bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable C∕P composition of organic production and its effect on ocean carbon storage in glacial-like model simulations
Authors: Ödalen Malin , Nycander Jonas , Ridgwell Andy , Oliver Kevin I. C. , Peterson Carlye D. , Nilsson Johan
Published: April 2020

Abstract. During the four most recent glacial maxima, atmospheric CO2 has been lowered by about 90–100 ppm with respect to interglacial concentrations. It is likely that most of the atmospheric CO2 deficit was stored in the ocean. Changes in the biological pump, which are related to the efficiency of the biological carbon uptake in the surface ocean and/or of the export of organic carbon to the deep ocean, have been proposed as a key mechanism for the increased glacial oceanic CO2 storage. The biological pump is strongly constrained by the amount of available surface nutrients. In models, it is generally assumed that the ratio between elemental nutrients, such as phosphorus, and carbon (C∕P ratio) in organic material is fixed according to the classical Redfield ratio. The constant Redfield ratio appears to approximately hold when averaged over basin scales, but observations document highly variable C∕P ratios on regional scales and between species. If the C∕P ratio increases when phosphate availability is scarce, as observations suggest, this has the potential to further increase glacial oceanic CO2 storage in response to changes in surface nutrient distributions. In the present study, we perform a sensitivity study to test how a phosphate-concentration-dependent C∕P ratio influences the oceanic CO2 storage in an Earth system model of intermediate complexity (cGENIE). We carry out simulations of glacial-like changes in albedo, radiative forcing, wind-forced circulation, remineralization depth of organic matter, and mineral dust deposition. Specifically, we compare model versions with the classical constant Redfield ratio and an observationally motivated variable C∕P ratio, in which the carbon uptake increases with decreasing phosphate concentration. While a flexible C∕P ratio does not impact the model's ability to simulate benthic δ13C patterns seen in observational data, our results indicate that, in production of organic matter, flexible C∕P can further increase the oceanic storage of CO2 in glacial model simulations. Past and future changes in the C∕P ratio thus have implications for correctly projecting changes in oceanic carbon storage in glacial-to-interglacial transitions as well as in the present context of increasing atmospheric CO2 concentrations.
Spatial variations in silicate-to-nitrate ratios in Southern Ocean surface waters are controlled in the short term by physics rather than biology
Authors: Demuynck Pieter , Tyrrell Toby , Naveira Garabato Alberto , Moore Mark Christopher , Martin Adrian Peter
Published: April 2020

Abstract. The nutrient composition (high in nitrate but low in silicate) of Subantarctic Mode Water (SAMW) forces diatom scarcity across much of the global surface ocean. This is because diatoms cannot grow without silicate. After formation and downwelling at the Southern Ocean's northern edge, SAMW re-emerges into the surface layers of the mid- and low-latitude oceans, providing a major nutrient source to primary producers in those regions. The distinctive nutrient composition of SAMW originates in the surface waters of the Southern Ocean, from which SAMW is formed. These waters are observed to transition from being rich in both silicate and nitrate in high-latitude areas of the Southern Ocean to being nitrate-rich but silicate-depleted at SAMW formation sites further north. Here we investigate the key controls of this change in nutrient composition with an idealised model, consisting of a chain of boxes linked by a residual (Ekman- and eddy-induced) overturning circulation. Biological processes are modelled on the basis of seasonal plankton bloom dynamics, and physical processes are modelled using a synthesis of outputs from the data-assimilative Southern Ocean State Estimate. Thus, as surface water flows northward across the Southern Ocean toward sites of SAMW formation, it is exposed in the model (as in reality) to seasonal cycles of both biology and physics. Our results challenge previous characterisations of the abrupt northward reduction in silicate-to-nitrate ratios in Southern Ocean surface waters as being predominantly driven by biological processes. Instead, our model indicates that, over shorter timescales (years to decades), physical processes connecting the deep and surface waters of the Southern Ocean (i.e. upwelling and entrainment) exert the primary control on the spatial distribution of surface nutrient ratios.
Seasonal methane dynamics in three different Siberian water bodies
Authors: Bussmann Ingeborg , Fedorova Irina , Juhls Bennet , Overduin Pier Paul , Winkel Matthias
Published: April 2020

