bluuebunny/crossref_metadata_2025_split huggingface dataset:
Listening for the Landing: Seismic Detections of Perseverance's Arrival at Mars With InSight
Authors: Fernando Benjamin , Wójcicka Natalia , Froment Marouchka , Maguire Ross , Stähler Simon C. , Rolland Lucie , Collins Gareth S. , Karatekin Ozgur , Larmat Carene , Sansom Eleanor K. , Teanby Nicholas A. , Spiga Aymeric , Karakostas Foivos , Leng Kuangdai , Nissen‐Meyer Tarje , Kawamura Taichi , Giardini Domenico , Lognonné Philippe , Banerdt Bruce , Daubar Ingrid J. 
Published: March 2021

AbstractThe entry, descent, and landing (EDL) sequence of NASA's Mars 2020 Perseverance Rover will act as a seismic source of known temporal and spatial localization. We evaluate whether the signals produced by this event will be detectable by the InSight lander (3,452 km away), comparing expected signal amplitudes to noise levels at the instrument. Modeling is undertaken to predict the propagation of the acoustic signal (purely in the atmosphere), the seismoacoustic signal (atmosphere‐to‐ground coupled), and the elastodynamic seismic signal (in the ground only). Our results suggest that the acoustic and seismoacoustic signals, produced by the atmospheric shock wave from the EDL, are unlikely to be detectable due to the pattern of winds in the martian atmosphere and the weak air‐to‐ground coupling, respectively. However, the elastodynamic seismic signal produced by the impact of the spacecraft's cruise balance masses on the surface may be detected by InSight. The upper and lower bounds on predicted ground velocity at InSight are 2.0 × 10−14 and 1.3 × 10−10 m s−1. The upper value is above the noise floor at the time of landing 40% of the time on average. The large range of possible values reflects uncertainties in the current understanding of impact‐generated seismic waves and their subsequent propagation and attenuation through Mars. Uncertainty in the detectability also stems from the indeterminate instrument noise level at the time of this future event. A positive detection would be of enormous value in constraining the seismic properties of Mars, and in improving our understanding of impact‐generated seismic waves.
Alkalinity Production Coupled to Pyrite Formation Represents an Unaccounted Blue Carbon Sink
Authors: Reithmaier Gloria M. S. , Johnston Scott G. , Junginger Tobias , Goddard Madeline M. , Sanders Christian J. , Hutley Lindsay B. , Ho David T. , Maher Damien T. 
Published: March 2021

AbstractBlue carbon ecosystems, including mangroves, saltmarshes, and seagrasses, mitigate climate change by storing atmospheric carbon. Previous blue carbon research has focused on organic carbon stocks. However, recent studies suggest that lateral inorganic carbon export might be equally important. Lateral export is a long‐term carbon sink if carbon is exported as alkalinity (TAlk) produced via sulfate reduction coupled to pyrite formation. This study evaluates drivers of pyrite formation in blue carbon ecosystems, compares pyrite production to TAlk outwelling rates, and estimates global pyrite stocks in mangroves. We quantified pyrite stocks in mangroves, saltmarshes, and seagrasses along a latitudinal gradient on the Australian East Coast, including a mangrove dieback area, and in the Everglades (Florida, USA). Our results indicate that pyrite stocks were driven by a combination of biomass, tidal amplitude, sediment organic carbon, sediment accumulation rates, rainfall, latitude, temperature, and iron availability. Pyrite stocks were three‐times higher in mangroves (103 ± 61 Mg/ha) than in saltmarshes (30 ± 30 Mg/ha) and seagrasses (32 ± 1 Mg/ha). Mangrove pyrite stocks were linearly correlated to TAlk export at sites where sulfate reduction was the dominant TAlk producing process. However, pyrite generation could not explain all TAlk outwelling. We present the first global model estimating pyrite stocks in mangroves, giving a first‐order estimate of 197 Mg/ha (RMSE = 24 Mg/ha). In mangroves, estimated global TAlk production coupled to pyrite formation (∼3 mol/m2/y) is equal to ∼24% of their global carbon burial rate, highlighting the importance of including TAlk export in future blue carbon budgets.
The Role of Sulfuric Acid in Continental Weathering: Insights From Dissolved Major Ions and Inorganic Carbon Isotopes of the Teesta River, Lower Brahmaputra System
Authors: Das Satyabrata , Tripathy Gyana Ranjan , Rai Santosh K. , Danish Mohd , Thakur Divya , Dutt Som , Sarangi Shushanta 
Published: March 2021

