bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of mid-glacial ice sheets on deep ocean circulation and global climate
Authors: Sherriff-Tadano Sam , Abe-Ouchi Ayako , Oka Akira
Published: March 2021

This study explores the effect of southward expansion of Northern Hemisphere (American) mid-glacial ice sheets on the global climate and the Atlantic Meridional Overturning Circulation (AMOC), as well as the processes by which the ice sheets modify the AMOC. For this purpose, simulations of Marine Isotope Stage (MIS) 3 (36ka) and 5a (80ka) are performed with an atmosphere-ocean general circulation model. In the MIS3 and MIS5a simulations, the global average temperature decreases by 5.0 °C and 2.2 °C, respectively, compared with the preindustrial climate simulation. The AMOC weakens by 3% in MIS3, whereas it strengthens by 16% in MIS5a, both of which are consistent with an estimate based on 231Pa/230Th. Sensitivity experiments extracting the effect of the southward expansion of glacial ice sheets from MIS5a to MIS3 show a global cooling of 1.1 °C, contributing to about 40% of the total surface cooling from MIS5a to MIS3. These experiments also demonstrate that the ice sheet expansion leads to a surface cooling of 2 °C over the Southern Ocean as a result of colder North Atlantic deep water. We find that the southward expansion of the mid-glacial ice sheet exerts a small impact on the AMOC. Partially coupled experiments reveal that the global surface cooling by the glacial ice sheet tends to reduce the AMOC by increasing the sea ice at both poles, and hence compensates for the strengthening effect of the enhanced surface wind over the North Atlantic. Our results show that the total effect of glacial ice sheets on the AMOC is determined by the two competing effects, surface wind and surface cooling. The relative strength of surface wind and surface cooling effects depends on the ice sheet configuration, and the strength of the surface cooling can be comparable to that of surface wind when changes in the extent of ice sheet are prominent.
Environmental factors during COVID – 19 pandemic in Campinas, Brazil
Authors: Kabke Bainy Bruno , Heuminski de Ávila Ana Maria
Published: March 2021

During COVID – 19 pandemic, the main strategy to prevent virus dissemination adopted worldwide was the social distancing, in different degrees (ranging from simple recommendations to the population, to complete lockdown). In this context, many studies were performed around the world to assess the impacts of such measures on the environment, specially on air quality. The reported results almost unanimously pointed to a reduction in air contaminants, mainly as a response to vehicular traffic depletion and, at some level, to reduced human and industrial activities.  On March 24th, 2020, a partial lockdown was decreed in São Paulo state, Brazil, and since then it has undergone, back and forth, several stages of strictness according to contamination and hospitalization rates, being stricter whenever intensive care units (ICU) occupation increased. Our study aims to evaluate environmental aspects (air quality and meteorology) in Campinas city (São Paulo, Brazil), during the pandemic, from March 24th to December 31st, and compare it with the weeks prior to the social distancing and with the previous year. In addition to the environmental variables, the “social distancing index” (obtained by using mobile phone data to assess displacements) and medical data (hospital admissions and deaths) were employed to a preliminary analysis of  the influence of environmental factors on COVID – 19 evolution in the city.
An efficient physic-based event detection algorithm inspired by music information retrieval
Authors: Dokht Dolatabadi Esfahani Reza , Scherbaum Frank , Cotton Fabrice , Ohrnberger Matthias
Published: March 2021

In the last decade, the increasing number and spatial density of seismological stations provide unprecedented opportunities for recording various natural and human-related events in continuous records. Diverse methods have been proposed for event detection, classification, and characterization, but few of them are based on the physical properties of the events. In this study, inspired by music information retrieval methods such as audio fingerprinting, we present a time-efficient event detection method based on capturing the physical properties of seismic signatures such as corner frequency, high-frequency fall-off, and complexity of signature. The zero-crossing rate of the recorded signal is used to estimate the corner frequency, which is the dominant frequency in the velocity domain of record. The high-frequency fall-off can be estimated in the time-frequency spectrogram by finding the frequency below which 75% of the energy of the spectrum is produced. The complexity of the spectrum of the recorded signal is finally represented by a second-order polynomial coefficient fitting the spectrum and capturing the slope of the source spectra. Also, we use the spectral flatness to quantify the noise properties. We validate the proposed procedure to synthetic data generated by the stochastic simulation method. We finally apply the method to real data sets to detect the seismic precursors for the Nuugaatsiaq landslide. We separate the earthquake event and precursory signals because of different corner frequencies and show that the precursory signals started for hours before the main landslide.

