bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport of Heat by Hydrothermal Circulation in a Young Rift Setting:  Observations from the Auka and JaichMaa Ja'ag' vent Field in the Pescadero Basin, Southern Gulf of California.
Authors: Negrete-Aranda Raquel , Neumann Florian , Contreras Juan , Harris Robert N. , Spelz Ronald M. , Zierenberg Robert , Caress David W.
Published: March 2021

New heat flow measurements collected throughout the Auka and JaichMaa Ja' ag' hydrothermal vent fields in the central graben of the Southern Pescadero Basin, southern Gulf of California, indicate that upflow of hydrothermal fluids associated with active rifting dissipate heat in excess of 10 W/m2 around faults that have a few tens-of-meters of displacement. Heat flow anomalies slowly decay to background values of ~2 W/m2 at distances of ~1 km from these faults following an inverse square-root distance law. We develop a physical model of the Auka vent field based on the fundamental Green's function solution of the heat equation. The model includes the effects of circulation in the porous networks of faults and the lateral seepage of geothermal brines through the fault walls to surrounding hemipelagic sediments.  We use an optimal fitting method to estimate the reservoir depth, permeability, and circulation rate. Our model indicates the heat source is at a depth of ~5.7 km; permeability and flow rates in the fracture system are ~10-14 m2 and 10-7 m/s, respectively, and ~10-16 m2 and 10-8 m/s in the basin aquitards, respectively. Model scaling laws point to the importance of faults in controlling sediment-hosted vent fields and slow circulation throughout low permeability sediments in controlling the brine's chemistry. Although the fault model seems appropriate and straightforward for the Pescadero vents, it does seem to be the exception to the other known sediment-hosted vent fields in the Pacific.
Quantitative characterization of crude oil cracking pressurization in the south of transition zone of Aman, Tarim Basin
Authors: Zhang Hongrui , Liu Hua
Published: March 2021

The overpressure has a significant effect on hydrocarbon migration and accumulation. Scholars have gradually focused on the quantitative characterization of overpressure, which proposes many overpressure quantitative models suitable for different overpressure mechanisms. However, there are few studies on quantitative characterization of overpressure in crude oil cracking. In view of this, taking the south of Aman transition zone in Tarim Basin as the research object, recovered the overpressure characteristics of the research area in the reservoir forming period, and established the quantitative model of crude oil cracking pressurization.

Firstly, according to the data about fluid inclusions tested by some experimental apparatus, the paleo-pressures were calculated by PVTx simulation method and basin simulation method. Next, based on the volume increment of crude oil cracking is equal to the volume reduction caused by overpressure compression, established the quantitative model for pressurization of total crude oil cracking. Moreover, equaled to the mass of residual oil plus the quality of cracked gas and pyrobitumen, put forward the quantitative model for pressurization of partial crude oil cracking and proposed these two model combined with some parameters, which included density and compressibility of oil, gas ,water and pyrobitumen and conversion rate of crude oil cracking and so on. Then, using these two models, calculated the intensity of pressurization of Shunnan gas reservoir. At last, the accuracy of the model was tested by restored paleo-pressure values.

The study shows that the southwest of Shunnan slope is a typical overpressure area. The formation pressure coefficients of Yijianfang formation and Yingshan formation are between 1.15 and 1.48, and those of Penglaiba formation are as high as 1.94. Based on the homogenization temperature of the inclusions and combined with burial history and thermal history, the paleo-pressure in Shunnan is restored through fluid inclusion method. There were two periods of overpressure in Cisuralian (292-280ma) and Neogene (21-2ma). The paleo-pressure coefficient of Neogene is 1.57-1.64, which is generally higher than that of Cisuralian(1.39～1.48). The main mechanism of overpressure in Shunnan area is the cracking of crude oil and the author tried to establish the quantitative characterization of crude oil cracking. The overpressure of crude oil cracking during Neogene reaches around 30 MPa, of which the contributions is respectively 66.7 %.
Petrotectonic implications of metabasites of the Eastern Andean Metamorphic Complex at Lago O´Higgins-San Martin, southern Patagonia
Authors: Rojo Diego , Calderón Mauricio , Ghiglione Matias , Suárez Rodrigo Javier , Quezada Paulo , Hervé Francisco , Babinski Marly , Fanning C. Mark
Published: March 2021