Abstract. Arctic regions and their water bodies are being affected by the most rapid climate warming on Earth. Arctic lakes and small ponds are known to act as an important source of atmospheric methane. However, not much is known about other types of water bodies in permafrost regions, which include major rivers and coastal bays as a transition type between freshwater and marine environments. We monitored dissolved methane concentrations in three different water bodies (Lena River, Tiksi Bay and Lake Golzovoye, Siberia, Russia) over a period of two years. Sampling was carried out under ice cover (April) and in open water (July/August). The methane oxidation (MOX) rate in water and melted ice samples from the late winter of 2017 was also investigated. In the Lena River winter methane concentrations were a quarter of the summer concentrations (8 vs 31 nmol L−1) and mean winter MOX rate was low (0.023 nmol L−1 d−1). In contrast, Tiksi Bay winter methane concentrations were 10-times higher than in summer (103 vs 13 nmol L−1). Winter MOX rates showed a median of 0.305 nmol L−1 d−1. In Lake Golzovoye, median methane concentrations in winter were 40-times higher than in summer (1957 vs 49 nmol L−1). However, MOX was much higher in the lake (2.95 nmol L−1 d−1) than in either the river or bay. The temperature had a strong influence on the MOX, (Q10 = 2.72 ± 0.69) compared to temperate environments. In the ice cores a median methane concentration of 9 nM was observed, with no gradient between the ice surface and the bottom layer at the ice-water-interface. MOX in the (melted) ice cores was mostly below the detection limit. Comparing methane concentrations in the ice with the underlaying water column revealed 100 – 1000-times higher methane concentration in the water column. The winter situation seemed to favor a methane accumulation under ice, especially in the lake with a stagnant water body. While on the other hand, in the Lena River with its flowing water no methane accumulation under ice was observed. Methane oxidation rate was not able to counteract this winter time accumulation.
Differential effects of redox conditions on the decomposition of litter and soil organic matter
Authors: Lin Yang , Campbell Ashley N. , Bhattacharyya Amrita , DiDonato Nicole , Thompson Allison M. , Tfaily Malak M. , Nico Peter S. , Silver Whendee L. , Pett-Ridge Jennifer
Published: April 2020

Abstract. Soil redox conditions exert substantial influence on biogeochemical processes in terrestrial ecosystems. Humid tropical forest soils are often characterized by fluctuating redox dynamics, yet how these dynamics affect patterns in soil versus litter decomposition and associated CO2 fluxes is not well understood. We used a 13C-labeled litter addition to explicitly follow the decomposition of litter-derived vs. native soil-derived organic matter in response to four different soil redox regimes – static oxic or anoxic, and two oscillating treatments – in soil from the Luquillo Experimental Forest, Puerto Rico. We coupled this incubation experiment with high-resolution mass spectrometry to characterize the preferential decomposition of specific classes of organic molecules. CO2 production from litter and soil organic matter (SOM) showed distinctly different responses to redox manipulation. The cumulative production of SOM-derived CO2 was positively correlated with the length of soil exposure to an oxic headspace (r = 0.89, n = 20), whereas cumulative 13C-litter-derived CO2 production was not linked to oxygen availability. The CO2 production rate from litter was highest under static anoxic conditions in the first half of the incubation period, and later dropped to the lowest among all redox treatments. In the consistently anoxic soils, we observed the depletion of more oxidized water-extractable organic matter (especially amino sugars, carbohydrates, and proteins) over time, suggesting that under anaerobic conditions, microbes preferentially used more oxidized litter-derived compounds during the early stages of decomposition. Results from kinetic modeling showed that more frequent anoxic exposure limited the decomposition of a slow-cycling C pool, but not a fast-cycling pool. Overall, our results demonstrate that substrate source – freshly added litter vs. native organic matter – plays an important role in the redox sensitivity of organic matter decomposition. In soil environments that regularly experience redox fluctuations, anaerobic heterotrophs can be surprisingly effective in degrading fresh plant litter.
Compound Hot-Dry and Cold-Wet Dynamical Extremes Over the Mediterranean
Authors: De Luca Paolo , Messori Gabriele , Faranda Davide , Ward Philip J. , Coumou Dim
Published: April 2020

Abstract. The Mediterranean (MED) basin is a climate change hot-spot that has seen drying and a pronounced increase in heatwaves over the last century. At the same time, it is experiencing increasing heavy precipitation during wintertime cold spells. Understanding and quantifying the risks from compound events over the MED is paramount for present and future disaster risk reduction measures. Here, we apply a novel method to study compound events based on dynamical systems theory and analyse compound temperature and precipitation anomalies over the MED from 1979 to 2018. The dynamical systems analysis measures the strength of the coupling between different atmospheric variables over the MED. Further, we consider compound hot-dry days in summer and cold-wet days in winter. Our results show that these hot-dry and cold-wet compound days are associated with maxima in the temperature–precipitation coupling parameter of the dynamical systems analysis. This indicates that there is a strong interaction between temperature and precipitation during compound events. In summer, we find a significant upward trend in the coupling between temperature and precipitation over 1979–2018, which is likely driven by a stronger coupling during hot and dry days. Thermodynamic processes associated with long-term MED warming can best explain the trend. No such trend is found for wintertime cold-wet compound events. Our findings suggest that long-term warming strengthens the coupling of temperature and precipitation which intensifies hot-dry compound events.
A new 30 000-year chronology for rapidly deposited sediments on the Lomonosov Ridge using bulk radiocarbon dating and probabilistic stratigraphic alignment
Authors: Muschitiello Francesco , O'Regan Matt , Martens Jannik , West Gabriel , Gustafsson Örjan , Jakobsson Martin
Published: April 2020