AbstractChemical weathering in the Himalayan river basins plays a key role in the global carbon cycle that controls the climate. In this contribution, the spatial distribution of dissolved major ions and (inorganic) carbon isotopic compositions of the Teesta River, a major tributary of the Brahmaputra River, has been investigated to constrain solute sources, weathering patterns, and acids involved in these processes. Mixing diagrams and piper plots of major ions indicate a dominant solutes supply by weathering of silicates and carbonates. The average sulfate concentration of the Teesta samples (92 ± 47 µM) is significantly higher than that reported earlier for atmospheric deposition (∼5 µM) in this basin. The carbon isotopic compositions of the dissolved inorganic fractions (δ13CDIC) of the samples vary between −11.87‰ and −3.82‰ (mean: −7‰ ± 2‰). Comparison of δ13CDIC – SO4/(SO4 + HCO3) – HCO3/(Ca + Mg) trends with their corresponding values expected for H2SO4 and H2CO3 acid‐mediated weathering indicates that both these acids contribute to chemical weathering in the Teesta river catchment. Inversion modeling of major ions and δ13CDIC data have been used to quantify the impact of carbonic (H2CO3) and sulfuric acids (H2SO4) on the Teesta water chemistry. On average, the fractions of cations derived from H2CO3‐mediated weathering of carbonates (0.27 ± 0.14) and silicates (0.20 ± 0.09) are comparable with H2SO4‐mediated carbonate (0.38 ± 0.18) and silicate (0.15 ± 0.11) weathering in this basin. These results show that the amount of CO2 uptake (via H2CO3‐mediated silicate weathering) and release (via H2SO4‐mediated carbonate weathering) are in balance for the Teesta River.
The Effect of the Martian 2018 Global Dust Storm on HDO as Predicted by a Mars Global Climate Model
Authors: Rossi Loïc , Vals Margaux , Montmessin Franck , Forget François , Millour Ehouarn , Fedorova Anna , Trokhimovskiy Alexander , Korablev Oleg 
Published: March 2021

AbstractThe deuterium to hydrogen (D/H) ratio is commonly used to investigate the history of water on Mars, yet the mechanisms controlling present‐day HDO behavior are poorly understood. Significant variations of the D/H ratio were first predicted on the basis of a 3D global climate model, which were later confirmed by ground‐based observations. This behavior, consisting of lower HDO/H2O ratios in the colder regions of Mars, is related to the isotopic fractionation occurring at condensation. We leverage this previous effort and present an updated implementation, using the modern version of the model, that remains in agreement with the older version. We explore the impact of the global dust storm (GDS) that occurred during Martian year 34 (MY34) on HDO. Our simulations indicate that HDO is on average 40% more abundant at 100 km during the MY34 GDS year than during a regular year, with likely large consequences for the escape flux of water that year.
Deadly Heat Stress to Become Commonplace Across South Asia Already at 1.5°C of Global Warming
Authors: Saeed Fahad , Schleussner Carl‐Friedrich , Ashfaq Moetasim 
Published: March 2021

AbstractSouth Asia (SA) is one of those hotspots where earliest exposure to deadly wet‐bulb temperatures (Tw >35°C) is projected in warmer future climates. Here we find that even today parts of SA experience the upper limits of labor productivity (Tw >32°C) or human survivability (Tw >35°C), indicating that previous estimates for future exposure to Tw‐based extremes may be conservative. Our results show that at 2°C global warming above pre‐industrial levels, the per person exposure approximately increases by 2.2 (2.7) folds for unsafe labor (lethal) threshold compared to the 2006–2015 reference period. Limiting warming to 1.5°C would avoid about half that impact. The population growth under the middle‐of‐the‐road socioeconomic pathway could further increase these exposures by a factor of ∼2 by the mid‐century. These results indicate an imminent need for adaptation measures, while highlighting the importance of stringent Paris‐compatible mitigation actions for limiting future emergence of such conditions in SA.
An Atmospheric Signal Lowering the Spring Predictability Barrier in Statistical ENSO Forecasts
Authors: Mukhin Dmitry , Gavrilov Andrey , Seleznev Aleksei , Buyanova Maria 
Published: March 2021

