bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biotic Response to Early Eocene Warming Events: Integrated Record From Offshore Zealandia, North Tasman Sea
Authors: Alegret L. , Harper D. T. , Agnini C. , Newsam C. , Westerhold T. , Cramwinckel Marlow J. , Dallanave E. , Dickens G. R. , Sutherland R. 
Published: July 2021

AbstractEnvironmental and biotic responses to early Eocene hyperthermal events in the southwest Pacific are critical for global paleoclimate reconstructions during Cenozoic greenhouse intervals, but detailed multidisciplinary studies are generally missing from this time and location. Eocene carbonate sediments were recovered during International Ocean Discovery Program Expedition 371 at Site U1510 on southern Lord Howe Rise in the Tasman Sea. Part of the Early Eocene Climatic Optimum (EECO; 53.26–49.14 Ma) and superimposed hyperthermal events have been identified based on refined calcareous nannofossil biostratigraphic data and carbon stable isotope records on bulk sediment and benthic foraminifera. Four negative carbon isotope excursions (CIEs) associated with negative oxygen isotope excursions are recognized within the EECO. Comparison with a global compilation of sites indicates these CIEs correlate to the K event (Eocene Thermal Maximum 3), and tentatively to the S, T, and U events. Sediments with a high carbonate content throughout the EECO provide an excellent opportunity to examine these CIEs, as carbonate dissolution often impacts correlative records elsewhere. Benthic foraminifera and calcareous nannoplankton taxa indicative of warm waters are most abundant during the K event, the most prominent hyperthermal of the EECO. Eutrophication of surface waters during the K event did not lead to increased trophic conditions at the seafloor, whereas a coupled response is observed during smaller hyperthermals. The biotic turnover sheds new light on the paleoenvironmental consequences of hyperthermal events.
Body‐Wave Tomographic Imaging of the Turkana Depression: Implications for Rift Development and Plume‐Lithosphere Interactions
Authors: Kounoudis R. , Bastow I. D. , Ebinger C. J. , Ogden C. S. , Ayele A. , Bendick R. , Mariita N. , Kianji G. , Wigham G. , Musila M. , Kibret B. 
Published: July 2021

AbstractThe Turkana Depression, a topographically subdued, broadly rifted zone between the elevated East African and Ethiopian plateaus, disrupts the N–S, fault‐bounded rift basin morphology that characterizes most of the East African Rift. The unusual breadth of the Turkana Depression leaves unanswered questions about the initiation and evolution of rifting between the Main Ethiopian Rift (MER) and Eastern Rift. Hypotheses explaining the unusually broad, low‐lying area include superposed Mesozoic and Cenozoic rifting and a lack of mantle lithospheric thinning and dynamic support. To address these issues, we have carried out the first body‐wave tomographic study of the Depression's upper mantle. Seismically derived temperatures at 100 km depth exceed petrological estimates, suggesting the presence of mantle melt, although not as voluminous as the MER, contributes to velocity anomalies. A NW–SE‐trending high wavespeed band in southern Ethiopia at 200 km depth is interpreted as refractory Proterozoic lithosphere which has likely influenced the localization of both Mesozoic and Cenozoic rifting. At 100 km depth below the central Depression, a single localized low wavespeed zone is lacking. Only in the northernmost Eastern Rift and southern Lake Turkana is there evidence for focused low wavespeeds resembling the MER, that bifurcate below the Depression and broaden approaching southern Ethiopia further north. These low wavespeeds may be attributed to melt‐intruded mantle lithosphere or ponded asthenospheric material below lithospheric thin‐spots induced by the region's multiple rifting phases. Low wavespeeds persist to the mantle transition zone suggesting the Depression may not lack mantle dynamic support in comparison to the two plateaus.
Multi‐Decadal Change in Western US Nighttime Vapor Pressure Deficit
Authors: Chiodi Andrew M. , Potter Brian E. , Larkin Narasimhan K. 
Published: July 2021