 
Near real-time air quality forecasts using the NASA GEOS model
Authors: Knowland K. Emma , Keller Christoph , Wargan Krzysztof , Weir Brad , Wales Pamela , Ott Lesley , Pawson Steven
Published: March 2021

NASA's Global Modeling and Assimilation Office (GMAO) produces high-resolution global forecasts for weather, aerosols, and air quality. The NASA Global Earth Observing System (GEOS) model has been expanded to provide global near-real-time 5-day forecasts of atmospheric composition at unprecedented horizontal resolution of 0.25 degrees (~25 km). This composition forecast system (GEOS-CF) combines the operational GEOS weather forecasting model with the state-of-the-science GEOS-Chem chemistry module (version 12) to provide detailed analysis of a wide range of air pollutants such as ozone, carbon monoxide, nitrogen oxides, and fine particulate matter (PM2.5). Satellite observations are assimilated into the system for improved representation of weather and smoke. The assimilation system is being expanded to include chemically reactive trace gases. We discuss current capabilities of the GEOS Constituent Data Assimilation System (CoDAS) to improve atmospheric composition modeling and possible future directions, notably incorporating new observations (TROPOMI, geostationary satellites) and machine learning techniques. We show how machine learning techniques can be used to correct for sub-grid-scale variability, which further improves model estimates at a given observation site.
Bridging the water demand gap with wastewater irrigation
Authors: Gobin Anne , Boeckaert Charlotte , Coudron Willem , De Cuypere Tim , De Swaef Tom , Huits Dominique , Lootens Peter , Pollet Sabien
Published: March 2021

Water availability and using the available water in a well-considered manner is becoming increasingly more important for farmers. An increase in dry summers (Gobin, 2018) confirms that in the future irrigation will have to take place in a smart manner, particularly in the water demanding horticultural sector. In times of water scarcity, governments may issue a ban on water extraction from natural water bodies. This on-going research investigates to what extent the supply of alternative water sources, such as treated waste water from domestic use or food processing , can be used for irrigation. In addition to the availability, the quality of irrigation water determines its suitability for crop utilisation. Treated domestic waste water may contain pathogens rendering the irrigated crop unfit for fresh consumption, whereas treated waste water from food companies may contain high salt concentrations affecting soil and crop health. The water demand was investigated on wastewater irrigated field trials and on irrigated farmers’ fields. Irrigation trials with various types of treated waste water elucidated the effects of these water sources on the crop yield, crop quality and the long-term impact on the soil quality. Soil moisture sensors were combined with a crop model, satellite images and meteorological information to monitor crop growth and performance of potato, spinach and cauliflower in on-farm conditions. The regional water demand for all irrigated crops was calculated with a water balance model based on actual evapotranspiration (Zamani et al., 2015) and linked to the supply of waste water sources in an online viewer, which makes it possible to promote water coalitions in regions where the water demand is high.

Acknowledgements

The research was funded by the Flemish Agency for Innovation and Entrepreneurship in Belgium under contract agreement HBC.2017.0817. 

References

Gobin, A., 2018. Weather related risks in Belgian arable agriculture. Agricultural Systems 159: 225-236. https://doi.org/10.1016/j.agsy.2017.06.009

Zamani, S., Gobin, A., Van de Vyver, H., Gerlo, J., 2015. Atmospheric drought in Belgium - Statistical analysis of precipitation deficit. International Journal of Climatology 36(8): 3056–3071. https://doi.org/10.1002/joc.4536

 
The importance of the time response of Electrochemical Concentration Cell (ECC) ozone sondes for measurements of tropical upper tropospheric and lower stratospheric ozone
Authors: Vömel Holger , Stauffer Ryan , Selkirk Henry , Thompson Anne , Diaz Jorge Andres , Kollonige Debra , Corrales Ernesto , Alan Alfredo
Published: March 2021

Accurate measurements of ozone in the upper tropical troposphere and lower stratosphere (UTLS) are challenging for most measuring systems, yet of great importance for the understanding of the chemical and dynamical processes in this region.

