanerozoic ― changes in climate, the carbon cycle, and biodiversity patterns remained extremely variable for several million years. In particular, the Smithian-Spathian boundary crisis, which occurred ca. 1.5 Ma after the Permian-Triassic boundary, coincided with drastic changes in global climate, a major extinction of nektonic organisms, and major shifts in the carbon and oxygen isotope compositions of marine carbonates and phosphates. However, the timing of these events and their interrelationships remain controversial. Previous studies concluded that the latest Smithian-earliest Spathian interval was a time of extremely high temperatures, which would have precluded marine (macro)-vertebrates from inhabiting the equatorial realm. Conversely, based on oxygen isotope measurements of conodont elements collected at high temporal resolution from the Salt Range record (Pakistan), we report a major cooling event during that time interval. These results suggest that the interplay between climate and biodiversity patterns is more complex than usually portrayed.

    更新日期:2019-01-18
  • Global Mean Climate and Main Patterns of Variability in the CMCC‐CM2 Coupled Model
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-18
    A. Cherchi; P. G. Fogli; T. Lovato; D. Peano; D. Iovino; S. Gualdi; S. Masina; E. Scoccimarro; S. Materia; A. Bellucci; A. Navarra

    Euro‐Mediterranean Centre on Climate Change coupled climate model (CMCC‐CM2) represents the new family of the global coupled climate models developed and used at CMCC. It is based on the atmospheric, land and sea ice components from the Community Earth System Model coupled with the global ocean model Nucleus for European Modeling of the Ocean. This study documents the model components, the coupling strategy, particularly for the oceanic, atmospheric, and sea ice components, and the overall model ability in reproducing the observed mean climate and main patterns of interannual variability. As a first step toward a more comprehensive, process‐oriented, validation of the model, this work analyzes a 200‐year simulation performed under constant forcing corresponding to present‐day climate conditions. In terms of mean climate, the model is able to realistically reproduce the main patterns of temperature, precipitation, and winds. Specifically, we report improvements in the representation of the sea surface temperature with respect to the previous version of the model. In terms of mean atmospheric circulation features, we notice a realistic simulation of upper tropospheric winds and midtroposphere geopotential eddies. The oceanic heat transport and the Atlantic meridional overturning circulation satisfactorily compare with present‐day observations and estimates from global ocean reanalyses. The sea ice patterns and associated seasonal variations are realistically reproduced in both hemispheres, with a better skill in winter. Main weaknesses of the simulated climate are related with the precipitation patterns, specifically in the tropical regions with large dry biases over the Amazon basin. Similarly, the seasonal precipitation associated with the monsoons, mostly over Asia, is weaker than observed. The main patterns of interannual variability in terms of dominant empirical orthogonal functions are faithfully reproduced, mostly in the Northern Hemisphere winter. In the tropics the main teleconnection patterns associated with El Niño–Southern Oscillation and with the Indian Ocean Dipole are also in good agreement with observations.

    更新日期:2019-01-18
  • A Simple Model of Convectively Coupled Equatorial Rossby Waves
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-17
    Željka Fuchs‐Stone; David J. Raymond; Stipo Sentić

    Intraseasonal oscillations affect the weather not just in the tropics but all around the globe. The convectively coupled equatorial Rossby wave is observed as the westward‐moving intraseasonal oscillation. The fundamental physics of its coupling is still unknown; thus, many questions remain unanswered. How is its phase speed altered by convection? What makes it unstable? Why is it an intraseasonal oscillation? Using the Fuchs and Raymond model with linearized governing equations on an equatorial beta plane, first baroclinic mode vertical structure, and moisture and wind‐induced surface heat exchange (WISHE) convective parametrizations, this paper seeks a fundamental analytical theory that can explain the basic features of the convectively coupled equatorial Rossby wave. The WISHE‐moisture theory leads to a large‐scale, unstable westward propagating mode in the n = 1 case, which we call the westward propagating WISHE‐moisture mode. We find that the westward propagating WISHE‐moisture mode is indeed the free equatorial Rossby wave in the absence of moisture closure and WISHE. It is propagating westward due to the beta effect, and it slows down when it is convectively coupled. Its phase speed decreases mainly due to WISHE and cloud‐radiation interactions. The x‐y structure of the pressure and horizontal winds is similar to the free and observed Rossby wave, with convergent net flow. The strongest easterlies are to the west of the precipitation maximum increasing the moisture in that area. The mode is unstable due to the interplay of surface fluxes and moisture, which increases as a function of zonal wavelength.

    更新日期:2019-01-18
  • Evaluating Marine Stratocumulus Clouds in the CNRM‐CM6‐1 Model Using Short‐Term Hindcasts
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-17
    Florent Brient; Romain Roehrig; Aurore Voldoire

    The representation of stratocumulus by the atmospheric component of the Centre National de Recherches Météorologiques model version 6 (CNRM‐CM6‐1) is assessed. An Atmospheric Model Intercomparison Project‐type simulation is first used to document the main model errors, namely, a large lack of stratocumulus over the eastern part of tropical ocean basins. Short‐term hindcasts, following the Transpose‐Atmospheric Model Intercomparison Project framework, are then used to better assess the timescales associated with the cloud bias growth and to highlight the processes leading to them. These biases are shown to appear within only a few hours, independently of errors in the large‐scale circulation that set up within a few days. Key processes underlying the low‐cloud formation are thus mainly local and, to the first order, do not imply any feedback between the model physics and the large‐scale dynamics. As a consequence, short‐term hindcasts provide a relevant framework to investigate whether the low‐cloud underestimate is related to errors in the large‐scale state variables or to errors in the model parameterizations. Sensitivity tests highlight that the involved processes arise (1) mostly from misrepresentation of subgrid effects on cloud formation and (2) partly from biases in drying induced by cloud‐top entrainment mixing. Improvements in the representation of stratocumulus in the CNRM‐CM6‐1 model might thus be expected by including a more realistic subgrid‐scale temperature and moisture distribution, that would link convective and turbulence processes. Finally, this study confirms the potential of short‐term hindcasts, which provide a trustworthy framework to evaluate and develop climate model parameterizations.

    更新日期:2019-01-18
  • Initialization and Ensemble Generation for Decadal Climate Predictions: A Comparison of Different Methods
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-17
    Iuliia Polkova; Sebastian Brune; Christopher Kadow; Vanya Romanova; Gereon Gollan; Johanna Baehr; Rita Glowienka‐Hense; Richard J. Greatbatch; Andreas Hense; Sebastian Illing; Armin Köhl; Jürgen Kröger; Wolfgang A. Müller; Klaus Pankatz; Detlef Stammer

    Five initialization and ensemble generation methods are investigated with respect to their impact on the prediction skill of the German decadal prediction system “Mittelfristige Klimaprognose” (MiKlip). Among the tested methods, three tackle aspects of model‐consistent initialization using the ensemble Kalman filter, the filtered anomaly initialization, and the initialization method by partially coupled spin‐up (MODINI). The remaining two methods alter the ensemble generation: the ensemble dispersion filter corrects each ensemble member with the ensemble mean during model integration. And the bred vectors perturb the climate state using the fastest growing modes. The new methods are compared against the latest MiKlip system in the low‐resolution configuration (Preop‐LR), which uses lagging the climate state by a few days for ensemble generation and nudging toward ocean and atmosphere reanalyses for initialization. Results show that the tested methods provide an added value for the prediction skill as compared to Preop‐LR in that they improve prediction skill over the eastern and central Pacific and different regions in the North Atlantic Ocean. In this respect, the ensemble Kalman filter and filtered anomaly initialization show the most distinct improvements over Preop‐LR for surface temperatures and upper ocean heat content, followed by the bred vectors, the ensemble dispersion filter, and MODINI. However, no single method exists that is superior to the others with respect to all metrics considered. In particular, all methods affect the Atlantic Meridional Overturning Circulation in different ways, both with respect to the basin‐wide long‐term mean and variability and with respect to the temporal evolution at the 26° N latitude.

    更新日期:2019-01-18
  • A statistical model for isolated convective precipitation events
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-17
    Christopher Moseley; Olga Henneberg; Jan O. Haerter

    We present a highly simplified model to describe the diurnal evolution of a convective cloud field in idealized large eddy simulations (LES). The life cycles of individual precipitation events are detected by a storm tracking algorithm which records the autonomous appearance and decay, as well as the merging and fragmentation of convective precipitation cells. Conditioned on the area covered by each cell, the tracking method records the time evolution of the precipitation intensity, the anomalies of near‐surface temperature and moisture, convective available potential energy (CAPE), and convective inhibition (CIN). For tracks that do not merge or split (termed solitary), many of these quantities show generic, often nearly linear relations that hardly depend on the forcing conditions of the simulations, such as surface temperature. This finding allows us to propose a simple idealized model of precipitation events, where the surface precipitation area is circular and a cell's precipitation intensity falls off linearly with the distance from the respective cell center. The drop‐off gradient is nearly independent of track duration and cell size. Multiple track properties, that is, track duration, peak and mean intensity, as well as the associated cell area can hence be specified by knowing only one remaining parameter. In contrast to the simple and robust behavior of solitary tracks, tracks that result from merging of two or more cells show a much more complicated behavior. The most intense, long lasting and largest tracks stem from tracks involved in repeated merging.

