bluuebunny/crossref_metadata_2025 huggingface dataset:
Revisiting ENSO impacts on the Indian Ocean SST based on a combined linear regression method
Authors: Zhang Lianyi , Du Yan
Published: March 2022

The El Niño-Southern Oscillation (ENSO) has great impacts on the Indian Ocean sea surface temperature (SST). In fact, two major modes of the Indian Ocean SST namely the Indian Ocean Basin (IOB) and Indian Ocean Dipole (IOD) modes, exerting strong influences on the IO rim countries, are both influenced by the ENSO. Based on a combined linear regression method, this study quantifies the ENSO impacts on the IOB and IOD during ENSO concurrent, developing, and decaying stages. After removing the ENSO impacts, the spring peak of the IOB disappears along with significant decrease in number of events, while the number of events is only slightly reduced and the autumn peak remains for the IOD. By isolating the ENSO impacts during each stage, this study reveals that the leading impacts of ENSO contribute to the IOD development, while the delayed impacts facilitate the IOD phase switch and prompt the IOB development. Besides, the decadal variations of ENSO impacts are various during each stage and over different regions. These imply that merely removing the concurrent ENSO impacts would not be sufficient to investigate intrinsic climate variability of the Indian Ocean, and the present method may be useful to study climate variabilities independent of ENSO.
Climatic context of blue ring formation in high elevation bristlecone pine (Pinus longaeva D.K. Bailey).
Authors: Siekacz Liliana , Pearson Charlotte , Salzer Matthew , Koprowski Marcin
Published: March 2022

'Blue Rings' (BRs) are distinct wood anatomical anomalies recently discovered in several tree species. Studies connect their occurrence to lower than normal temperatures during the cell wall lignification phase of xylogenesis which usually continue after radial growth is completed, following the growth season. BRs are also potentially more sensitive to temperature than frost rings which require freezing temperatures (linked with the forcing of volcanic eruptions) to form. Therefore, systematic analysis of blue rings can add another level of time resolution and/or sensitivity to dendroclimatic studies.  North American bristlecone pine is an invaluable resource for paleoclimatological reconstruction due to its extreme longevity (its specimens are reported to commonly exceed the age of 4000 years), high durability and favourable environmental conditions which hamper decay, enabling the construction of chronologies spanning more than 8000 years. Preliminary results for the last 1000 years reveal that BRs in bristlecone pine coincide significantly with major volcanic eruptions. Detailed analysis of recorded temperature conditions in the years of BRs formation can therefore provide additional information on the impact of volcanic eruptions on climate in periods where meteorological observations are unavailable. To establish baselines for this, we present the climatic context of BR occurrence in bristlecone pine for the period since 1895 where modelled surface mean monthly temperatures are available for the grid cell pertaining to the study area location (4km spatial resolution, from PRISM Climate Group, Oregon State University). A group of 83 cores of bristlecone pine (originating from the vicinity of the Sheep Mountain/Patriarch Grove area of the Ancient Bristlecone Pine Forest in the White Mountains of California, 37.5 W 118.2 N) was thin sectioned on a GSL 1 microtome and further prepared following Gärtner & Schweingruber (2013) safranine and astrablue staining procedures to reveal lignified cell walls in red and underlignified cell walls in blue. Scanned and digitized thin-sections were measured and cross-dated noting years of BR occurrence.  A generalized linear mixed-effects model (GLMM) was fit with mean monthly temperatures and distance from treeline (DTL) as independent variables, and a binary response variable representing the absence (0) or presence (1) of a BR in a particular year, in a particular sample. Results indicate that BRs positively correlate with mean monthly temperatures of February and October and negatively with April, June, August, September and DTL. BR formation most strongly correlates with September temperatures, and interestingly, also lacks correlation with July temperatures.
Tide-topography interactions: the influence of an along-shelf current on the internal wave spectrum
Authors: He Yangxin , Lamb Kevin
Published: March 2022

We investigate the influence of a barotropic geostrophic current on
the internal wave (IW) generation over a shelf slope.
It is well known that most of the energy in the tide-topography
generated waves lies in waves with tidal frequency $\sigma_T$. 
Here we restrict our attention on the frequencies other than the dominant frequency $\sigma_T$. 
The current $V_g(x)$ is modeled as an idealized Gaussian function centered at
$x_0$ with width $x_r$ and maximum velocity $V_{max}$.
The bathymetry is modelled as a linear slope with smoothed corners.
Since the center of the current lies on the slope, there will always
be a region on the slope where the effective frequency $f_{eff}$ is
greater than the Coriolis parameter $f$ and another region where
$f_{eff} < f$. Parametric subharmonic instability (PSI) occurs where
waves with approximately half of the primary wave frequency, in this
case $\sigma_T/2$, are generated. In the presence of a large current,
PSI can occur where $f_{eff} < \sigma_T/2 < f$. This could not
happen without a current, i.e. $f_{eff} = f > \sigma_T/2$. Other interesting
interactions, including interharmonics and strong tidal harmonics, are also observed.
A dammed palaeo-lake at the middle Yarlung Tsangpo River, Tibet
Authors: Hu Hai-Ping , Feng Jin-Liang , King Georgina
Published: March 2022