The Eastern Andean Metamorphic Complex (EAMC) in southwestern Patagonia (4°-52°S) is a 450 km long belt mainly composed by low-grade metasedimentary rocks of Upper Devonian-lower Carboniferous, and Permian-lower Triassic ages. Previous works have suggested a passive margin environment for the deposition of the protolith.  The EAMC comprise scarce interleaved tectonic slices of marbles, metabasites, and exceptional serpentinite bodies. At Lago O´Higgins-San Martin (48°30’S-49°00’S) the metasedimentary sucessions are tectonically juxtaposed with lenses of pillowed metabasalts and greenschists having OIB, N-MORB, BABB and IAT geochemical affinities. The Nd-isotopic composition of metabasalts is characterized by εNd(t=350 Ma) of +6 and +7. The metabasalts show no signal of crustal contamination, instead, the mantle source was probably modified by subduction components. New and already published provenance data based on mineralogy, geochemistry and zircon geochronology indicate that the quartz-rich protolith of metasandstones were deposited during late Devonian-early Carboniferous times (youngest single zircon ages around of latest Devonian-earliest Carboniferous times) sourced from igneous and/or sedimentary rocks located in the interior of Gondwana, as the Deseado Massif, for instance. Noticeable, the detrital age patterns of all samples reveal a prominent population of late Neoproterozoic zircons, probably directly derived from igneous and/or metaigneous rocks of the Brasiliano/Pan-African orogen or from reworked material from variably metamorphosed sedimentary units that crops out at the same latitudes in the extra-Andean region of Patagonia. We propose that the protolith of metabasites formed part of the upper part of an oceanic-like lithosphere generated in a marginal basin above a supra-subduction zone, where plume-related oceanic island volcanoes were generated. The closure of the marginal basin, probably in mid-Carboniferous times, or soon after. The oceanic lithosphere was likely underthrusted within an east-to-northeast-dipping subduction zone, where ophiolitic rocks and metasedimentary sequences were tectonically interleaved at the base of an accretionary wedge.
Wet-range physical realism in a model of soil water retention 
Authors: Nimmo John R.
Published: March 2021

Most models of soil water retention represent the wettest range simplistically, reflecting a high priority on facilitating computation without recognition of the active physical processes. Commonly the wet range is misleadingly represented by a straight line of zero slope, or by default using the same formulation as for the middle range, even though the mechanisms of water retention are different for the wet and middle portions of the range. Though adequate for some purposes, such treatment causes problems for applications that are sensitive to wet-range processes. It prevents accurate prediction of critical but challenging wet-range phenomena such as domain exchange between preferential flow paths and soil matrix. It limits the choices available for quantifying flow problems, for example a blowing-up of derivatives on approach to saturation prohibits the use of diffusivity-based formulations.

A new model addresses these issues for the important case where the medium is soil matrix material exclusive of macropores, thus having a well-defined air-entry value, and the moisture dynamics are the typical wet and dry cycling that achieves maximum wetness at field saturation, with a presence of trapped air at zero matric potential. The range between the air-entry value and field saturation is dominated by trapped air expansion in response to pressure change, as well as a process that increases the sensitivity to changing matric pressure. This enhanced sensitivity may be related in part to a collapse of liquid bridges between air pockets as they expand. For this wet range, the new model incorporates the Boyles’ law inverse-proportionality of trapped air volume and pressure, amplified by an empirical factor to account for the additional processes. To cover the full range of possible moisture, this wet-range formula is supplemented by two others. The middle range of capillary advance/retreat and Haines jumps is represented by a new adaptation of the lognormal distribution function. The adsorption-dominated dry range is represented by a logarithmic relation used in earlier models. Joined together with a continuous first-derivative constraint, the overall formulation recognizes the dominant processes within three segments of the full range. Optimization of five parameters can fit the model to a full data set.

Tests have demonstrated excellent fits, using measured data that have many closely spaced points in the wet and middle ranges. With their basis in process, the model’s parameters have a strong physical interpretation, and potentially can be assigned values without fitting, from knowledge of fundamental relationships or individual measurements. This basis in process also may permit accommodation of hysteresis by a systematic adjustment of the relation between the wet and middle ranges, and with minimal additional data may serve to facilitate estimation of other properties such as hydraulic conductivity, diffusivity, and sorptivity.
Tectonic evolution of Paleo-Tethys in NE Iran
Authors: Chu Yang , Wan Bo , Allen Mark B. , Chen Ling , Lin Wei , Talebian Morteza
Published: March 2021

The timings of the onset of oceanic spreading, subduction and collision are crucial in plate tectonic reconstructions, but not always straightforward to resolve. The evolution of the Paleo-Tethys Ocean dominated the Paleozoic-Early Mesozoic tectonics of West Asia, but the timeline of events is still poorly-constrained. In this study we present detrital zircon ages from NE Iran, in order to determine the timing of tectonic events in the region, and the wider implications for regional tectonics, paleogeography and climate change. Paleozoic clastic rocks record two major age peaks at ~800 Ma and ~600 Ma. The consistency in age patterns shows a dominant provenance from the Neoproterozoic basement of northern Gondwana. We interpret deposition on a long-lasting passive continental margin after the initial spreading of the Paleo-Tethys Ocean. Initial collision between the South Turan (Eurasia) and Central Iran (Gondwana) blocks caused coarse clastic deposition, the protolith of the Mashhad Phyllite, in a peripheral foreland basin on the Paleozoic passive margin. The Mashhad Phyllite yields major zircon age clusters at 450-250 Ma and 1900-1800 Ma, with a clear provenance from the active, Eurasian, margin. The Paleozoic ages reveal a long-lived subduction zone under the South Turan Block began in the latest Ordovician. Analysis of the age spectra allows us to constrain the timing of initial collision as no later than 228 Ma, which is also a constraint on the maximum depositional age of the Mashhad Phyllite. Based on our new results and previous data, we discuss the interaction between the Rheic and Paleo-Tethys oceans, and explain how a new subduction zone may have initiated after continental collision. The timing of collision is similar to the Carnian Pluvial Event (CPE). Paleo-Tethys collision has previously been suggested as the trigger for this climatic change, and our study provides timing evidence that reinforces Paleo-Tethys closure as a causal mechanism for the CPE.
Supervised learning from noisy observations: Combining machine-learning techniques with data assimilation
Authors: Gottwald Georg , Reich Sebastian
Published: March 2021

