bluuebunny/crossref_metadata_2025 huggingface dataset:
Cloud-Radiative Impacts On Tropical Circulation Change in GFDL AM4.1
Authors: Iipponen Juho , Donner Leo
Published: March 2020

We use the Geophysical Fluid Dynamics Laboratory (GFDL) state-of-the-art AM4.1 atmospheric model to assess the impact of clouds on the change in tropical circulation. Slab-ocean experiments where cloud microphysical properties are locked to either the pre-industrial or 4xCO2 conditions allow us to cleanly separate the circulation changes into a part caused by the cloud radiative effects (CREs), and to a part caused by the CO2 changes. The CO2-induced SST changes are shown to dominate the response in the boundary layer, but are rivaled by the impacts of CREs in the mid to upper troposphere. The reduction in the east-to-west sea level pressure difference over the Pacific is solely caused by the increasing CO2 and SST, but they only account for about half of the change in the mid-tropospheric Walker circulation. The weakening of the free-tropospheric circulation is shown to be mostly caused by the near-equal contributions the CO2 and CREs make to the changes in dry-static and gross moist stability. Also, concerning the meridional circulation, we show that the response in the strength of the southern branch of the Hadley cell is largely due to CREs, while they have a much smaller impact in the north.
QBO, ENSO and Solar Cycle Effects in Short-term Nonmigrating Tidal Variability on Planetary Wave Timescales from SABER - An Information-Theoretic Approach
Authors: Kumari Komal , Oberheide Jens
Published: March 2020

Earth’s atmosphere supports a variety of internal wave motion which are responsible for spatio-temporal changes in temperature, winds, density, and chemical constituents. One of the most striking dynamical features of the upper atmosphere (i.e. mesosphere and lower thermosphere [MLT], 50-120 km) are atmospheric tides. In particular, the eastward-propagating nonmigrating diurnal tide with zonal wave number 3 (DE3), originating from tropical deep convection, introduces a large longitudinal and local time variability in temperature, wind and density in the MLT region. The DE3 is thus key to understanding how tropospheric weather influences space weather. However, DE3 short-term tidal variability is not well understood and part of the motivation for constellation missions. Single satellites such as TIMED nevertheless provide a pathway to identify multi-timescale tidal variability from days to years. We utilize 16 years of SABER (an instrument onboard the TIMED satellite) DE3 “tidal deconvolution” diagnostic that provides a unique opportunity to investigate interannual changes in short-term (days to weeks) tidal variability on various planetary wave time scales. The approach is based on information-theoretic techniques using Bayesian statistics, time dependent probability density functions and Kullback-Leibler divergence followed by multiple linear regression analysis. In this presentation, we focus on interannual changes in short-term DE3 variability on a 10-day planetary wave timescale and how it changes as a function of the quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO) and the solar cycle.
Challenging Escape from Climate Change: A learning Experience
Authors: Liapi Vasiliki
Published: March 2020

The 3rd graders of the 18th Primary School of Rhodes, Greece during the school year 2018-2019, had the opportunity to increase their understanding of global climate change through sustainability themed escape-rooms in their school.

Teachers of this school had realized that escape rooms had become increasingly popular among pupils the last years. So they thought that giving them an educational twist, they can fit the needs of their pupils to foster teamwork, leadership, creative thinking, problem solving and communication in a way that is engaging for them.

The 3rd graders had interacted with peers from across Europe through an e- twining project called “Help! Save the Planet” which included many kinds of activities so to raise awareness of the Sustainable Development Goal 13, the Climate Action.

As a consequence of this project, school escape rooms had emerged as a new type of inquiry based learning activity, under the promise of enhancing students’ learning through highly engaging experiences about Climate Change/Global Warming. These escape rooms covered the concepts: Green House Effect, Global Warming, Causes and Effects of Climate Change, Ways to Help.

The escape rooms’ games focused on pupils finding out facts and information and using these to solve puzzles, riddles, decode different ciphers as curious climate detectives and move forward.

Our escape rooms from climate change were run on April 22 -24, in recognition of Earth Day and as a part of our school’s commitment to sustainability and a healthier planet.

This challenging project was a great learning experience for all the school community, based on pupils’ and teachers’ cooperation, creating and innovating through the implementation of modern educational approaches and practices that promote 21st century skills.