Abstract. We present a new marine chronostratigraphy from a
high-accumulation rate Arctic Ocean core at the intersection of the
Lomonosov Ridge and the Siberian margin, spanning the last ∼ 30 kyr. The chronology was derived using a combination of bulk 14C dating and stratigraphic correlation to Greenland ice-core records. This was
achieved by applying an appositely developed Markov chain Monte Carlo
algorithm for Bayesian probabilistic alignment of proxy records. The
algorithm simulates depositionally realistic alignments that are consistent
with the available radiocarbon age estimates and allows deriving uncertainty bands associated with the inferred alignment. Current composite chronologies from this region are reasonably consistent with our age model during the Holocene and the later part of deglaciation. However, prior to
∼ 14 kyr BP they yield too old age estimates with offsets that
linearly increase up to ∼ 40 kyr near the onset of Marine
Isotope Stage (MIS) 2. Our results challenge the robustness of previous
regional chronostratigraphies and provide a new stratotype for correlation
of sediment cores from this sector of the Lomonosov Ridge and East Siberian
slope. In particular, they call for a re-interpretation of events in recent
sea-ice proxy reconstructions (Xiao et al., 2015) inaccurately
attributed to MIS 3 and the Last Glacial Maximum.
Review article: Natural hazard risk assessments at the global scale
Authors: Ward Philip J. , Blauhut Veit , Bloemendaal Nadia , Daniell James E. , de Ruiter Marleen C. , Duncan Melanie J. , Emberson Robert , Jenkins Susanna F. , Kirschbaum Dalia , Kunz Michael , Mohr Susanna , Muis Sanne , Riddell Graeme A. , Schäfer Andreas , Stanley Thomas , Veldkamp Ted I. E. , Winsemius Hessel C.
Published: April 2020

Abstract. Since 1990, natural hazards have led to over 1.6 million fatalities globally, and economic losses are estimated at an average of around USD 260–310 billion per year. The scientific and policy communities recognise the need to reduce these risks. As a result, the last decade has seen a rapid development of global models for assessing risk from natural hazards at the global scale. In this paper, we review the scientific literature on natural hazard risk assessments at the global scale, and we specifically examine whether and how they have examined future projections of hazard, exposure, and/or vulnerability. In doing so, we examine similarities and differences between the approaches taken across the different hazards, and we identify potential ways in which different hazard communities can learn from each other. For example, there are a number of global risk studies focusing on hydrological, climatological, and meteorological hazards that have included future projections and disaster risk reduction measures (in the case of floods), whereas fewer exist in the peer-reviewed literature for global studies related to geological hazards. On the other hand, studies of earthquake and tsunami risk are now using stochastic modelling approaches to allow for a fully probabilistic assessment of risk, which could benefit the modelling of risk from other hazards. Finally, we discuss opportunities for learning from methods and approaches being developed and applied to assess natural hazard risks at more continental or regional scales. Through this paper, we hope to
encourage further dialogue on knowledge sharing between disciplines and
communities working on different hazards and risk and at different spatial
scales.
Responses to severe weather warnings and affective decision-making
Authors: Weyrich Philippe , Scolobig Anna , Walther Florian , Patt Anthony
Published: April 2020

Abstract. Informing people of an impending hazard can lead them to adopt behavior to mitigate the harm. In this study we examine whether giving more information, and giving it earlier, leads to a greater behavioral response. Our results, which are contextually dependent, show that providing more information has no effect on behavior, and that longer lead times lead to less behavioral change. These results conflict with those from previous studies. These previous studies differed from ours in terms of the research methods: while past studies examined people's anticipated responses to hypothetical warnings, we conducted a field experiment to observe people's responses to actual warnings of real hazards. Theory from cognitive science suggests that this difference matters. In situations of high stress people may make decisions using a faster decision pathway that is rather emotion-driven, while in less stressful situations they are more likely to base their decisions on information. The difference between actual and hypothetical warnings would capture this mismatch in stress levels, and account for the divergent findings. At the same time, the cognitive theory has been hard to test in the field, because of the ethical challenge of submitting people to actually dangerous conditions. Therefore, our results are not only relevant for the design of warning information, but also provide important empirical support for the theory of different decision-making pathways.
IoT technology and big data processing for monitoring and analysing land subsidence in Central Taiwan
Authors: Hung Wei-Chia , Chen Yi-An , Hwang Cheinway
Published: April 2020

Abstract. Over 1992–2018, groundwater overexploitation had caused
large-scale land subsidence in the Choshui River Alluvial Fan (CRAF) in
Taiwan. The Taiwan High Speed Railway (THSR) passes through an area of
severe subsidence in CRAF, and the subsidence poses a serious threat to its
operation. How to effectively monitor land subsidence here has become a
major issue in Taiwan. In this paper, we introduce a multiple-sensor
monitoring system for land subsidence, including 50 continuous operation
reference stations (CORS), multi temporal InSAR (MT-InSAR), a
1000 km levelling network, 34 multi-layer compaction monitoring wells and 116
groundwater monitoring wells. This system can monitor the extent of land
subsidence and provide data for studying the mechanism of land subsidence.
We use the Internet of Things (IoT) technology to control and manage the
sensors and develop a bigdata processing procedure to analyse the
monitoring data for the system of sensors. The procedure makes the land
subsidence monitoring more efficient and intelligent.
Integrated monitoring of subsidence due to hydrocarbon production: consolidating the foundation
Authors: Ketelaar Gini , Bähr Hermann , Liu Shizhuo , Piening Harry , van der Veen Wim , Hanssen Ramon , van Leijen Freek , van der Marel Hans , Samiei-Esfahany Sami
Published: April 2020