Data-driven prediction and physics-agnostic machine-learning methods have attracted increased interest in recent years achieving forecast horizons going well beyond those to be expected for chaotic dynamical systems.  In a separate strand of research data-assimilation has been successfully used to optimally combine forecast models and their inherent uncertainty with incoming noisy observations. The key idea in our work here is to achieve increased forecast capabilities by judiciously combining machine-learning algorithms and data assimilation. We combine the physics-agnostic data-driven approach of random feature maps as a forecast model within an ensemble Kalman filter data assimilation procedure. The machine-learning model is learned sequentially by incorporating incoming noisy observations. We show that the obtained forecast model has remarkably good forecast skill while being computationally cheap once trained. Going beyond the task of forecasting, we show that our method can be used to generate reliable ensembles for probabilistic forecasting as well as to learn effective model closure in multi-scale systems.
Numerical simulation of thermal effects of urban green enhancements in different urban environments in the city of Augsburg (Bavaria, SE Germany)
Authors: Beck Christoph , Buse Katharina , Fritsch Marisa , Irber Philipp
Published: March 2021

The interdisciplinary research project Abc (Augsburg bleibt cool – Augsburg stays cool) – funded by the German Federal Ministry for Environment, Nature Conservation and Nuclear Safety – deals with different aspects of heat-stress exposure and adaptation to heat-stress in indoor and outdoor urban environments in the urban area of Augsburg (Bavaria, SE Germany).

As one essential research approach this includes the estimation of the thermal effects of vegetation enhancements in different urban environments via numerical simulations performed with the ENVI-met V4 numerical model.

For several model domains – each of them covering 300 m x 300 m with a 2 m x 2 m horizontal resolution - model runs have been performed utilizing observational data for a heat wave end of July 2019 as meteorological forcing, thus serving as a climate analogue for thermal conditions expected to appear more frequently under future climate change conditions. For each domain model runs for the current-state and several adaptation scenarios have been performed. Adaptation scenarios thereby comprise varying measures for enhancing urban green (street and facade greening) and blue infrastructure.

In this contribution we present and discuss selected model settings and scenarios.

Model results indicate the general capability of vegetation enhancements to counteract heat-stress exposure in urban environments. However, partly also contrary effects emerge pointing to the complex interdependencies within the urban climate system which have to be taken into account when projecting urban heat island adaptation strategies.
The estimation of sea spray at wind speeds ranging from light to extreme
Authors: Xu Xingkun , Voermans Joey , Babanin Alexander , Ma Hongyu , Guan Changlong
Published: March 2021

As one of typical elements in the air-sea boundary layer, sea spray is expected to mediate energy flux exchange in the air and ocean boundary layers, and therefore it is of crucial importance to the meteorology, oceanology, and regional climatology. In addition, the spray is also considered as one of the missing physical mechanisms in atmospheric and oceanic numerical models. Hence, it is necessary to accurately predict how much sea spray is produced at the air-sea boundary layer. Though spray has been studied for a number of decades, large uncertainties still linger. For instance, uncertainties in qualifying how much spray is produced on the sea surface reach 106 times. This is because of the rarity of spray observations in the field, especially under strong wind condition.

To give a reliable spray production model, scientists tried to employ laser-based facilities in the field to observe sea spray by interpreting infrared laser-beam intensity into sea spray volume flux over the water surface. Hence, in the current study, we collected datasets in the field measured by laser-based facilities on the North-West Shelf of the coast of Western Australia, thereafter, further analyzed, and calibrated them through a series of academic, statistical, and physical analysis to ensure the data quality. After that, assuming the existence of spray drops in the air-sea layer would attenuate the infrared laser-beam intensity, the weakening extends of laser-beam intensity is used to estimate the volume flux of sea spray above the ocean surface at winds speed ranging from light to extreme during the passage of Tropical Cyclone Olwyn (2015). It should be noted that our observations of sea spray volume flux are within the ranges of existing models and are consistent with the model proposed by Andreas (1992) in both trend and magnitude.