AbstractThe loss of autocorrelations of tropical sea surface temperatures (SST) during late spring, also called the spring predictability barrier (SPB), is a factor that strongly limits the predictability of El Nino Southern Oscillation (ENSO), and especially the statistical SST‐based ENSO forecasts starting from the winter‐spring season. Recent studies show that Pacific atmospheric circulation anomalies in winter‐spring may have a long‐term impact on the summer tropical climate via the SST footprint. Here, we infer an index based on sea level pressure (SLP) data from February to March in a single area surrounding Hawaii, and show that this area is the most informative part of the large SLP pattern initiating the SST footprinting mechanism. We then construct a statistically optimal linear model of the Nino 3.4 index taking this atmospheric index as a forcing. We find that this forcing efficiently lowers the SPB and provides significant improvements of interseasonal Niño 3.4 forecasts.
Poroelasticity Contributes to Hydraulic‐Stimulation Induced Pressure Changes
Authors: Dutler N. O. , Valley B. , Amann F. , Jalali M. , Villiger L. , Krietsch H. , Gischig V. , Doetsch J. , Giardini D. 
Published: March 2021

AbstractHigh‐pressure fluid injections cause transient pore pressure changes over large distances, which may induce seismicity. The zone of influence for such an injection was studied at high spatial resolutions in six decameter‐scaled fluid injection experiments in crystalline rock. Pore pressure time series revealed two distinct responses based on the lag time and magnitude of pressure change, namely, a near‐ and far‐field response. The near‐field response is due to pressure diffusion. In the far‐field, the fast response time and decay of pressure changes are produced by effective stress changes in the anisotropic stress field. Our experiments confirm that fracture fluid pressure perturbations around the injection point are not limited to the near field and can extend beyond the pressurized zone.
Spatiotemporal Heterogeneity of Aerosol and Cloud Properties Over the Southeast Atlantic: An Observational Analysis
Authors: Chang Ian , Gao Lan , Burton Sharon P. , Chen Hong , Diamond Michael S. , Ferrare Richard A. , Flynn Connor J. , Kacenelenbogen Meloë , LeBlanc Samuel E. , Meyer Kerry G. , Pistone Kristina , Schmidt Sebastian , Segal‐Rozenhaimer Michal , Shinozuka Yohei , Wood Robert , Zuidema Paquita , Redemann Jens , Christopher Sundar A. 
Published: March 2021

AbstractThe southeast Atlantic has expansive aerosol plumes overlying clouds for a third of each year. Aerosol optical depths (AODs) were measured from the airborne Sun photometer and lidar during the 2016 NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) field campaign. We compare these measurements with one another and with collocated Moderate Resolution Imaging Spectroradiometer (MODIS) observations at native spatial resolutions using <15‐min and 3‐h temporal collocation criteria. We find better statistical relationships for the <15‐min temporal resolution, indicating that AODs in the southeast Atlantic commonly vary below three‐hourly temporal scales over MODIS spatial resolutions. We also use the airborne Solar Spectral Flux Radiometer (SSFR) to conduct the first comprehensive evaluation of attenuation‐corrected below‐aerosol cloud optical depths (CODs) from MODIS and the Spinning Enhanced Visible and Infrared Imager (SEVIRI). MODIS COD retrievals improve their agreement with the SSFR when accounting for overlying aerosol attenuation whereas SEVIRI CODs are mostly underestimated.
More Significant Impacts From New Particle Formation on Haze Formation During COVID‐19 Lockdown
Authors: Tang Lizi , Shang Dongjie , Fang Xin , Wu Zhijun , Qiu Yanting , Chen Shiyi , Li Xin , Zeng Limin , Guo Song , Hu Min 
Published: March 2021

AbstractDuring the COVID‐19 lockdown in 2020, large‐scale industrial and transportation emissions were reduced, but high PM2.5 concentration still occurred. This study investigated the variation of particle number size distribution during the lockdown, and analyzed the characteristics of new particle formation (NPF) events and its potential impact on haze formation. Through measurement conducted in urban Beijing during the first 3 months of 2020, and comparison with year‐over‐year data, the decrease of primary Aitken‐mode particles was observed. However, frequencies, formation rates and growth rates of NPF events remained stable between 2020 and 2019 in the same period. As a result, >25 nm particles produced by NPF events, would play a more important role in serving as the haze formation “seeds” compared to those produced by primary emissions. This finding emphasizes the significance on the understanding of NPF mechanisms when making pollution mitigation policy in the future.
How Robust Is the Apparent Break‐Down of Northern High‐Latitude Temperature Control on Spring Carbon Uptake?
Authors: Joyce Peter , Brienen Roel , Buermann Wolfgang , Wilson Chris , Chipperfield Martyn P. , Claret Mariona , Gloor Manuel 
Published: March 2021