 

 

 
Magnetotail flows near lunar orbit and their relation to substorms
Authors: Kiehas Stefan , Runov Andrei , Angelopoulos Vassilis , Korovinskiy Daniil
Published: March 2020

We perform a five year statistical study of fast flows in the Earth's magnetotail observed by ARTEMIS to investigate their occurrence rate, dawn-dusk asymmetry and relation with magnetospheric substorms. Almost half of the observed flows are directed earthward and their percentage decreases with increasing flow speed. While no clear dawn-dusk asymmetry is observed for earthward directed flows, about 60% of the tailward flows occur in the dusk sector. For tailward flows this asymmetry is similar for different AL thresholds. However, earthward flows become strongly asymmetric towards dusk for higher AL thresholds. A correlation of flow events with the AL index also shows a clear correlation of tailward flows with a decrease in AL, while such a correlation can not be seen for earthward flows. 
A new method for studying the extratropical response to tropical precipitation anomalies and its role in improving projections of Northern Hemisphere climate variability
Authors: Senior Natasha , Joshi Manoj , Matthews Adrian , Deb Pranab
Published: March 2020

Intensification of extreme precipitation and weather events are some of the projections under a 2°C average global temperature increase scenario. Rossby wave trains may be triggered by anomalous tropical precipitation through the interaction of the associated upper level divergent wind and the vorticity gradients of the subtropical jet streams. In this way, anomalous tropical precipitation can influence weather patterns in the Northern Hemisphere. Owing to the quasi-linearity of this teleconnection pattern, it may be studied statistically as a series of signal-response functions. Here the anomalous precipitation events are treated as input forcings and the resulting geopotential height anomalies are the output signals. Through calculating the response functions we are able to realistically capture the 250 hPa geopotential height response to a step-like change in precipitation over the Maritime Continent or the eastern Indian Ocean during the boreal winter. When examining these responses using the same forcing for a selection of CMIP5 models, we find that there is a large inter-model spread, owing to differences in the model basic state. Since these teleconnection patterns are not faithfully represented in climate models, this can obscure our ability to develop realistic projections of atmospheric circulation and extreme weather. We discuss the potential of the linear response theory method to provide improved projections for Northern Hemisphere climate variability.
On the relation between tree foliage clumping at the branch scale and light and water limitations
Authors: Beland Martin , Baldocchi Dennis
Published: March 2020

Foliage clumping is known to have a significant effect on the radiative transfer and mass and energy exchanges in forests. It is an important component of canopy structure to consider for the estimation of photosynthesis rates and the interpretation of observed solar induced fluorescence (SIF). Yet, relatively little is known about the drivers of foliage clumping, and few observations of foliage clumping are available at the branch scale. Here, we report on a study using laser light to estimate foliage clumping at the tree branch scale in eight broadleaf species, at different heights above ground, from four sites located in two climatic zones: one water limited, and one light limited. We also integrate our results with published foliage clumping estimates from two sites (one in each climatic zone). We find that foliage arrangement on branches exposed to high solar irradiance tend to be random at the dry sites, but are very clumped at humid sites where competition for light is high. Branches sampled at the top of tall canopies at humid sites showed that foliage clumping increased with tree height, suggesting that higher competition for light results in the production of larger numbers of leaves grouped together which reduces the light interception efficiency on a per leaf area basis. Comparison with landscape clumping values suggests that the spatial availability of a limiting resource is a major driver of foliage clumping in forests.  
Estimation of Stomatal Conductance using Crop Water Stress Index based on the Thermal Image at a Leaf Scale
Authors: Jeong Hoejeong , Ryu Jae-Hyun , Na Sang-il , Cho Jaeil
Published: March 2020

  In 1980s, Crop Water Stress Index (CWSI) is suggested to indicate the water stress of crops. CWSI is based on the leaf energy balance, which is closely related to leaf temperature. To calculate CWSI, meteorological factors such as air temperature and vapor pressure deficit should be measured besides leaf temperature. As recent technology has been developed, leaf temperature can be easily observed by thermal camera or infrared thermometer. Stomatal conductance (gs, mmol m-2 s-1) is one of the critical factors to understand crop photosynthesis and water demand. In addition, the behaviors of gs can represent the biotic and abiotic plant stresses. In abnormal condition, such as drought, insects or disease, gs getting lower. The observation of gs will make better to evaluate and predict crop growth and conditions. Therefore, the time series data of gs is useful for the monitoring of crop growth and the quick detection of abnormal crop condition in smart-farming system but there are some limitations to measure gs continuously and easily.

  We assume that there is some relationship between CWSI and gs because both has strong relation to leaf temperature. Thus, the aim of this study is to investigate possibility of estimation of gs using CWSI which is derived from thermal image. Through the data collected from literatures, negative correlations between CWSI and gs were revealed. The slope of correlation was changed according to crop types. In addition, as a result of simulation, there is almost linear negative relationship between CWSI and gs, and the slope was determined by maximum stomatal conductance (gs_max). Field measurement in this study was also demonstrated to identify such correlation. Further, various methods to measure CWSI were tested. This relationship will contribute to not only monitoring of crop stress for irrigation scheduling in smart farm system but also estimating evapotranspiration, photosynthesis, and crop yield.
Implementation of GRACE and GRACE-FO observation covariance estimates at JPL
Authors: Ellmer Matthias , Wiese David , McCullough Christopher , Yuan Dah-Ning , Fahnestock Eugene
Published: March 2020

Developing meaningful uncertainty quantifications for GRACE or GRACE-FO derived products, e.g. water storage anomalies, requires a robust understanding of the information and noise content in the observables employed in their estimation.