Abstract. This paper describes several geodetic studies that
consolidate the reliability and precision of monitoring subsidence due to
hydrocarbon production: the deployment of Integrated Geodetic Reference
Stations (IGRS); the application of high resolution InSAR; the comparison of
different GNSS processing methodologies; the implementation of an efficient
InSAR stochastic model, and the framework of integrated geodetic processing
(levelling, GNSS, InSAR). The advances that have been made are applicable
for any other subsidence monitoring project.
Subsidence monitoring with TerraSAR-X data in Beijing Central Business District and subway tunnelings, China
Authors: Li Fengkai , Gong Huili , Chen Beibei , Gao Mingliang , Zhou Chaofan
Published: April 2020

Abstract. Land subsidence caused by large-scale engineering
construction may damage the surrounding infrastructures and cause huge
economic losses in inner-city environments. In this study, we used PS-InSAR
technology on 68 TerraSAR-X images to acquire deformation in the Beijing
Plain between February 2010 and December 2018. Then, we calculated the
additional stress derived from building loads using the method proposed by
Boussinesq in the Central Business District (CBD). We found that the depth
of influence of additional stresses induced by building loads was 80 m and
that spatial distribution pattern of the land subsidence rate agreed well
with the additional stress. We found that the influence range of ground
subsidence caused by metro construction is 200 m at Ciqikou station by
analyzing the subsidence rate profile perpendicular to subway line No. 7 and
that the maximum land subsidence rate is 23.2 mm yr−1. Time series
analysis of PS around Ciqikou station shows that land subsidence caused by
excavation activities mainly occurs in the period of metro construction.
Ground deformation rate decreases gradually after 372 d of subway
operation. The results of both cases show that large-scale engineering
construction will lead to significant land subsidence which should be
considered in future urbanization.
Application of distributed fiber optic sensing technique in land subsidence monitoring in coastal areas: a case study in Tianjin, China
Authors: Liu Su-Ping , Shi Bin , Gu Kai , Zhang Cheng-Cheng , Zhang Song , Yang Peng , Yang Ji-Long
Published: April 2020

Abstract. Land subsidence is a worldwide geohazard caused by various factors, and its direct impact is loss of elevation, which is especially severe in coastal areas due to sea level rise. Quantifying contributions of compressed strata is significant for evaluating the subsidence. In this paper, we used distributed fiber optic sensing (DFOS) with Brillouin scattering to monitor the strain distribution along optical cables embedded in a borehole located in Tianjin, China. The novel technique revealed that the land subsidence rate was 21.2 mm a−1 from 2017 to 2019. The strata contributed to the subsidence have been identified in the range of 3 to 35 m. The results showed good agreement with those obtained by a group of extensometers. We demonstrated that DFOS could be a supplement to land subsidence monitoring technologies in coastal areas.
Reliability of InSAR satellite monitoring of buildings near inner city quay walls
Authors: Venmans Arjan A. M. , op de Kelder Martin , de Jong Jarco , Korff Mandy , Houtepen Martijn
Published: April 2020

Abstract. Amsterdam currently has a huge task of assessing and
potentially upgrading its quay walls along the historic canals. Before
replacement can take place, Amsterdam needs to determine the potential
impact the replacement can have on the nearby buildings. The rate of
vertical deformation of the adjacent buildings is used as indicator of
potential foundation problems. To determine that rate, the current practice
is to monitor the buildings by levelling for two years at least. This study
shows that application of satellite measurements using Permanent Scatterer
Interferometric Synthetic Aperture Radar (PS-InSAR) could reduce the
monitoring period to a few months. The paper describes the statistical
procedure that has been applied to levelling and satellite measurements to
verify their reliability and determine the rate of vertical deformation of
the buildings. The procedure was applied in three case studies. The rates of
deformation observed in the InSAR measurements are in good agreement with
the rates of deformation observed in the levelling in two of the case
studies. The locally optimized InSAR data set with observations in the
period 2014–2019 provides an almost 100 % coverage of reliable data
points for all buildings in the case studies. More experience will need to
be gained in the interpretation of InSAR measurements with respect to
vulnerability of the buildings. Also, the procedure may be extended to
include analysis of non-linear trends such as second order trends and
seasonal effects.
Land subsidence contribution to coastal flooding hazard in southeast Florida
Authors: Wdowinski Shimon , Oliver-Cabrera Talib , Fiaschi Simone
Published: April 2020

Abstract. Over the past decade, several coastal communities in
southeast Florida have experienced a significant increase in flooding
frequency, which has caused significant disturbance to property, commerce,
and overall quality of life. The increased flooding frequency reflects the
contribution of global, regional, and local processes that affect elevation
difference between coastal communities and rising sea level. In a recent
project, funded by the state of Florida, we monitor coastal subsidence in
southeast Florida using GPS and InSAR observations, in order to evaluate the
contribution of local subsidence to the increased coastal flooding hazard.
Preliminary results reveal that subsidence occurs in localized patches
(< 0.02 km2) with magnitude of up to 3 mm yr−1, in urban areas
built on reclaimed marshland. These results suggest that contribution of
local land subsidence affect only small areas along the southeast Florida
coast, but in those areas coastal flooding hazard is significantly higher
compared to non-subsiding areas.
Determination of land subsidence value under permanent drainage conditions at the site of highway tunnel in Moscow
Authors: Anikeev Aleksandr V. , Eremina Olga N. , Kozliakova Irina V.
Published: April 2020

