bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface meltwater routing through the supraglacial-proglacial river system on the northwestern Greenland Ice Sheet
Authors: Li Ya , Yang Kang , Smith Laurence , Fettweis Xavier , Gao Shuai , Zhang Wensong
Published: March 2021

Large, complex supraglacial river networks are widely distributed on the northwestern Greenland Ice Sheet (GrIS) each summer. Owing to the absence of moulins and crevasses on the ice surface, meltwater is continuously routed on the ice surface by supraglacial river networks to feed proglacial rivers on land. This continuous supraglacial-proglacial river system controls the magnitude and timing of surface meltwater runoff on the northwestern GrIS but remains poorly studied. In this study, we first mapped the supraglacial-proglacial river system across the Inglefield Land on the northwestern GrIS during 2016–2019 melt seasons using ninety Sentinel-2 and forty-five Landsat-8 images. Then, we proposed two quantitative river metrics, i.e., surface meltwater area fraction and proglacial river width, to quantify the seasonal and annual evolutions of the supraglacial-proglacial river system. Next, we correlated these satellite-derived river metrics with surface meltwater runoff estimated by two Surface Mass Balance (SMB) models (MAR v3.11 and MERRA-2), and estimated the optimal meltwater routing lag times. Our results showed that: (1) two satellite-derived river metrics, surface meltwater area fraction and proglacial river width, are strongly and positively correlated, indicating that the northwestern GrIS supraglacial-proglacial river system can efficiently route surface meltwater from the ice surface to the proglacial zone; (2) these two satellite-derived river metrics are also positively correlated with simultaneous surface runoff simulated by MAR and MERRA-2, indicating that SMB models can capture the general runoff pattern but exhibit considerable discrepancy with satellite observations; and (3) delayed MAR surface runoff better match two satellite-derived river metrics than simultaneous MAR surface runoff, and the optimal lag times are both two days, suggesting that supraglacial routing accounts for most of the lag time whereas rapid proglacial routing accounts for short lag time. Overall, the northwestern GrIS supraglacial-proglacial river system is a unique and efficient meltwater routing system, and multi-temporal satellite observations of this river system raise prospects for directly estimating surface meltwater runoff on the poorly-studied northwestern GrIS.
Substantial Increase in the Joint Occurrence and Human Exposure of Heatwave and High‐PM Hazards Over South Asia in the Mid‐21st Century
Authors: Wu Xiaokang , Xu Yangyang , Kumar Rajesh , Barth Mary , Diao Chenrui , Gao Meng , Lin Lei , Jones Bryan , Meehl Gerald
Published: March 2021

Extreme heat occurrence worldwide has increased in the past decades. Greenhouse gas emissions, if not abated aggressively, will lead to large increases in frequency and intensity of heat extremes. At the same time, many cities are facing severe air pollution problems featuring high‐PM episodes that last from days to weeks. Based on a high‐resolution decadal‐long model simulation using a state‐of‐the‐science regional chemistry‐climate model that is bias corrected against reanalysis, here we show that when daily average wet‐bulb temperature of 25 °C is taken as the threshold for severe health impacts, heat extremes frequency averaged over South Asia increases from 45 ± 5 days/year in 1997–2004 to 78 ± 3 days/year in 2046–2054 under RCP8.5 scenario. With daily averaged PM2.5 surface concentration of 60 μg/m3 defined as the threshold for such “unhealthy” extremes, high‐PM extremes would occur 132 ± 8 days/year in the Decade 2050 under RCP8.5. Even more concerning, due to the potential health impacts of two stressors acting in tandem, is the joint occurrence of the heatwave and high‐PM hazard (HHH), which would have substantial increases of 175% in frequency and 79% in duration. This is in contrast to the 73–76% increase for heatwave or high PM when assessed individually. The fraction of land exposed to prolonged HHH increases by more than tenfold in 2050. The alarming increases in just a few decades pose great challenges to adaptation and call for more aggressive mitigation. For example, under a lower emission pathway, the frequency of HHH will only increase by 58% with a lower frequency of high‐PM extremes.
Lithospheric buckling dominates the Cenozoic subsidence of the Qaidam Basin, NE Tibetan Plateau
Authors: Xiaoyi Hu , Lei Wu
Published: March 2021