The stochastic models for GRACE and GRACE-FO K-Band, LRI, and GPS carrier phase and pseudorange observables employed in upcoming JPL solutions, along with notes on their implementation and development, will be presented. Within these models, the time-domain correlations for each of the observations are estimated, and then applied in the least squares estimate of monthly gravity field solutions. Reproducing results from other groups, the resulting formal errors of monthly solutions are improved.

It is envisioned that possible new Level 3 products can make these improved uncertainty quantifications accessible to the GRACE user community at large. Possible specifications for such products will be presented, and feedback from the community and discussion will be appreciated.
Improving spatial representation of erosion sources using Sediment Fingerprinting with terrain data and sediment budget modelling
Authors: Vale Simon , Smith Hugh
Published: March 2020

Sediment fingerprinting quantifies proportional contributions of catchment sediment sources to downstream sediment mixtures and deposits. While the sediment fingerprinting technique is well established it is still challenged by the coarse spatial resolution of sediment source discrimination which hinders understanding of catchment sediment dynamics and limits its usefulness for land management where finer resolution spatial information is required.

Here, two conventional sediment fingerprinting datasets from New Zealand are used to show how spatial modelling of source loads can improve 1) the usefulness of sediment fingerprinting approaches and 2) visualization of results for end-users by combining source apportionment with terrain information and sediment budget modelling. The two case studies involve unmixing sediment source contributions to 1) overbank deposits within the Oroua River catchment, where six sediment sources (Mountain Range, Mudstone, Hill Subsurface, Hill Surface, Unconsolidated Sandstone, and Channel Bank) across two size fractions (<63 µm and 125–300 µm) were characterized using bulk geochemical and radionuclide tracers and 2) suspended sediment in the Manawatu catchment, where a similar six sources were characterized using bulk geochemical tracers to determine changes in source contributions to hourly suspended sediment samples during a 53hr storm event.

The proportional source contributions for each case study are applied to modelled sediment loads and spatially distributed using terrain information for rock type, slope and channel network extent to produce specific sediment yield maps for both catchments and spatial visualization of sediment generation during the Manawatu catchment storm event. Integrating sediment fingerprinting results with spatial datasets and modelling can enhance interpretation of source apportionment results and improve the utility of this information for end-users focused on the spatial targeting of erosion sources for mitigation to reduce downstream sediment impacts.   
Mesoscale Modulation of Dissolved Oxygen in the Tropical Pacific
Authors: Eddebbar Yassir
Published: March 2020

The distribution of dissolved oxygen in the tropical Pacific acts as a major control on marine ecosystems habitats and the foraging range of tuna fiheries in this region. A basic understanding of processes driving the mean structure and variability of the oxygen minimum zones (OMZs) in this region, however, remains challenged by sparse observations and coarse model resolution. In this study, we examine the influence of mesoscale processes on equatorial Pacific oxygen distribution and variability, with a particular focus on tropical instability vortices (TIVs). We employ an eddy-resolving configuration of the Community Earth System Model (CESM) and Lagrangian analysis to evaluate the impacts and governing mechanisms by which TIVs influence oxygen distribution and budgets in this region. The westward seasonal propagation of TIVs from summer through winter is found to drive a deepening of the oxygen minima along the equatorial Pacific band (10oN-10oS), and thus a seasonal expansion of the equatorial oxygenated tongue separating the north and south tropical Pacific OMZs. Strong hemispheric asymmetry is evident in TIV impacts on oxygen due to relatively weaker TIV activity and less pronounced oxygen gradients south of the equator. Mechanisms governing TIV oxygenation of the upper equatorial Pacific include a complex interplay of physical and biogeochemical processes. Isopycnal displacements act in concert with vortex trapping and lateral stirring to mix oxygenated waters from the upper layers into the equatorial boundaries of the north and south tropical Pacific OMZs. TIV-induced advection and upwelling, on the other hand, intensifies nutrient supply and productivity, organic carbon export, and oxygen respiration demand at depth, thus acting (though only slightly) to counteract the physical effects. The influence of these processes varies with TIV phase, from vortex generation in the eastern Pacific through vortex dissipation in the west. TIVs are found to have a profound influence on upper equatorial Pacifc oxygen distribution and budget, with major implications for understanding the coupling between oxygen and ocean circulation, predicting marine ecosystem dynamics, and designing observation networks in this region.
Projections of climate change effects on pasture productivity, GHG exchanges and soil carbon stocks
Authors: Puche Nicolas , Viovy Nicolas , Kirschbaum Miko , Chabbi Abad
Published: March 2020