Using the field observations of the sea spray volume flux, a sea spray volume flux model can be constructed. Given that sea spray droplets are generated at the ocean surface through breaking waves and wind shear, the sea spray volume flux is expected to be dominated by the properties of the local wind and wave field. For physical consistency across the wide range of scales observed in the field and laboratory, non-dimensional parameters (i.e., non-dimensional wind speed and the mean wave steepness) were adopted to construct the model. Consequently, a power-law non-dimensional spray volumetric flux model is suggested based on the estimation of the spray volume flux. It should be noted that one sensitive test was conducted to substantiate the inclusion of wave breaking process, here simply included with the mean wave steepness, improves spray volume flux parameterization.
Tree species from Andean forest are complementary in their effect on ecohydrological processes
Authors: Cano-Arboleda Laura V. , Villegas Juan Camilo , Restrepo Aura Cristina , Ocampo-Montoya Elizabeth , Quintero-Vallejo Estela
Published: March 2021

Vegetation affects water balance partitioning via effects on incoming precipitation, local radiation balance and hydrological dynamics of soil. The extent of these effects is determined by plant functional traits. Commonly, the role of plant species on hydrological regulation has been assessed considering vegetation as homogeneous cover, even more, that approach underestimates the importance of species in this process. Nevertheless, in recent years, new focus has been placed on species study based on their functional traits and their roles in ecosystem functions as hydrological regulation. Still new tendencies are considering vegetation cover consisting of different species, each of them having different effects on hydrological regulation because they have different functional traits. In an 8-year old ecosystem restoration project established in Medellín (Colombia), we explored the relations between plant functional traits of 10 dominant species and ecohydrological processes that determine precipitation partitioning in the canopy via stemflow and throughfall. Here we show that functional traits describing tree crowns are significantly related with stemflow and throughfall. Our species exhibit differences in their functional traits and ecohydrological processes, forming a gradient of variation of ecohydrological processes and crown functional traits: from wide and less dense crowns in Alnus acuminata to smaller but more dense crowns in Quercus humboldtii, related with less throughfall temporal variability, and less stemflow temporal variability, respectively; the other species are placed along this gradient. This result suggests a complementary effect of species on the hydrological processes and consequently on the hydrological function, highlighting the importance of considering species diversity on hydrological regulation assessment. More specifically, our results emphasize the need to include information about the effects of species planted in ecological restoration projects over ecohydrological processes, via ecological criteria such as plant functional traits. This approach permits a more objective and complete study of hydrological regulation that brings key information for an adequate ecosystem management and restoration based on ecological roles of species that, through biological diversity, optimize ecosystem functions and services.
Architecture and dynamics of the magmatic system feeding the 2018 offshore Mayotte eruption from satellite gravity data
Authors: Le Mével Hélène , Miller Craig A. , Zhan Yan
Published: March 2021

In May 2018, a submarine eruption started offshore Mayotte (Comoros archipelago, Indian Ocean), and was first detected as a series of earthquake swarms. Since then, at least 6.4 km3 of lava has erupted from a newly mapped volcanic edifice (MAYOBS campaigns), about 50 km east of Mayotte island. Since the onset of the eruption, GNSS stations on the island have recorded subsidence (up to 17 cm) and eastward displacement (up to 23 cm). We combine marine gravity data derived from satellite altimetry with finite element models to examine the magmatic system structure and its dynamics. First, we calculate the Mantle Bouguer Anomaly (MBA) by taking into account the gravitational effect of the bathymetry and the Moho interfaces, assuming a crust of constant thickness of 17.5 km and correction densities of 2.8 g/cm3 and 3.3 g/cm3 for the crust and mantle, respectively. We then invert the MBA to determine the anomalous density structures within the lithosphere, using the mixed Lp-norm inversion and Gauss-Newton optimization implemented in the SimPEG framework. The gravity inversion reveals two zones of low density, east of Mayotte island. The first is located NE of Petite Terre island between ~15 and 35 km depth, and the second is located further east, south of La Jumelle seamounts and extends from ~25 to 35 km depth. We interpret these low density regions as regions of partial melt stored in the lithosphere and estimate the volume of stored magma. Finally, we use the newly imaged low density bodies to constrain the magma reservoir geometry and simulate magma flow from this reservoir to the eruptive vent in a 3D, time-dependent, numerical model. The model parameters are adjusted by minimizing the misfit between the modeled surface displacement and that measured at the 6 GPS sites, between May 2018 and 2020. The deformation modeling reveals the temporal evolution of the magma flux during the eruption, and the resulting stress distribution in the crust explains the patterns of recorded seismicity. Together with the existing seismic and geodetic studies, the gravity data analysis and FEM models bring new constraints on the architecture of the magma plumbing system and the magmatic processes behind the largest submarine eruption ever documented.
Inversion of argon data implies extreme extension in and below the orogenic lid of the European Alps during Eocene–Oligocene collision
Authors: Lister Gordon , Forster Marnie , Muston Jack , Price Jason , Manatschal Gianreto
Published: March 2021