    更新日期:2019-01-18
  • Vertical Characterization and Source Apportionment of Water-soluble Organic Aerosol with High-resolution Aerosol Mass Spectrometry in Beijing, China
    ACS Earth Space Chem. Pub Date : 2019-01-17
    Yanmei Qiu, Qiaorong Xie, Junfeng Wang, Weiqi Xu, Linjie Li, Qingqing Wang, Jian Zhao, Yuntao Chen, Yanfang Chen, Yangzhou Wu, Wei Du, Wei Zhou, James Daniel Lee, Chuanfeng Zhao, Xinlei Ge, Pingqing Fu, Zifa Wang, Douglas R. Worsnop, Yele Sun

    Water-soluble organic aerosol (WSOA) constitutes a large fraction of organic aerosol (OA), and plays an important role in affecting aerosol hygroscopicity and cloud condensation nuclei formation. Here we characterized WSOA in fine particles that collected at ground level and 260 m on a meteorological tower in Beijing in winter using offline aerosol mass spectrometry (AMS) and compared them with the simultaneous real-time online AMS measurements. Our results showed large increases in WSOA from non-heating season to heating season by 43% and 53% at ground level and 260 m, respectively. WSOA was highly oxidized in winter with higher oxygen-to-carbon ratio (O/C = 0.69) at 260 m than ground level (0.63). On average, WSOA contributed 47% and 52% to the total OA at ground level and 260 m, respectively. Positive matrix factorization analysis further showed that primary OA was the dominant source of WSOA (52 – 61%) with coal combustion (CCOA) and biomass burning OA (BBOA) being two major contributors. The vertical differences in water-soluble CCOA and BBOA however were very different with ubiquitously higher CCOA at 260 m than ground level. Comparatively, more than 50% of secondary OA in winter was found to be water-insoluble highlighting the influences of fossil emissions. The observed high water-solubilities of CCOA (42 – 53%) and BBOA (61 – 78%) may have significant implications in severe haze formation in winter in Beijing through a positive feedback mechanism between substantial increases in primary emissions during heating season and the subsequent changes in aerosol liquid water content, radiative forcing and boundary layer which is not considered in chemical-transport models yet.

    更新日期:2019-01-18
  • Maximizing the quantitative utility of airborne hyperspectral imagery for studying plant physiology: An optimal sensor exposure setting procedure and empirical line method for atmospheric correction
    Int. J. Appl. Earth Obs. Geoinf. (IF 4.003) Pub Date : 2019-01-16
    Phuong D. Dao, Yuhong He, Bing Lu

    Proper calibration of airborne hyperspectral imagery is essential for maximizing the quantitative utility of remotely-sensed imagery, especially when distinguishing subtle changes in spectral curves related to specific plant physiological properties (e.g. chlorophyll and water). Many studies use the empirical line approach with reference reflectance taken from dark and bright targets to calibrate airborne images. However, few have paid attention to the issue of sensor oversaturation due to the exposure setting of the imaging sensor, and no studies have investigated the effects this has placed on image calibration. With limited radiometric resolution, a sensor would become saturated by energy reflected from bright targets when its exposure is set to maximize signals reflected from a feature of interest, for example vegetation. This would result in large bias in the reflectance calibration process, and should be addressed for enormous amounts of high spatial and spectral resolution data that have been increasingly taken by manned or unmanned aircraft. In this study, we test the exposure setting of a hyperspectral sensor for maximizing vegetation signal and investigate potential reference targets in an airborne scene, and propose a more suitable airborne hyperspectral imaging and an empirical line atmospheric correction procedure by taking into account: 1) imaging sensor exposure setting, 2) spectral extrapolation, 3) sensor saturation of targets’ signal, and 4) optimal materials and grey levels for field reference reflectance for the empirical line method. The imaging experiment was conducted over a grassland field with the Micro-Hyperspec VNIR sensor. Using field hyperspectral data to validate the calibration results, we found that our proposed empirical line calibration approach improved the reflectance accuracy significantly. Vegetation indices calculated from the calibrated spectra were able to estimate chlorophyll content with success. Our work offers insights into image calibration and describes a feasible method to maximize quantitative utilities of airborne Hyperspectral imagery for vegetation studies.

    更新日期:2019-01-17
  • Unraveling weathering episodes in Tertiary regoliths by kaolinite dating (Western Ghats, India)
    Gondwana Res. (IF 5.657) Pub Date : 2019-01-17
    M. Mathian, J. Aufort, J.J. Braun, J. Riotte, M. Selo, E. Balan, E. Fritsch, S. Bhattacharya, T. Allard
    更新日期:2019-01-17
  • Unique environmental conditions required for dawsonite formation: Implications from dawsonite synthesis experiments under alkaline condition
    ACS Earth Space Chem. Pub Date : 2019-01-16
    Yutaro Takaya, Miao Wu, Yasuhiro Kato

    Although many numerical simulation studies suggest the formation of dawsonite in CO2 reservoirs and its resulting contribution to secure geological carbon storage, dawsonite formation is not observed in experimental studies. In addition, the natural occurrence of dawsonite is scarce. The lack of certainty in “whether dawsonite forms in CO2 reservoirs” is a major concern for evaluating the security of geological carbon storage and has been discussed for decades. This study performed dawsonite synthesis experiments with co-existing elements (K, Ca, and Mg) and investigated the unique formation conditions of dawsonite. Our experiments clearly show that co-existing magnesium (MgCl2) inhibits dawsonite formation to form hydrotalcite and/or manasseite instead of dawsonite under alkaline conditions. As magnesium is widespread in the Earth’s crust, dawsonite could be formed only under extremely restricted conditions (Mg-poor condition) and is unlikely to form in CO2 reservoirs during the post-injection period. We also indicate that the discrepancy between numerical simulations and experiments arises from the incompleteness of thermodynamic databases. Our results significantly contribute to resolving the long-running controversy regarding the formation of dawsonite in CO2 reservoirs.

    更新日期:2019-01-17
  • ROLE OF TRACE ELEMENTS IN THE 226-RADIUM INCORPORATION IN SULFATE MINERALS (GYPSUM AND CELESTITE)
    ACS Earth Space Chem. Pub Date : 2019-01-16
    Leslie Lestini, Catherine Beaucaire, Thomas Vercouter, Marine Ballini, Michael Descostes

    Incorporation of 226Ra within gypsum (CaSO4.2H2O(s)) and celestite (SrSO4(s)) was assessed through dedicated batch experiments monitored over hundreds of days. Dissolution/recrystallization and co-precipitation experiments were carried out to investigate a range of chemical conditions, close to or far from equilibrium conditions. These data were used to establish the ability of gypsum and celestite to incorporate 226Ra. Celestite shows a high 226Ra incorporation, with a partition coefficient around 105. On the contrary, 226Ra is not significantly incorporated into pure gypsum. A very low value of (8.8±1.5).10-4 has been estimated, which is much lower than the values reported in the literature. This may explain why 226Ra incorporation in gypsum is enhanced when Sr impurities are present (above 0.1 molar %). Under such conditions, the radium distribution coefficient is around 0.15± 0.09. This behavior can be explained by an ion-exchange mechanism between 226Ra and Sr, consistently with the existence of a solid solution between celestite and radium sulfate, similarly to the barite (BaSO4(s)) and radium sulfate solid solution. These results highlight the key role of trace compounds in the incorporation of 226Ra in sulfate bearing minerals and bring new insights in our understanding of the 226Ra behavior in the environment. This is illustrated by the radium content observed and modelled within the porewaters of uranium mining tailings.

    更新日期:2019-01-17
  • Impact of Divalent Cations on Dark Production of Hydroxyl Radicals from Oxygenation of Reduced Humic Acids at Anoxic-Oxic Interfaces
    ACS Earth Space Chem. Pub Date : 2019-01-16
    Peng Liao, Yuzhen Liang, Zhenqing Shi

    Humic acids (HAs) are redox-active and can serve as either electron acceptors or electron donors to participate in multiple redox reactions. In nature water, HA can be intimately associated with divalent cations, such as Fe2+, Ca2+, and Mg2+, through a series of reactions which may in turn affect the redox reactivity of HA. Recent advances have demonstrated that the oxygenation of reduced HA in the dark can produce •OH at anoxic-oxic interfaces. However, little is known about the roles of the divalent cations complexed with HA on the production of •OH from reduced HA. This study provides new knowledge regarding the impact of Fe2+, Ca2+, and Mg2+ ions on the dark production of •OH from oxygenation of reduced HA at anoxic-oxic interfaces over a wide range of environmentally relevant conditions. Results show that the rates and yields of •OH production increase with increasing Fe2+ concentration (0.18–0.89 mM). This is largely attributed to the formation of complexed Fe(II) with HA, which increases the number of Fe(II)/Fe(III) cycles and enhances the decomposition of formed H2O2, accelerating the rates of Fenton reactions under circumneutral conditions. However, the promotional effect of Fe2+ on •OH formation is greatly suppressed in the coexistence of high Ca2+/Mg2+ concentration (5–20 mM), likely due to the retarded formation of HA-Fe(II) complexes and competition of HA’s surface reactive sites by Ca2+/Mg2+ ions. Findings improve the current understanding of the dark production of •OH from reduced HA and provide valuable insights towards understanding of carbon cycling and contaminant fate at anoxic-oxic interfaces.