Agriculture is intimately affected by climate change (atmospheric CO2 concentration, temperature, precipitation and patterns of climate extremes), and there are major societal concerns about climate change effects on agriculture lands and hence food security in the 21st century. Despite those concerns, there is still only poor understanding of the possible impacts of climate change on the productivity and carbon dynamics of rain-fed pastoral systems in France, particularly their direction and magnitude over long time scales. The present study uses 3 scenarios (e.g. RCP 2.6, 4.5 and 8.5) of possible future climatic conditions and assesses their effects on productivity and SOC stocks of mowed and rotationally grazed grasslands. We used the CenW ecosystem model to simulate carbon, water, and nitrogen cycles in response to changes in environmental drivers and management practices. The simulations indicated that grassland productivity was increased through CO2 fertilization and higher water use efficiencies but that SOC losses between 5% and 23% (if CO2 fertilization is not accounted for in the simulations) are expected due to higher temperatures and biomass exports. Such losses may further affect climate feedback loop and jeopardize the agroecosystem sustainability. More extreme climate events were expected under more pessimistic climate change scenarios with very different outcomes if the CO2 fertilization effect is accounted for or not. This study showed that under the current management practices implemented at the study site, soil C losses were expected over the 21st century under climate change conditions, highlighting the need to modify/adapt farming practices.
Fault modeling and stress drop estimation based on millimeter-scale tsunami records of an M6 earthquake detected by the dense and wide pressure gauge array
Authors: Tatsuya Kubota , Saito Tatsuhiko , Suzuki Wataru
Published: March 2020

Tsunamis observed by offshore ocean-bottom pressure gauges have been used to infer fault models and stress drops for major (M > 7) offshore earthquakes, to understand the earthquake and tsunamigenesis (e.g., Satake et al. 2013). However, it is challenging to observe tsunamis due to moderate (M ~6) earthquakes with reasonable quality by those, previous, few and remote pressure gauge arrays. Recently, a new, dense and wide pressure gauge network, the Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench (S-net), was constructed off eastern Japan (Kanazawa et al. 2016). This array observed tsunamis associated with a moderate (M~6) earthquake which occurred inside the array, with amplitudes of less than one cm. We analyzed these millimeter-scale tsunami records to infer the finite fault model and stress drop, and to examine its relationship with other interplate earthquake phenomena.

We analyzed the pressure data associated with an Mw 6.0 earthquake off Sanriku on August 20, 2016. This earthquake was located at the shallowest part of the plate boundary off Sanriku, Japan, near the northern edge of the rupture area of the 1896 Sanriku tsunami earthquake (Kanamori, 1972). Although the signal-to-noise ratio is not high, the westward tsunami propagation with the velocity of ~0.1 km/s could be recognized when the waveforms were aligned according to the station locations. Using these data, we constrained the rectangular fault model with a uniform slip across the fault. As a result, the fault model was located ~10 km to the west of the Global CMT centroid (a seismic moment M0= 1.4 × 1018 Nm, Mw 6.0, and a stress drop of Δσ = 1.5 MPa). The stress drop seems not so small as expected in tsunami earthquakes such as the 1896 Sanriku tsunami earthquake (≪ ~1 MPa, e.g., Kanamori 1972) even if the uncertainty of the stress drop estimation is considered (Δσ > ~ 0.7 MPa). We also found the rupture area was unlikely to overlap with regions where slow earthquakes are active, such as low-frequency-tremors and very-low-frequency-earthquakes (e.g., Matsuzawa et al. 2015; Nishikawa et al. 2019; Tanaka et al. 2019).

This result demonstrates that the S-net new dense and wide pressure gauge array dramatically increases the detectability of a millimeter-scale tsunami and the constraints on earthquake source parameters of moderate earthquakes off eastern Japan. It is expected that more tsunamis due to minor-to-moderate offshore earthquakes are recorded by this new array, which will reveal the spatial variation of the stress drops, or mechanical properties, along the plate interface with much higher resolution than previously possible.
Building a sustainable international research data infrastructure - Lessons learnt in the IGSN 2040 project
Authors: Klump Jens , Lehnert Kerstin , Wyborn Lesley , Ramdeen Sarah ,   IGSN 2040 Steering Committee
Published: March 2020

Like many research data infrastructures, the IGSN Global Sample Number started as a research project. The rapid uptake of IGSN in the last five years as well as the expansion of diversity of use cases, in particular beyond the geosciences, mean that IGSN has outgrown its current structure as implemented in 2011, and the technology is in urgent need of a refresh. The expected exponential growth of the operation requires the IGSN Implementation Organization (IGSN e.V.) to better align the organisation and technical architecture.

In 2018, the Alfred P. Sloan Foundation awarded a grant to redesign and improve the IGSN, to “achieve a trustworthy, stable, and adaptable architecture for the IGSN as a persistent unique identifier for material samples, both technically and organizationally, that attracts, facilitates, and satisfies participation within and beyond the Geosciences, that will be a reliable component of the evolving research data ecosystem, and that is recognized as a trusted partner by data infrastructure providers and the science community alike.” 

IGSN is not the first PID service provider to make the transition from project to product and there are lessons to be learnt from other PID services. To this end, the project invited experts in the field of research data infrastructures and facilitated workshops to develop an organisational and technological strategy and roadmap towards long-term sustainability of the IGSN. 