The Yarlung Tsangpo River follows the Indus-Tsangpo suture through the southern Tibetan Plateau, and then becomes the Brahmaputra, following a bend into India through the Yarlung Tsangpo Gorge. In the middle reaches, narrow gorges alternate with broad valleys (Zhang, et al. 1998). In the section with steep and narrow gorges, the river is easily dammed by landslides, glaciers and/or moraines, rock avalanches and debris flows. Palaeo-lake sediments were discovered in the broad Xigazê valley and Dazhuka-Yueju gorge in the middle reach of the Yarlung Tsangpo River in Tibet. The river was likely dammed by a glacier and/or moraine at the eastern end of the Dazhuka-Yueju gorge. AMS 14C and OSL ages of lacustrine sediments indicate the palaeo-lake was formed during the period from ~30.2 to 32.3 cal. kyr BP, and failed at ~13.2 cal. kyr BP (Hu et al., 2018). The elevation of the dammed lake was 3811 m a.s.l., and its length, maximum water depth, and volume were 185 km, 211 m, and ~22.55 km3, respectively (Hu et al., 2022). The volume of the sediment was ~11.56 km3, which was calculated from the dam location, sediment surface elevation, and the ASTER GDEM2 data. Therefore, the backwater volume was 10.99 km3, and the peak flood possibly exceeded 3.4 × 105 m3/s during the dam failure. The dammed palaeo-lakes in the vallyes downstream of the middle Yarlung Tsangpo River were also discharged during ~13 ka, and they were likely interconnected by hydrological processes. Hence, the failure of the dam and related flooding from the Dazhuka-Yueju gorge probably triggered a chain reaction of dam failures downstream, forming a megaflood. However, the dammed event in the Dazhuka-Yueju valley probably had a limited effect on the landforms at downstream because of the presence of another dammed palaeo-lake in the broad Zetang valley. So the ages of the dammed palaeo-lakes at the middle Yarlung Tsangpo River need to constrained more precisely.

References

Hu, H.-P., Feng, J.-L., Chen, F., 2018. Sedimentary records of a palaeo-lake in the middle Yarlung Tsangpo: Implications for terrace genesis and outburst flooding. Quaternary Science Reviews, 192, 135-148.

Hu, H.-P., Liu, J.-H., Feng, J.-L., Ye, C.-S., Lv, F., Chen, F., Gong, Z.-J., Chen, L.-Q., Du, D.-D., 2022. Geomorphic processes of a dammed palaeo-lake in the middle Yarlung Tsangpo River, Tibet. Science of the Total Environment, 811C, 151949.

Zhang, D.D., 1998. Geomorphological problems of the middle reaches of the Tsangpo River, Tibet. Earth Surface Processes and Landforms, 23(10): 889-903.
The Impact of Angiosperms Physiological Evolution on Earth Systems
Authors: Guo Jiaqi , Hu Yongyun , Liu Yonggang
Published: March 2022

The physiological evolution of vegetation affects the interaction between vegetation and climate. Angiosperms have higher leaf vein density than all other plants throughout evolutionary history, contributing to higher transpiration capacities. However, the climatic response to changes in physiological functions of angiosperms has remained to be determined. Here, Community Earth System Model (CESM) version 1.2.2 and BIOME4 vegetation model are applied to simulate the world without angiosperms by reducing the maximum carboxylation rate (Vmax) to 1/4 (Boyce et al, 2009), in conditions of both fixed and non-fixed vegetation distribution. First, we maintain the pre-industrial vegetation distribution, the results illustrate that the world without angiosperms would have less productivity, higher global mean temperature, consisting with the results of Boyce and Lee (Boyce and Lee, 2010). In addition, the warmer southern hemisphere and colder northern hemisphere are identified, which are caused by the decrease of the strength of Atlantic Meridional Overturning Circulation (AMOC). Second, we consider changes of vegetation structure, the results show that temperature and precipitation would vary significantly locally, and the area of tropical forest would decline sharply in the world without angiosperms, which may affect biodiversity. The evolution of physiological functions of angiosperms influences climate and provides potential competitive advantages for angiosperms to dominate modern vegetation.
Seamount effect of a deep seamount on phytoplankton in the tropical western Pacific
Authors: Dai Sheng
Published: March 2022

It is generally believed that the enhancement of phytoplankton appears only in shallow and intermediate depth seamounts, while the phenomenon has also been observed in some deep seamounts by satellites recently. To figure out what effect do deep seamounts have on phytoplankton and the relevant mechanisms, the phytoplankton biomass and community on the Kocebu Seamount (depth: 1198 m) were studied. The results showed that high Chl a patches (> 0.2 mg·m-3) were mainly distributed within 20 km of the peak, and both nitrate and orthophosphate were obviously uplifted at the peak. The physical data indicated the uplifted of nutrients could be caused by the internal tides, which generated by the interaction of topography and tide. This is the first time that the promotion of phytoplankton was observed in situ on a deep seamount, and this study expounded relevant mechanisms and suggested that the ecological functions of deep seamounts may have been previously neglected.
African easterly wave evolution and tropical cyclogenesis in a pre-Helene (2006) hindcast using the Model for Prediction Across Scales (MPAS)
Authors: Núñez Ocasio Kelly , Ríos-Berríos Rosimar
Published: March 2022