Abstract. The paper discuses one of the most complicated cases in tunnel construction practice in the water-saturated fine-grained deposits in Moscow. Due to the imperfectness of enclosing engineering structures, groundwater and water-saturated soils broke through to the tunnel at the time of its construction. This resulted in the formation of decompaction zones in the enclosing ground massif as well as in deformation of buildings and land surface subsidence. After the end of construction, settling of land surface near tunnel has almost stopped; however, groundwater seepage to the tunnel still continues despite numerous percolation-control measures. As a result, the decision was made to arrange the permanently operating drainage, which could have sustain the groundwater level at the required depth. The possible settling of the land surface has been calculated for the area near the tunnel due to the soil compaction upon the water drawdown. The calculation is based on the principle of linear deformability of soils and on the Terzaghi law about the stresses of two kinds in a ground massif. The results obtained prove that the settlement values will not exceed the critical values adopted by standard regulatory documents. It appears virtually impossible to take account in calculations the transformation of ground massif parameters at the sites of soil breakthrough to the tunnel. Therefore, it is necessary to keep continuous observations over the deformation of buildings and the land subsidence in the tunnel zone. Monitoring and permanent drainage should ensure the safe operation of the tunnel.
Hydrologic control on natural land subsidence in the shallow coastal aquifer of the Ravenna coast, Italy
Authors: Antonellini Marco , Giambastiani Beatrice Maria Sole , Greggio Nicolas , Bonzi Luciana , Calabrese Lorenzo , Luciani Paolo , Perini Luisa , Severi Paolo
Published: April 2020

Abstract. Multiple processes contributing to natural land subsidence in a shallow coastal aquifer near Ravenna (Italy) were identified by analysing the relationships among different data set time series (water table level, rainfall, land reclamation drainage, sea level, etc.) and establishing the correlations with vertical ground motion observed at a high-resolution settlement gauge. Our study highlights the presence of three deformation components related to different processes controlling land subsidence: elastic, delayed-elastic, and irreversible (plastic) components. The elastic and delayed-elastic components are closely related to water table fluctuations that change the effective stress in two portions of the coastal aquifer at a daily (in the sandy unconfined portion) and seasonal
time scales (in the layered clay-rich semi-confined prodelta portion),
respectively. The irreversible component represents the trend in the land
subsidence time series and is due to primary consolidation (pore pressure
dissipation) of the fine-grained prodelta levels above where the settlement
gauge is located. The amplitudes of the elastic component can be up to
0.2–0.3 mm whereas the amplitude of the delayed-elastic component reaches
0.89 mm. The primary consolidation rate of deformation is 0.9 mm yr−1 and constrains the likely age of prodelta sediments deposition to 1300–2800 years before present. The delayed-elastic subsidence rate has similar magnitude to that due to primary consolidation and is connected to poroelastic effects in the prodelta sequence following seasonal variations in water table. Our findings are important for planning land subsidence management and monitoring strategies especially where the surface aquifer structure is heterogeneous due to different depositional settings. The natural land subsidence rate in the Holocene sediments of the shallow coastal aquifer of Ravenna (North eastern Italy) that we measured in this study accounts for 10 %–20 % of the total current land subsidence rate observed in this portion of Ravenna coastal area (10–20 mm yr−1).
Leaking recharge mechanism in the multi-layer aquifer system of a typical land subsidence area in Beijing
Authors: Lei Kunchao , Ma Fengshan , Liu Jiurong , Luo Yong , Cui Wenjun , Zhou Yi , Liu He , Wang Xinghui , Tian Miaozhuang , Zhao Long
Published: April 2020

Abstract. It is of great significance to reveal the mechanism of
land subsidence to further find out the mechanism of leakage flow in
multi-layer aquifer systems and the water-release compression of weak
aquifers. In this paper, conditions of groundwater leakage flow are
expounded, and the initial hydraulic gradient calculation formula in the
aquitards are deduced. The data of Tianzhu Land Subsidence Monitoring
Station are selected to preliminarily discuss the leakage flow mechanism of
the multi-layer groundwater system and water-release compression of weak
aquifers. The results show that, firstly the weak aquifer layers in the
shallow strata above 91.32 m in Tianzhu Land Subsidence Station are all in
the state of unidirectional drainage consolidation, and the water heads in
the upper strata are higher than those in the lower strata. However, the
hydraulic gradient between the two adjacent aquifers is smaller than the
initial hydraulic gradient in the weak aquifer layer, so no leakage recharge
effect is generated. Secondly, the water level of the two adjacent aquifers
in the deep formation below 91.32 m shows a continuous downward trend, among
which the weak aquifer is drained and consolidated on both sides, and the
pore water head in the middle of the weak aquifer is the lowest. Although
the strata has a large amount of compression, no leakage recharge phenomenon
occurs. Thirdly, in a multi-layer aquifer system, when the head difference
between adjacent aquifers is small and there is a thick viscous layer
between them, it is difficult for the upper aquifer to overcome the shear
strength of the bound water in the weak aquifer below, leaking recharge
barely occurs.
The Secondary Consolidation (Creep) due to Geohistorical Overburden Pressure in the Houston-Galveston Region, Texas
Authors: Liu Yi , Li Jiang , Fang Zheng N. , Rashvand Mojtaba , Griffin Tranell
Published: April 2020