To be sustainable, a research data infrastructure like IGSN has to have a clearly defined service or product, underpinned by a scalable business model and technical system. We used the Lean Canvas to define the IGSN services. The resulting definition of service components helped us define IGSN user communities, cost structures and potential income streams. The workshop discussions had already highlighted the conflicting aims between offering a comprehensive service and keeping services lean to reduce their development and operational costs. Building on the Lean Canvas, the definition of a minimum viable product helped to define the role of the IGSN e.V. and the roles for actors offering value-added services based in IGSN outside of the core operation.
Unravelling intraplate Cenozoic magmatism in Mongolia: Reflections from the present-day mantle or a legacy from the past?
Authors: Papadopoulou Martha , Barry Tiffany , Rutson Alex
Published: March 2020

In Mongolia, East Asia, intraplate magmatism has occurred intermittently from the late Cretaceous to present day. During the Mesozoic, basaltic volcanism was widespread across much of the southern and eastern parts of Mongolia. In contrast, the Cenozoic magmatism mainly extends in central parts of the country in a band trending north to south. This magmatism occurs in small, diffusely dispersed and relatively small volume (<30km2) plateaus (Barry et al., 2003). An exception to this is the Dariganga plateau in the southeast of Mongolia with >200 volcanic cones, covering an area of >10,000km2. Windley et al., (2010) and Sheldrick et al., (2018), proposed that the Mesozoic magmatism was caused by widespread but patchy removal of lithospheric mantle from beneath parts of Mongolia, NE China and Russia. Although several models have tried to explain the Cenozoic magmatism in Mongolia, there is no clear evidence for the cause of the volcanic activity. Isotopic studies on volcanic rocks from the Hangai Dome in central Mongolia revealed an asthenospheric origin for the melts (Barry et al., 2003). Could the Cenozoic volcanism be the result of melts that originated during a Mesozoic event? These melts could have been trapped in the lithospheric mantle since the Mesozoic and variably remobilised more recently. Or is there a mechanism causing melting during the Cenozoic, which can give insights into present-day conditions in the underlying mantle? Here, we examine the possibilities of (a) a direct link between the late Mesozoic and Cenozoic volcanic events in Mongolia leading to a multistage modification of the melt composition and (b) mechanism(s) in the asthenosphere/lithosphere causing present-day melting. In order to assess these possibilities we will compare the melt sources of the magmatism, focusing on three contrasting regions. (1) In central Mongolia, Cenozoic basalts occur on the flanks of the uplifted Hangai Dome, which is thought to have been uplifted in the Mesozoic (McDannell et al., 2018) but did not experience any volcanism at the time. (2) The Gobi Altai, which experienced both Mesozoic and Cenozoic magmatism, separated by ~40-50 Ma gap, but did not undergo any Mesozoic uplift. And finally, (3) the Dariganga plateau, which has experienced extensive volcanism during the late Cenozoic but not during the Mesozoic and in contrast to Hangai, underwent Mesozoic basin development rather than uplift. We will compare and contrast mantle sources of these regions to determine whether Mesozoic events have influenced the composition of the Cenozoic magmatism. Additionally, study of tomographic images from the upper mantle below central Mongolia will help us identify possible mechanisms that could have contributed towards the present-day melting of the upper mantle.
Farewell to IceBridge: 10 years of polar sea ice remote sensing
Authors: Boisvert Linette , MacGregor Joseph , Medley Brooke , Kurtz Nathan , Kwok Ron , Blanchard-Wrigglesworth Edward , Petty Alek , Harbeck Jeremy
Published: March 2020

NASA’s Operation IceBridge (OIB) was a multi-year, multi-platform, airborne mission which took place between 2009-2019. OIB was designed and implemented to continue monitoring the changing sea ice and ice sheets in both the Arctic and Antarctic by ‘bridging the gap’ between NASA’s ICESat (2003–2009) and ICESat-2 (launched September 2018) satellite missions. OIB’s instrument suite most often consisted of laser altimeters, radar sounders, gravimeters and multi-spectral imagers. These instruments were selected to study polar sea ice thickness, ice sheet elevation, snow and ice thickness, surface temperature and bathymetry. With the launch of ICESat-2, the final year of OIB consisted of three campaigns designed to under fly the satellite: 1) the end of the Arctic growth season (spring), 2) during the Arctic summer to capture many different types of melting surfaces, and 3) the Antarctic spring to cover an entirely new area of East Antarctica. Over this ten-year period a coherent picture of Arctic and Antarctic sea ice and snow thickness and other properties have been produced and monitored. Specifically, OIB has changed the community’s perspective of snow on sea ice in the Arctic. Over the decade, OIB has also been used to validate other satellite altimeter missions like ESA’s CryoSat-2. Since the launch of ICESat-2, coincident OIB under flights with the satellite were crucial for measuring sea ice properties. With sea ice constantly in motion, and the differences in OIB aircraft and ICESat-2 ground speed, there can substantial drift in the sea ice pack over the same ground track distance being measured.Therefore, we had to design and implement sea ice drift trajectories based on low level winds measured from the aircraft in flight, adjusting our plane’s path accordingly so we could measure the same sea ice as ICESat-2. This was implemented in both the Antarctic 2018 and Arctic 2019 campaigns successfully. Specifically, the Spring Arctic 2019 campaign allowed for validation of ICESat-2 freeboards with OIB ATM freeboards proving invaluable to the success of ICESat-2 and the future of sea ice research to come from these missions.