Despite recent advancements in our understanding of tropical cyclogenesis (TCG), it remains an elusive research topic. Here, the Model for Prediction Across Scales (MPAS) is used to study the TCG case of the African easterly wave (AEW) that became Hurricane Helene (2006). This study has two main objectives: 1) evaluate MPAS high-resolution AEW hindcast capability by comparing MPAS simulations—initialized with data from both the Integrated Forecasting System (IFS) and the Global Forecast System (GFS)—with observations and, 2) analyze the role of moisture in the mechanisms that lead to Helene’s TCG. Both 15-km horizontal grid resolution simulations developed a more intense wave and ultimately tropical depression compared to observations. However, the track, intensity, and rainfall of the simulated pre-Helene when initializing with IFS were more comparable to those of observations than the simulation initialized with GFS. The simulated pre-Helene initialized with GFS was more intense than the IFS-initialized pre-Helene, with the track of the wave deviating farther east of the observed track, especially as it reached the west coast of Africa. The more intense GFS-initialized pre-Helene is associated with larger moisture availability in the boundary layer (BL), and stronger West African monsoon southwesterly winds in the mean state when compared to the IFS simulation and observations. A moisture flux convergence budget centered on the wave trough shows that during the wave’s lifetime the convergence term in the BL dominates and increases as the wave approaches TCG. However, TCG only happens when conditions are optimal—net moisture flux in the BL at the center of the wave increases in addition to increased mass convergence. These results could potentially be the link that explains the intersection between recent TCG theories. In the moisture-vortex instability (MVI), the wave-related flow advects moisture and temperature towards the synoptic-scale vortex, creating a favorable environment for convection near the vortex center, promoting TCG. The pre-genesis top-heavy profile to bottom-heavy profile during genesis, which provides vorticity convergence associated with TCG, could be a consequence of MVI attainment. It is the increase in wave-centered net moisture flux in combination with wave-centered mass flux convergence increase in the BL that ultimately could bring these theories together and help explain how TCG is achieved.
Analysis of debris flow according to the location of the check dam: suggesting the optimal location by numerical simulation
Authors: Lee Seungjun , An Hyunuk , Kim Minseok
Published: March 2022

The shallow landslide-generated debris flow on hillside catchments plays a critical role in the change of landscape features caused by natural hazards. When these debris flows occur in dams or reservoirs, they reduce the efficiency of facilities, and when they occur in residential areas, they cause many casualties and property damage. To minimize such damages, some methods can be performed through 1) installation of the warning system and 2) construction of check dam. However, in the case of rainfall-induced debris flow, preparation through a warning system is challenging because debris flows very rapidly. Therefore, to reduce the damage caused by debris flow events, the check dam needs to be installed, and for an efficient installment, a study on numerical modeling needs to figure out. Therefore, in this study, the Deb2D numerical model was used to analyze the mitigation effect through the check dam. This model is a two-dimensional debris flow simulation software based on quadtree-grid. The debris flow was simulated by Voellmy rheology, and the erosion, entrainment, and deposition processes that must be considered for the analysis of debris flow were simulated through the algorithm suggested in our recent study. The Raemian apartment and Galram-ri debris flow events were analyzed which occurred at Mt. Umyeon in 2011 and Gangwon-do in the Republic of Korea. In addition, a check dam was hypothetical by changing the distance from the collapse zone. The efficient location can be suggested through the simulation results.

Keywords: Debris flow; Numerical model; Check dam; Mitigation effect

Acknowledgments

This subject is supported by the Korea Ministry of Environment as “The SS projects; 2019002830001”
Deciphering Neoarchean polymetamorphism and crustal melting in the northern Wyoming Province using garnet petrochronology
Authors: Dragovic Besim , Guevara Victor , Caddick Mark , Inglis Jeremy , Raimondo Tom , Kylander-Clark Andrew
Published: March 2022

High-grade metamorphic rocks can record the dynamic processes that lead to crustal heating and a departure from normal crustal geothermal gradients. High temperatures in the Archean crust led to particularly significant melt generation and cratonic stabilization, and understanding the depths, temperatures and rates of Archean metamorphism may reflect our clearest window into possible tectonic styles at this time. However, several Archean metamorphic terranes record polymetamorphism, and unravelling the pressure-temperature-time (P-T-t) histories of such terranes has proven difficult, with complexity inherent in both chronologic and petrologic data.

Here we synthesize results of a multi-analytical study in which garnet and monazite petrochronology, coupled with thermodynamic and diffusion modeling, were applied to Archean granulites from the Beartooth Mountains in the northern Wyoming Province, U.S.A. The data reveal two phases of garnet growth and high-temperature metamorphism. Garnet cores grew coeval with emplacement of a granitoid batholith at ~2.78-2.76 Ga. This was followed by a distinct, second phase of peritectic garnet rim growth at ~2.71 Ga, during biotite breakdown melting at peak temperatures of ~750˚C. Diffusion modeling of chemical zoning in garnet rims shows that this second event was brief: near-peak temperatures were maintained for < 1 Myrs. In contrast, core and rim dates of garnet from a meta-granitoid from the same outcrop record only the initial phase of growth, most likely because a lack of grain boundary fluids inhibited further crystallization in these rocks. Evidence for this second event is cryptic in other granitoid samples, such that this period of heating to at least 750˚C, ~50-100 Myrs after initial batholith emplacement, is poorly recorded in the broader rock record of the Beartooths.