Abstract. The combination of groundwater withdrawal, hydrocarbon
extraction, salt-dome movement and faulting have caused widespread
subsidence in the Houston-Galveston region (HGR). Subsidence results from
primary consolidation consisting of inelastic (nonrecoverable) and elastic
(recoverable) compaction caused by subsurface fluid withdrawal and secondary
consolidation (creep) over time caused by overburden pressure. Subsidence in
the HGR is monitored using borehole extensometers that were installed at 13
locations across Harris and Galveston counties between 1962 and 1980. By
1977, withdrawals from the Chicot and Evangeline aquifers resulted in
groundwater-level declines of about 114 and 115 m relative to
predevelopment water levels, respectively in parts of Harris County. By
1979, as much as 3 m of land subsidence was estimated to have occurred in
localized areas of the HGR. Land subsidence can be hazardous in populated
areas because it exacerbates the effects of storm surge and impedes
storm-water runoff by decreasing land-surface elevations in areas where
water accumulates. To assess aquifer compaction in response to changes in
groundwater levels, a bulk land-surface subsidence rate is assumed to be the
sum of the primary consolidation rate and the negligibly variable component
of overburden pressure referred to as the “pseudo-constant secondary
consolidation rate.” From 1931 to 1976, groundwater levels decreased as
groundwater withdrawal rates increased from 0.57 to 4.3 million m3 d−1,
causing pressure heads in aquitards the Chicot and Evangeline aquifers to
continually decline. In response to reductions in groundwater withdrawal
rates from 4.3 to 3.0 million m3 d−1 between 1976 and 2001, groundwater
levels rebounded, decreasing inelastic compaction rates in some parts of the
HGR from as much as about 40 mm yr−1 in the early 1980s to
negligible amounts by 2000. Inelastic consolidation from about 1937 to 2000
contributed to land-surface subsidence and its associated effects.
Land-surfaces have rebounded in localized areas of the HGR where groundwater
levels rebounded significantly. Pseudo-constant secondary consolidation
rates were computed at each of the 13 extensometers and ranged from 0.48 to
8.49 mm yr−1 in areas where groundwater levels in the two
aquifers were stabilizing. This secondary consolidation subsidence is beyond
the control of any groundwater-level management schemes because it is caused
by geohistorical overburden pressure on the two aquifers.
Altered surface hydrology as a potential mechanism for subsidence in coastal Louisiana
Authors: Nienhuis Jaap H. , Törnqvist Torbjörn E. , Erkens Gilles
Published: April 2020

Abstract. The natural wetlands of coastal Louisiana are
experiencing rapid subsidence rates averaging 9±1 mm yr−1. Recent
measurements based on GPS data and CRMS surface elevation tables (SETs) have
shown that most of the subsidence is shallow and occurs in the uppermost 5
meters. Sources of subsidence and the origin of their spatial variability
are strongly debated. Here we use CRMS SETs together with historic maps of
coastal Louisiana to explore two hypotheses: (i) shallow subsidence is a
result of accommodation created by (long-term) deep subsidence processes and
self-weight consolidation, and (ii) changes in marsh hydrology (groundwater
and surface water flows) have led to a recent increase in shallow
subsidence. First, we find that, although self-weight consolidation would result in
generally high observed shallow subsidence rates, it does not explain the
rates nor the spatial variability of the CRMS SET data. Second, based on
historic maps, we find that shallow subsidence rates are significantly
higher for CRMS sites where shipping canals have reduced their distance to
the marsh edge. This is potentially a result from increased sediment
deposition, but CRMS data also show altered groundwater levels near the
marsh edge. We find some indication that prolonged periods of low water
could have led to increases in effective stresses that explain some of the
rapid rates of shallow subsidence observed along Louisiana's coastline.
Land subsidence due to groundwater extraction and tectonic activity in Pingtung Plain, Taiwan
Authors: Tran Duc-Huy , Wang Shih-Jung
Published: April 2020

Abstract. Pingtung coastal plain, located at the active convergent
boundary between Philippine Sea Plate and Eurasian Plate, is one of the most
active areas regarding tectonic deformation in Taiwan. Groundwater
over-pumping for aquaculture along the coast area of Pingtung plain induced
a serious land subsidence problem for decades. How much land subsidence
contributed by tectonic activity and groundwater pumping is a crucial issue
for tectonic study and groundwater management in this area. This study
collected the data in different fields and proposed a conceptual model to
calculate the quantities of land subsidence caused by natural (tectonic) and
human (pumping) factors. The data from the Global Positioning System (GPS)
are used to illustrate the total subsidence concerning vertical
displacement. A system called the multi-level compaction monitoring well
(MCMW) is able to measure the vertical compaction in different depths from
the earth surface to the depth of 200 m. Two GPS stations, named CLON and
FALI, close to two MCMWs, named Jiadong and Fangliao, are adopted for
analysis The data during 2007 and 2016 taken from MCMWs and groundwater
observation wells indicate that the compaction in the shallow depth should
be mainly caused by groundwater over-pumping due to their high correlation
coefficients (from 0.58–0.95). The difference of the vertical deformation
between GPS and MCMW indicates that there is deformation beyond the depth
within 200 m. From the data and literature, the further vertical deformation
should be due to tectonic activity associated with tectonic escape and
extrusion of the Taiwan orogen with average vertical deformation from −3.0
to −4.4 mm. Therefore, the quantities of land subsidence contributed by
local groundwater over-pumping and regional tectonic activities are
successfully separated. The method and concept proposed in this study can be
used in land subsidence quantification due to both tectonic activity and
groundwater over-pumping.
Land subsidence modelling for decision making on groundwater abstraction under emergency situation
Authors: Aichi Masaatsu
Published: April 2020