AbstractVegetation growth in northern high‐latitudes during springtime is strongly temperature limited, and thus anomalously warm springs are expected to result in an increased drawdown of carbon dioxide (CO2). However, a recent analysis of the relationship between spring temperature anomalies and atmospheric CO2 anomalies at Point Barrow, Alaska, suggests that the link between spring carbon uptake by northern ecosystems and temperature anomalies has been weakening over recent decades due to a diminishing control of temperature on plant productivity. Upon further analysis, covering the 1982–2015 period, we found no significant change in the relationship between spring vegetation productivity derived from remote sensing data and air temperature. We showed that a reduction in spatial coherence of temperature anomalies, alongside a significant sensitivity to atmospheric transport, is likely responsible for the apparent weakening. Our results, therefore, suggest that spring temperature remains as an important control of northern high‐latitude CO2 uptake.
Extracting Near‐Field Seismograms From Ocean‐Bottom Pressure Gauge Inside the Focal Area: Application to the 2011 Mw 9.1 Tohoku‐Oki Earthquake
Authors: Kubota Tatsuya , Saito Tatsuhiko , Tsushima Hiroaki , Hino Ryota , Ohta Yusaku , Suzuki Syuichi , Inazu Daisuke 
Published: March 2021

AbstractRecent studies have shown that ocean‐bottom pressure gauges (OBPs) can record seismic waves in addition to tsunamis and seafloor permanent displacements, even if they are installed inside the focal area where the signals are extremely large. We developed a method to extract dynamic ground motion waveforms from near‐field OBP data consisting of a complex mixture of various signals, based on an inversion analysis along with a theory of tsunami generation. We applied this method to the OBP data of the 2011 Tohoku‐Oki earthquake. We successfully extracted the low‐frequency vertical seismograms inside the focal area (f < ∼0.05 Hz), although those of the Mw ∼9 megathrust earthquake had never previously been reported. The seismograms suggested two dominant energy releases around the hypocenter. The seismic wave signals recorded by the near‐field OBP will be important not only to reveal earthquake ruptures and tsunami generation processes but also to conduct real‐time tsunami forecasts.
Simulated Thermocline Tilt Over the Tropical Indian Ocean and Its Influence on Future Sea Surface Temperature Variability
Authors: Wang Guojian , Cai Wenju , Santoso Agus 
Published: March 2021

AbstractMost coupled climate models simulate an overly shallow thermocline over the southeastern equatorial Indian Ocean (SEIO). Through the Bjerknes feedback loop, the associated unrealistic thermocline tilt leads to warmer sea surface temperature (SST) over the western equatorial Indian Ocean than the SEIO, which is conducive to equatorial easterly winds. Similar to phase 5 of the Coupled Model Intercomparison Project (CMIP), phase 6 of the CMIP continues to simulate such overly tilted thermocline. On the one hand, this leads to overly strong SST variability, and on the other hand, it provides an inherent limit for the thermocline to incline further under greenhouse warming. Consequently, models with a more realistic tilt in the present‐day climate project a greater shoaling of the thermocline under global warming, which facilities upwelling of cool subsurface water, leading to stronger increase in SST variability over the SEIO, compared to models with an overly large thermocline tilt.
The Synoptic to Decadal Variability in the Winter Surface Wind Speed Over China by the Weather Regime View
Authors: Zhang Zhengtai , Wang Kaicun 
Published: March 2021

AbstractThe observed surface wind speed (SWS) has declined over the past 4 decades over China, which have has been examined from a climatological perspective. However, the SWS is highly variable and is dependent on the weather regime (WR). This study investigates the variability of winter SWS under six typical WRs and assesses the variability at the synoptic to decadal time scales. Our results reveal that the WRs impose important impacts on the spatial pattern and inter‐annual variability of SWS over China. The Siberian high pressure exerts an important influence on the WR occurrence over Eastern Asia and affects the SWS variations, with more prominent impacts at the decadal time scale. The Aleutian low pressure exhibits weak inter‐annual correlations with the SWS under all WRs but reveals closer decadal connections under certain WRs. However, WRs cannot sufficiently explain the decreasing trend of SWS from 1980 to 2017.
Whistler‐Mode Waves Trapped by Density Irregularities in the Earth's Magnetosphere
Authors: Ke Yangguang , Chen Lunjin , Gao Xinliang , Lu Quanming , Wang Xueyi , Chen Rui , Chen Huayue , Wang Shui 
Published: March 2021