AbstractAmid reports from western US wildland fire managers that, compared to when many started their careers, fires are burning longer throughout the day before reducing in intensity overnight, we examined decadal changes in nighttime vapor pressure deficits over the western United States with a focus on the summer fire season. We calculated changes using a recently updated observation‐assimilating reanalysis (ERA5) available at hourly resolution over the 1980–2019 period. Analysis identifies the proximate cause (atmospheric temperature vs. moisture content) of the observed changes and the extent to which they have been captured in climate model simulations. Increases in nighttime vapor pressure deficits of >50% in 40 years are evident over foothills of mountains ranges adjacent to arid plateaus. The largest observed increases greatly exceed the forced climate‐model response. Correlation analysis reveals a broad link between the variability of western US summer‐nighttime vapor pressure deficit and the Pacific Decadal Oscillation.
Plate Boundary and Triple Junction Control of Shatsky Rise Formation and Implications for Other Ocean Plateaus
Authors: Georgen Jennifer E. , Shotorban A. Katrina 
Published: July 2021

AbstractIn the study of marine large igneous provinces, investigations often focus on the importance of mantle plumes in generating excess magmatism. Few studies, however, have addressed the role of plate boundary processes in promoting widespread and extensive mantle melting. This study investigates how spreading center geometry may have facilitated the emplacement of Shatsky Rise, an oceanic plateau in the western Pacific Ocean. The largest structure within Shatsky Rise, Tamu Massif, was created ∼140–150 Ma at the Pacific‐Izanagi‐Farallon (PIF) ridge‐ridge‐ridge triple junction. Moreover, the PIF triple junction was one of three triple junctions operating in close proximity at the time, as the nascent Pacific Plate (NPP) began to expand in size. This study suggests that the thermal conditions of the NPP, which likely resulted in a large area of thin lithosphere, could have significantly facilitated widespread mantle melting as well as the magmatic expression of any nearby mantle plume.
Sources of Uncertainty in Multimodel Large Ensemble Projections of the Winter North Atlantic Oscillation
Authors: McKenna C. M. , Maycock A. C. 
Published: July 2021

AbstractProjections of the winter North Atlantic circulation exhibit large spread. Coupled Model Intercomparison Project archives typically provide only a few ensemble members per model, rendering it difficult to quantify reducible model structural uncertainty and irreducible internal variability (IV) in projections. We estimate using the Multimodel Large Ensemble Archive that model structural differences explain two‐thirds of the spread in late 21st century (2080–2099) projections of the winter North Atlantic Oscillation (NAO). This estimate is biased by systematic model errors in the forced NAO response and IV. Across the North Atlantic, the NAO explains a substantial fraction of the spread in mean sea level pressure (MSLP) projections due to IV, except in the central North Atlantic. Conversely, the spread in North Atlantic MSLP projections associated with model differences is largely unexplained by the NAO. Therefore, improving understanding of the NAO alone may not constrain the reducible uncertainty in North Atlantic MSLP projections.
Interseismic Deformation From Sentinel‐1 Burst‐Overlap Interferometry: Application to the Southern Dead Sea Fault
Authors: Li Xing , Jónsson Sigurjón , Cao Yunmeng 
Published: July 2021

AbstractInterferometric Synthetic Aperture Radar (InSAR) data are increasingly being used to map interseismic deformation with ascending and descending‐orbit observations allowing for resolving the near‐east and vertical displacement components. The north component has, however, been difficult to retrieve due to the limited sensitivity of standard InSAR observations in that direction. Here, we address this problem by using time‐series analysis of along‐track interferometric observations in burst‐overlap areas of the Terrain Observation with Progressive Scan imaging mode of the Sentinel‐1 radar satellites. We apply this method to the southern part of the near‐north striking Dead Sea transform fault to show that the ∼5 mm/year relative motion is well recovered. Furthermore, the results indicate the locking depth of the fault decreases toward the south as it enters the transtensional Gulf of Aqaba basin. Our results show that time‐series analysis of burst‐overlap interferometric observations can be used to obtain meaningful interseismic deformation rates of slow‐moving and northerly striking faults.
Fluxes of Carbon Dioxide From Managed Ecosystems Estimated by National Inventories Compared to Atmospheric Inverse Modeling
Authors: Chevallier Frédéric 
Published: July 2021