 
Long term change observation of river terrain due to dam removal in Central Taiwan
Authors: Liu Tingray , Wu Chunhung
Published: March 2020

This research focuses on the long-term geomorphologic change in the upstream of the silt dams in the Lan-daw rivers watershed in central Taiwan, adopts the long-term rainfall records in the Lan-daw rivers watershed to calculate the 1-day, 2-days, 3-days accumulated rainfall with different return period, and analyzes the relationship between the geomorphologic change and the accumulated rainfall. This research builds the Digital Surface Models based on the photos shot by UAV at 9 different times. The river in upstream of the Lan-daw rivers watershed is sinuous. The research classifies 3 time periods from 2010 to August, 2019, including the first time period from 2010 to June, 2017, the second time period from June, 2017 to Nov. 2018, and the third time period from Nov. 2018 to Aug. 2019. The target in the first time period is to observe the geomorphologic change after the first dam removal, that in the second time period to observe the geomorphologic change in the 2 years after dam removal, and that in the third time period to observe the geomorphologic change after the second dam removal.

The longitudinal slopes in the first, second, and third time periods are -30.3%, 14.8%, and 5.98%, and the knickpoint in the longitudinal profile in the first and second time periods occur in the upstream 20 m of the silt dam and that in the third time periods occurs in the upstream 45 m of the silt dam. The research classifies the cross-sections profiles into 3 groups, including the first group from C1 to C7 cross sections, the second group from C8 to C14 cross sections, and the third group from C15 to C22 cross sections. The geomorphologic change in the first group near the silt dam is the most obvious in the three groups. The geomorphologic change in the three groups in the first time period are -6.43 m to -8.13 m (scouring), those in the second time period are 0.23 m to 0.34 m (deposition), and those in the third time period are 0.46 m (deposition) to -1.78 m (scouring). Based on the analysis of the long-term rainfall record in the Lan-daw river watershed, the return period of the heaviest rainfall from 2015 to Aug. 2019 is less than 20-year return period. This means that the geomorphologic change in upstream of silt dam in the Lan-Daw river watershed is easy induced in the short time after dam removal.
Assessment of nitrate sources in groundwater of Monterrey Valley using a multi-tracer approach combined with a probability isotope mixing model
Authors: Torres-Martinez Juan Antonio , Mora Abrahan , Knappett Peter S.K. , Ornelas-Soto Nancy , Mahlknecht Jürgen
Published: March 2020

Groundwater quality deterioration by nitrate pollution due to the intensive use of fertilizers in agriculture, release of untreated urban sewage and industrial wastewater, and atmospheric deposition is a worldwide concern. The urbanized and industrialized Monterrey valley has a long record of elevated nitrate concentrations in groundwater with multiple potential pollution sources. This study aimed to fingerprint different sources and transformation processes of nitrate pollution in Monterrey using a suite of chemical and isotopic tracers (δ2H-H2O, δ18O-H2O, δ15N-NO3, δ18O-NO3) combined with a Bayesian isotope mixing model. The results suggest that soil nitrogen and sewage were the most important nitrate sources. However, the concentrations of nitrate were controlled by denitrification processes in the transition and discharge zones. The approach followed in this study is useful for establishing effective pollution management strategies in contaminated aquifers.
Investigation into the influence of the Réunion plume on the Central Indian Ridge
Authors: Vincent Clément , Park Jung-Woo , Lee Sang-Mook , Kim Jonguk , Pak Sang-Joon
Published: March 2020

Plume-ridge interaction is an important thermal and geological process, which results in various physical and chemical anomalies along a significant length of the global mid-ocean ridge system. Despite numerous studies, some remaining questions to be solved are the origin and mechanisms of geochemical variations and their possible correlation with the morphology of mid-ocean ridges.

The Central Indian Ridge, with a slow to intermediate spreading rate, provides an ideal opportunity to explore the long-distance plume-ridge interactions. Presently, the ridge is moving away from the Réunion hotspot which is located 1000 km away from the Central Indian Ridge at Réunion Island. Paleogeographic reconstruction suggests that the hotspot crossed the middle part of the Central Indian Ridge (MCIR) between 8°S and 17°S at ~34 Ma. Previous studies argue that the plume material currently flows into the Central Indian Ridge at around 19°S, south of Marie Celeste Fracture Zone (MCFZ) and geochemical enrichments of the mid-ocean ridge basalts (MORB) from the MCIR 14°S and 19°S segments can be attributed to a fossil Réunion plume component. However, a recent geophysical study has suggested that the geochemical anomalies along the Rodrigues segment (18-21°S) can be ascribed to the asthenospheric flow from the Réunion plume, reopening the debate about the origin of the enriched anomalies along the MCIR (14-19°S).