Flexural basins are the common geological feature in convergent settings, and usually regarded as the result of flexural subsidence of the margins of under-thrusting cratons in response to the gravitational load of over-riding orogens. This process usually causes the fastest tectonic subsidence and thickest orogenic-related deposits in the basin margins adjacent to the orogens, such as India Foreland Basin in front of the Himalaya. The Qaidam Basin, which is the largest sedimentary basin within the Tibetan Plateau interior, was once interpreted to belong to this type and form by flexural subsidence on its south and north margins in response to loading of the Qiman Tagh and the South Qilian Shan orogenic belts, respectively. However, the latest studies present sedimentary and structural features that contrast to a typical foreland basin. These features include (1) depocenters being located along the central axis, rather than the margins, with thickest sediments up to 15 km, and (2) development of many high-angle reverse faults, rather than thin-skinned thrusts, to generate upper-crustal shortening as low as 10-15% (20 – 30 km), indicating that the widths of the orogenic belts juxtaposed atop the basin margins are limited. These features cannot be explained by the flexural subsidence of basin margins and/or sediment load. Herein, we investigate the impact of lithospheric buckling, which has been ignored in most studies of basin formation in compressional settings, on the tectonic subsidence of the Qaidam Basin through numerical simulation based on finite elastic plate model. We first use the flexural backstripping method to calculate the tectonic subsidence of the Cenozoic basement across the Qaidam Basin. And then, we simulate the tectonic subsidence caused by (1) gravitational load of orogenic belts alone, and (2) combined gravitational load and lithosphere buckling. The result shows that the simulated tectonic subsidence curve fits well with the real one only when considering the effect of lithospheric buckling that accounts for >90% tectonic subsidence. Our finding indicates for the first time that lithospheric buckling is also an important mechanism for the subsidence of intramountain basins like the Qaidam Basin, and should not be ignored when studying lithospheric-scale deformation across large orogenic belts.
Kinetic Modeling of the Impact of Solar Wind Discontinuities on the Magnetopause
Authors: Berchem Jean , Lapenta Giovanni , Richard Robert L. , Escoubet Philippe , Wing Simon
Published: March 2021

An important step in comprehending the effects of solar wind structures on the magnetosphere is to develop an understanding of their impact on the dayside magnetopause.  While most of the time global magnetohydrodynamic (MHD) models describe adequately the large-scale effects of solar wind structures on the magnetopause, recent spacecraft observations in the near Earth solar wind indicate that solar wind discontinuities have plasma features that are often not accurately described by MHD.  In this presentation, we report our progress in gaining a comprehensive understanding of kinetic processes occurring at the magnetopause as solar wind structures impact the dayside magnetosphere. Our approach combines implicit PIC simulations with global MHD simulations of the solar wind-magnetosphere-ionosphere system. The global simulation sets the overall configuration of the magnetosphere, while fields and plasma moments of a sub-domain of the global simulation are used to set initial and boundary conditions of the PIC code. Results are discussed in the context of spacecraft observations.
Isotopic evidence for importance of atmospheric acidity on sulfate formation in the Mt. Everest region
Authors: Hattori Shohei , Wang Kun , Lin Mang , Ishino Sakiko , Alexander Becky , Kamezaki Kazuki , Yoshida Naohiro , Kang Shichang
Published: March 2021

Oxygen-17 anomaly (Δ17O) has been used as a probe to constrain the relative importance of different pathways leading to sulfate formation. Here, we report the Δ17O values in atmospheric sulfate collected at a remote site in the Mt. Everest region to decipher the possible formation mechanisms of sulfate in such a pristine environment. The Δ17O in non-dust sulfate show higher values than most existing data in modern atmospheric sulfate. The seasonality of Δ17O in non-dust sulfate exhibits high values in the pre-monsoon and low values in the monsoon, opposite to the seasonality in Δ17O for both sulfate and nitrate (i.e., minima in warm season and maxima in cold season) observed from diverse geographic sites. This high Δ17O in non-dust sulfate found in this region clearly indicates the important role of the S(IV) + O3 pathway in atmospheric sulfate formation promoted by high cloud water pH conditions. In turn, this study highlights observational evidence that atmospheric acidity plays an important role in controlling sulfate formation pathways particularly for dust-rich environments.
Volcanic rocks and pseudotachylytes from sources of crust-mantle complementary layers: Insight into geodynamics of the Baikal Rift System, Southern Siberia
Authors: Chuvashova Irina , Rasskazov Sergei , Yasnygina Tatiana , Ailow Youseph , Saranina Elena , Rodionova Viktoriya
Published: March 2021

We present results of detail geochemical study of 18–12 Ma volcanic rocks from the Kamar-Stanovoy Zone of Hot Transtension (KSZHT), located in the central Baikal Rift System (BRS), and older pseudotachylytes from the Main Sayan Fault (MSF). These rocks designate geochemically distinguished from the OIB sources that are referred to the Slyudyanka zone of paleocollision occurred between the Khamardaban terrane and Siberian paleocontinent about 488 Ma ago. We define crustal and mantle signatures (with and without garnet, respectively) for the KSZHT volcanic rocks and crustal ones for the MSF basic pseudotachylytes. The signatures are indicative for tracing complementary relations between layers of the crust–mantle transition (CMT). We infer that the KSZHT volcanic activities accompanied rifting of a paleocontinental margin but got quiescent after a structural separation of the South Baikal Basin from the Tunka Valley, when the former had been sufficiently extended and subsided in contrast to the latter, which had been notably compressed and uplifted. From geological evidence and a detail seismic tomography model, we suggest that the KSZHT crust–mantle magmatic processes were due to delamination of a thickened root part of the South Baikal Orogen that preceded rifting in the South Baikal Basin area in the Late Cretaceous and Paleogene. Volcanic rocks of the past 17 Ma from the southwestern BRS denoted similar CMT sources and delamination processes beneath the East Hangay orogen and adjacent Orkhon-Selenga saddle. In the central and southwestern BRS, the CMT sources marked mutually overlapping deformational fields related to Indo-Asian convergence and pool-to-axis forces of the Japan-Baikal geodynamic corridor.