    更新日期:2019-01-17
  • Holocene land cover change in south-western Amazonia inferred from paleoflood archives
    Glob. Planet. Change (IF 3.982) Pub Date : 2019-01-16
    Umberto Lombardo, Javier Ruiz-Pérez, Leonor Rodrigues, Adrien Mestrot, Francis Mayle, Marco Madella, Sönke Szidat, Heinz Veit

    This study provides new data on the evolution of the landscape in south-western Amazonia during the Holocene and the impact of climate change and fluvial dynamics on the region's ecosystems. South-western Amazonia is covered by an extensive seasonally flooded savannah, known as the Llanos de Moxos. Severe drought during the southern hemisphere winter, followed by months of permanent waterlogging, means that forests only grow on the most elevated parts of the landscape, mostly river and paleoriver levees and crevasse splays. Paleoclimate reconstructions from surrounding areas show that a shift to wetter conditions at around 4 kyr BP caused an increase in forest cover. However, the impact that this change in climate had on the landscape of the Llanos de Moxos is unknown. Published lacustrine archives from the area only cover the last 2 kyr. Here we present new data from the analysis of paleosols located along a 300 km transect across the central Llanos. The analyses of stable carbon isotopes, from 36 paleosols, and biogenic silica, from 29 paleosols, show that the patchwork of forests and savannahs that we see today was established after the 4 kyr BP climate change. During the dry period between 8 and 4 kyr BP, most of the central Llanos de Moxos, nowadays covered with seasonally flooded savannah, were covered by Cerrado-like savannah in the west and by forest in the east. However, results also suggest that, at both regional and local scales, vegetation cover has been influenced by changes in topography resulting from the region's river dynamics.

    更新日期:2019-01-16
  • Mapping invasive plant with UAV-derived 3D mesh model in mountain area—A case study in Shenzhen Coast, China
    Int. J. Appl. Earth Obs. Geoinf. (IF 4.003) Pub Date : 2019-01-15
    Zhaocong Wu, Min Ni, Zhongwen Hu, Junjie Wang, Qingquan Li, Guofeng Wu

    Invasive plants constitute one of the major causes of biodiversity loss, and its monitoring plays an important role in the management of coastal ecological systems. This study aimed to apply high precision 3D mesh-model and digital orthophoto map (DOM) derived from unmanned aerial vehicle (UAV) multi view images to monitor the invasive plants over coastal mountain region in Shenzhen, China. To overcome the limitations of RGB images, the Gray-level Co-occurrence Matrix (GLCM) features of images were analyzed and combined with spectral features to obtain the 2-dimentional distribution of invasive plants first, using an object-based image analysis technique. A fine analysis was then introduced to obtain a more accurate 3-dimentional distribution of invasive plant by combining 2-dimentional distribution of invasive plant and 3D mesh model. the results have shown that: (1) Although the UAV RGB image has limited spectral information, the low-altitude makes the spatial resolution very high, which can effectively enhance the effectiveness of the texture in mapping invasive plants, and finally achieved an overall accuracy of 93.25%. (2) The use of 3D mesh model, on the one hand, could significantly alleviate the impact of undulatory terrain over mountain area and improve the classification result; on the other hand, it could better visualize the final results, helping us more intuitively understanding the distribution of invasive plants. This study demonstrated the great potential of UAV-derived 3D mesh model in accurate natural resource management over mountain areas.

    更新日期:2019-01-16
  • Detrital zircon provenance constraints on the final closure of the middle segment of the Paleo-Asian Ocean
    Gondwana Res. (IF 5.657) Pub Date : 2019-01-16
    Qian Liu, Guochun Zhao, Yigui Han, Yanlin Zhu, Bo Wang, Paul R. Eizenhöfer, Xiaoran Zhang
    更新日期:2019-01-16
  • Evidence-based strategies to combat scientific misinformation
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-14
    Justin Farrell, Kathryn McConnell, Robert Brulle

    Nowhere has the impact of scientific misinformation been more profound than on the issue of climate change in the United States. Effective responses to this multifaceted problem have been slow to develop, in large part because many experts have not only underestimated its impact, but have also overlooked the underlying institutional structure, organizational power and financial roots of misinformation. Fortunately, a growing body of sophisticated research has emerged that can help us to better understand these dynamics and provide the basis for developing a coordinated set of strategies across four related areas (public inoculation, legal strategies, political mechanisms and financial transparency) to thwart large-scale misinformation campaigns before they begin, or after they have taken root.

    更新日期:2019-01-16
  • Constraining glacier elevation and mass changes in South America
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-14
    Matthias H. Braun, Philipp Malz, Christian Sommer, David Farías-Barahona, Tobias Sauter, Gino Casassa, Alvaro Soruco, Pedro Skvarca, Thorsten C. Seehaus

    Excluding the large ice sheets of Greenland and Antarctica, glaciers in South America are large contributors to sea-level rise1. Their rates of mass loss, however, are poorly known. Here, using repeat bi-static synthetic aperture radar interferometry over the years 2000 to 2011/2015, we compute continent-wide, glacier-specific elevation and mass changes for 85% of the glacierized area of South America. Mass loss rate is calculated to be 19.43 ± 0.60 Gt a−1 from elevation changes above ground, sea or lake level, with an additional 3.06 ± 1.24 Gt a−1 from subaqueous ice mass loss not contributing to sea-level rise. The largest contributions come from the Patagonian icefields, where 83% mass loss occurs, largely from dynamic adjustments of large glaciers. These changes contribute 0.054 ± 0.002 mm a−1 to sea-level rise. In comparison with previous studies2, tropical and out-tropical glaciers — as well as those in Tierra del Fuego — show considerably less ice loss. These results provide basic information to calibrate and validate glacier-climate models and also for decision-makers in water resource management3.

    更新日期:2019-01-16
  • Bluetongue risk under future climates
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-14
    Anne E. Jones, Joanne Turner, Cyril Caminade, Andrew E. Heath, Maya Wardeh, Georgette Kluiters, Peter J. Diggle, Andrew P. Morse, Matthew Baylis

    There is concern that climate change will lead to expansion of vector-borne diseases as, of all disease types, they are the most sensitive to climate drivers1. Such expansion may threaten human health, and food security via effects on animal and crop health. Here we quantify the potential impact of climate change on a vector-borne disease of livestock, bluetongue, which has emerged in northern Europe in response to climate change2,3,4, affecting tens of thousands of farms at huge financial cost and causing the deaths of millions of animals5. We derive future disease risk trends for northern Europe, and use a detailed spatial transmission model6 to simulate outbreaks in England and Wales under future climatic conditions, using an ensemble of five downscaled general circulation models7. By 2100, bluetongue risk extends further north, the transmission season lengthens by up to three months and outbreaks are larger on average. A 1 in 20-year outbreak at present-day temperatures becomes typical by the 2070s under the highest greenhouse gas emission scenario. However, animal movement restrictions are sufficient to prevent truly devastating outbreaks. Disease transmission uncertainty dominates over climate uncertainty, even at the longest prediction timescales. Our results suggest that efficient detection and control measures to limit the spread of vector-borne diseases will be increasingly vital in future, warmer climates.

    更新日期:2019-01-16
  • General and specific motivations
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-14
    Andrea Louise Taylor

    General and specific motivations General and specific motivations, Published online: 14 January 2019; doi:10.1038/s41558-018-0395-3 Climate change adaptation encompasses a wide range of behaviours in response to a variety of short- and long-term risks. Now meta-analyses identify which motivational factors are consistent predictors of adaptation action, and which are more context-specific.

    更新日期:2019-01-16
  • A reconciled estimate of the influence of Arctic sea-ice loss on recent Eurasian cooling
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-14
    Masato Mori, Yu Kosaka, Masahiro Watanabe, Hisashi Nakamura, Masahide Kimoto

    Northern midlatitudes, over central Eurasia in particular, have experienced frequent severe winters in recent decades1,2,3. A remote influence of Arctic sea-ice loss has been suggested4,5,6,7,8,9,10,11,12,13,14; however, the importance of this connection remains controversial because of discrepancies among modelling and between modelling and observational studies15,16,17. Here, using a hybrid analysis of observations and multi-model large ensembles from seven atmospheric general circulation models, we examine the cause of these differences. While all models capture the observed structure of the forced surface temperature response to sea-ice loss in the Barents–Kara Seas—including Eurasian cooling—we show that its magnitude is systematically underestimated. Owing to the varying degrees of this underestimation of sea-ice-forced signal, the signal-to-noise ratio differs markedly. Correcting this underestimation reconciles the discrepancy between models and observations, leading to the conclusion that ~44% of the central Eurasian cooling trend for 1995–2014 is attributable to sea-ice loss in the Barents–Kara Seas. Our results strongly suggest that anthropogenic forcing has significantly amplified the probability of severe winter occurrence in central Eurasia via enhanced melting of the Barents–Kara sea ice. The difference in underestimation of signal-to-noise ratio between models therefore calls for careful experimental design and interpretation for regional climate change attribution.

    更新日期:2019-01-16
  • Meta-analyses of factors motivating climate change adaptation behaviour
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-14
    Anne M. van Valkengoed, Linda Steg

    Adaptation behaviour is of critical importance to reduce or avoid negative impacts of climate change. Many studies have examined which factors motivate individuals to adapt. However, a comprehensive overview of the key motivating factors of various adaptation behaviours is lacking. Here, we conduct a series of meta-analyses using data from 106 studies (90 papers) conducted in 23 different countries to examine how 13 motivational factors relate to various adaptation behaviours. Descriptive norms, negative affect, perceived self-efficacy and outcome efficacy of adaptive actions were most strongly associated with adaptive behaviour. In contrast, knowledge and experience, which are often assumed to be key barriers to adaptation, were relatively weakly related to adaptation. Research has disproportionally focused on studying experience and risk perception, flooding and hurricanes, and preparedness behaviours, while other motivational factors, hazards and adaptive behaviours have been understudied. These results point to important avenues for future research.