The results of our study show that different parts of the metamorphic history of a rock may be recorded differently between garnet and accessory phases. Lastly, while field and petrologic evidence for polymetamorphism may be cryptic, direct dating of distinct garnet growth zones with preserved major and trace element zonation allows for a clear interpretation between isotopic dates and the metamorphic history of the rock.
Tracking moisture sources of precipitation over Central Asia: A study based on the water-source-tagging method
Authors: Jiang Jie
Published: March 2022

Central Asia is a semiarid to arid region that is sensitive to hydrological changes. We use the Community Atmosphere Model, version 5 (CAM5), equipped with a water-tagging capability, to investigate the major moisture sources for climatological precipitation and its long-term trends over central Asia. Europe, the North Atlantic Ocean, and local evaporation, which explain 33.2% ± 1.5%, 23.0% ± 2.5%, and 19.4% ± 2.2% of the precipitation, respectively, are identified as the most dominant moisture sources for northern central Asia (NCA). For precipitation over southern central Asia (SCA), Europe, the North Atlantic, and local evaporation contribute 25.4% ± 2.7%, 18.0% ± 1.7%, and 14.7% ± 1.9%, respectively. In addition, the contributions of South Asia (8.6% ± 1.7%) and the Indian Ocean (9.5% ± 2.0%) are also substantial for SCA. Modulated by the seasonal meridional shift in the subtropical westerly jet, moisture originating from the low and midlatitudes is important in winter, spring, and autumn, whereas northern Europe contributes more to summer precipitation. We also explain the observed drying trends over southeastern central Asia in spring and over NCA in summer during 1956–2005. The drying trend over southeastern central Asia in spring is mainly due to the decrease in local evaporation and weakened moisture fluxes from the Arabian Peninsula and Arabian Sea associated with the warming of the western Pacific Ocean. The drying trend over NCA in summer can be attributed to a decrease in local evaporation and reduced moisture from northern Europe that is due to the southward shift of the subtropical westerly jet.
Evidence of high effusion Deccan volcanism proceeding the KPg boundary at Elles, Tunisia
Authors: Sillitoe-Kukas Steffanie , Humayun Munir , Adatte Thierry , Keller Gerta
Published: March 2022

Massive volcanic eruptions of the Deccan coincided with the end-Cretaceous mass extinction. Precisely dating when the most intense eruptions occurred is challenging because the resolution of geochronological techniques does not yet resolve events shorter than 20 kiloannum (ka). Volcanic eruptions outgas volatile metals, e.g., Cd, Te and Hg, along with SO2 and other gases that may have contributed to high-stress environments for planktic foraminifera the 200 ka preceding the end-Cretaceous. Trace metals like Cd accumulate in sediments by deposition of aerosols, where the excess Cd reflects the intensity of volcanic emissions. Models show high frequency, low effusion rate eruptions result in low Cd enrichments, whereas low frequency, high effusion rate eruptions, the type likely to lead to deadly consequences, result in high enrichments of Cd within the sediments. The KPg section at Elles represents a middle neritic depositional environment with an average sedimentation rate of 4.7 cm/1,000 years for the late Maastrichtian. A series of sediment samples (marly limestone to shale) were taken from about 1 meter above the boundary to about 15 meters below the boundary. Elemental compositions of sediments (50 elements) were obtained by solution ICP-MS. Cadmium abundances ranged from values close to upper continental crust (UCC) to values approximately eight times higher. Such high enrichments were found in sediments from the 100 ka period preceding the boundary corresponding to the Poladpur phase of Deccan volcanism. A lack of correlation between Zn, P2O5, and Mo below the boundary suggest the Cd enrichments are not from an influx of biogenic detritus or TOC burial. Above the boundary, there is a 25 ka period of normal shale Cd values interpreted here to represent the period between the Ambenali and Poladpur phases. We have previously shown from the neighbouring El Kef section, representing ~ 10 ka, that Cd and Re are correlated in proportions similar to those from intraplate volcanoes. The Cd data for Elles complement Te and Hg data, all of which demonstrate the presence of volcanogenic trace metals over most of the period of the Poladpur phase of the Deccan eruption. Cadmium as a tracer enables better correlation between foram-based chronology and intense pulses of the Deccan eruption. The data obtained thus far confirm that the period prior to the extinction was dominated by intense volcanism followed by relative quiescence during the earliest Danian recovery with important implications for the cause of the extinction.
Laboratory rainfall simulation for surface runoff generation on tephra-covered slopes with different fine particle content
Authors: Hiraoka Marino , Imamori Naoki , Shimizu Takeshi , Ishida Koji
Published: March 2022