AbstractThe UNFCCC reporting guidelines on annual emission inventories have been encouraging comparison of national inventory reports with atmospheric measurements or atmospheric inverse modeling. We have initiated a framework to compare two CO2 atmospheric inversions with the net agricultural, forestry and other land use (AFOLU) fluxes reported by 10 parties to the UNFCCC. Our study highlights large conceptual differences or ambiguities (temporal support, spatial perimeter, scope of the processes) between inventory reports and between these reports and what the atmosphere sees. We recommend that more effort be invested into documenting the inventories in order to allow unambiguous conversion between reported values and the way they are seen by the atmosphere. We also highlight the potential of Bayesian atmospheric inversion products generated in quasi‐near‐real time with robust error bars and consistently across the world, to directly inform international CO2 flux accounting for the AFOLU sector in large countries or groups of countries.
North American East Coast Sea Level Exhibits High Power and Spatiotemporal Complexity on Decadal Timescales
Authors: Little Christopher M. , Piecuch Christopher G. , Ponte Rui M. 
Published: July 2021

AbstractTide gauges provide a rich, long‐term, record of the amplitude and spatiotemporal structure of interannual to multidecadal coastal sea‐level variability, including that related to North American east coast sea level “hotspots.” Here, using wavelet analyses, we find evidence for multidecadal epochs of enhanced decadal (10–15 year period) sea‐level variability at almost all long (70 years) east coast tide gauge records. Within this frequency band, large‐scale spatial covariance is time‐dependent; notably, coastal sectors north and south of Cape Hatteras exhibit multidecadal epochs of coherence (1960–1990) and incoherence (1990‐present). Results suggest that previous interpretations of along coast covariance, and its underlying physical drivers, are clouded by time‐dependence and frequency‐dependence. Although further work is required to clarify the mechanisms driving sea‐level variability in this frequency band, we highlight potential associations with the North Atlantic sea surface temperature tripole and Atlantic Multidecadal Variability.
Formation of Horizontally Deflected Slabs in the Mantle Transition Zone Caused by Spinel‐to‐Post‐Spinel Phase Transition, Its Associated Grainsize Reduction Effects, and Trench Retreat
Authors: Mao Wei , Zhong Shijie 
Published: July 2021

AbstractSeismic observations indicate accumulation of subducted slabs in the mantle transition zone in many subduction zones. By systematically conducting 2‐D numerical experiments, we demonstrate that a weak layer or zone beneath the spinel‐to‐post‐spinel phase transition leads to horizontally deflected (stagnant) slab structures in the mantle transition zone, which is consistent with recent studies of 3‐D global mantle convection models. Trench retreat velocity, Clapeyron slope and the viscosity contrast between the lower mantle and mantle transition zone also affect horizontally deflected slab formation. By considering grain size dependent viscosity and grainsize evolution for slabs going through the phase change in the lower mantle, our models with a dynamically generated weak zone beneath the phase boundary indicate that the geometry and viscosity reduction of the weak zone is strongly affected by grain growth rate. A smaller grain growth rate results in a thicker and wider weak zone that promotes deflected slab formation.
Quantifying the Imprints of Stratospheric Contributions to Interhemispheric Differences in Tropospheric CFC‐11, CFC‐12, and N2O Abundances
Authors: Lickley Megan , Solomon Susan , Kinnison Doug , Krummel Paul , Mühle Jens , O'Doherty Simon , Prinn Ronald , Rigby Matthew , Stone Kane A. , Wang Peidong , Weiss Ray , Young Dickon 
Published: July 2021

AbstractFor trace gases destroyed in the stratosphere, mass flux across the tropopause can substantially influence observed surface hemispheric differences (NH‐SH). Here, we quantify associations between observed stratospheric and tropospheric NH‐SH growth rate anomalies of CFC‐11, CFC‐12, and N2O. We employ a chemistry climate model along with satellite and global surface station observations. Our model explains 60% of observed N2O NH‐SH growth rate variability from 2005 to 2019, compared to 30% for CFC‐11% and 40% for CFC‐12, supporting evidence that unexpected anthropogenic emissions caused sustained positive NH‐SH anomalies in these CFCs from 2012 to 2017. Between 2012 and 2015, the observed CFC‐11 NH‐SH difference grew by 1.7 ppt; our model explains 0.5 ± 0.1 ppt of this growth, but not the duration. Our model suggests that in the absence of further emission anomalies, new NH‐SH positive tracer anomalies should have occurred in 2020, and predicts small negative anomalies in 2021.
Ion Scattering and Energization in Filamentary Structures Through Earth's Magnetosheath
Authors: Chaston C. C. , Travnicek P. 
Published: July 2021