    更新日期:2019-01-16
  • 更新日期:2019-01-16
  • Biodegradation as an important sink of aromatic hydrocarbons in the oceans
    Nat. Geosci. (IF 14.391) Pub Date : 2019-01-14
    Belén González-Gaya, Alicia Martínez-Varela, Maria Vila-Costa, Paulo Casal, Elena Cerro-Gálvez, Naiara Berrojalbiz, Daniel Lundin, Montserrat Vidal, Carmen Mompeán, Antonio Bode, Begoña Jiménez, Jordi Dachs
    更新日期:2019-01-15
  • Antarctic ice-sheet sensitivity to obliquity forcing enhanced through ocean connections
    Nat. Geosci. (IF 14.391) Pub Date : 2019-01-14
    R. H. Levy, S. R. Meyers, T. R. Naish, N. R. Golledge, R. M. McKay, J. S. Crampton, R. M. DeConto, L. De Santis, F. Florindo, E. G. W. Gasson, D. M. Harwood, B. P. Luyendyk, R. D. Powell, C. Clowes, D. K. Kulhanek
    更新日期:2019-01-15
  • The Pangaea Megamonsoon records: Evidence from the Triassic Mungaroo Formation, Northwest Shelf of Australia
    Gondwana Res. (IF 5.657) Pub Date : 2019-01-15
    Zhiwei Zeng, Hongtao Zhu, Xianghua Yang, Hongliu Zeng, Xiaolin Hu, Chenchen Xia
    更新日期:2019-01-15
  • 更新日期:2019-01-15
  • Paleoclimate proxies for cyclostratigraphy: Comparative analysis using a Lower Triassic marine section in South China
    Earth Sci. Rev. (IF 7.491) Pub Date : 2019-01-15
    Mingsong Li, Chunju Huang, James Ogg, Yang Zhang, Linda Hinnov, Huaichun Wu, Zhong-Qiang Chen, Zhuoyan Zou

    Multiple proxies for paleoclimatic and paleoenvironmental change within sedimentary sequences have been developed; but understanding their relationships and their relative strengths or weaknesses are required to access a wealth of untapped paleoclimate information. We propose two main criteria for multiple proxy datasets to estimate their individual signal-to-noise levels and to decipher the relationship between multiple proxies. First, for proxies affected by similar processes, then their time-dependent changes should be similar. Second, a paleoclimate proxy that is more sensitive to an external forcing, such as astronomical forcing, is more useful than those that do not have such a response. We introduce two methods to evaluate these criteria: (1) hierarchical cluster analysis (HCA) probes the relationships among multiple proxies based on similarities of their oscillation patterns, and (2) power decomposition analysis (PDA) tests proxy sensitivity to external climate forcing.We evaluate 16 high-resolution paleoclimate proxies in detail for their applications in paleoclimatology from the marine Lower Triassic Daye Formation at the Daxiakou section in the Three Gorges region of South China, which has carbonate-claystone cycles deposited on an outer ramp. The proxies are spectral gamma ray (gamma-ray intensity, potassium, uranium, thorium, thorium/uranium and thorium/potassium), rock color lightness (L*), redness (a*) and yellowness (b*), magnetic susceptibility (measured in both laboratory and outcrop), anhysteretic remanent magnetization (ARM), lithologic rank, simplified lithologic rank and non-carbonate fraction, carbonate thickness and couplet thickness. Hierarchical cluster analysis (HCA) gathers these proxies into groups likely affected by the same process. The ARM and thorium/uranium proxies seem to reflect the hinterland-weathering process during the Early Triassic. Gamma-ray, potassium, uranium, thorium, magnetic susceptibility and non-carbonate fraction proxies refer to terrestrial input. The L*, a* and lithologic rank proxies indicate the productivity, the redox state and the relative sea level, respectively at this section. This case study contributes to the understanding of the sensitivity of these types of proxies within marine strata for deep-time paleoclimate and astronomical-tuned time scales.

    更新日期:2019-01-15
  • Chronostratigraphic synthesis of the latest cretaceous dinosaur turnover in South-Western Europe
    Earth Sci. Rev. (IF 7.491) Pub Date : 2019-01-14
    V. Fondevilla, V. Riera, B. Vila, A.G. Sellés, J. Dinarès-Turell, E. Vicens, R. Gaete, O. Oms, À. Galobart

    In south-western Europe, the uppermost Cretaceous continental deposits in the different sedimentary basins of Iberia (Portugal and north and central Spain), the Pyrenees (Spain and France) as well as Languedoc and Provence (southern France) provide one of the few terrestrial records that allow a comprehensive study of the Campanian-Maastrichtian dinosaur assemblages. For the last years the southern Pyrenees has been the target of intense geological, palaeontological and geochronological research. Hundreds of fossil localities are now framed in high-resolution lithological sections. The succession of these sites, most of them located in the Tremp Syncline, is based on the physical correlation of rock bodies, as permitted by the general outcropping conditions. Outside this syncline, correlation is supported by geochronologic and biostratigraphic data (mainly magnetostratigraphy and planktic foraminifera biostratigraphy). The integration of the entire dataset sheds new light on the Maastrichtian dinosaur turnover, characterized by a shift from a sauropod-dominated to a hadrosauroid-dominated faunal assemblage. This turnover was progressive and involved immigrants from North America, Eurasia and Gondwana, which probably reached the study area after a sea level drop. This faunal change was mainly triggered by the arrival of lambeosaurine hadrosauroids, a group that rapidly displaced the rest of the herbivorous clades of the region. Some of the extinction events suffered by the “pre-turnover” faunas during the Maastrichtian coincide with marine isotopic and sea-level drop events, suggesting that faunal competition was not the only cause of the observed changes in dinosaur composition. Despite this faunal replacement, the resulting ecosystem after the turnover shows no major loss of biodiversity before the Cretaceous-Paleogene extinction event.

    更新日期:2019-01-15
  • Present-day uplift of the European Alps: Evaluating mechanisms and models of their relative contributions
    Earth Sci. Rev. (IF 7.491) Pub Date : 2019-01-14
    Pietro Sternai, Christian Sue, Laurent Husson, Enrico Serpelloni, Thorsten W. Becker, Sean D. Willett, Claudio Faccenna, Andrea Di Giulio, Giorgio Spada, Laurent Jolivet, Pierre Valla, Carole Petit, Jean-Mathieu Nocquet, Andrea Walpersdorf, Sébastien Castelltort

    Recent measurements of surface vertical displacements of the European Alps show a correlation between vertical velocities and topographic features, with widespread uplift at rates of up to ~2–2.5 mm/a in the North-Western and Central Alps, and ~1 mm/a across a continuous region from the Eastern to the South-Western Alps. Such a rock uplift rate pattern is at odds with the horizontal velocity field, characterized by shortening and crustal thickening in the Eastern Alps and very limited deformation in the Central and Western Alps. Proposed mechanisms of rock uplift rate include isostatic response to the last deglaciation, long-term erosion, detachment of the Western Alpine slab, as well as lithospheric and surface deflection due to mantle convection. Here, we assess previous work and present new estimates of the contributions from these mechanisms. Given the large range of model estimates, the isostatic adjustment to deglaciation and erosion are sufficient to explain the full observed rate of uplift in the Eastern Alps, which, if correct, would preclude a contribution from horizontal shortening and crustal thickening. Alternatively, uplift is a partitioned response to a range of mechanisms. In the Central and Western Alps, the lithospheric adjustment to deglaciation and erosion likely accounts for roughly half of the rock uplift rate, which points to a noticeable contribution by mantle-related processes such as detachment of the European slab and/or asthenospheric upwelling. While it is difficult to independently constrain the patterns and magnitude of mantle contributions to ongoing Alpine vertical displacements at present, future data should provide additional insights. Regardless, interacting tectonic and surface mass redistribution processes, rather than an individual forcing, best explain ongoing Alpine elevation changes.

    更新日期:2019-01-15
  • The Vertical Momentum Budget of Shallow Cumulus Convection: Insights From a Lagrangian Perspective
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-15
    Yang Tian; Zhiming Kuang; Martin S. Singh; Ji Nie

    A Lagrangian Particle Dispersion Model is embedded into large eddy simulations to diagnose the responses of shallow cumulus convection to a small‐amplitude large‐scale temperature perturbation. The Lagrangian framework allows for a decomposition of the vertical momentum budget and diagnosis of the forces that regulate cloudy updrafts. The results are used to shed light on the parameterization of vertical velocity in convective schemes, where the treatment of the effects of entrainment as well as buoyancy‐induced and mechanically induced pressure gradients remains highly uncertain. We show that both buoyancy‐induced and mechanically induced pressure gradients are important for the vertical momentum budget of cloudy updrafts, whereas the entrainment dilution term is relatively less important. Based on the analysis of the dominant force balance, we propose a simple model to derive the perturbation pressure gradient forces. We further illustrate that the effective buoyancy and dynamic perturbation pressure can be approximated to a good extent using a simple cylindrical updraft model given the cloud radius. This finding has the potential for improving the parameterization of vertical velocity in convective schemes and the development of a unified scheme for cumulus convection.

    更新日期:2019-01-15
  • Modeling the Global Sowing and Harvesting Windows of Major Crops Around the Year 2000
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-15
    Toshichika Iizumi; Wonsik Kim; Motoki Nishimori

    The lack of spatially detailed crop calendars is a significant source of uncertainty in modeling, monitoring, and forecasting crop production. In this paper, we present a rule‐based model to estimate the sowing and harvesting windows of major crops over the global land area. The model considers field workability due to snow cover and heavy rainfall in addition to crop biological requirements for heat, chilling, and moisture. Using daily weather data for the period 1996–2005 as model input, we derive calendars for maize, rice, winter and spring wheat, and soybeans around the year 2000 with a spatial resolution of 0.5° in latitude and longitude. Separate calendars for rainfed and irrigated conditions and three representative varieties (short‐, medium‐ and long‐season varieties) are estimated. The daily probabilities of sowing and harvesting derived using the model well capture the major characteristics of reported calendars. Our modeling reveals that field workability is an important determinant of sowing and harvesting dates and that multicropping patterns influence the calendars of individual crops. The case studies show that the model is capable of capturing multicropping patterns such as triple rice cropping in Bangladesh, double rice cropping in the Philippines, winter wheat‐maize rotations in France, and maize‐winter wheat‐soybean rotations in Brazil. The model outputs are particularly valuable for agricultural and hydrological applications in regions where existing crop calendars are sparse or unreliable.