Balloon-borne observations using Electrochemical Concentration Cell (ECC) ozone sondes are the most widely used in situ technology to measure vertical profiles of ozone in networks such as the Southern Hemisphere ADditional Ozonesondes (SHADOZ) network of tropical and subtropical ozone sonde stations.

The tropical upper troposphere and the layers of near-zero ozone within the ozone hole are most sensitive to processing and preparation variations that may affect the accuracy and possibly trend estimates of ozone in low ozone regions. It is now appreciated that the complex chemistry within the ECC used to detect ozone exhibits two different time constants (τfast≈20 s, τslow≈25 min), which modify the response of the ECC during a profile. Although not well understood, the chemistry of the slow reaction is likely to represent what has conventionally been assumed a constant “background current”. The fast reaction causes some delay in the response of the ECC to changes in the vertical profile of ozone. Here we show how correcting for both improves the estimate of the lowest ozone concentration in the upper troposphere as well as the steepness of the gradient in the transition into the stratosphere. The steady state bias, which describes the contribution of the slow reaction, is the largest source of uncertainty overall; the response time of the fast reaction dominates the uncertainty in the region of the sharp gradient of ozone above the tropopause.
An Aitken mode aerosol formation event in the high Arctic: evidence for aggregate breakup
Authors: Lawler Michael , Saltzman Eric , Karlsson Linn , Zieger Paul , Salter Matthew , Baccarini Andrea , Schmale Julia , Leck Caroline
Published: March 2021

The summertime high Arctic is an extremely low-aerosol region, where even small inputs of particles can have significant impacts on cloud formation and therefore on the surface energy budget. The relative importance of new particle formation from gas phase precursors and primary sea spray production in this region remains uncertain, as does the role of atmospheric transport. We made direct, time-resolved composition measurements of Aitken mode (~20-60 nm diameter) aerosol over the high Arctic pack ice in August-September 2018, including during an intense Aitken mode formation event on August 30-31. The event particles contained both primary sea spray materials (sodium, potassium, and polysaccharide-like organics) and secondary components (non-sea-salt sulfate, methanesulfonic acid, non-sea-salt iodine, and secondary organics), most of which could be quantified on the basis of analytical standards. The composition is consistent with primary sea spray that had been atmospherically processed, and the aerosol size distribution dynamics imply the action of a process by which larger atmospheric particles or aggregates broke up to form smaller particles. Hypotheses to explain the results will be discussed.
Hard as a rock? Looking for typical and atypical reference sites in the Greek network
Authors: Ktenidou Olga-Joan , Gkika Faidra , Pikoulis Erion-Vasilis , Evangelidis Christos
Published: March 2021

Although it is nowadays desirable and even typical to characterise site conditions in detail at modern recording stations, this is not yet a general rule in Greece, due to the large number and geographical dispersion of stations. Indeed, most of them are still characterised merely through geological descriptions or proxy-based parameters, rather than through in-situ measurements. Considering: 1. the progress made in recent years with sophisticated ground motion models and the need to define region-specific rock conditions based on data, 2. the move towards large open-access strong-motion databases that require detailed site metadata, and 3. that Greek-provenance recordings represent a significant portion of European seismic data, there are many reasons to improve our understanding of site response at these stations. Moreover, it has been shown recently in several regions that even sites considered as rock can exhibit amplification and ground motion variability, which has given rise to more scientific research into the definition of reference sites. For Greece, in-situ-characterisation campaigns for the entire network would impose unattainable time/budget constraints; so, instead, we implement alternative empirical approaches using the recordings themselves, such as the horizontal-to-vertical spectral ratio technique and its variability. We present examples of 'well-behaved', typical rock sites, and others whose response diverges from what is assumed for their class.