AbstractMulti‐point measurements on kinetic scales through Earth's magnetosheath have revealed a spectrum of filamentary currents and vortical flows advected with the shocked plasmas outside the magnetopause. The spectral energy density in these structures is correlated with enhanced ion temperatures. Using an empirically derived statistical model based on fluid‐kinetic theory for these structures we demonstrate how they act to scatter magnetosheath ions. Through the combined action of energization in the direction perpendicular to the background magnetic field along chaotic orbits, and pitch‐angle scattering into the parallel direction appreciable ion energization occurs. These dynamics drive heating while generating non‐thermal energetic tails similar to that observed. It is shown how the operation of this process depends on the field topology with deviations from planar form and counter‐propagation required to drive significant energization. This process will modulate ion anisotropies through the magnetosheath independent of both adiabatic effects and the action of anisotropy instabilities.
Ground Observation of Negative Sprites Over a Tropical Thunderstorm as the Embryo of Hurricane Harvey (2017)
Authors: Wang Yongping , Lu Gaopeng , Cummer Steven A. , Lucena Frankie , Cohen Morris B. , Ren Huan , Li Jiagen , Cheng Zhengwei , Zhang Shoubao 
Published: July 2021

AbstractWe report on the observation of six red sprites produced by negative cloud‐to‐ground (CG) lightning strokes in a tropical thunderstorm that later evolved into Hurricane Harvey (2017). Most of these sprites conformed to the morphological characteristics of typical negative sprites previously observed over continental thunderstorms. The sprite‐producing CG strokes were located in or near the deep convection region and their impulse charge moment changes all exceeded −500 C‐km. During the sprite generation stage, the CG lightning stroke rate declined and the tropical thunderstorm structure appeared stable. Our analysis suggests that tropical marine meteorological systems, such as tropical disturbances, depressions, and thunderstorms are more likely to be main production systems of negative sprites. The frequent occurrence of 18 gigantic jets produced by the same thunderstorm further indicates that the thundercloud charge structures of sprite‐producing oceanic thunderstorms are significantly different from that of continental thunderstorms.
Gravity Wave Observations by the Mars Science Laboratory REMS Pressure Sensor and Comparison With Mesoscale Atmospheric Modeling With MarsWRF
Authors: Guzewich Scott D. , de la Torre Juárez Manuel , Newman Claire E. , Mason Emily , Smith Michael D. , Miller Nina , Khayat Alain S. J. , Kahanpää Henrik , Viúdez‐Moreiras Daniel , Richardson Mark I. 
Published: July 2021

AbstractSurface pressure measurements on Mars have revealed a wide variety of atmospheric phenomena. The Mars Science Laboratory Rover Environmental Monitoring Station pressure sensor data set is now the longest duration record of surface pressure on Mars. We use the first 2580 Martian sols, nearly 4 Mars years, of measurements to identify atmospheric pressure waves with periods of tens of minutes to hours using wavelet analysis on residual pressure after the tidal harmonics are removed. We find these waves have a clear diurnal cycle with strongest activity in the early morning and late evening and a seasonal cycle with the strongest waves in the second half of the martian year (Ls = 180–360°). The strongest such waves of the entire mission occurred during the Mars Year 34 global dust storm. Comparable atmospheric waves are identified using atmospheric modeling with the MarsWRF general circulation model in a “nested” high spatial resolution mode. With the support of the modeling, we find these waves best fit the expected properties of inertia‐gravity waves with horizontal wavelengths of O(100s) of km.
Evolution of Ocean Productivity in the Sub‐Tropical West Pacific Ocean Across the Last Deglaciation
Authors: Hu Bangqi , Zhang Handan , Ouyang Siqi , Zhao Jingtao , Wang Feifei , Li Qing , Jaccard Samuel L. , Luo Yiming 
Published: July 2021