This work is supported by the RSF grant 18-77-10027.
Multiple Timescales of the Southern Annular Mode
Authors: Zhang Qiuyan , Zhang Yang , Wu Zhaohua
Published: March 2021

Using the ensemble empirical mode decomposition (EEMD) method, this study systematically investigates the multiple timescales of the Southern Annular Mode (SAM) and identifies their relative contributions to the low-frequency persistence of SAM. Analyses show that the subseasonal sustaining of SAM mainly depends on the contribution of longer-timescale variabilities, especially the cross-seasonal variability. When subtracting the cross-seasonal variability from the SAM, the positive covariance between the eddy and zonal flow, which is suggested the positive eddy feedback in SAM, disappears. Composite analysis shows that only with strong cross-seasonal variability, the meridional shift of zonal wind, eddy momentum forcing and baroclinicity anomalies can be maintained for more than 20 days, mainly resulting from the longer-timescale (especially the cross-seasonal timescale) eddy-zonal flow interactions. This study further suggests that the dipolar sea surface temperature (SST) anomalies in the mid latitude of Southern Hemisphere (SH) is a possible cause for the cross-seasonal variability. Analysis shows that about half of the strong cross-seasonal timescale events are accompanied by evident dipolar SST anomalies, which mostly occur in austral summer. The cross-seasonal dependence of the eddy-zonal flow interactions suggests the longer-timescale (especially the cross-seasonal timescale) contribution cannot be neglected in subseasonal prediction of SAM.
Interannual variability in primary productivity driven by sea-ice phenology in the Amundsen Sea polynyas, not ice shelves melting.
Authors: Liniger Guillaume , Moreau Sebastien , Lannuzel Delphine , Paolo Fernando , Strutton Peter
Published: March 2021

Ice shelves have been melting, thinning and retreating along the coast of West Antarctica for the past four decades, most notably in the Amundsen Sea sector. This area hosts two highly productive coastal polynyas, the Pine Island polynya and the Amundsen Sea polynya, whose opening triggers two of the largest phytoplankton blooms in the Southern Ocean. Previous work in the area suggests that ice shelf melting and thinning increases the iron content of coastal seawater, which could potentially boost ocean primary productivity locally. In this work, we use historical (1992-2017) remote sensing observations of net primary productivity, sea-ice concentration and rate of ice shelves melting to investigate the strength of this connection for these two large polynyas. We used the Abbot, Cosgrove, Pine Island, Thwaites, Dotson and Getz ice shelves for our analyses. Our initial results suggest no significant trends in net primary productivity though time but a large interannual variability for both polynyas. The basal melt rate and ice thinning seem to not be the main drivers of this interannual variability in these polynyas, but sea-ice coverage variability does seem to play a strong role, potentially allowing increased light availability and stratification. Further investigations of circumpolar deep water inputs and climate modes related to ice shelves melting such as El Niño or the southern annular mode are needed to clarify our findings. Our preliminary study points the complexity of ice-ocean systems, where several co-occurring processes influence coastal primary productivity, with consequences for carbon cycling and the climate system.
Effects of Temperature increase on N2O Emissions from Intertidal Area along the East China Coast
Authors: Chen Shu , Wang Dongqi
Published: March 2021

Coasts and estuaries are key contributors to atmospheric nitrous oxide (N2O) emissions. Here, we used laboratory incubation experiments to investigate temperature (12, 25, and 35 °C) and tidal effects on N2O fluxes in sediments sampled from three contrasting latitudinal subareas along the East China Coast (ECC) (North, Mid, and South). Overall, responses of N2O emissions to increasing temperature varied among the three climatic zones. During non-flood and flooding, mean N2O fluxes in sediments sampled from the North subarea increased exponentially with temperature (49.0 ±40.6 nmol m-2 h-1 at 12 °C to 3160 ±3960 nmol m-2 h-1 at 35 °C, and 741 ±518 nmol m-2 h-1 at 12 °C to 1020 ±1400 nmol m-2 h-1 at 35 °C, respectively). However, mean N2O fluxes in sediments sampled from the South subarea decreased at higher temperatures during flooding (977 ±306 nmol m-2 h-1 at 12 °C to 68.0 ±47.5 nmol m-2 h-1 at 35 °C) and non-flood (233 ±292 nmol m-2 h-1 at 12 °C to 183 ±142 nmol m-2 h-1 at 35 °C). Under ongoing global warming, intertidal areas at temperate may act as potential sources of N2O, whereas the contribution of low latitude coastal sediments to N2O budget may decrease. In addition, there is a combined impact of temperature and tidal fluctuation on N2O emissions that controls N2O production and consumption. Our results improve understanding of the diverse feedbacks of N2O emissions from coastal area to global climate change.
Karst generation in three-dimensional jointed layered rocks
Authors: Jiang Chuanyin , Wang Xiaoguang
Published: March 2021

We use numerical models to investigate the generation of incipient karst in layered geological systems, and specifically to investigate the effects of the structural and hydraulic properties of both joints and bedding planes on the distribution of the developed karst cavities. We develop a numerical model which couples the processes of ﬂuid ﬂow, mass transport and dissolution kinetics that govern the growth of fracture aperture, based on three-dimensional discrete fracture networks. The synthetic fracture networks made up of two jointed layers separated by a horizontal bedding plane are generated to represent the typical layered fracture systems often formed in carbonate rocks. We assume a relatively uniform aperture field with a small variance for each joint set and for the bedding plane, but different joint sets and the bedding plane can have non-identical mean apertures. Results show that the aperture ratio of the joint sets to the bedding plane is found to dominate the flow heterogeneity on the bedding plane, leading to various behaviors of karst development. We further suggest that the distinct flow regimes, i.e., joint-dominated, transitional and bedding plane-dominated, controlled by the magnitude of the aperture ratio, are responsible for the different types of incipient karst morphologies. Our investigations have an important application on the understanding of clustering behaviors of karst cavities in layered fractured carbonate rocks.