    更新日期:2019-01-15
  • The Impact of Biomass Heat Storage on the Canopy Energy Balance and Atmospheric Stability in the Community Land Model
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-15
    Sean C. Swenson; Sean P. Burns; David M. Lawrence

    Atmospheric models used for weather prediction and future climate projections rely on land models to calculate surface boundary conditions. Observations of near‐surface states and fluxes made at flux measurement sites provide valuable data with which to assess the quality of simulated lower boundary conditions. A previous assessment of the Community Land Model version 4.5 using data from the Niwot Ridge Subalpine Forest AmeriFlux tower showed that simulated latent heat fluxes could be improved by adjusting a parameter describing the maximum leaf wetted area, but biases in midday sensible heat flux and nighttime momentum flux were generally not reduced by model parameter perturbations. These biases are related to the model's lack of heat storage in vegetation biomass. A biomass heat capacity is parameterized in Community Land Model version 5 with measurable quantities such as canopy height, diameter at breast height, and tree number density. After implementing a parameterization describing the heat transfer between the forest biomass and the canopy air space, the biases in the mean midday sensible heat and mean nighttime momentum fluxes at Niwot Ridge are reduced from 47 to 13 W/m2 and from 0.12 to −0.03 m/s, respectively. The bias in the mean nighttime canopy air temperature was reduced from −5.9 to 0.4 °C. Additional simulations at other flux tower sites demonstrate a consistent reduction in midday sensible heat flux, a lower ratio of the sum of sensible and latent heat flux to net radiation, and an increase in nighttime canopy temperatures.

    更新日期:2019-01-15
  • Developments in the MPI‐M Earth System Model version 1.2 (MPI‐ESM 1.2) and its response to increasing CO2
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-13
    Thorsten Mauritsen; Jürgen Bader; Tobias Becker; Jörg Behrens; Matthias Bittner; Renate Brokopf; Victor Brovkin; Martin Claussen; Traute Crueger; Monika Esch; Irina Fast; Stephanie Fiedler; Dagmar Fläschner; Veronika Gayler; Marco Giorgetta; Daniel S. Goll; Helmuth Haak; Stefan Hagemann; Christopher Hedemann; Cathy Hohenegger; Tatiana Ilyina; Thomas Jahns; Diego Jimenez de la Cuesta Otero; Johann Jungclaus; Thomas Kleinen; Silvia Kloster; Daniela Kracher; Stefan Kinne; Deike Kleberg; Gitta Lasslop; Luis Kornblueh; Jochem Marotzke; Daniela Matei; Katharina Meraner; Uwe Mikolajewicz; Kameswarrao Modali; Benjamin Möbis; Wolfgang A. Müller; Julia E. M. S. Nabel; Christine C. W. Nam; Dirk Notz; Sarah‐Sylvia Nyawira; Hanna Paulsen; Karsten Peters; Robert Pincus; Holger Pohlmann; Julia Pongratz; Max Popp; Thomas Raddatz; Sebastian Rast; Rene Redler; Christian H. Reick; Tim Rohrschneider; Vera Schemann; Hauke Schmidt; Reiner Schnur; Uwe Schulzweida; Katharina D. Six; Lukas Stein; Irene Stemmler; Bjorn Stevens; Jin‐Song von Storch; Fangxing Tian; Aiko Voigt; Philipp de Vrese; Karl‐Hermann Wieners; Stiig Wilkenskjeld; Alexander Winkler; Erich Roeckner

    A new release of the Max Planck Institute for Meteorology Earth System Model (MPI‐ESM 1.2) is presented. The development focused on correcting errors in and improving the physical processes representation, as well as improving the computational performance, versatility and overall user friendliness. In addition to new radiation‐ and aerosol parameterizations of the atmosphere, several relatively large, but partly compensating, coding errors in the model's cloud, convection and turbulence parameterizations were corrected. The representation of land processes was refined by introducing a multi‐layer soil hydrology scheme, extending the land biogeochemistry to include the nitrogen cycle, replacing the soil and litter decomposition model, and improving the representation of wildfires. The ocean biogeochemistry now represents cyano‐bacteria prognostically in order to capture the response of nitrogen fixation to changing climate conditions, and further includes improved detritus settling and numerous other refinements. As something new, in addition to limiting drift and minimizing certain biases, the instrumental record warming was explicitly taken into account during the tuning process. To this end a very high climate sensitivity of around 7 K caused by low‐level clouds in the tropics as found in an intermediate model version was addressed, as it was not deemed possible to match observed warming otherwise. As a result, the model has a climate sensitivity to a doubling of CO2 over pre‐industrial conditions of 2.77 K, maintaining the previously identified highly non‐linear global mean response to increasing CO2 forcing, which nonetheless can be represented by a simple two‐layer model.

    更新日期:2019-01-14
  • 更新日期:2019-01-13
  • Elevation-dependent warming of land surface temperatures in the Andes assessed using MODIS LST time series (2000–2017)
    Int. J. Appl. Earth Obs. Geoinf. (IF 4.003) Pub Date : 2019-01-12
    Jaime Aguilar-Lome, Raúl Espinoza-Villar, Jhan-Carlo Espinoza, Joel Rojas-Acuña, Bram Leo Willems, Walter-Martín Leyva-Molina

    In this study, we report on the assessment of elevation-dependent warming processes in the Andean region between 7 °S and 20 °S, using Land Surface Temperature (LST). Remotely sensed LST data were obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) sensor in an 8-day composite, at a 1 km resolution, and from 2000 to 2017 during austral winter (June-July-August, JJA). We analysed the relation between mean monthly daytime LST and mean monthly maximum air temperature. This relation is analysed for different types of coverage, obtaining a significant correlation that varies from 0.57 to 0.82 (p < 0.01). However, effects of change in land cover were ruled out by a previous comparative assessment of trends in daytime LST and normalized difference vegetation index (NDVI). The distribution of the winter daytime LST trend was found to be increasing in most areas, while decreasing in only a few areas. This trend shows that winter daytime LST is increasing at an average rate of 1.0 °C/decade. We also found that the winter daytime LST trend has a clear dependence on elevation, with strongest warming effects at higher elevations: 0.50 °C/decade at 1000–1500 masl, and 1.7 °C/decade above 5000 masl. However, the winter nighttime LST trend shows a steady increase with altitude increase. The dependence of rising temperature trends on elevation could have severe implications for water resources and high Andean ecosystems.

    更新日期:2019-01-13
  • 更新日期:2019-01-13
  • Satellite scatterometer estimation of urban built-up volume: Validation with airborne lidar data
    Int. J. Appl. Earth Obs. Geoinf. (IF 4.003) Pub Date : 2019-01-11
    Adam J. Mathews, Amy E. Frazier, Son V. Nghiem, Gregory Neumann, Yun Zhao

    Accurately mapping urban infrastructure and extent is a high priority for resource management and service allocation as well as for addressing environmental, socioeconomic, and geopolitical concerns. Most available data products only document surficial (two-dimensional) land use and land cover (LULC), yet a substantial component of urban growth occurs in the vertical dimension. Light detection and ranging (lidar) data offer the potential for monitoring three-dimensional (3D) change, but the extreme lack of systematic lidar coverage worldwide inflicts considerable gaps in both spatial and temporal coverage. Satellite scatterometer (radar) data may serve as an alternative data source for characterizing urban growth and development in both the horizontal and vertical directions. The accuracy of these radar-based datasets for estimating building volumes remains to be validated quantitatively. For nine U.S. cities, we test whether scatterometer data can be used to estimate 3D urban built-up volume. We found strong, linear correlations between the lidar-derived and radar-derived building volume estimates for all cities with r2 values as high as 0.98 when using spatial trend analysis. Given the high expense that limits lidar data acquisition to small areas at sporadic points in time, satellite scatterometer data provide a breakthrough method for monitoring both vertical growth and horizontal expansion of cities across the world with a continuous decadal time scale.

    更新日期:2019-01-13
  • Mapping soil moisture across the Tibetan Plateau plains using Aquarius active and passive L-band microwave observations
    Int. J. Appl. Earth Obs. Geoinf. (IF 4.003) Pub Date : 2019-01-11
    Qiang Wang, Rogier van der Velde, Paolo Ferrazzoli, Xuelong Chen, Xiaojing Bai, Zhongbo Su

    An algorithm is developed for retrieving soil moisture at plateau scale by combined usage of Aquarius active and passive L-band observations. In this algorithm, Look-Up-Tables (LUTs) are established for bare soil and vegetated areas by using the physical based Tor Vergata discrete electromagnetic model (hereafter, TV-DEM). In the case of vegetated area, the LUT is built based on simulations with varying soil moisture and Leaf Area Index (LAI). Only soil moisture is variable for the bare soil case, and values calibrated in previous works are adopted for the other TV-DEM parameters. Soil moisture is then retrieved by minimizing a squared difference object function based on the emissivity and backscatter coefficient observed by Aquarius and the corresponding TV-DEM simulations included in the LUT. The soil moisture retrievals are assessed at Aquarius footprint scale using in-situ measurements collected at three regional scale networks spread across the Tibetan Plateau. The unbiased root mean squared differences (ubRMSDs) from the three networks vary from 0.016 to 0.050 m3 m−3 and coefficients of determination (R2) are from 0.274 to 0.499 (-). This ubRMSD and R2 is in the same order of the passive-only official Aquarius product, Metop-A Advanced SCATterometer (ASCAT) L2 soil moisture product (hereafter ASCAT) as well as reanalysis data generated by European Centre for Medium-Range Weather Forecasts (hereafter, ERA-Interim). At Plateau-scale, all four soil moisture products capture the seasonal trend, whereby the dynamic range during the monsoon season captured by the ERA-Interim product is relatively small. Further, the northwest-southeast dry-wet gradient due to precipitation and evapotranspiration is well captured by the soil moisture spatial distributions produced by TV-DEM Aquarius, official Aquarius and ASCAT products, but less pronounced in the ERA-Interim product. This study demonstrates that the TV-DEM based algorithm can be used to retrieve soil moisture over a Plateau scale with robust results in terms of error statistics (e.g. bias, R2 and ubRMSD) and can generate realistic spatial patterns for soil moisture at Plateau-scale.