 
Including the spatial observation error correlation in data assimilation of AMSU-A radiances
Authors: Terasaki Koji , Miyoshi Takemasa
Published: March 2021

Recent developments in sensing technology increased the number of observations both in space and time. It is essential to effectively utilize the information from observations to improve numerical weather prediction (NWP). It is known to have correlated errors in observations measured with a single instrument, such as satellite radiances. The observations with the horizontal error correlation are usually thinned to compensate for neglecting the error correlation in data assimilation. This study explores to explicitly include the horizontal observation error correlation of Advanced Microwave Sounding Unit-A (AMSU-A) radiances using a global atmospheric data assimilation system NICAM-LETKF, which comprises the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) and the Local Ensemble Transform Kalman Filter (LETKF). This study performs the data assimilation experiments at 112-km horizontal resolution and 38 vertical layers up to 40 km and with 32 ensemble members.

In this study, we estimate the horizontal observation error correlation of AMSU-A radiances using innovation statistics. The computation cost of inverting the observation error covariance matrix will increase when non-zero off-diagonal terms are included. In this study, we assume uncorrelated observation errors between different instruments and observation variables, so that the observation error covariance matrix becomes block diagonal with only horizontal error correlations included. The computation time of the entire LETKF analysis procedure is increased only by up to 10 % compared with the case using the diagonal observation error covariance matrix. The analyses and forecasts of temperature and zonal wind in the mid- and upper-troposphere are improved by including the horizontal error correlations. We will present the most recent results at the workshop.
How does the soil moisture influence the surface energy fluxes? An observational study at La Herrería Forest (Central Spain)
Authors: Valverde Jorge , Román-Cascón Carlos , Yagüe Carlos , Maqueda Gregorio
Published: March 2021

This work presents the characterization and comparison of the response of evapotranspiration (ET) to variations in shallow soil moisture (SM) in three years with different precipitation regimes: 2017, 2018 and 2019, through the analysis of tower data from La Herrería site, a forest site in the foothills of the Guadarrama Mountains in Spain. The aim of this work is to improve the comprehension of the relations of these variables (ET and SM) and their dependence on rain regimes in the studied years. To assess this, monthly SM regimes are considered, with three main types: transitional, wet and dry. The study shows the highly variable response of ET to variations in SM, which depends on the three considered SM regimes. In transitional regimes, SM strongly constrains ET variability, in wet regimes, SM does not impact ET variability, and in dry regimes, SM has a small impact in ET variability, due to its small variations. In particular, the months which suit satisfactorily to these regimes are identified, such as July 2018 (transitional, r=0.73), November 2019 (wet, r=-0.27) and August 2018 (dry, r=0.36), being r the coefficient of linear correlation between ET and SM. Some months that do not fit in the proposed scheme are also identified, and they have to be analyzed independently. This research shows the need to take into account different physical processes that affect ET, the complexity in the treatment of observational (tower) data for this type of analysis, and illustrates how the election of the length of the studied period is important for this type of analysis. Hence, it should be carefully chosen, because the interpretation of the results can be different depending on this choice.
Decomposing the Critical Components of Flash Drought Using the Standardized Evaporative Stress Ratio
Authors: Basara Jeffrey , Edris Stuart , Christian Jordan , Illston Bradley , Hunt Eric , Otkin Jason , Salesky Scott
Published: March 2021

Flash droughts occur rapidly (~1 month timescale) and have produced significant ecological, agricultural, and socioeconomical impacts. Recent advances in our understanding of flash droughts have resulted in methods to identify and quantify flash drought events and overall occurrence. However, while it is generally understood that flash drought consists of two critical components including (1) anomalous, rapid intensification and (2) the subsequent occurrence of drought, little work has been done to quantify the spatial and temporal occurrence of the individual components, their frequency of covariability, and null events. Thus, this study utilized the standardized evaporative stress ratio (SESR) method of flash drought identification applied to the North American Regional Reanalysis NARR) to quantify individual components of flash drought from 1979 – 2019. Individual case studies were examined and the the drought component was assessed using the United States Drought Monitor for 2010 – 2019.   Additionally, the flash component was assessed using results of previous flash drought studies. Further, the correlation coefficient and composite mean difference was calculated between the flash component and flash droughts identified to determine what regions, if any, experienced rapid intensification but did not fall into flash drought. The results yielded that SESR was able to represent the spatial coverage of drought well for regions east of the Rocky Mountains, with mixed success regarding the intensity of the drought events. The flash component tended to agree well with other flash drought studies though some differences existed especially for areas west of the Rocky Mountains which experience rapid intensification at high frequencies but did not achieve drought designations due to hyper-aridity.
Paleomagnetic results from the western Himalaya indicate multi-stage India-Eurasia collision
Authors: Martin Craig R , Jagoutz Oliver , Upadhyay Rajeev , Royden Leigh H , Eddy Michael P , Bailey Elizabeth , Nichols Claire I O , Weiss Benjamin P
Published: March 2021