After pyroclastic materials are deposited in a watershed following a volcanic eruption, the risk of debris flow initiation may increase during subsequent rainfall events. Clarifying the rainfall-runoff process on tephra-covered slopes is essential to understand the mechanism of debris flow initiation after an eruption. Because the quality and quantity of pyroclastic materials vary from volcano to volcano, and from eruption to eruption of the same volcano, each rainfall-runoff process is expected to differ accordingly. Laboratory rainfall simulation is useful to highlight parameters (rainfall and sample conditions) that may affect the surface runoff process on slopes during and after a volcanic eruption. In this study, a laboratory experiment was conducted using a calibrated rainfall simulator to investigate how the occurrence of surface runoff during the first rainfall after an eruption depends on the fine particle content. Pyroclastic material was volcanic ash collected on Mount Sakurajima, Japan and the fine particle content Fc was adjusted using artificial silt: Sample A (Fc = 20%, control) and Sample B (Fc = 30%, adjusted). The experimental plots (1723.4 cm2 of the projection area) were prepared by filling each sample with a 5 cm thickness at a constant pressure on highly permeable silica sand, and placed at an inclination of 10°. The initial moisture condition of both samples was assumed to be dry (≈ 5% of water content ratio). The rainfall simulation was performed for 3 hours on each sample at an intensity of 30 mm h-1. Runoff water including sediment from the experimental plot during the simulation was captured at the lower end of the plot and the weight was recorded. Two soil moisture sensors were buried 2.5 cm below the surface of each sample to measure the change in volumetric water content (VWC) over time. Runoff water including sediment occurred and increased with time on Sample B though hardly occurred on Sample A. In both samples, the VWC increased with time and eventually approached a constant value. However, the maximum value of the VWC, and the time to reach the maximum value, were different; lower and slower in Sample B. The saturated hydraulic conductivity of Sample B was one order of magnitude lower than that of Sample A. These comparative results suggested that surface runoff may be greater during the first rainfall after an eruption because the infiltration is lower when the fine particle content, that is particle size distribution, in pyroclastic materials is high.
Bulk cloud microphysical properties as seen from numerical simulation and remote sensing products: case study of a hailstorm event over La Plata basin
Authors: Vara-Vela Angel , Crespo Natalia , Benavente Noelia , Bueno de Morais Marcos , Martins Jorge , Phillips Vaughan , Gonçalves Fabio , da Silva Dias Maria
Published: March 2022

Severe thunderstorms develop over La Plata basin, in southeastern South America, more often during austral wintertime, between June and August. These systems have significant socioeconomic impacts over the region, and, therefore, a better understanding of how atmospheric drivers modulate their formation is important to improve the forecast of such phenomena. In this study, we selected a hailstorm event observed over southeastern La Plata basin during 14-15 July 2016, and simulated it using three Brazilian developments on the Regional Atmospheric Modeling System (BRAMS) model configurations, each driven by a different global forcing: Global Forecast System (GFS), Climate Forecast System version 2 (CFSv2), and ECMWF Reanalysis v5 (ERA5). The ability of the BRAMS model in simulating cloud microphysical properties was evaluated by comparing the model output with satellite- and radar-based observations. Model results showed good skill in capturing the basic characteristics of the thunderstorm in terms of the spatial distribution of hydrometeors. The location of the maximum concentrations of hydrometeors was realistically represented by all simulations; however, slight to moderate differences in cloud properties between observations and model simulations were observed, with BRAMS/CFSv2 and BRAMS/ERA5 simulations performing best and worst, respectively, against measurements. In addition, these two simulations were able to reproduce ground-level hail concentrations over some of the reported hail fall areas. This study provides a first assessment of the BRAMS model to reproduce microphysical features of a severe thunderstorm captured by remote sensing observations over southeastern La Plata basin, one of the most hail-damage prone areas in the world.
Future Changes of the ENSO-Indian Summer Monsoon Teleconnection: The temporal vs ensemble-wise approach
Authors: Lee June-Yi , Bodai Tamas
Published: March 2022

Coupled ocean-atmosphere teleconnections are characteristics of internal variability which have a forced response just like mean states. It is not trivial how to correctly and optimally estimate the forced response and changes of the El Niño-Southern Oscillation (ENSO)-Indian summer monsoon (ISM) teleconnection under greenhouse forcing. Here we use two different approaches to address it. The first approach, based on the conventional temporal method applied to 30 model simulations in Coupled Model Intercomparison Project Phase 6, suggests no model consensus on changes in the teleconnection on interannual timescale under global warming. The second approach is based on a converged infinite single model initial condition large ensemble (SMILE) and defines the relationship in an instantaneous climatological sense. In view of several characteristics of the teleconnection, a robust long-term strengthening of the teleconnection is found in the MPI-GE but not in the CESM1-LE. We discuss appropriateness and limitations of the two methods. 
Antarctic grounding line retreat enhanced by subglacial freshwater discharge
Authors: Greenbaum Jamin S. , Dow Christine , Pelle Tyler , Morlighem Mathieu , Fricker Helen , Adusumilli Susheel , Jenkins Adrian , Rutishauser Anja , Blankenship Donald , Coleman Richard , Galton-Fenzi Benjamin , Lee Won Sang , Roberts Jason , Yoon Seung-Tae
Published: March 2022