 
Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles
Authors: Ruffolo David , Chhiber Rohit , Matthaeus William H. , Usmanov Arcadi V. , Tooprakai Paisan , Chuychai Piyanate , Goldstein Melvyn L.
Published: March 2021

The random walk of magnetic field lines is an important ingredient in understanding how the connectivity of the magnetic field affects the spatial transport and diffusion of charged particles. As solar energetic particles (SEPs) propagate away from near-solar sources, they interact with the fluctuating magnetic field, which modifies their distributions. We develop a formalism in which the differential equation describing the field line random walk contains both effects due to localized magnetic displacements and a non-stochastic contribution from the large-scale expansion. We use this formalism together with a global magnetohydrodynamic simulation of the inner-heliospheric solar wind, which includes a turbulence transport model, to estimate the diffusive spreading of magnetic field lines that originate in different regions of the solar atmosphere. We first use this model to quantify field line spreading at 1 au, starting from a localized solar source region, and find rms angular spreads of about 20 – 60 degrees. In the second instance, we use the model to estimate the size of the source regions from which field lines observed at 1 au may have originated, thus quantifying the uncertainty in calculations of magnetic connectivity; the angular uncertainty is estimated to be about 20 degrees. Finally, we estimate the filamentation distance, i.e., the heliocentric distance up to which field lines originating in magnetic islands can remain strongly trapped in filamentary structures. We emphasize the key role of slab-like fluctuations in the transition from filamentary to more diffusive transport at greater heliocentric distances. This research has been supported in part by grant RTA6280002 from Thailand Science Research and Innovation and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165).  MLG acknowledges support from the Parker Solar Probe FIELDS MAG team.  Additional support is acknowledged from the  NASA LWS program  (NNX17AB79G) and the HSR program (80NSSC18K1210 & 80NSSC18K1648).
Ecological turnover and megafaunal ghost ranges during the Pleistocene-Holocene transition in central Yukon, Canada as revealed by palaeoenvironmental DNA
Authors: Murchie Tyler J. , Monteath Alistair J. , Long George S. , Karpsinski Emil , Cocker Scott , Zazula Grant , MacPhee Ross , Froese Duane , Poinar Hendrik
Published: March 2021

The multitude of factors alleged to have contributed to the late Quaternary mass extinction of some two-thirds of Earth’s megafauna is complicated by the coarse record of buried macro-fossils. In response, micro-methods such as ancient DNA have been increasingly able to augment discontinuous palaeontological records to investigate the relative timings of vegetation turnover versus megafaunal extirpations—all in the absence of biological tissues. Here, we present sedimentary ancient DNA data retrieved using the PalaeoChip Arctic-1.0 bait-set diachronically identifying fauna and flora from permafrost cores recovered from the Klondike region of central Yukon, Canada dating between 30,000–6000 calendar years BP. We observe a substantial turnover in ecosystem composition between 13,000–10,000 BP with the rise of woody shrubs and the disappearance of mammoth-steppe vegetation. We also identify a lingering signal of Equus sp. (North American horse) and Mammuthus primigenius (woolly mammoth) from multiple samples thousands of years after their last dated macro-fossils, possibly as late as the mid-Holocene.
Visualizing uncertainty of one-dimensional land subsidence prediction by preparing various local optimal solutions with a genetic algorithm
Authors: Akitaya Kento , Aichi Masaatsu
Published: March 2021

This study tried to visualize the predictive uncertainty while predicting future land subsidence caused by the groundwater pumping. Because land subsidence modeling is highly uncertain, it is impossible to determine the distribution of subsurface physical property values uniquely. Therefore, we prepared various local optimal solutions through the inversion analysis with a genetic algorithm in order to visualize land subsidence prediction uncertainty. The inversion analysis was conducted using the long-term land subsidence monitoring data at Kawajima in the Kanto Plain, Japan. In this study site, the seasonal groundwater level fluctuations have caused plastic compaction in summer and elastic expansion in winter every year. Obtained multiple sets of subsurface properties were within the range of typical values in the existing literature and satisfactorily reproduced the observed subsidence, showing that the inversion analysis worked well. In addition, the groundwater level scenario analysis was conducted using obtained property sets. This revealed that the subsidences predicted for a sudden groundwater level drop and rapid recovery scenario are more volatile than the subsidences predicted for the stable scenario. This means that it is important to have multiple sets of subsurface properties to predict future land subsidence caused by unprecedented groundwater level fluctuations.
Reanalysis of Flash Floods and Debris Flows on two continents and their management strategies
Authors: Rios-Arboleda Juan Daniel
Published: March 2021

This research expands the original analysis of Baker and Costa (1987) including data from Europe and South America with the objective to understand if there are emerging latitudinal patterns. In addition, the threshold proposed by Zimmermann et al. (1997) it is evaluated with the data from tropical zones finding that this is a good predictor.