In this study, we revisited the MCIR from 14°S to 17°S with new geochemical data obtained based on high-resolution sampling and ship-board high-resolution bathymetry data to constrain the influence of the Réunion plume on geochemistry and bathymetry of the MCIR. The results show that trace element ratios and isotopic compositions of on-axis MORB vary in association with ridge discontinuities such as transform faults and non-transform fault discontinuities. The MORB from the northern parts of segments display substantially enriched geochemical features and the enrichments correspond to a shallower axial bathymetry. We attribute the chemical and morphological anomalies along the ridge to the influence of a Réunion plume component focussed by a hotspot leading edge effect. The hotspot leading segments are offset in the direction of the plume and are more efficiently affected by the enriched plume materials. These findings suggest that lithospheric discontinuities such as transform faults and fracture zones may control the flow of mantle plume material into the ridge and the geometry of the ridge coupled to its hotspot proximity may play an important role, particularly in the long-distance plume-ridge interaction.
Precise Distributed Acoustic Sensing measurements by using seafloor optical fiber cable system for seismic monitoring
Authors: Shinohara Masanao , Yamada Tomoaki , Akuhara Takeshi , Mochizuki KImihiro , Sakai Shin'ichi
Published: March 2020

Distributed Acoustic Sensing (DAS) measurements which utilize an optical fiber itself as a sensor can be applied for various purposes. An observation of earthquakes using an optical fiber deployed on the seafloor with DAS technology is attractive because DAS measurements enable a dense seismic observation as a long linear array. Spatial resolution of the observation reaches a few meters. The length of the array is determined by the measurement range of the DAS interrogator deployed on the optical fiber, and a fine spatial sensor interval can be configured. DAS measurements have become increasingly accurate and the current state of technology exhibit high signal quality. Because DAS measurement is useful for earthquake observation, there were some trials for an observation of earthquakes using an optical fiber deployed on the land or the seafloor. However, There are few observations using DAS technology on seafloor until the present.

In 1996, a seafloor seismic tsunami observation system using an optical fiber cable was deployed off the coast of Sanriku by Earthquake Research Institute, the University of Tokyo. The system has three seismic stations and two tsunami-meters, and a length of the cable is approximately 115 km. The system has six spare (dark) optical fibers which are dispersion shifted single mode type, and have been incorporated for future extension of the observation system. We have started development of a seafloor seismic observation system utilizing DAS technology on the Sanriku cable observation system as a next generation of marine seismic observation system. In 2019, we performed DAS measurements using a dark fiber from Sanriku seafloor observation system three times. An interrogator was installed in the cable landing station temporarily. Data were recorded with various values of parameters, such as length of data collection (array aperture), gauge length, ping rate, acquisition offset, for evaluation of data quality and signal to noise ratios. The total recording period for three measurements was approximately three weeks. As a result, many earthquakes including micro-earthquakes were recorded. The obtained data will be used to develop data processing techniques for seismic observations utilizing DAS measurements.

 
Focal mechanisms for small to intermediate earthquakes in the northern part of the Alps and their seismotectonic interpretation
Authors: Plenefisch Thomas , Barth Laura ,   AlpArray working group
Published: March 2020

In the framework of the AlpArray project more than 600 broadband stations have been installed and operated in the Alps and the surroundings. Together with the permanent stations in the area it is one of the most densely spaced seismic networks worldwide. Thereby, it offers an excellent opportunity to investigate the seismicity and seismotectonics of the Alpine chain. Due to the huge number of stations focal mechanisms can be calculated even for small magnitude earthquakes with high accuracy. The focal mechanisms are one important key to reveal the contemporary stress field and thus contribute to a better understanding of the geodynamic processes of the Alps.

In our study we focus on small to intermediate earthquakes in the Northern Alps, namely on four distinct sub-regions. These are from West to East the Lake Constance, the Arlberg region, the area of Garmisch-Partenkirchen and the broader region of Innsbruck. In order to calculate the focal mechanisms, we apply the FOCMEC program (Snoke, 2003), which inverts for a pure double-couple source. P-polarities as well as amplitude ratios of SH to P are used as input parameters for the inversion. Thanks to the dense network a good coverage of the focal sphere is achieved in most cases.