Accurate prediction of sea level rise requires detailed understanding of processes contributing to ice sheet mass loss. Antarctica’s ice shelves are thinning, resulting in enhanced flow of grounded ice due to weakened ice shelf buttressing. Glaciers feeding ice shelves with the highest melt rates are also experiencing some of the most rapid grounding zone retreat. However, these ice shelf melt rates reach values that cannot be explained by ocean forcing alone and are not reproduced in ocean models. We present subglacial hydrology model outputs for four major Antarctic glaciers (Pine Island, Thwaites, Totten and Denman), which flow through the deepest and most extensive Antarctic marine subglacial basins and feed rapidly thinning ice shelves. We show that the areas of high ice shelf melting rates and grounding line retreat coincide closely with areas of high subglacial discharge. We posit that the subglacial discharge provides the missing component driving the high melt rates, and identify positive feedbacks between ice dynamics, steepening of ice shelf basal slope, and subglacial outflow. If surface temperatures increase as expected in Antarctica over the coming decades, surface meltwater could flow to the ice sheet base, as observed in Greenland. The surface meltwater hydrological cycle could therefore contribute to seasonal variations in subglacial meltwater and ice shelf basal melt, leading to accelerated grounding line retreat into Antarctica’s deepest subglacial basins. Invoking these feedbacks could reconcile sea level records and ice sheet model simulations that remain overly stable in warmer periods.
Stratigraphic record of dynamic topography in the Andean foreland basin, South America
Authors: Horton Brian K.
Published: March 2022

Variations in subduction configuration and mantle dynamics can be detected in retroarc foreland basins.  Modern and ancient examples from western South America show how discrete geodynamic mechanisms drive regional unconformity development in the Andean foreland basin.  Positive dynamic topography in the basin, fold-thrust belt, and broader convergent plate margin can be generated by (1) flat slab subduction, (2) slab window formation, (3) slab breakoff, (4) elevated intraplate (in-plane) stress, or (5) mantle flow variations.  A survey of long duration (>1–20 Myr) unconformities considers these and alternative mechanisms, including (6) local shortening-induced uplift in the frontal thrust belt and proximal foreland, (7) growth and advance of a broad flexural forebulge in the distal foreland, (8) uplift of intraforeland basement blocks along crustal-scale reverse faults, (9) tectonic quiescence with regional isostatic rebound, and (10) diminished accommodation or sediment supply due to changes in sea level, climate, erosion, or sediment transport.  These contrasting mechanisms can be readily observed in the modern foreland, particularly in the case of increased interplate coupling during active flat slab subduction and slab window generation associated with subduction of an active oceanic spreading ridge.  In the ancient record, the operative geodynamic mechanisms can be distinguished on the basis of the spatial distribution, stratigraphic position, paleoenvironmental context, and duration of foreland unconformities within the Cretaceous to Quaternary geodynamic framework of the Andean orogenic system.
Upwind droughts enhance heat waves in Eastern China
Authors: Zhou Shiyu , Yuan Xing
Published: March 2022

Heat wave is one of the most severe natural disasters in the mid-latitude regions. Due to climate change and urbanization, heat waves have been intensified in the past, and are projected to be more severe in the future. Droughts and heat waves usually occur simultaneously, which are referred to as compound extreme events. Antecedent or simultaneous droughts enhance heat waves through local land-atmosphere interaction, but a few case studies show that upwind droughts can have a significant impact on heat waves through sensible heat advection. In order to systematically study the impact of upwind droughts on heat waves, this study uses a Lagrangian integrated trajectory model driven by reanalysis data to analyze the heat wave events in northern part of Eastern China from 1979 to 2019. We find that half of the heat waves are enhanced by upwind droughts. For the related heat waves, the upwind droughts contributed to 67.9% of the heat anomalies. The impact of flash drought on heat waves in Eastern China is also being explored, with particular interest to extract heat wave signals from antecedent flash drought to provide early warning for extreme heat waves over downwind areas.
Zonal jets in the eastern North Pacific in an ensemble of eddy-resolving ocean general circulation model runs
Authors: Furue Ryo , Nonaka Masami , Sasaki Hideharu
Published: March 2022

It has been known for some time that the ocean basins are populated by what is known as ‘‘zonal jets’’, ‘‘deep zonal jets’’, or ‘‘striations’’. Since the oceanic flow is, at least weakly, chaotic, it is not known whether the positions of the jets are ‘‘deterministic’’, that is, entirely determined by external parameters. A number of theories have been proposed to explain them, some of them predicting zonal jets at fixed latitudes and others implying that the positions of the jets are random. To investigate how deterministic the zonal jets are in the eastern North Pacific, a ten-member ensemble of long-term integrations of a semi-global, eddy-resolving ocean general circulation model is analyzed.

The positions of the equatorial jets, even their variability, seem to obey deterministic dynamics and some of the jets in the tropics (5°–15°N) migrate poleward coherently (similarly between ensemble members). The jets in the subtropics (15°–45°N) systematically migrate equatorward but their positions are less coherent; the jets in the subpolar region (45°N–) are random and without systematic migration. Jets near the coast of North and South America tend to have shorter meridional wavelengths than interior ones and those in the northern hemisphere are fairly coherent whereas those in the southern hemisphere seem more random. There are a few quasi-barotropic jets which are anchored to steep bottom topographic features and which also appear to trap shallower counter-flows on their poleward and equatorward flanks.
A comparison of biological responses of benthic and planktic foraminifera to alteration in seawater CO2 and pH
Authors: Lei Yanli , Dong Shuaishuai , Li Tiegang , Jian Zhimin
Published: March 2022