Here we demonstrate conjoint inversion of data combined from 40Ar/39Ar geochronology and ultra-high-vacuum (UHV) 39Ar diffusion experiments using potassium feldspar. The method allows precise definition of diffusion parameters for a collection of domains, using an approximation to a fractal geometry. Using the MacArgon program, we could constrain possible temperature histories followed by individual mineral grains in and below the orogenic lid of the European Alps, during its history of mountain building. Tests of the sensitivity of the obtained fits provides insight into the possible range of allowed temperature-time (T-t) paths, and recognition of ‘events’ during which microstructural modification may have taken place. The results suggest a sequence of abrupt cooling events, which could reflect, either: i) cycles of crustal shortening followed by detachment faulting; or ii) initial terrane-stacking beneath the orogenic lid followed by repeated rapid crustal stretching events, each event involving upward stepping of the active detachment fault. Substantial movement on low-angle normal faults and shear zones has taken place, consistent with extreme extension of the mountain belt at high-angles to the convergence direction, in front of the advancing Adriatic indentor. The magnitude of the temperature drop implies that a rapid extension event took place at the time of the Eocene—Oligocene transition, and reduced the thickness of the orogenic lid to a few kilometres.
Thermocline warming induced extreme Indian Ocean Dipole in 2019
Authors: Du Yan , Zhang Yuhong , Zhang Lian-Yi , Tozuka Tomoki , Cai Wenju
Published: March 2021

The 2019 positive Indian Ocean Dipole (IOD) was the strongest event since the 1960s which developed independently without coinciding El Niño. The dynamics is not fully understood. Here we show that in March-May, westward propagating oceanic Rossby waves, a remnant consequence of the weak 2018 Pacific warm condition, led to anomalous sea surface temperature warming in the southwest tropical Indian Ocean (TIO), inducing deep convection and anomalous easterly winds along the equator, which triggered the initial cooling in the east. In June-August, the easterly wind anomalies continued to evolve through ocean-atmosphere coupling involving Bjerknes feedback and equatorial nonlinear ocean advection, until its maturity in September-November. This study clarifies the contribution of oceanic Rossby waves in the south TIO in different dynamic settings and reveals a new triggering mechanism for extreme IOD events that will help to understand IOD diversity.
Exploring the role of lags and legacies in the productivity of Australian ecosystems
Authors: Page Jon , De Kauwe Martin , Abramowitz Gab
Published: March 2021

The vegetation’s response to climate change is a major source of uncertainty in terrestrial biosphere model (TBM) projections. Constraining carbon cycle feedbacks to climate change requires improving our understanding of both the direct plant physiological responses to global change, as well as the role of legacy effects (e.g. reductions in plant growth, damage to the plant’s hydraulic transport system), that drive multi-timescale feedbacks. In particular, the role of these legacy effects - both the timescale and strength of the memory effect - have been largely overlooked in the development of model hypotheses. This is despite the knowledge that plant responses to climatic drivers occur across multiple time scales (seconds to decades), with the impact of climate extremes (e.g. drought) resonating for many years. Using data from 13 eddy covariance sites, covering two rainfall gradients in Australia, in combination with a hierarchical Bayesian model, we characterised the timescales of influence of antecedent drivers on fluxes of net carbon exchange and evapotranspiration. Using our data assimilation approach we were able to partition the influence of ecological memory into both biological and environmental components. Overall, we found that the importance of ecological memory to antecedent conditions increased as water availability declines. Our results therefore underline the importance of capturing legacy effects in TBMs used to project responses in water limited ecosystems.
Transport dynamics of pelagic sargassum in the Mexican Caribbean: sensitivity studies to the wind and depth of the transporting ocean layer
Authors: Lara-Hernández Julio Antonio , Enríquez-Ortiz Cecilia , Zavala-Hidalgo Jorge , Uribe-Martínez Abigail , Cuevas-Flores Eduardo
Published: March 2021

The possible fate of pelagic sargassum in the Mexican Caribbean during aug-2018, sep-2018, and apr-2019 is analyzed using a particle-tracking model coupled to diverse datasets of wind [ERA5 reanalysis and the NCEP Climate Forecast System (CFSv2)] and ocean current velocities (HYCOM experiments of high and lower resolution). Advection of particles was computed considering 0, 1, 2, or 3 % of the wind magnitude and either surface currents (0 m) or the averaged currents from the surface to 5 m depth. For each day of the three months, virtual particles were initially located at the vertices of a uniform mesh within the Mexican Caribbean and subsequently tracked for 10 days. Results revealed that the percentage of the wind magnitude accounted for the transport had the greatest impact on the number of particles that ran aground in the Mexican Caribbean: with a higher percentage of the wind magnitude more particles reached the land. The depth of the layer of the ocean currents used in the transport was also important in the results: particle stranding was higher when only surface currents were used. On the other hand, the different data sources had less influence in the results: the simulations using CFSv2 winds resulted in more stranding of particles than those using ERA5 winds, although the differences were relatively small. The number of stranded particles was virtually insensitive to the selection of the ocean data resolution (i. e. HYCOM of high or lower resolution). In general, virtual particles located closer to the coast and further south in the Mexican Caribbean showed the highest probability of running aground on the shores of the Mexican Caribbean. The arrival time depended on the distance from the shore and the wind magnitude. With the wind and current conditions of the three months used for the study, particles located less than 50 km from the shore usually required less than 3 days to run aground. Particles between 50 and 200 km from the shore usually had an arrival time between 3 and 10 days. The dynamics of the particles were similar during each of the months. However, the greatest differences corresponded to apr-2019, when shifting winds and northerlies were observed. This provides an insight of the variations that most likely would result for different months and years. However, sargassum arrivals are expected to occur during the summer, hence these results are relevant for the local preparedness of managing strategies for massive sargassum stranding in the Mexican Caribbean.
Evolution of the ocean monsoon regions over the past 250 million years
Authors: Han Jing , Hu Yongyun , Liu Yonggang
Published: March 2021