    更新日期:2019-01-13
  • Gold Transport in Hydrothermal Chloride-Bearing Fluids: Insights from in Situ X-ray Absorption Spectroscopy and ab Initio Molecular Dynamics
    ACS Earth Space Chem. Pub Date : 2019-01-11
    Boris R. Tagirov, Alexander L. Trigub, Olga N. Filimonova, Kristina O. Kvashnina, Maximilian S. Nickolsky, Sara Lafuerza, Dmitriy A. Chareev
    更新日期:2019-01-13
  • A Multi‐Timescale EnOI‐Like High‐Efficiency Approximate Filter for Coupled Model Data Assimilation
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-11
    X. Yu; S. Zhang; J. Li; L. Lu; Z. Liu; M. Li; H. Yu; G. Han; X. Lin; L. Wu; P. Chang

    Because it uses a set of model integrations to simulate the temporally varying background probability distribution function and implement Bayes' theorem, the ensemble Kalman filter (EnKF), which produces an optimal data assimilation solution that coherently combines model dynamics and observational information, has been widely used in weather and climate studies. However, in practice, the EnKF has two limitations: (1) the insufficient representation of error statistics of low‐frequency background flows due to its finite ensemble size and model integration over time and (2) the high demand of computational power for ensemble model integrations in high‐resolution coupled Earth system models. Given that background error statistics consist of stationary, slow‐varying, and fast‐varying parts, a multi‐timescale, high‐efficiency approximate EnKF (MSHea‐EnKF) is designed to increase the representation of low‐frequency background error statistics and enhance its computational efficiency. The MSHea‐EnKF is a combination of multi‐timescale filters implemented by regressions based on data sampled from the time series of a single‐model solution. Validation shows that with the improved representation of stationary and slow‐varying background statistics, the MSHea‐EnKF only requires a small fraction of computer resources and shows a comparable performance relative to a finite size EnKF. Our experiments also show that the result can be further improved by using a small set of MSHea‐EnKFs through second‐stage EnKF filtering if sufficient computer resources are available. This new algorithm makes it practical to assimilate multisource observations into any high‐resolution coupled Earth system model that is intractable with current computing power for weather‐climate analysis and predictions.

    更新日期:2019-01-11
  • Empirical Run‐Time Bias Correction for Antarctic Regional Climate Projections With a Stretched‐Grid AGCM
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-11
    Gerhard Krinner; Julien Beaumet; Vincent Favier; Michel Déqué; Claire Brutel‐Vuilmet

    This work presents snapshot simulations of the late 20th and late 21st century Antarctic climate under the RCP8.5 scenario carried out with an empirically bias‐corrected global atmospheric general circulation model (AGCM), forced with bias‐corrected sea‐surface temperatures and sea ice and run with about 100‐km resolution over Antarctica. The bias correction substantially improves the simulated mean late 20th century climate. The simulated atmospheric circulation of the bias‐corrected model compares very favorably to the best available AMIP (Atmospheric Model Intercomparison Project)‐type climate models. The simulated interannual circulation variability is improved by the bias correction. Depending on the metric, a slight improvement or degradation is found in the simulated variability on synoptic timescales. The simulated climate change over the 21st century is broadly similar in the corrected and uncorrected versions of the atmospheric model, and atmospheric circulation patterns are not geographically “pinned” by the applied bias correction. These results suggest that the method presented here can be used for bias‐corrected climate projections. Finally, the authors discuss different possible choices in terms of the place of bias corrections and other intermediate steps in the modeling chain leading from global coupled climate simulations to impact assessment.

    更新日期:2019-01-11
  • A Variational Method for Sea Ice Ridging in Earth System Models
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-11
    Andrew F. Roberts; Elizabeth C. Hunke; Samy M. Kamal; William H. Lipscomb; Christopher Horvat; Wieslaw Maslowski

    We have derived an analytic form of the thickness redistribution function, Ψ, and compressive strength of sea ice using variational principles. By using the technique of coarse‐graining vertical sea ice deformation, or ridging, in the momentum equation of the pack, we isolate frictional energy loss from potential energy gain in the collision of floes. The method accounts for macroporosity of ridge rubble, ϕR, and by including this in the state‐space of the pack, we expand the sea ice thickness distribution, g(h), to a bivariate distribution, g(h, ϕR). The effect of macroporosity is for the first time included in the large‐scale mass conservation and momentum equations of frozen oceans. We make assumptions that have simplified the problem, such as treating sea ice as a granular material in ridges, and assuming that bending moments associated with ridging are perturbations around an isostatic state. Regardless of these simplifications, the coarse‐grained ridge model is highly predictive of macroporosity and ridge shape. By ensuring that vertical sea ice deformation observes a variational principle both at the scale of individual ridges and over the pack as a whole, we can predict distributions of ridge shapes using equations that can be solved in Earth system models. Our method also offers the possibility of more accurate derivations of sea ice thickness from ice freeboard measured by space‐borne altimeters over polar oceans.

    更新日期:2019-01-11
  • Optimization of the Eddy‐Diffusivity/Mass‐Flux shallow cumulus and boundary‐layer parameterization using surrogate models
    J. Adv. Model. Earth Syst. (IF 3.97) Pub Date : 2019-01-10
    W. Langhans; J. Mueller; W. D. Collins

    Physical parameterizations in global atmospheric and ocean models typically include free parameters that are not theoretically or empirically constrained. New methods are required to determine the optimal parameter combinations for such models in an objective, exhaustive, yet computationally feasible manner. Here, we propose to apply computationally inexpensiveradial basis function (RBF) surrogate models to minimize a “cost”, or error, function of an atmospheric model or a physical parameterization. The RBF is iteratively updated as more input‐output pairs are obtained during the optimization. The approach is used to optimize the Eddy‐Diffusivity/Mass‐Flux (EDMF) boundary‐layer parameterization of the convective boundary‐layer in a single‐column (SCM) framework.

    更新日期:2019-01-11
  • Dynamics of Vulcano Island (Tyrrhenian Sea, Italy) investigated by long-term (40 years) geophysical data
    Earth Sci. Rev. (IF 7.491) Pub Date : 2019-01-11
    Salvatore Alparone, Alessandro Bonforte, Salvatore Gambino, Francesco Guglielmino, Francesco Obrizzo, Rosanna Velardita

    Vulcano Island is a composite volcanic edifice located in the south-central sector of the Aeolian Archipelago (Tyrrhenian Sea, Italy). Historic activity has been characterized by frequent transitions from phreatomagmatic to minor magmatic activity. The last eruption in 1888–90 saw powerful explosive pulses and this eruption defines what we call ‘vulcanian’ also for other volcanoes. Since then, volcanic activity has been in the form of fumarolic emanations of variable intensity and temperature, mainly concentrated at “La Fossa” crater.We investigated Vulcano dynamics through ca. 40 years of ground deformation and seismicity data collected by the discrete and continuous INGV monitoring networks. We considered levelling, GPS, EDM, seismic and tilt data. EDM and levelling measurements began in the middle of the 1970s; since the late 1990s, the EDM benchmarks have been measured using GPS.We performed a data inversion identifying, for the 1999–2013 period, the action of a deflating magmatic source, located under Vulcanello at 4–5 km a.s.l, just at the top of a wide regional tectonic tabular source.We analyzed data on time-space scales, distinguishing the dynamics of different sectors of Vulcano (Piano, Vulcanello, La Fossa cone and Caldera) and three periods (1974–1984, 1984–1999, 1999–2013) and the time evolution of the dynamics of the island. We also show how the regional tectonic stress plays an important role in the transition of the volcanic system from a phase of stability to one of unrest, inducing the heating and expansion of shallow hydrothermal fluids.

    更新日期:2019-01-11
  • A review and reinterpretation of the architecture of the South and South-Central Scandinavian Caledonides—A magma-poor to magma-rich transition and the significance of the reactivation of rift inherited structures
    Earth Sci. Rev. (IF 7.491) Pub Date : 2019-01-10
    Johannes Jakob, Torgeir B. Andersen, Hans Jørgen Kjøll

    Interpretations of the pre-Caledonian rifted margin of Baltica commonly reconstruct it as a simple, tapering, wedge-shaped continental margin dissected by half graben, with progressively more rift-related magmas towards the ocean-continent transition zone. It is also interpreted to have had that simple architecture along-strike the whole length of the margin. However, present-day rifted margins show a more complex architecture, dominated by different and partly diachronous segments both along and across strike. Here, we show that the composition and the architecture of the Baltican-derived nappes of the South and South Central Scandinavian Caledonides are to a large extend rift-inherited. Compositional variations of nappes in similar tectonostratigraphic positions can be ascribed to variations along-strike the rifted margin, including a magma-rich, a magma-rich to magma-poor transition zone, and a magma-poor segment of the margin. The architecture of the nappe stack that includes the Baltican-derived nappes was formed as a result of the reactivation of rift-inherited structures and the stacking of rift domains during the Caledonian Orogeny.