AbstractChanges in marine export productivity may have played a prominent role in the atmospheric CO2 rise and associated warming of the last deglaciation, via their impact on the air‐sea partitioning of CO2. To study the evolution of marine export production in the western subtropical Pacific Ocean during the last deglaciation and the mechanisms governing these changes, 230Th‐normalization has been applied on a sediment core retrieved from the Okinawa Trough. The reconstructed export productivity record shows two prominent peaks, centered around 14 and 17 ka. Given that phytoplankton growth at our study site is limited by the availability of nutrients today, elevated macro‐nutrient supply must have been responsible for sustaining the two deglacial productivity peaks. Specifically, higher nutrient supply originating from the subpolar gyre via subsurface water advection, with enhanced vertical mixing in the subpolar gyre during early HS1 and enhanced wind‐driven upwelling during the B/A, would have fueled phytoplankton productivity and export. In contrast, reduced nutrient supply to the euphotic zone caused by gyre circulation changes would have lead to decreased export production during the Holocene. These observations lend support to a predominant control of nutrient availability on the evolution of the marine carbon cycle in the subtropical west Pacific Ocean across the last deglaciation.
Retracted: Control of Multiple Detachments on Structural Development in the Southern Junggar Fold‐and‐Thrust Belt, Northern Tian Shan: Implications for Seismic Hazard Assessment
Authors: Qiu Jianhua , Rao Gang , Yu Yangli , Wang Xin , Peng Zhenyu , Gao Lin , Yang Disheng , Xiao Lixin , Yao Qi 
Published: July 2021

AbstractAs large earthquakes in contractional fold‐and‐thrust belts are usually associated with complex ruptures along multiple faults or fault splays, the evaluation of potential rupture extent and relevant hazards continues to be challenging. We present a case study on the geometry and kinematic evolution of the southern Junggar fold‐and‐thrust belt, northern Tian Shan, where the 1906 M 8 Manas earthquake occurred. Our interpretations of seismic reflection profiles acquired during oil and gas exploration demonstrate that multiple detachments played significant roles in controlling the structural segmentation. We speculate that seismic potential in active fold‐and‐thrust belts can be under‐estimated by relying on the mapped surface fault traces. Structural analysis of subsurface images in sufficient detail may provide important insights into seismic hazard evaluation and hence complement traditional paleo‐seismic studies, particularly in densely populated regions such as the city of Urumqi.
Microplastics accumulate fungal pathogens in terrestrial ecosystems
Authors: Gkoutselis Gerasimos , Rohrbach Stephan , Harjes Janno , Obst Martin , Brachmann Andreas , Horn Marcus A. , Rambold Gerhard 
Published: July 2021

AbstractMicroplastic (MP) is a pervasive pollutant in nature that is colonised by diverse groups of microbes, including potentially pathogenic species. Fungi have been largely neglected in this context, despite their affinity for plastics and their impact as pathogens. To unravel the role of MP as a carrier of fungal pathogens in terrestrial ecosystems and the immediate human environment, epiplastic mycobiomes from municipal plastic waste from Kenya were deciphered using ITS metabarcoding as well as a comprehensive meta-analysis, and visualised via scanning electron as well as confocal laser scanning microscopy. Metagenomic and microscopic findings provided complementary evidence that the terrestrial plastisphere is a suitable ecological niche for a variety of fungal organisms, including important animal and plant pathogens, which formed the plastisphere core mycobiome. We show that MPs serve as selective artificial microhabitats that not only attract distinct fungal communities, but also accumulate certain opportunistic human pathogens, such as cryptococcal and Phoma-like species. Therefore, MP must be regarded a persistent reservoir and potential vector for fungal pathogens in soil environments. Given the increasing amount of plastic waste in terrestrial ecosystems worldwide, this interrelation may have severe consequences for the trans-kingdom and multi-organismal epidemiology of fungal infections on a global scale.