Abstract. This study presents an inversion scheme with uncertainty
analysis for a land subsidence modelling by a Monte Carlo filter in order to
contribute to the decision-making on the groundwater abstraction. For real
time prediction and uncertainty analysis under the limited computational
resources and available information in emergency situations, one dimensional
vertical land subsidence simulation was adopted for the forward modelling
and the null-space Monte Carlo method was applied for the effective
resampling. The proposed scheme was tested with the existing land subsidence
monitoring data in Tokyo lowland, Japan. The results demonstrated that the
prediction uncertainty converges and the prediction accuracy improves as the
observed data increased with time. The computational time was also confirmed
to be acceptable range for a real time execution with a laptop.
Understanding the dynamic behaviour for the Madrid aquifer (Spain): insights from the integration of A-DInSAR and 3-D groundwater flow and geomechanical models
Authors: Bonì Roberta , Meisina Claudia , Teatini Pietro , Zucca Francesco , Zoccarato Claudia , Franceschini Andrea , Ezquerro Pablo , Béjar-Pizarro Marta , Fernández-Merodo José A. , Guardiola-Albert Carolina , Pastor José L. , Tomás Roberto , Herrera Gerardo
Published: April 2020

Abstract. Advanced Differential Interferometric Synthetic Aperture
Radar (A-DInSAR) techniques and 3-D groundwater flow and geomechanical models
are integrated to improve our knowledge about the Tertiary detritic aquifer
of Madrid (TDAM). In particular, the attention is focused on the
Manzanares-Jarama well field, located to the northwest of Madrid, which
experienced five cycles of extensive groundwater withdrawal followed by
natural recovery, to cope with the droughts occurred in summer 1995, 1999,
2002, 2006, and 2009. Piezometric records and A-DInSAR data acquired by
ERS-1/2 and ENVISAT satellites during the periods 1992–2000 and 2002–2010,
respectively, have been used to calibrate the groundwater flow and the
geomechanical models. A time-lag of about one month between the hydraulic
head changes and the displacements of the land surface has been detected by
a joint wavelet analysis of A-DInSAR and piezometer head time series.
Overall, the results show the effectiveness of the proposed integrated
approach composed of A-DInSAR and 3-D geomechanical model to characterize the
aquifer-system response during and after the groundwater withdrawal.
Analogue model of ground ruptures due to groundwater pumping in an aquifer above a bedrock ridge
Authors: Cerca Mariano , Carreón-Freyre Dora , Teatini Pietro
Published: April 2020

Abstract. We report preliminary results of physical experiments
of rupture occurrence and propagation associated with land subsidence
driven by groundwater pumping and compare our analogue model results with
corresponding previously reported numerical results. In particular, we aim
to test the development of tensile stresses above a bedrock ridge that forms the base of an aquifer system. The experiment reproduces the main
deformation and ruptures observed in field cases and in the numerical
analysis.
Assessment of Subsidence Risk Associated with Brackish Groundwater Development in the Coastal Lowlands Aquifer, Houston, Texas, USA
Authors: Deeds Neil , Turco Michael , Kelley Van , Petersen Christina , Baird Susan
Published: April 2020

Abstract. Significant undeveloped brackish groundwater resources
exist within the Coastal Lowlands Aquifer System (Gulf Coast Aquifer System)
near Houston, Texas, USA. As the development of these frontier resources is
imminent, an improved understanding of the impact development may have on
the availability of the resource and land subsidence is needed. In this
region, land subsidence is caused by the depressurization of the aquifer and
compaction of the many clay lenses in the subsurface. The Gulf Coast Aquifer
System in the study area includes three primary water bearing units (from
shallow to deep): the Chicot (Pleistocene and Pliocene) and Evangeline
(Pliocene and Miocene) aquifers, and the Jasper aquifer (Miocene). Although
there has been much research and data supporting the causal relation between
water-level decline and subsidence in the areas of fresh groundwater
development, little data exists to inform on the potential subsidence
impacts upon deeper brackish groundwater development. Data were compiled,
and multiple hydrologic parameters were utilized to improve the
understanding of the brackish resources within the study area. Geophysical
logs were compiled and analysed to refine the aquifer stratigraphy,
determine the binary classification of sand and clay, and estimate the
groundwater salinity. These data were used to develop a MODFLOW groundwater
flow model to estimate the risk of compaction and land subsidence upon the
development of brackish zones within the Jasper aquifer. Compiled data
detailing the total clay thickness, clay bed thickness, and clay bed
location were input into the model along with a hypothetical stress to
predict compaction within the Jasper aquifer across the study area while
incorporating the observed heterogeneity in clay properties. Using the
results from the model simulations and two other risk performance measures
(depth of burial and surface flood risk), the total subsidence normalized
risk score was estimated. The results of this study confirm the potential
for compaction in the Jasper aquifer and for land subsidence to occur upon
development. Areas with the highest risk are located in the up-dip, inland
areas, near where the aquifer becomes fresh and is currently used for
municipal supply. The results will inform water managers and planners in the
Houston area on the future availability of brackish groundwater resources.
Detection and measurement of land subsidence and uplift using interferometric synthetic aperture radar, San Diego, California, USA, 2016–2018
Authors: Brandt Justin T. , Sneed Michelle , Danskin Wesley R.
Published: April 2020