    更新日期:2019-01-11
  • Publisher Correction: Beliefs about minority groups
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-10
    Jenn Richler

    Publisher Correction: Beliefs about minority groups Publisher Correction: Beliefs about minority groups, Published online: 10 January 2019; doi:10.1038/s41558-019-0403-2 Publisher Correction: Beliefs about minority groups

    更新日期:2019-01-11
  • Phosphate Uptake by Cyanobacteria Is Associated with Kinetic Fractionation of Phosphate Oxygen Isotopes
    ACS Earth Space Chem. Pub Date : 2019-01-10
    Hagar Lis, Tal Weiner, Frances D. Pitt, Nir Keren, Alon Angert
    更新日期:2019-01-11
  • 更新日期:2019-01-11
  • Quantifying the contributions of snow/glacier meltwater to river runoff in the Tianshan Mountains, Central Asia
    Glob. Planet. Change (IF 3.982) Pub Date : 2019-01-10
    Chen Haiyan, Chen Yaning, Li Weihong, Li Zhi

    This study investigated the contributions of snow/glacier meltwater to river runoff in the northern and central Tianshan Mountains (Central Asia). Based on end- member mixing analysis (EMMA), the hydrograph separation was carried out in six benchmark catchments with different glacier area ratios (GARs) and snow area ratios (SARs) during a typical snow melt period (TSMP) and a typical glacier melt period (TGMP). The results indicate that the contribution of snow/glacier meltwater to river runoff is positively correlated with GARs or maximum SARs. The contribution ratios of snowmelt water vary from 22% to 49% in TSMP. The contribution ratios of glacier meltwater vary from 12% to 59% in TGMP. The contribution ratios of snow meltwater in the northern Tianshan Mountains (36%) are higher than central Tianshan Mountains (31%), while the contribution ratios of glacier meltwater in the northern Tianshan Mountains (36%) are lower than central Tianshan Mountains (42%). The contribution of rainfall to river runoff is higher in TGMP (9%–23%) than in TSMP (5%–9%). Baseflow is the most important recharge source to river runoff, with the contribution ratios vary from 44% to 73% in TSMP, and vary from 30% to 75% in TGMP. The spatial and temporal variations in tracer concentrations in streamflow components were found to responsible to the uncertainties in hydrograph separation.

    更新日期:2019-01-10
  • 更新日期:2019-01-10
  • Review: Implications of vertebrate fossils for paleo-elevations of the Tibetan Plateau
    Glob. Planet. Change (IF 3.982) Pub Date : 2019-01-09
    Tao Deng, Xiaoming Wang, Feixiang Wu, Yang Wang, Qiang Li, Shiqi Wang, Sukuan Hou

    The uplift of the Tibetan Plateau is an important geological event, but there is considerable controversy about its growth history. Different geological observations contribute to this controversial issue, while data from geochemistry, tectonics, and paleontology further fuel the debate. Vertebrate fossils have provided significant evidence for documenting the uplift of the Tibetan Plateau in the geologic past. The earliest fossil evidence recently collected from the Oligocene Dingqing Formation in central Tibet includes the climbing perch and cyprinine fish fossils whose modern close relatives are distributed in the tropical zone of Asia and Africa. These discoveries not only are significant for the phylogeny and zoogeography of fishes, but also imply that the hinterland of the Tibetan Plateau was a warm and humid lowland at ~26 Ma. The co-existing plant assemblage, which includes palms and golden rain trees among others, indicates that the warm and humid airs from the Indian Ocean could flow deeply into central Tibet, consistent with the inference from the fish fossils. Since that time, the geographical features and natural environments within the Tibetan Plateau have greatly changed. The Tibetan Plateau was consistently uplifted in the Early Miocene and reached an elevation of ~3000 m, which was demonstrated by fish, mammal, and plant fossils. The endemic schizothoracines (snow carps) originated from the Miocene when the Tibetan Plateau turned into a barrier for mammalian migrations between north and south sides. A series of fish and mammal fossils provided unequivocal evidence that the Tibetan Plateau uplifted close to its modern elevation in the Pliocene and developed a cryospheric environment. As a result, the plateau region became the origination center for the cold-adapted Quaternary Ice Age fauna.

    更新日期:2019-01-09
  • Establishing tephrostratigraphic frameworks to aid the study of abrupt climatic and glacial transitions: a case study of the Last Glacial-Interglacial Transition in the British Isles (c. 16-8 ka BP)
    Earth Sci. Rev. (IF 7.491) Pub Date : 2019-01-09
    Rhys G.O. Timms, Ian P. Matthews, J.John. Lowe, Adrian P. Palmer, Dorothy J. Weston, Alison MacLeod, Simon P.E. Blockley

    Distally dispersed tephra layers have become an important tool in the investigation of palaeoenvironmental and archaeological records across the globe. They offer possibilities for the synchronisation and improved chronological control in those records to which they can be traced and hence contribute to an improved understanding of the pattern and timing of environmental and archaeological change during periods of rapid climatic adjustment. However, their use as robust isochronous markers for synchronising records is frequently compromised by uncertainties relating to stratigraphical context, precise chronology and chemical composition. Here we collate and review the tephrostratigraphical information dating to the Last Glacial-Interglacial Transition (LGIT; c. 16-8 ka BP) in the British Isles based on published and unpublished records obtained from 54 sites. Based on details of their stratigraphic position, chronology and chemical composition, we propose that 26 individual eruption events may be represented in this collective record which spans the LGIT. The great majority of these eruptives can be traced in origin to Iceland, but we also report on the recent discoveries of ultra-distal tephra from the North American Cascades range, including for the first time the Mount St Helens J Tephra at a site in southern Ireland. These particular ultra-distal discoveries have resulted from a reinterpretation of older data, demonstrating the potential importance of ‘unknown’ analyses in older tephra datasets. The outcome of this review is a comprehensive but provisional tephrostratigraphic framework for the LGIT in the British Isles, which helps to focus future research on parts of the scheme that are in need of further development or testing. The results, therefore, make an important contribution to the wider European tephrostratigraphic framework, while adding new discoveries of transcontinental isochronous tephra markers.

    更新日期:2019-01-09
  • Author Correction: Contrasting responses of autumn-leaf senescence to daytime and night-time warming
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-09
    Chaoyang Wu, Xiaoyue Wang, Huanjiong Wang, Philippe Ciais, Josep Peñuelas, Ranga B. Myneni, Ankur R. Desai, Christopher M. Gough, Alemu Gonsamo, Andrew T. Black, Rachhpal S. Jassal, Weimin Ju, Wenping Yuan, Yongshuo Fu, Miaogen Shen, Shihua Li, Ronggao Liu, Jing M. Chen, Quansheng Ge

    Author Correction: Contrasting responses of autumn-leaf senescence to daytime and night-time warming Author Correction: Contrasting responses of autumn-leaf senescence to daytime and night-time warming, Published online: 09 January 2019; doi:10.1038/s41558-018-0392-6 Author Correction: Contrasting responses of autumn-leaf senescence to daytime and night-time warming

    更新日期:2019-01-09
  • Are Slope Streaks Indicative of Global‐Scale Aqueous Processes on Contemporary Mars?
    Rev. Geophys. (IF 13.529) Pub Date : 2019-01-09
    Anshuman Bhardwaj; Lydia Sam; F. Javier Martín‐Torres; María‐Paz Zorzano

    Slope streaks are prevalent and intriguing dark albedo surface features on contemporary Mars. Slope streaks are readily observed in the equatorial and subequatorial dusty regolith regions with low thermal inertia. They gradually fade over decadal timescales. The proposed mechanisms for their formation vary widely based on several physicochemical and geomorphological explanations. The scientific community is divided in proposing both dry and wet mechanisms for the formation of slope streaks. Here we perform a systematic evaluation of the literature for these wet and dry mechanisms. We discuss the probable constraints on the various proposed mechanisms and provide perspectives on the plausible process driving global‐scale slope streak formation on contemporary Mars. Although per our understanding, a thorough consideration of the global distribution of slope streaks, their morphology and topography, flow characteristics, physicochemical and atmospheric coincidences, and terrestrial analogies weighs more in favor of several wet mechanisms, we acknowledge that such wet mechanisms cannot explain all the reported morphological and terrain variations of slope streaks. Thus, we suggest that explanations considering both dry and wet processes can more holistically describe all the observed morphological variations among slope streaks. We further acknowledge the constraints on the resolutions of remote sensing data and on our understanding of the Martian mineralogy, climate, and atmosphere and recommend continuous investigations in this direction using future remote sensing acquisitions and simulations. In this regard, finding more wet and dry terrestrial analogs for Martian slope streaks and studying them at high spatiotemporal resolutions can greatly improve our understanding.

    更新日期:2019-01-09
  • The Teleconnection of El Niño Southern Oscillation to the Stratosphere
    Rev. Geophys. (IF 13.529) Pub Date : 2019-01-08
    Daniela I.V. Domeisen; Chaim I. Garfinkel; Amy H. Butler

    El Niño and La Niña events in the tropical Pacific have significant and disrupting impacts on the global atmospheric and oceanic circulation. El Niño Southern Oscillation (ENSO) impacts also extend above the troposphere, affecting the strength and variability of the stratospheric polar vortex in the high latitudes of both hemispheres, as well as the composition and circulation of the tropical stratosphere. El Niño events are associated with a warming and weakening of the polar vortex in the polar stratosphere of both hemispheres, while a cooling can be observed in the tropical lower stratosphere. These impacts are linked by a strengthened Brewer‐Dobson circulation. Anomalous upward wave propagation is observed in the extratropics of both hemispheres. For La Niña, these anomalies are often opposite. The stratosphere in turn affects surface weather and climate over large areas of the globe. Since these surface impacts are long‐lived, the changes in the stratosphere can lead to improved surface predictions on time scales of weeks to months. Over the past decade, our understanding of the mechanisms through which ENSO can drive impacts remote from the tropical Pacific has improved. This study reviews the possible mechanisms connecting ENSO to the stratosphere in the tropics and the extratropics of both hemispheres while also considering open questions, including nonlinearities in the teleconnections, the role of ENSO diversity, and the impacts of climate change and variability.