AbstractWhistler‐mode waves are electromagnetic waves pervasively observed in the Earth's and other planetary magnetospheres. They are considered to be mainly responsible for producing the hazardous radiation and diffuse aurora, which heavily relies on their properties. Density irregularities, frequently observed in the Earth's magnetospheres, are found to change largely the properties of whistler‐mode waves. Here we report, using Van Allen Probes measurements, whistler‐mode waves strongly modulated by two different density enhancements. With particle‐in‐cell simulations, we propose wave trapping caused by field‐aligned density irregularities (ducts) may account for this phenomenon. Simulation results show that whistler‐mode waves can be trapped inside the enhanced density ducts. These trapped waves remain quasi‐parallel and usually get much larger amplitudes than those unducted whistler waves during propagation away from the magnetic equator, and tend to focus at a spatially narrow channel, consistent with observations. Our results imply density irregularities may be significant to modulate radiation‐belt electrons.
A New Method to Calculate the Fluxgate Magnetometer Offset in the Interplanetary Magnetic Field: 1. Using Alfvén Waves
Authors: Wang Guoqiang , Pan Zonghao 
Published: March 2021

AbstractMagnetic field measurements are essential to explore space. However, the measurement of the fluxgate magnetometer (FGM) is not zero in the null magnetic field. Three methods have been provided to calculate the zero offset of the FGM on‐board spacecraft in the solar wind based on the assumption that the fluctuations are Alfvén waves. Here, we develop a new method to calculate the zero offset O based on the characteristic of Alfvén waves. We first build an offset cube based on the possible range of O since the strength of the interplanetary magnetic field is limited. The variance of the modified BT (marked as δ) at a point in the offset cube can be obtained. We find that the point with the minimum δ in each plane along a certain axis forms a straight line, which is referred to as the optimal offset line. Interestingly, this line crosses the point with a value equal to O, and its direction is associated with the ambient magnetic field of Alfvén waves. We also find that different optimal offset lines have an intersection with a value of O, suggesting that these characteristics of the optimal offset line can be used to determine the zero offset of the FGM. The test results show that our method can get a zero offset with a high accuracy. We suggest that the new method is a useful technique to find the zero offset of the magnetometer for solar wind monitors.
Paleointensity Results From Pliocene Lavas of the Lesser Caucasus Obtained Using the Multispecimen Parallel Differential pTRM Method: A Comparison With Thellier‐Thellier and IZZI Data
Authors: Sánchez‐Moreno Elisa M. , Calvo‐Rathert Manuel , Goguitchaichvili Avto , Vashakidze George T. , Camps Pierre , Morales‐Contreras Juan , Vegas‐Tubía Néstor , Lebedev Vladimir A. 
Published: March 2021

AbstractWe report paleointensity results obtained with the multispecimen method (MSP) over the Pliocene sequence of Apnia (Georgia) which records a polarity reversal. Paleointensity determinations with the multispecimen technique were performed on 12 flows with the original (MSP‐DB) and the domain‐state corrected (MSP‐DSC) protocol. Eight MSP‐DSC determinations passed the proposed quality criteria. To obtain highly reliable data through the agreement between intensity values from different methods, MSP results were combined with paleointensities from a previous study with Thellier‐type methods and especially strict selection criteria (RCRIT) on same flows (Sánchez‐Moreno et al., 2020). Application of this multimethod procedure resulted in three new paleointensities including both MSP and Thellier‐type results and an additional one obtained with two different Thellier‐type methods, yielding one paleointensity of 36.9 µT in the normal‐polarity, and three paleointensities between 19.2 and 24.1 µT in the reverse‐polarity section. Additionally, Thellier‐type data have been reinterpreted in this study with more flexible criteria (TTP) and the results combined with the MSP data. As a result, four flows yield paleointensities including MSP and Thellier‐type determinations and seven include paleointensities obtained with two different Thellier‐type methods. Results range from 37.2 and 44.3 μT in the normal‐polarity and from 12.5 to 24.6 μT in the reverse‐polarity section. Comparison of results from the four flows yielding multimethod determinations applying RCRIT criteria with those from the same flows under TTP criteria yields no significant difference in paleointensity values and their experimental uncertainty. Thus, application of a multimethod approach supports the possibility of using TTP criteria.