A set of deep-time climate simulations each 10Ma years from 250Ma to PI are conducted by using the NCAR-CESM1.2, for understanding the evolution of the ocean monsoon regions driven by tectonic dynamics over the past 250 million years and exploring its variation mechanisms. In recent years, scientists have proposed the concept of a global monsoon system, which includes not only typical monsoon regions (such as the African monsoon region and South Asian monsoon region), but also the atypical Northwest Pacific Ocean monsoon region. Research on the ocean monsoon is very limited, especially in the field of paleoclimate. The results in this paper show that the horizontal gradients of the thickness of the ocean mixed layer may be more important for the formation of the ocean monsoon than land-sea thermal contrast, which is confirmed by the aquaplanet simulations with various gradients of the ocean mixed-layer thickness. Near the Pacific monsoon region in the northern hemisphere, the thickness of the ocean mixed layer has obvious meridional and zonal gradients, which will correspond to the meridional and zonal thermal contrasts. In addition, there are obvious seasonal reversals in the gradients of the ocean mixed-layer thickness in summer and winter, and the corresponding longitudinal and zonal thermal contrast produce seasonal reversals. Over the past 250 million years, the thickness of the ocean mixed layer on the east side of the Pacific Ocean Basin in the Northern Hemisphere has deepened, and the corresponding ocean monsoon area on the east side of the Pacific Ocean has decreased. The changes in the thickness of the ocean mixed layer are closely related to the changes in the surface wind field. Examining the changes in the atmospheric circulations, we find that the Pacific subtropical high strengthens and extends from east to the west bank of the ocean basin, where the atmospheric low-level anticyclonic circulation causes the ocean surface layer to converge and sink and thus causes the ocean mixed layer to deepen. The changes in the Pacific subtropical high are related to changes in the continental monsoon region. Since the 170Ma, the Pangea supercontinent splits up, causing the supercontinent's inland water vapor to increase, the land monsoon area to increase, and the ocean monsoon area to decrease. According to the "monsoon-desert mechanism" of Rodwell and Hoskins, we can understand the relationship between the strengthening of land monsoon condensation heating and the formation of subtropical high over the western ocean.
Application of Image Processing and Big Data Science for Flood Label Detection
Authors: Pally Jaku Rabinder Rakshit , Samadi Vidya
Published: March 2021

Due to the importance of object detection in video analysis and image annotation, it is widely utilized in a number of computer vision tasks such as face recognition, autonomous vehicles, activity recognition, tracking objects and identity verification. Object detection does not only involve classification and identification of objects within images, but also involves localizing and tracing the objects by creating bounding boxes around the objects and labelling them with their respective prediction scores. Here, we leverage and discuss how connected vision systems can be used to embed cameras, image processing, Edge Artificial Intelligence (AI), and data connectivity capabilities for flood label detection. We favored the engineering definition of label detection that a label is a sequence of discrete measurable observations obtained using a capturing device such as web cameras, smart phone, etc. We built a Big Data service of around 1000 images (image annotation service) including the image geolocation information from various flooding events in the Carolinas (USA) with a total of eight different object categories. Our developed platform has several smart AI tools and task configurations that can detect objects’ edges or contours which can be manually adjusted with a threshold setting so as to best segment the image. The tool has the ability to train the dataset and predict the labels for large scale datasets which can be used as an object detector to drastically reduce the amount of time spent per object particularly for real-time image-based flood forecasting.  This research is funded by the US National Science Foundation (NSF).
Understanding the Hydrologic Response Mechanisms of California’s Largest Lake in a Highly Managed Endorheic Basin
Authors: Acero Triana Juan Sebastian , Ajami Hoori
Published: March 2021

In recent decades, saline lakes are being globally shrunk at alarming rates due to the combined effect of global warming and long-term water mismanagement to support agriculture and industrial demand. These factors have altered the fragile balance of these ecosystems triggering serious environmental issues. A well-known case in the Southwestern US is the Salton Sea, the largest lake in California. While the Salton Sea Basin (SSB) is considered as one of the most productive agricultural regions in North America, improvements in the agricultural water use efficiency to sustain and increase food production have imbalanced the lake’s water budget. Lake's water level has declined by 33% between 2000 and 2018 causing increases in salinity and anoxia, and the spreading of toxic dust from the exposed playa. Considering the key role of the Salton Sea in ecohydrological regulation and the wide spectrum of ecosystem services (e.g., wildlife habitat, transport, recreation), greater science-based efforts are needed to formulate timely adaptation and mitigation strategies for lake restoration and conservation. However, prior to formulating these strategies, it is crucial to understand the hydrologic response mechanisms of the basin to natural and anthropogenic stressors as well as the historic causal factors that have dictated its environmental deterioration. In this study, we developed a semi-distributed modeling framework using the Soil and Water Assessment Tool (SWAT) to quantify the regional water balance and understand interrelationships among ecological, hydrological, and human-impact variables. Preliminary results determined that the water contribution from the major lake tributaries has not been significantly affected over time and the imbalances in the lake’s water budget may be associated with changes in groundwater-surface water interactions due to agricultural water management. The final results of this study are expected to assist decision-makers with a robust modeling tool to evaluate the environmental tradeoffs in implementing distinct management alternatives across SSB while minimizing its economic consequences.
Do you want Seamless Subseasonal Streamflow Forecasts?    Ask MuTHRE!
Authors: Thyer Mark , McInerney David , Kavetski Dmitri , Laugesen Richard , Tuteja Narendra , Kuczera George
Published: March 2021