The ocean absorbs large amounts of CO2 emitted from human activities, which lead a decrease in seawater pH and has potential damage to marine calcareous organisms. Foraminifera is one of the most important marine calcareous organisms in the ocean, while the biological response of benthic and planktic foraminifera to seawater CO2 increase and pH decline is still unknown. In this study, a comparison of the biological response of benthic and planktic foraminifera to seawater CO2 increase and pH decline was studied through series of culture experiments. Our experimental results showed the increase of CO2 or decrease of seawater pH adversely affected the biological processes of both benthic and planktic foraminifera may resulted in declining community diversity, weaker predation, slower growth, lighter shells and more deformities. In addition, we found microalgae that lives with planktic foraminifera are also killed under low pH conditions. Our study provided experimental data for understanding the biological response of calcareous micro-organisms to ocean acidification. Our results indicated that ongoing ocean acidification may retard the growth and calcification by changing their biological processes. This would have profound effects (e.g., reduced carbonate deposition and predation) on the carbon cycle and energy flow in the marine food web (This research received financial supports from the following projects: National Natural Science Foundation of China (Grant No, 41976058); The Strategic Priority Research Program of the Chinese Academy of Sciences (XDB42000000).
AI-enhanced Integrated Alert System for effective Disaster Management
Authors: Dalela Pankaj Kumar , Basu Saurabh , Sharma Sandeep , Kumar Anugandula Naveen , Behera Suvam Suvabrata , Upadhyay Rajkumar
Published: March 2022

Effective communication systems supported by Information and Communication Technologies (ICTs) are integral and important components for ensuring comprehensive disaster management. Continuous warning monitoring, prediction, dissemination, and response coordination along with public engagement by utilizing the capabilities of emerging technologies including Artificial Intelligence (AI) can assist in building resilience and ensuring Disaster Risk Reduction. Thus, for effective disaster management, an Integrated Alert System is proposed which encapsulates all concerned disaster management authorities, alert forecasting and disseminating agencies under a single umbrella for alerting the targeted public through various communication channels. Enhancing the capabilities of the system through AI, its integral part includes the data-driven citizen-centric Decision Support System which can help disaster managers by performing complete impact assessment of disaster events through configuration of decision models developed by learning inter-relationships of different parameters. The system needs to be capable of identification of possible communication means to address community outreach, prediction of scope of alert, providing influence of alert message on targeted vulnerable population, performing crowdsourced data analysis, evaluating disaster impact through threat maps and dashboards, and thereby, providing complete analysis of the disaster event in all phases of disaster management. The system aims to address challenges including limited communication channels utilization and audience reach, language differences, and lack of ground information in decision making posed by current systems by utilizing the latest state of art technologies.
The society interactions with floods in the modern Chinese history: a comparison between 1931 and 1954 floods
Authors: Liu Chang , Kawasaki Akiyuki , Shiroyama Tomoko
Published: March 2022

As the longest river in Asia, the Yangtze River has shown its impact on human societies with floods recorded since 12th century. In 1931, the Yangtze River has manifested its force again with one of the deadliest floods ever recorded in Chinese history, causing 422,499 deaths, damages to more than 25.2 million people and 58.7 billion m2 farmland. Similar flood occurred again in 1954, resulting in 31,762 deaths, damages to 18.9 million people and 31.7 billion m2 farmland. Researches have shown that 1954 flood being larger and higher compared to 1931 flood. However, it is still unclear for what reason that a more severe flood leading to less damage. Was it because of the change of residents’ interactions and for what extent had it affected the damage? To answer this question, first, we constructed a conceptual framework of 1930s and 1950s agricultural society. From which drastic changes has been detected (e.g., increase of absentee landlords, land reform) and the residents’ interactions with floods have been analyzed. Then, we reconstructed the flood inundation process of 1931 and 1954 floods with gauged rainfall dataset. After referring to the investigation report, the inundation information was applied to re-estimate the flood damage on farmland, houses, and residents. With the simulation and modification, we found that the inundated farmland of 1931 is about 83% more than former, indicating a much more severe influence on residents’ lives than we used to think. On the contrary, the total increase of influence farmland in 1954 is around 50% after modification, suggesting a relative success in reducing flood damage. To quantitatively explain it, the countermeasures during 1954 flood were estimated, showing that the reinforcement of levees in 1950s was more effective in reducing inundation area of 7%, while the construction of detention basins accounted for only 2%. Such results revealed that the countermeasures against 1954 flood being more successful than 1931. Moreover, the changes of agricultural interactions with floods have also been estimated using the potential crop production (PCP), indicating an improvement in disaster mitigation in 1954. Our results demonstrate how society changes are likely to affect the response towards natural hazards, the knowledge and method of which are expected to be applicable to many other regions and times.
Rainfall thresholds for shallow landslides triggering in El Salvador
Authors: Reyes Mario
Published: March 2022

El Salvador is a country that is geologically young in most of its territory, with steep slopes covered with unconsolidated volcanic sediments. It is frequently affected by extreme weather events and it also has the highest population density in Central America, which makes it very vulnerable to landslides. Therefore, predicting when landslides will occur it is necessary, and rainfall thresholds are a useful tool for that purpose. In this study, thresholds represented by cumulated rainfall (E, in mm) and duration (D, in hours) for shallow landslide initiation in El Salvador have been generated, with the objective of using them in the future in a national landslide early warning system. The thresholds have been delineated with the CTRL-T code (Melillo et al, 2018), which automatically reconstructs the rainfall conditions that triggered the landslides and determines thresholds at different non-exceedance probabilities. Rainfall data from an automatic rain gauge network and landslide data occurred in the period of 2004 to 2019 were used. A validation of the thresholds with the procedure introduced by Gariano et al (2015) has been conducted, using rainfall and landslide data for the year 2020. There are not previous ED thresholds at national level created for El Salvador, so a comparison with global and national thresholds from other countries was done.