Altogether, we calculated focal mechanisms for 25 earthquakes in the magnitude range between 2.5 and 3.5 from the time period 2016 to 2019. Most of the focal mechanisms represent reverse or strike-slip faulting, normal faulting events are rather rare. The mechanisms are analysed with respect to lateral changes along the Northern Alpine. On one hand we compare the mechanisms with mechanisms of older studies as well as with moment tensors of events of slightly larger magnitudes. Those events are the scope of another subproject in the framework of the AlpArray (Petersen et al., 2019). On the other hand, we compare our mechanisms with geological indicators, namely orientation of faults. Finally, the focal mechanisms are used as input to invert for the stress field.
Drying Lakes: A Review on The Health Conditions and Restoration Strategies
Authors: Anchita Anchita , Tussupova Kamshat , Hjorth Peder
Published: March 2020

Abstract: Decrease of saline lakes, which comprises of 44% of all the available lake water, is a major concern. It additionally brings to desertification process to the region. Thus, various countries have taken different actions in protecting their lake’s water level. The aim of this paper is to assess different strategies directed to tackle the decreasing saline lake water levels. Lake Urmia and the Aral Sea which split into North Aral and South Aral were among the world's largest saline lakes and now have reduced to 10% of their original size. A thorough review of academic reports, official documents and databases were considered. Although the dry-up of the lake is a natural process, it has been sped up by human interventions in the hydrology cycle. Dust storms (strong winds) in the case of the Aral Sea, transmit the pollutants from dry lake surface which initially accumulated in the lakebed causing severe health issue. Various strategies were implemented to manage the socio-economic conditions caused due to the drying of lakes. The strategy implemented for the North Aral Sea was to restore the lake by reducing the water withdrawal from tributary rivers which leads to increased water level in the sea. The strategy implemented for Lake Urmia was to restore the lake by water transfer activities from neighbouring water sources which until now show no increase in water level. The strategy implemented for the South Aral Sea was to use a dry lakebed to diversify the economy by oil and mineral extraction which shows the adaptation to the environmental conditions with no restoration strategy. As a conclusion, it is found that there is no common best solution for this kind of problem. The best fit depends on the local context and it is strongly path dependent. 

Keywords: Drying saline lake; Dust storms; Aral sea; Health impacts; Lake Urmia; Restoration of saline lake; Strategies.
Effect of Aerosol Particles on Orographic Clouds: Sensitivity to Autoconversion Schemes
Authors: Xiao Hui
Published: March 2020

Aerosol particles can serve as cloud condensation nuclei (CCN) to influence orographic clouds. Autoconversion, which describes the initial formation of raindrops from the collision of cloud droplets, is an important process for aerosol–cloud–precipitation systems. In this study, seven autoconversion schemes are used to investigate the impact of CCN on orographic warm-phase clouds. As the initial cloud droplet concentration is increased from 100 cm−3 to 1000 cm−3 (to represent an increase in CCN), the cloud water increases and then the rainwater is suppressed due to a decrease in the autoconversion rate, leading to a spatial shift in surface precipitation. Intercomparison of the results from the autoconversion schemes show that the sensitivity of cloud water, rainwater, and surface precipitation to a change in the concentration of CCN is different from scheme to scheme. In particular, the decrease in orographic precipitation due to increasing CCN is found to range from −87% to −10% depending on the autoconversion scheme. Moreover, the surface precipitation distribution also changes significantly by scheme or CCN concentration, and the increase in the spillover (ratio of precipitation on the leeward side to total precipitation) induced by increased CCN ranges from 10% to 55% under different autoconversion schemes. The simulations suggest that autoconversion parameterization schemes should not be ignored in the interaction of aerosol and orographic cloud.
Scenario Analysis of Cooperation Dynamics on the Columbia River under Changing Conditions using Socio-Hydrological Modelling
Authors: Cherry Charlotte , Souza Felipe Augusto Arguello , Park Samuel , Shrestha Ashish , Yang Liu , Barendrecht Marlies , Garcia Margaret , Yu David , Wei Jing , Tian Fuqiang
Published: March 2020

The Columbia River Treaty, signed in 1961, solidifies cooperation between the United States and Canada to manage the operation of the Columbia River’s extensive dam network jointly to optimize benefits for the whole system. Under the treaty, Canada operates dams to provide flood protection and maximize hydropower potential downstream. In exchange, the U.S. compensates Canada with half of the estimated benefits of the treaty, which provides an economic incentive to cooperate not seen in many other transboundary basins. However, since the treaty was established, this highly-managed system has responded to unanticipated external social and environmental factors. For example, mounting social pressure in the 1990s to protect the aquatic environment resulted in operational changes to U.S. dams to accommodate flows for fish migration, which ultimately resulted in financial losses for hydropower producers. These changes affected the relative benefits each country receives from cooperation. Utilizing a range of hydrological, economic, social, and environmental datasets, a socio-hydrological model was developed that simulates system operations using historical data to mimic operational changes, shifts in flood control and hydropower production, and cooperation dynamics.

Renegotiations of the Columbia River Treaty started in 2018, and the new treaty in 2024 must include provisions for environmental protection that were, originally, not considered. The purpose of this study is to use the established model to envision how changing conditions such as climate change, spring fish flows, and First Nation rights would affect each country’s willingness to cooperate. For example, how would changes in snowpack upstream or seasonal changes in precipitation alter the hydrology of the basin and, in turn, the benefits each country receives from cooperation. This scenario analysis provides insight into how a revised treaty that takes future uncertainties into account would affect the balance of benefits to maintain or disrupt cooperation on the Columbia River.