Mainly, recent Debris Flow occurred in South America are analyzed with the aim of identifying the best risk management strategies and their replicability for developing countries, particularly, the cases that have occurred in Colombia and Venezuela in the last 30 years are analyzed in order to compare management strategies and understand which are the most vulnerable areas to this phenomenon.

It is concluded that large-scale and multinational projects such as SED ALP are required in South America to better characterize events that have left multiple fatalities (sometimes hundreds of people) and better understand how to manage the risk on densely populated areas.

Finally, the use of amateur videos is proposed to characterize these events in nations with limited budgets for projects such as SED ALP, methodology that will be described extensively in later works.
Imaging the Hydrothermal Plumbing Architecture of Steamboat Geyser Using a Dense Nodal Array and Seismic Interferometry
Authors: Wu Sin-Mei , Lin Fan-Chi , Farrell Jamie
Published: March 2021

The plumbing architecture of a hydrothermal feature (e.g., geyser and spring) exerts direct control over its eruption and recharge dynamics. During an active geyser’s recharge, in response to the evolution of temperature and hydrostatic pressure within the plumbing, this two-phase-flow system experiences intensive steam bubble nucleation and collapse throughout the eruption cycle. Such steam-liquid phase transitions generate seismic signals observed as hydrothermal tremor, thus the spatiotemporal pattern of its origin can depict the plumbing architecture and illuminate how the geyser operates internally. Steamboat, the tallest active geyser on Earth, is thought to have a complex architecture and dynamics owing to the hydrologic interaction with the nearby Cistern Spring, ~100 m SW of Steamboat. To study the system, in 2019 we deployed a dense array across the Steamboat-Cistern area with an aperture of ~250 m. The array was composed of 50 three-component geophones and had a spacing of 15–35 m. During the deployment, 6 eruption cycles with intervals ranging from 3 to 8 days were recorded. We observe distinct 1–5 Hz tremor emitted from Steamboat and Cistern, which are persistent and show no isolated events and discernable arrivals. To simultaneously locate the tremor from both features, we perform multicomponent cross-correlation to isolate and enhance the coherent signals of interest with each station as the virtual source. We apply the same normalization to the 3-component data so that the particle motion excited by each virtual source is retained. We observe prevalent seismic P waves at receivers near the source, with complex wavefield transition and interference at distant receivers. Using the P wave linearity, we back project the polarized directions to constrain the 3D source location. The results provide the first 4D view of the tremor throughout the eruption cycles with hourly resolution.

 

The 4D view reveals the conduit beneath Steamboat is vertical and extends down to ~120 m depth and the plumbing of Cistern includes a shallow vertical conduit connecting with a deep, large, and laterally offset reservoir ~60 m southeast of the surface pool. No direct connection between Steamboat and Cistern plumbing structures is found above ~120 m. The temporal variation of the tremor combined with in situ temperature and water depth measurements of Cistern, do reveal the interaction between Steamboat and Cistern throughout the eruption/recharge cycles. The observed delayed responses of Cistern in reaction to Steamboat eruptions and recharge suggest the two plumbing structures might be connected through a fractured/porous medium instead of a direct open channel, consistent with our inferred plumbing structure.
Effects of low-cost rehabilitation measures on gully sediment yields and vegetation in a savanna rangeland 
Authors: Koci Jack , Wilkinson Scott , Hawdon Aaron , Kinsey-Henderson Anne , Bartley Rebecca , Goodwin Nicholas
Published: March 2021

Gully rehabilitation is often applied as part of catchment management aimed at reducing downstream sediment yields, yet the observed responses globally are variable. In the semi-arid tropics, there is limited data available to evaluate the performance of individual rehabilitation measures. This study investigated the effects of several low-cost gully rehabilitation strategies on sediment yields and vegetation establishment, in a savanna rangeland, north-east Queensland, Australia, over an eight-year period. Four gullies were monitored as untreated control gullies. Two gullies were subject to treatments aimed at: (i) reducing runoff to gully head cuts; (ii) increasing sediment trapping on gully floors; and (iii) increasing vegetation cover on gully walls and floors. Vegetation was monitored in nine gullies under long-term grazing exclosure as an additional reference to measure vegetation recovery. A runoff diversion structure reduced headcut erosion from 4.3 m2 y-1 to 1.2 m2 y-1. Total sediment yields were substantially lower in gullies treated with small porous check dams and cattle exclusion fencing, with mean total sediment yields reduced by 0.3-2.4 t ha y-1. These treatments, however, had negligible effect on gully fine sediment (silt and clay) yields. While sediment deposited behind porous check dams was found to contain much less fine silt and clay than parent material, it contained several times that measured in untreated gullies. Organic matter and fine material deposited behind porous check dams were sufficient to trap seeds and initiate vegetation re-establishment on the gully floor, including native perennial tussock grasses and woody trees and shrubs. In this water-limited landscape, long-term rehabilitation will be strongly influenced by prevailing climatic conditions, with periods of recovery following wetter periods, and regression during extended dry periods. Understanding linkages between rehabilitation measures, their hydrologic, hydraulic and vegetation effects and gully sediment yields is important to defining the conditions for their success.
Early Cretaceous syn- to post-rift evolution of the Mentelle Basin on the southwest Australian rifted margin (IODP Expedition 369 Sites U1513–U1516)
Authors: Lee Eun Young , Wolfgring Erik , Tejada Maria Luisa G. , Chun Seung Soo , Yi Sangheon , Schentger Bernhard , Brumsack Hans-Jürgen , Riquier Laurent , Meszar Maria
Published: March 2021