References

Gariano S.L., Brunetti, M.T., Iovine, G., Melillo, M., Peruccacci, S., Terranova, O., Vennari, C., Guzzetti, F. (2015). Calibration and validation of rainfall thresholds for shallow landslide forecasting in Sicily, southern Italy. Geomorphology 228:653–665.

Melillo, M., Brunetti, M. T., Peruccacci, S., Gariano, S. L., Roccati, A., & Guzzetti, F. (2018). A tool for the automatic calculation of rainfall thresholds for landslide occurrence. Environmental Modelling & Software, 105:230-243.
A Comparative Study on Factors Affecting Thermal Response Test Analysis
Authors: Oh Hae-Rim , Park Byeong-Hak , Baek Ji-Young , Lee Kang-Kun
Published: March 2022

Accurately estimating thermal parameters of ground is important for the sustainable and efficient operation of shallow geothermal systems. A thermal response test (TRT) has been widely performed for the thermal characterization. In this study, four cases (three field tests and one laboratory test) were analyzed using four analytical models with different assumptions of heat source to investigate the influence of three factors (starting time, test duration, and data acquisition interval (DAI)) related to the experimental condition. To compare effects of each factor, the base case was established and various comparison scenarios were generated by varying the factors within specific ranges. The influence degree was demonstrated in the order of starting time, test duration, and DAI, and in particular, the starting time significantly contributed to the thermal conductivity change up to 27.18%. On the other hand, the test duration and the DAI, the other two factors, had maximum impacts of 7.32% and 1.07%. As a result, it was confirmed that the factors should be taken into account when setting the experimental condition of TRT.

Acknowledgement: This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT (MSIT) of South Korean government (No. 2017R1A2B3002119). This work was also supported by Korea Environment Industry & Technology Institute(KEITI) through "Activation of remediation technologies by application of multiple tracing techniques for remediation of groundwater in fractured rocks" funded by Korea Ministry of Environment (MOE) (Grant number: 20210024800002/1485017890). This work was also supported by the Institute for Korea Spent Nuclear Fuel (iKSNF) and National Research Foundation of Korea (NRF) grant funded by the Korean government (Ministry of Science and ICT, MSIT) (Grant number: 2021M2E1A1085200).
Extreme lake expansion on the Tibetan Plateau: Observations and consequences
Authors: Lei Yanbin , Yao Tandong , Sheng Yongwei , Yang Kun , Zhou Jing
Published: March 2022

After the considerable lake level decrease in 2015 in response to the super 2015/2016 El Niño and lake level recovery in 2016, an extreme lake expansion occurred on the central and northern TP in the following two years (2017 and 2018), in contrast with the slight lake level changes on the southern TP. In-situ observations at Zhari Namco near Cuoqing County show that lake level increased abruptly by 1.4 m and 1.7 m in summer 2017 and 2018, respectively, which was even close to the accumulated lake level increase between 2000 and 2015. At Dazeg Co near Nima Country, lake level increased by 0.9 m and 1.4 m in summer 2017 and 2018, respectively, which is about 3 times as large as the increasing rate between 2000 and 2015. At Eya Co and Cedo Caka near Shuanghu County, lake level accumulatively increased by 1.5 m and 2.0 m, respectively, in the two years. The extreme lake expansion had significant impact on geomorphology and even posed great threat on the infrastructures such as road and bridges around the lakes. Causes of the extreme lake expansion are investigated by examining precipitation data and changes in large scale circulations. 
Static Gravity Field Recovery and Accuracy Analysis Based on Reprocessed GOCE Level 1b Gravity Gradient Observations
Authors: Chen Jianhua , Zhang Xingfu , Chen Qiujie , Shen Yunzhong , Nie Yufeng
Published: March 2022

Gravity gradient observations of GOCE (Gravity field and steady-state Ocean Circulation Explorer) provide important data support for the recovery of the short-wavelength part of the static gravity field, in which the influence of time-varying gravity signals should be reduced first. In this contribution, we carried out the following investigations on the static gravity field recovered from GOCE level 1b gravity gradient observations: (1) We updated the background models and according to the IERS2010 convention to remove the time-varying signals in the gravity gradient observations, and analyzed their influence on the subsequent static gravity field recovery; (2) We set up the 300 degrees and order(d/o) GOCE gravity gradient normal equations by the direct method with the reprocessed GOCE Level 1b gravity gradient observations; (3) In order to effectively treat the influence of polar gap, we combined the 300 d/o of the GOCE gravity gradient normal equation with 180 d/o Tongji-Grace02s normal equation and the Kaula’s regularization constraints; (4) GNSS/Leveling data, quasi-geoid model and DTU marine gravity anomaly are used to validate the accuracy of our combined solution, which shows that the accuracy of it is comparable to the state-of-art GOCO06s model.