The classical model for the collision between India and Eurasia, which resulted in the formation of the Himalayan orogeny, is a single-stage continent-continent collision event at around 55 – 50 Ma. However, it has also been proposed that the India-Eurasia collision was a multi-stage process involving an intra-oceanic Trans-Tethyan subduction zone south of the Eurasian margin. We present paleomagnetic data constraining the location the Kohistan-Ladakh arc, a remnant of this intra-oceanic subduction zone, to a paleolatitude of 8.1 ± 5.6 °N between 66 – 62 Ma. Comparing this result with new paleomagnetic data from the Eurasian Karakoram terrane, and previous paleomagnetic reconstructions of the Lhasa terrane reveals that the Trans-Tethyan Subduction zone was situated 600 – 2,300 km south of the contemporaneous Eurasian margin at the same time as the first ophiolite obduction event onto the northern Indian margin. Our results confirm that the collision was a multistage process involving at least two subduction systems. Collision began with docking between India and the Trans-Tethyan subduction zone in the Late Cretaceous and Early Paleocene, followed by the India-Eurasia collision in the mid-Eocene. The final stage of India-Eurasia collision occurred along the Shyok-Tsangpo suture zone, rather than the Indus-Tsangpo. The addition of the Kshiroda oceanic plate, north of India after the Paleocene reconciles the amount of convergence between India and Eurasia with the observed shortening across the India–Eurasia collision system. Our results constrain the total post-collisional convergence accommodated by crustal deformation in the Himalaya to 1,350 – 2,150 km, and the north-south extent of the northwestern part of Greater India to < 900 km.
Geological occurrence, mineralogical character and preliminary risk assessment of carcinogenic erionite in New Zealand
Authors: Patel Janki , Brook Martin , Di Giuseppe Dario , Scognamiglio Valentina , Gualitieri Alessandro F.
Published: March 2021

Erionite is a naturally-occurring zeolite mineral that has emerged as a well-known health hazard over the last few decades. Human exposure to erionite fibers has been unequivocally linked to malignant mesothelioma, a disease also associated with inhalation of airborne asbestos. Indeed, erionite is now classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen (i.e., carcinogenic to humans), but it appears to be more toxic than asbestos. Since volcaniclastic rocks containing erionite are widely present in New Zealand, there is a concern over potential health issues following inhalation of dust particles in particular areas.  Indeed, New Zealand is one of a number of high-income countries with elevated incidence of malignant mesothelioma (2.6 per 100,000), and this has traditionally been thought to be a result of occupational exposure to airborne asbestos fibers. However, recent cases of malignant mesothelioma have emerged without a known link to asbestos exposure, and in 2015, the New Zealand Government acknowledged that erionite was a more potent carcinogen than asbestos. Despite this, there are no established occupational exposure limits for erionite in New Zealand or globally. We are currently using a multi-methodological approach, based upon field investigation, morphological characterization, scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS), Transmission Electron Microscopy (TEM), and X-ray powder diffraction (XRPD) to analyse erionite from sites around New Zealand. Preliminary results are reported here, including erionite from Miocene tuff in Auckland. The erionite appears to be erionite-K. From the dimensional analysis, 45.6% of minerals satisfied the requirements for a respirable airborne fibre (length, L ≥ 5 μm, a diameter, w ≤ 3 μm, and L/w value ≥ 3:1). The presence of this mineral is of concern for risk to human health, especially considering the land development in the Auckland region and the quarries and mining-related activities that are operating in the zeolite host rocks elsewhere in New Zealand. Thus, there is a need for a detailed risk assessment in parts of the country indicative of potential hazard. Further assessments of erionite species, quantification of the potentially respirable airborne fibers, and targeted epidemiological surveillance are planned.
Quantifying Teleconnection pathways leading to Low Rainfall anomalies during Boreal Summer in Indonesian Borneo
Authors: Lam Timothy , Kretschmer Marlene , Adams Samantha , Arribas Alberto , Prudden Rachel , Saggioro Elena , Catto Jennifer , Barciela Rosa
Published: March 2021