    更新日期:2019-01-09
  • Geochemical and SIMS U-Pb rutile and LA–ICP–MS U-Pb zircon geochronological evidence of the tectonic evolution of the Mudanjiang Ocean from amphibolites of the Heilongjiang Complex, NE China
    Gondwana Res. (IF 5.657) Pub Date : 2019-01-08
    Yu Dong, Wen-chun Ge, Hao Yang, Xi-wen Liu, Jun-hui Bi, Zheng Ji, Wen-liang Xu

    This study presents new secondary-ion mass spectrometry (SIMS) rutile and laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) zircon U-Pb geochronological and whole-rock geochemical data for amphibolites of the Heilongjiang Complex, located within the Yilan area of NE China, to constrain the tectonic evolution of the Mudanjiang Ocean between the Songnen–Zhangguangcai Range and Jiamusi massifs. Magmatic zircon from amphibolites collected from the Yilan Marble Quarry yields a weighted mean 206Pb/238U age of 274 ± 2 Ma, which is interpreted as the protolithic age. Amphibolites from the Longlangang and Tuanshanzi areas yield rutile U-Pb ages of 177 ± 11 Ma and 172 ± 5 Ma, respectively, which are interpreted to reflect the cooling of these rocks below the closure temperature of Pb diffusion in rutile. Amphibolites from the Yilan Marble Quarry are enriched in light rare earth elements (LREEs) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta and P) relative to large ion lithophile elements (LILEs). Amphibolites from the Longlangang and Tuanshanzi areas have relatively flat chondrite-normalized rare earth element (REE) patterns, and remarkable negative Nb and Ta anomalies. Moreover, all of the amphibolites from the Heilongjiang Complex in the Yilan area have tholeiitic and arc-type geochemical affinities. These amphibolites formed by similar petrogenetic processes, but from distinct mantle sources. The magmas that formed these units were generated by the partial melting of mantle sources metasomatized by subducted slab fluids, and the magma that formed the amphibolites within the Yilan Marble Quarry may have also incorporated sedimentary material. Mantle peridotite from the garnet-spinel transition zone is a possible source for the protolith of amphibolites in the Yilan Marble Quarry, and spinel-peridotites may have been the magma sources for the protoliths of amphibolites in the Longlangang and Tuanshanzi areas. Combining our data for amphibolites from the Heilongjiang Complex in the Yilan area with the results of previous research on Late Paleozoic–Early Mesozoic arc magmatism and metamorphism, we infer that the Late Paleozoic–Early Mesozoic tectonic evolution of the Mudanjiang Ocean was characterized by double-sided subduction. These data indicate that the Mudanjiang Ocean closed during the Jurassic (180–160 Ma).

    更新日期:2019-01-08
  • Taking climate model evaluation to the next level
    Nat. Clim. Change (IF 19.181) Pub Date : 2019-01-07
    Veronika Eyring, Peter M. Cox, Gregory M. Flato, Peter J. Gleckler, Gab Abramowitz, Peter Caldwell, William D. Collins, Bettina K. Gier, Alex D. Hall, Forrest M. Hoffman, George C. Hurtt, Alexandra Jahn, Chris D. Jones, Stephen A. Klein, John P. Krasting, Lester Kwiatkowski, Ruth Lorenz, Eric Maloney, Gerald A. Meehl, Angeline G. Pendergrass, Robert Pincus, Alex C. Ruane, Joellen L. Russell, Benjamin M. Sanderson, Benjamin D. Santer, Steven C. Sherwood, Isla R. Simpson, Ronald J. Stouffer, Mark S. Williamson

    Earth system models are complex and represent a large number of processes, resulting in a persistent spread across climate projections for a given future scenario. Owing to different model performances against observations and the lack of independence among models, there is now evidence that giving equal weight to each available model projection is suboptimal. This Perspective discusses newly developed tools that facilitate a more rapid and comprehensive evaluation of model simulations with observations, process-based emergent constraints that are a promising way to focus evaluation on the observations most relevant to climate projections, and advanced methods for model weighting. These approaches are needed to distil the most credible information on regional climate changes, impacts, and risks for stakeholders and policy-makers.

    更新日期:2019-01-08
  • Late glacial and holocene vegetation and climate variations at Lake Tangra Yumco, central Tibetan Plateau
    Glob. Planet. Change (IF 3.982) Pub Date : 2019-01-07
    Qingfeng Ma, Liping Zhu, Xinmiao Lü, Junbo Wang, Jianting Ju, Thomas Kasper, Gerhard Daut, Torsten Haberzettl

    Reconstructing vegetation and climate changes after the Last Glacial Maximum on the Tibetan Plateau (TP) is a key to understand past Indian Summer Monsoon (ISM) dynamics and the interplay between the ISM and Westerlies. In this study, a pollen record covering the last deglaciation and Holocene from Lake Tangra Yumco on the central TP is presented. A regional vegetation and climate history on the TP during the late glacial period is inferred, corresponding to long-term variations in the atmospheric circulation systems. Prior to 16,100 cal a BP, most areas of the TP are covered by treeless vegetation, mostly affected by the Westerlies. After that three major vegetation shifts to more humid-preferring vegetation types on the TP are detected during 16,100–14,600, 13,600–13,000, 12,400–10,400 cal a BP. These shifts should indicate three rapid intensifications in the ISM. During the Holocene (11400–3000 cal a BP), alpine steppe persists in the Tangra Yumco basin. Moistest conditions with strongest ISM occur prior to 8600 cal a BP. After 8600 cal a BP, climate is probably drier with a weakened ISM. Moreover, drought events at 9600–9300, 8200–7400, 5500, 4700–3700, 3200 cal a BP indicate the weakening events of ISM. Vegetation and climate changes on the central TP are mainly insolation driven, but are also associated with the influence of Holocene abrupt cold events in the North Atlantic region.

    更新日期:2019-01-07
  • Cyclostratigraphy and astronomical tuning of the middle eocene terrestrial successions in the Bohai Bay Basin, Eastern China
    Glob. Planet. Change (IF 3.982) Pub Date : 2019-01-05
    Juye Shi, Zhijun Jin, Quanyou Liu, Rui Zhang, Zhenkai Huang

    The Eocene is an enigmatic and interesting period due to the critical thermal events that occurred during the gradual global cooling, which have been demonstrated in the marine realm but remain poorly reported in terrestrial basins. In this study, a continuous ~404-m interval of the Middle Eocene terrestrial succession in Bohai Bay Basin, eastern China, was recovered from Well Fanye-1 in the Shengli Oilfield. This interval provides a unique record that can be used to better clarify the terrestrial sedimentary responses to astronomically forced climate changes, especially the Middle Eocene Climatic Optimum (MECO). Here, a high-resolution cyclostratigraphic framework from the lower third member (Es3l) to the upper fourth chun member (Es4cu) of the Shahejie Formation (Middle Eocene) was constructed by using magnetic susceptibility (MS) as a palaeoenvironmental proxy, in association with new paleomagnetic data. Power spectral analysis of the MS series reveal that the wavelength ratios of stratigraphic cycles are ~43.1–25:15.3–7.5:4.5–3:2.2–1.4, consistent with the period ratios of astronomical cycles. Moreover, a high-resolution astronomical time scale (ATS) for Well Fanye-1 was established by tuning the MS curves to the astronomical solution in combination with the magnetic stratigraphic framework. The method for establishing a high-resolution ATS with magnetostratigraphy and cyclostratigraphy was well applied in Well Fanye-1, making it possible to recalculate the ages in the Jiyang Depression. Finally, the terrestrial record across the MECO event was constructed and characterized based on the widespread “interbedded” argillaceous limestone. The resulting record is consistent with the time frame based on marine records and highlights the apparently primary role of the MECO event in shaping Asian paleoenvironments.

    更新日期:2019-01-06
  • Trace fossils evidence of a complex history of nutrient availability and oxygen conditions during Heinrich Event 1
    Glob. Planet. Change (IF 3.982) Pub Date : 2019-01-06
    Francisco J. Rodríguez-Tovar, Javier Dorador, David A.V. Hodell

    The relationship between the behavior of tracemakers and paleoenvironmental conditions has been shown to be a useful tool in paleoceanographic studies. Here we present a detailed ichnological analysis of Heinrich Event 1 (H1), the youngest glacial North Atlantic large iceberg discharge, from Integrated Ocean Drilling Program Site U1308 in the central North Atlantic, located 2800 km from the mouth of the Hudson Strait. The ichnoassemblage consists of small trace fossils such as Phycosiphon, “Mycellia”/Trichichnus and Chondrites, and large ones including Planolites and Thalassinoides. The bioturbation index is generally low, from no bioturbation, to 30% of total bioturbated surface. Significant variations in composition, diversity and abundance of trace fossils are recorded, associated with the dual nature of H1 (comprising H1.1 and H1.2) and the period intervening between the two. Bottom- and pore-water oxygenation and benthic food availability are found to be the main limiting conditions for the tracemaker community, with some variations during the time span of H1, while factors such as sea water temperature had a minor impact.

    更新日期:2019-01-06
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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