The Mentelle Basin is a large and deep-water sedimentary basin located on the southwest Australian rifted margin. The basin lies west of the Perth Basin, east of the Naturaliste Plateau and south of the Perth Abyssal Plain. The rifted margin formed when the Greater Indian plate separated from the Australian-Antarctic plate during the Jurassic to early Cretaceous. Based on seismic reflection data, several km thick sediments infilling the basin have been interpreted. However, due to lack of geological and geophysical data, the basin has not been studied enough to understand its evolution. In 2017, International Ocean Discovery Program (IODP) Expedition 369 drilled four sites, U1513–U1516, in the Mentelle Basin and recovered important cores including late Jurassic to Early Cretaceous sections. At Site U1515 on the eastern margin of the basin, drilling penetrated below the seismically imaged breakup unconformity into the middle Jurassic to earliest Cretaceous syn-rift strata. Holes at Site U1513 on the western margin cored the syn-rift volcanic sequence, the Hauterivian to early Aptian volcaniclastic-rich sandstone sequence spanning the syn- to post-rift phase, and the Aptian to Albian post-rift claystone sequence. Drilling at Sites U1514 and U1516 in the central part reached the Albian post-rift sequence. Using a combination of shipboard and post-expedition data, we interpret the lithological, paleontological and geochemical characteristics of the syn- to post-rift sequences. The results allowed us to reconstruct the Early Cretaceous stratigraphy, tectonics, paleo-environment, and basin evolution of the Mentelle Basin. During the syn-rift phase, the middle Jurassic to lower Cretaceous non-marine sediments were deposited in the eastern Mentelle Basin, while volcanic rocks were emplaced in the western part. The 82 m thick volcanic sequence consists of alternating basalt flows and volcaniclastics with dolerite dikes, which indicate multiple volcanic eruption events in subaerial to shallow water environments. It was overlain by the 235 m thick volcaniclastic-rich sequence consisting of massive or laminated sandstone layers, deposited in shelf to upper bathyal depths. The deposition period spans the syn- to post-rift phase of the basin but decreasing sedimentation rate and shallow marine setting suggest that the post-rift thermal subsidence did not immediately follow the final continental breakup. We interpret that the delayed thermal subsidence was likely to be induced by adjacent mantle plume activities. Deep marine claystone sequences blanketing most of the basin indicate Aptian to Albian post-rift thermal subsidence.
The Scale Height of Charged Particles in Jupiter’s Magnetosphere
Authors: Khurana Krishan , Hospodarsky George , Paranicas Chris
Published: March 2021

We have recently developed a new technique that uses the timings of any three consecutive current sheet crossings to determine the instantaneous motion of Jupiter’s current sheet relative to the spacecraft. Using this information on the instantaneous location of Jupiter’s current sheet, we have modeled the external field of the magnetic disc observed by Juno and Galileo spacecraft in terms of a Harris current sheet type equilibrium and obtained a map of the thickness of the Jovian current sheet over all local times and radial distances. Our modeling of Juno and Galileo magnetic field data shows that in all local times the current sheet thickness increases with radial distance. We also find that the Jovian current sheet thickness is highly asymmetric in local time, being at its thinnest in the dawn sector and the thickest in the dusk sector. The current sheet thickness on the dayside is comparable to that in the dusk sector. The nightside current sheet is intermediate in its thickness to the dawn and the dusk sectors.

In this presentation, we use the instantaneous location of the current sheet to model the electron densities measured by the plasma or plasma wave instrument. We show that overall, the scale height of electrons and the current sheet tend to be identical. However, we have encountered many cases where the electrons have a two scale-height structure where a thin plasma sheet is embedded within a thicker current sheet, the cause for which is not known. By using the magnetic field and electron density data, we have computed the plasma content of flux tubes in several local time locations in the magnetosphere. We relate the plasma content of these flux tubes to plasma rotation, plasma density and current sheet thickness. It appears that as flux tubes rotate to the dusk side, they slow down and the plasma scale height increases but the total plasma content remains constant.
Analysis of earthquake triggered landslides with slope geometry and 3D coseismic deformation
Authors: Liu Ru , Wang Teng
Published: March 2021

In mountainous areas, triggering of landslides is one of the main reasons for causing casualties during large earthquakes. These landslides are also important for shaping the landscapes by transporting large volume of sediment from slopes to catchments. The dynamic landslide triggering mechanism have been well studies with seismic derived rupture processes and ground shaking simulations. However, whether the static coseismic displacements play a role is less investigated. Here, given the high-resolution 3D coseismic displacements of three large earthquakes, we study how landslides with different slope and aspect angles response to the directions and magnitudes of coseismic displacements, in order to better understand the landslides distribution along ruptured faults.