Sub-seasonal streamflow forecasts (with lead times of 1-30 days) provide valuable information for many consequential water resource management decisions, including reservoir operation to meet environmental flow and irrigation demands, issuance of early flood warnings, and others. A key aim is to produce “seamless” forecasts, with high quality performance across the full range of lead times and time scales.  

This presentation introduces the Multi-Temporal Hydrological Residual Error model (MuTHRE) to address the challenge of obtaining “seamless” sub-seasonal forecasts, i.e., daily forecasts with consistent high-quality performance over multiple lead times (1-30 days) and aggregation scales (daily to monthly).

The model is designed to overcome common errors in streamflow forecasts:

Seasonality

Dynamic biases due to hydrological non-stationarity

Extreme errors poorly represented by the common Gaussian distribution.

The model is evaluated comprehensively over 11 catchments in the Murray-Darling Basin, Australia, using multiple performance metrics to scrutinize forecast reliability, sharpness and bias, across a range of lead times, months and years, at daily and monthly time scales.

The MuTHRE model provides ”high” improvements, in terms of reliability for

Short lead times (up to 10 days), due to representing non-Gaussian errors

Stratified by month, due to representing seasonality in hydrological errors

Dry years, due to representing dynamic biases in hydrological errors.

Forecast performance also improved in terms of sharpness, volumetric bias and CRPS skill score; Importantly, improvements are consistent across multiple time scales (daily and monthly).

This study highlights the benefits of modelling multiple temporal characteristics of hydrological errors, and demonstrates the power of the MuTHRE model for producing seamless sub-seasonal streamflow forecasts that can be utilized for a wide range of applications.

 

 

 
Greenhouse-gas contribution to Arctic sea-ice loss
Authors: Kim Yeon-Hee , Min Seung-Ki
Published: March 2021

Arctic sea-ice area (ASIA) has been declining rapidly throughout the year during recent decades, but a formal quantification of greenhouse gas (GHG) contribution remains limited. This study conducts an attribution analysis of the observed ASIA changes from 1979 to 2017 by comparing three satellite observations with the Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model simulations using an optimal fingerprint method. The observed ASIA exhibits overall decreasing trends across all months with stronger trends in warm seasons. CMIP6 anthropogenic plus natural forcing (ALL) simulations and GHG-only forcing simulations successfully capture the observed temporal trend patterns. Results from detection analysis show that ALL signals are detected robustly for all calendar months for three observations. It is found that GHG signals are detectable in the observed ASIA decrease throughout the year, explaining most of the ASIA reduction, with a much weaker contribution by other external forcings. We additionally find that the Arctic Ocean will occur ice-free in September around the 2040s regardless of the emission scenario.
The Cenozoic structural evolution of the northwestern Tarim Basin, China
Authors: Liu Wenhang , krzywiec Piotr , Mazur Stanisław , Meng Fanwen , Chen Zhuxin
Published: March 2021

The vast Tarim basin is surrounded by Tian Shan Mountains in the north, West Kunlun Mountains in the southwest, and the Altyn Mountains in the southeast. The southwestern Tarim Basin developed within the foreland of the West Kunlun Mountains and cumulated up to 10 km of Cenozoic strata. Despite several decades of geological studies its structural styles and details of its geological evolution are still being debated. In this study, we used seven regional seismic transects from the Yecheng - Hotan area calibrated by deep wells to assess lateral variations of a structural style and syn-tectonic sedimentation in this part of the basin.

The basement of the SW Tarim Basin is covered by Paleozoic and Cenozoic strata, as revealed by several deep calibration wells. The regional north-directed basement thrust together with two evaporitic detachments including the Middle Cambrian evaporites (Awatage Formation) and Paleogene evaporites (Aertashi Formation) controlled the overall tectonic framework and structural evolution of this part of the basin. The visible growth strata on seismic data indicate progressive development of the structural wedge within the frontal W Kunlun Mountains from the Late Miocene to the Present day.