Abstract. Land subsidence associated with groundwater-level declines is stipulated as an “undesirable effect” in California's Sustainable Groundwater Management Act (SGMA), and has been identified as a potential issue in San Diego, California, USA. The United States Geological Survey (USGS), the Sweetwater Authority, and the City of San Diego, undertook a cooperative study to better understand the hydromechanical response of the coastal aquifer system using Interferometric Synthetic Aperture Radar (InSAR) techniques. Three periods of interest were analyzed for this study that correspond to the periods before and after two substantial changes were made to the location and volume of pumpage: (1) April–August 2016 when groundwater levels and land surface elevation were relatively stable during normal pumping, (2) September 2016–May 2017 when groundwater levels recovered and the land surface uplifted during a period of substantially reduced pumping, (3) June 2017–October 2018 when groundwater levels declined and land subsidence occurred when pumpage resumed and expanded to new wells. Spatial and temporal characterization of the hydromechanical response to changes in pumpage is important for managing land subsidence. Further study using InSAR techniques, especially when combined with ground-based geodetic and monitoring-well networks, will provide water managers information to help effectively manage groundwater resources as stipulated in the SGMA.
Elasto-viscoplastic modeling of subsidence above gas fields in the Adriatic Sea
Authors: Gemelli Fabrizio , Corradi Anna , Volonté Giorgio , Mantica Stefano , De Simoni Michela
Published: April 2020

Abstract. From the analysis of GPS monitoring data collected above gas
fields in the Adriatic Sea, in a few cases subsidence responses have been
observed not to directly correlate with the production trend. Such behavior,
already described in the literature, may be due to several physical
phenomena, ranging from simple delayed aquifer depletion to a much more
complex time-dependent mechanical response of subsurface geomaterials to
fluid withdrawal. In order to accurately reproduce it and therefore to be
able to provide reliable forecasts, in the last years Eni has enriched its
3D finite element geomechanical modeling workflow by adopting an advanced
constitutive model (Vermeer and Neher, 1999), which also considers the
viscous component of the deformation. While the numerical implementation of
such methodology has already been validated at laboratory scale and tested
on synthetic hydrocarbon fields, the work herein presents its first
application to a real gas field in the Adriatic Sea where the phenomenon has
been observed. The results show that the model is capable to reproduce very
accurately both GPS data and other available measurements. It is worth
remarking that initial runs, characterized by the use of model parameter
values directly obtained from the interpretation of mechanical laboratory
tests, already provided very good results and only minor tuning operations
have been required to perfect the model outcomes. Ongoing R&D projects
are focused on a regional scale characterization of the Adriatic Sea basin
in the framework of the Vermeer and Neher model approach.
Land subsidence modelling using a long short-term memory algorithm based on time-series datasets
Authors: Li Huijun , Zhu Lin , Gong Huili , Sun Hanrui , Yu Jie
Published: April 2020

Abstract. With the rapid growth of data volume and the development
of artificial intelligence technology, deep-learning methods are a new way to
model land subsidence. We utilized a long short-term memory (LSTM)
model, a deep-learning-based time-series processing method to model the land
subsidence under multiple influencing factors. Land subsidence has non-linear
and time dependency characteristics, which the LSTM model takes into account.
This paper modelled the time variation in land subsidence for 38 months from
2011 to 2015. The input variables included the change in land subsidence
detected by InSAR technology, the change in confined groundwater level, the
thickness of the compressible layer and the permeability coefficient. The
results show that the LSTM model performed well in areas where the
subsidence is slight but poorly in places with severe subsidence.
Mapping the autonomous subsidence for the rural and urban areas in Woerden, the Netherlands
Authors: van der Putte Erik
Published: April 2020

Abstract. Autonomous subsidence plays a major role in the landscape
of the western parts of the Netherlands. For a lot of municipalities and
waterboards this autonomous subsidence brings immense maintenance costs and
discussions about sustainable land use. For the municipality of Woerden the
autonomous subsidence is assessed for both rural and urban areas. For the
rural areas the oxidation of peat and the consolidation due to gradually
lowering of the water table are the main contributors. Using the modified
“Phoenix” model the autonomous subsidence is predicted to be approximately
5 to 6 mm yr−1. In the urban areas the water table is stable and
therefore the ageing of clay and creep are the driving forces for the
autonomous subsidence. Using satellite data the autonomous subsidence is
determined to range from 0 to 4 mm yr−1 for most parts of the city.