The 2008 Wenchuan earthquake in China, the 2015 Gorkha earthquake in Nepal, and the 2016 Kaikoura earthquake in New Zealand all triggered numerous landslides distributed in the epicenter regions. The locations of these landslides have been carefully mapped by remote sensing and field investigations. Their coseismic displacements have also been well captured by Synthetic Aperture Radar (SAR) imaging geodesy from different geometries. Surrounding each coseismic landslide, we can calculate the 3D coseismic displacements from SAR images. Their slope and aspect angles can be obtained from topography data. For nearby landslides with similar peak ground acceleration, we can project the 3D displacement along and normal to the sliding slops, and then quantitively evaluate which slope geometry favors triggering landslides. Our geostatistical analysis can help hazards mitigation in mountainous area with threads of seismic events, and also shed lights on understanding the role of landslides in shaping the topography.

Key Words: SAR imaging geodesy; coseismic landslide; coseismic deformation
Bushfire impacts on a threatened swamp ecosystem: responses of the soil microbial communities and restoration
Authors: Machado de Lima Nathali , Thomsen Alexandria , Ooi Mark , Muñoz-Rojas Miriam
Published: March 2021

Australia faced the most extreme and prolonged fire season in 2019-2020, resulting in tragic habitat loss for many threatened species and the destruction of many ecological communities.  Newnes Plateau Shrub Swamps are peatlands located in the upper Blue Mountains region of New South Wales, Australia. These ecosystems perform many important ecological functions while absorbing and filtering water and releasing it slowly back to the environment. Their functions are related to the control of peak flow events, water purification and the harboring of many threatened plant and animal species. Despite their ecological importance, the area has been intensively degraded through longwall mining processes, resulting in the lowering and loss of water tables in the area. In December 2019 these impacts were compounded by an intense prolonged drought period and extensive wildfire. While the effects of these combined factors on the vegetation have been analysed and revealed remarkable negative impacts in the swamps under mining pressures, the effects on the soil microbial communities and related soil functions have not yet been studied. To investigate both drivers (fire and mining activities), we selected three mined swamps and three unmined swamps to assess their soil microbial composition and diversity through Next Generation Sequencing, and to characterise the soil chemical composition. At each site, we collected samples considering three treatments, one in the swamp valley fill and two at two different heights of the swamp valley margin, focusing on the soil close to specific groups of plants (e.g. sedges and shrubs). For each site and treatment, three soil samples (~ 10 m from each other) of 10x10 cm and ~ 3 to 5 cm of depth were collected using a trowel. We aim to build 16S rRNA gene libraries and co-relate them with the soil chemical variables, to assess the impact on these microbial communities and their possible use as environmental indicators and basis for future applied initiatives in conservation and restoration.

 
Diffusive contaminant transport in a multi-layered aquifer-aquitard system
Authors: Jang Seonggan , Yang Minjune
Published: March 2021

A flow chamber experiment was conducted to investigate solute diffusion in a multi-layered aquifer-aquitard system. The two-dimensional flow chamber consisted of a finite thickness aquitard (kaolinite, 2 cm) bounded by two parallel aquifers at the top (unconfined aquifer, 2 cm) and bottom (confined aquifer, 4 cm). New Coccine (red dye) of 500 mg/L in the top aquifer and distilled water in the bottom aquifer were injected with 0.02 mL/min for 13 days. One-dimensional analytical solutions were developed for advection and diffusion through a finite aquitard and compared with the measured data to evaluate experimental validation. The simulated aquitard concentration profiles (E > 0.97) and breakthrough curve (E = 0.95) showed good agreement with the measured data. During the experiment, the penetration distance in the aquitard increased over time and the vertical concentration distribution showed a linear profile through the aquitard after 7 days of loading in the top aquifer, indicating steady-state diffusion. The New Coccine diffused across the aquitard to the bottom aquifer after 1 day of loading. The bottom aquifer concentration increased at early times and was maintained after 7 days of loading (11 ~ 12 mg/L). This study provides experimental validation of the developed analytical solutions and quantitatively evaluates contaminant occurrences of the confined aquifer through the aquitard.
Internal variability and unforced trends of all-sky and clear-sky SSR: quantitative estimates using CMIP6
Authors: Chtirkova Boriana , Folini Doris , Ferreira Correa Lucas , Wild Martin
Published: March 2021