Four main Cenozoic evolutionary stages of the W Kunlun Mountains and adjacent SW Tarim Basin have been determined. At the end of Paleogene, evaporites of the Aertashi Formation have been deposited in SW Tarim Basin; their thickness, as indicated by seismic data, increases towards the Kunlun orogenic wedge which suggests their deposition within the flexural foreland basin. Then, during the Early to Middle Miocene, about 4000m of sediments have been deposited in rapidly subsiding foreland basin. Towards the end of Late Miocene-Pliocene, tectonic wedging along thrust front led to significant uplift of the Kunlun Mountains that presently form S margin of the Tarim Basin. Quaternary migration of compressional deformations towards the North, towards the basin interior led to formation of the intra-basinal Jade anticline that was re-interpreted as a thin-skinned syn-depositional “fish tail” structure detached within the Paleogene evaporites. Present-day activity along some deeply buried thrusts of the Kunlun Mts. tectonic wedge might be related to current earthquakes.
Historical landscape condition study of discontinued river corridor based on satellite image data analysis
Authors: Xu Xiaoming
Published: March 2021

The historical landscape condition of discontinued river before discontinued flow is one of the core research fields of river ecological restoration and an important historical reference for the ecological restoration of discontinued river corridor. In this paper, the landscape condition of Yongding River, a discontinued river in northern China, is analyzed before its cut-off. Through the early KEYHOLE satellite high-definition image data interpretation analysis, the landscape type map of the river corridor before its cut-off was drawn. The overall winding degree (1.27) and the overall horizontal and vertical structure of the river before its cut-off were determined. In addition, the area proportion of the key landscape types in river corridor, such as channel, mid-channel bar and floodplain, is 12.82%, 8.8% and 16.29% respectively, and the morphological characteristics and distribution of the above key landscape types in each section of the river can be determined by quantitative analysis. On this basis, the landscape pattern index analysis method can be used to analyze and calculate the overall landscape pattern of the river corridor before cut-off. Combined with relevant historical hydrological data, the historical state of the river before its cut-off can be restored to a certain extent. These results are of great support to the channel ecological restoration, floodplain ecological reconstruction and riverbank ecological restoration.
Lamprophyres of Kayla pipe and their mantle xenocrysts, SE Yakutia
Authors: Vladykin Nikolai , Ashchepkov Igor , Sotnikova Irina , Mevedev Nikolai
Published: March 2021

The bulk rock and geochemistry of the Kayla and Khatastyr lamproites is similar to other Aldan lamproites and lamprophyres.  The ultramafic varieties are close to cratonic Ol- lamproites and alkaline Al, Si-rich varieties are closer to orogenic type.

Trace element bulk rock trace element (TRE) spider diagrams show inclined patterns with the LILE, Sr, Pb, U, peaks and Ta, Nb minima suggesting melting of originally depleted metasomatized Phl peridotites and mixed ancient (EMII, Nd, Sr isotopes) source (low crust)  and later olivine and clinopyroxene fractionation. They are dated 132-134 Ma (Late Cretaceous plume) similar to Chompolo lamprophyres and many alkaline complexes.

Thermobarometry for the deep-seated xenocrysts gives the low temperature and Sp-Gar and Gar facies for Cr- diopsides and chromites. Low - Cr- clinopyroxenes derived from lamproites give hot 90 mw/m2 advective branches. 

The REE patterns for Cr-diopsides are more inclined for deeper varieties and reveal Ba, Th, U, Sr peaks and minima Ta, Nd and smaller in Zr-Hf. The `low Cr diopsides show flatter REE and HFSE minima TRE patterns of parental melts are lamproitic. Salites reveal hot crust conditions.

Lamproites melted from Phl peridotite eclogites mixture in the lithosphere base and interacted with mantle beneath Moho.

The work was supported by the Ministry of Science and Higher Education of the Russian Federation RBRF grants 19-05-00788a, 18-05-00073a;  Government tasks for Institute of Geochemistry SB RAS and Institute of Geology and Mineralogy SB RAS and the governmental assignment in terms of Project IX. 129.1.4
Phosphorus regulates ecosystem carbon dynamics after permafrost thaw
Authors: Yang Yuanhe , Yang Guibiao , Peng Yunfeng , Abbott Benjamin W. , Biasi Christina , Wei Bin , Zhang Dianye , Wang Jun , Yu Jianchun , Li Fei , Wang Guanqin , Kou Dan , Liu Futing
Published: March 2021

The ecosystem carbon (C) dynamics after permafrost thaw depends on more than just climate change since soil nutrient status may also impact ecosystem C balance. It has been advocated that the potential nitrogen (N) release upon permafrost thaw could promote plant growth and thus offset soil C loss. However, compared with the widely accepted C-N interactions, little is known about the potential role of soil phosphorus (P) availability. Here we combined two-year field observations along a permafrost thaw sequence (constituted by four thaw stages, i.e., non-collapse and 5, 14, and 22 years since collapse) with an in-situ fertilization experiment (included N and P additions at the level of 10 g N m-2 yr-1 and 10 g P m-2 yr-1, respectively) in a Tibetan swamp meadow to evaluate ecosystem C-nutrient interactions upon permafrost thaw. Our results showed that changes in soil P availability rather than N availability played an important role in regulating the increases in gross primary productivity and the decreases in net ecosystem exchange along the thaw sequence. The fertilization experiment further confirmed that P addition had stronger effects on plant growth than N addition in this permafrost ecosystem. These two lines of evidence highlight the crucial role of soil P availability in altering the trajectory of permafrost C cycle under climate warming.