Quantifying trends in surface solar radiation (SSR) of unforced simulations is of substantial importance when one tries to quantify the anthropogenic effect in forced trends, as the net effect may be dampened or amplified by the internal variability of the system. In our analysis, we consider trends on different temporal scales (10, 30, 50 and 100 years) from 58 global climate models, participating in the Coupled Model Intercomparison Project - Phase 6 (CMIP6). We calculate the trends at the grid-box level for all-sky and clear-sky SSR using annual mean data of the multi-century pre-industrial control (piControl) experiments. The trends from both variables are found to depend strongly on the geographical region, as the most pronounced trends of the all-sky variable are observed in the Tropical Pacific, while the largest clear-sky trends are found in the large desert regions. Inspecting for each grid cell the statistical distribution of occurring N-year trends  shows that they are normally distributed in the majority of grid cells for both all-sky and clear-sky SSR. The 75-th percentile taken from these distributions (i.e. a positive trend with a 25 % chance of occurrence) varies with geographical region, taking values in the ranges 0.79 - 12.03 Wm-2/decade for 10-year trends, 0.15 - 2.05 Wm-2/decade for 30-year trends, 0.07 - 0.92 Wm-2/decade for 50-year trends and 0.02 - 0.29 Wm-2/decade for 100-year trends for all-sky SSR. The unforced trends become less significant on longer timescales – the trend medians, corresponding to the above ranges, are 3.18 Wm-2/decade, 0.62 Wm-2/decade, 0.29 Wm-2/decade, 0.10 Wm-2/decade respectively. The trends for clear-sky SSR are found to differ from the all-sky SSR by a factor of 0.16 on average, independent of the trend length. The model spread becomes greater at longer trend timescales, the differences being more substantial between large model families rather than between individual models. To elucidate the dominant causes of variability in different regions, we examine the correlations of the SSR variables with ambient aerosol optical thickness at 550 nm, atmosphere mass content of water vapour, cloud area fraction and albedo.
Using an Artificial Neural Network to improve operational wind prediction in a small unresolved valley
Authors: Chinyoka Sinclair , Hedde Thierry , Steeneveld Gert-Jan
Published: March 2021

Forecasting valley winds over complex terrain using a coarse horizontal resolution mesoscale model is a challenging task. Mesoscale models such as
the Weather Research and Forecasting (WRF) model tend to perform poorly over such regions. In this study, we assess the added value of downscaling
WRF wind forecasts using artificial neural networks (ANN) over the Cadarache Valley which is located in southeast France. Wind forecasts over the Cadarache valley are generated using WRF with a horizontal resolution of 3km on a daily basis. We used performance metrics such as Directional ACCuracy (DACC) and mean absolute error (MAE) for the evaluation of the WRF and ANN. WRF horizontal wind components at 110m and the near surface vertical potential temperature gradient were used as input data and observed horizontal wind components at 10m within the valley as targets during ANN training. We found an increase of DACC from 56% to 79% after post-processing WRF forecasts with ANN. Further analysis show that the ANN performed well during day and night, but poorly during morning and afternoon transition. The performance of WRF has a huge influence on ANN performance with bad WRF forecasts affecting ANN performance. However, the ANN improves the poor WRF forecasts to a DACC exceeding 60%. A change in lead time and domain resolution showed negligible impact suggesting that 3km resolution and a lead time of 24-47h is effective and relatively cheap to apply. Additionally, WRF performs well in near-neutral conditions and poorly in other atmospheric stability conditions. However ANN showed a consistent improvement in wind forecast during all stability classes with a DACC of nearly 80%. The study clearly demonstrates the ability to improve Cadarache valley wind forecasts using ANN from WRF simulations on a daily basis.
Developing Climate Change Literacy to Combat Climate Change and Its Impacts
Authors: Johnston Julie
Published: March 2021

If literacy can be defined as competence or knowledge in a specific area, then climate change literacy is competence or knowledge in the area of climate change, its impacts, and its solutions. Climate change literacy is a vital element in strategies for meeting the United Nations Sustainable Development Goal (SDG) 13: "Take urgent action to combat climate change and its impacts" — and, frankly, safeguarding the survival of the human species and most life on Earth. Developing climate change literacy in individuals, institutions, and societies entails understanding why it is important, who must be involved, what it includes, where and when it takes place, how to deal with challenges that arise, and what the end result, a climate-change-literate citizen, will look like.
Former bay of the desiccating Aral Sea as the newly formed world’s largest heliothermal lake 
Authors: Izhitskiy Alexander , Kirillin Georgiy , Goncharenko Igor , Kurbaniyazov Abilgazy , Zavialov Peter
Published: March 2021

The Aral Sea desiccation is the worst aquatic ecological disaster of the last century, important for understanding the worldwide trends to degradation of arid lakes under water use and climate change. Formerly the fourth largest lake worldwide, the Aral Sea has lost ~90% of its water since the early 1960s due to irrigation in its drainage basin. Basing on field observations and numerical simulations, we show that the former bay of the Aral Sea — Chernyshev — turned to a meromictic heliothermal water body with extreme temperature, light and chemical regimes. The heliothermal regime of Chernyshev keeps the deep monimolimnion warm (about 15-16°C) throughout cold winter. Among less than 30 heliothermal waters worldwide, Chernyshev with its area of ~80-90 km2 is the largest heliothermal lake, the second one being permanently ice-covered Antarctic lake Vanda. Chernyshev is also the youngest heliothermal lake, emerged within the last half-century. Seasonal themal cycle of the basin, scenarios of its formation and possible consequences for the ecosystem are discussed.

The study is funded by the Russian Foundation for Basic Research (RFBR project № 20-55-12007) and German Research Foundation (DFG KI 853-16/1).