Teleconnections are sources of predictability for regional weather and climate, which can be represented by causal relationships between climate features in physically separated regions. In this study, teleconnections of low rainfall anomalies in Indonesian Borneo are analysed and quantified using causal inference theory and causal networks. Causal hypotheses are first developed based on climate model experiments in literature and then justified by means of partial regression analysis between NCEP reanalysis sea surface temperatures and climate indices (drivers) and rainfall data in Indonesian Borneo from various sources (target variable). We find that, as previous studies have highlighted, El Niño Southern Oscillation (ENSO) has a profound effect on rainfall in Indonesia Borneo, with positive Niño 3.4 index serving as a direct driver of low rainfall, also partially through reduced sea surface temperatures (SSTs) over Indonesian waters. On the other hand, while Indian Ocean Dipole (IOD) influences Indonesian Borneo rainfall through SSTs over the same area as a thermodynamic effect, its remaining effect has shifted at multidecadal timescale, opening the rooms for further research. This work informs the potential of a systematic causal approach to statistical inference as a powerful tool to verify and explore atmospheric teleconnections and enables seasonal forecasting to strengthen prevention and control of drought and fire multihazards over peatlands in the study region.

Keywords: Tropical teleconnections, Causal inference, Climate variability, Drought, Indonesia
Development of space-time rainfall intensity duration frequency curves based on a multifractal approach
Authors: Serrano David , Maskey Mahesh Lal , Rizo Adrian , Peñaranda Victor
Published: March 2021

Changing climate signals and urban populations' growth requires proper hydrologic risk analysis to create and operate water resource infrastructures in a sustainable way. Although modernized computational facilities are becoming popular to understand different complex systems, the scientific community is still behind in proper analysis of extreme rainfall events as they are erratic in time and space. To fill the existing knowledge gap, it becomes obvious to incorporate spatiotemporal rainfall variability in designing rainfall Intensity Duration Frequency (IDF) curves.  Many statistical approaches have been suggested to describe the space-time structure of rainfall; nevertheless, none of them is enough to represent, for all observational scales, the geometrical structure observed in either rainfall time series or rainfall-derived spatial fields. This research presents a more holistic approach to derive the IDF curves without losing information and (or) statistical assumptions.  This study uses such a promising notion to understand the rainfall field's space-time geometrical structure via codimension functions. The results show us the space-time structure of rainfall exhibits a dynamical scaling, and it suggests the idea of a double multifractal spectrum for representing time and space. Based on the idea of a double multifractal spectrum, IDF curves can be shifted to Intensity – Area – Frequency – Duration (IADF) curves to get a better approach for engineering and scientific purposes. Furthermore, this research suggests that changes of parameters for this approach could reflect climate-change signals and would be useful to generate non-stationary IADF curves and improve engineering design practices.
The influence of mesoscale atmospheric convection on local and regional infrasound propagation
Authors: Alter Ross , Swearingen Michelle , McKenna Mihan
Published: March 2021

Infrasound can propagate over a variety of spatiotemporal ranges and is therefore affected by spatiotemporally diverse atmospheric conditions.  However, studies of the influence of meteorology on infrasound propagation have historically utilized weather data that rely on point sources or coarser spatiotemporal resolutions, which often gloss over the effects of mesoscale meteorological phenomena.  In light of this knowledge gap, this study examines the influence of mesoscale meteorological features on infrasound propagation on local and regional scales.  To accomplish this task, output from simulations using the Weather Research and Forecasting (WRF) meteorological model is fed into an infrasound propagation model to generate infrasound predictions using realistic meteorological conditions.  The WRF simulations covered a range of horizontal resolutions – from 1 to 15 km – enabling an analysis of the sensitivity of the infrasound predictions to the horizontal resolution of the WRF output.  The main result is that convective precipitation events can appreciably alter the transmission loss patterns emanating from infrasonic sources, which is especially evident at finer horizontal resolutions.  This demonstrates that high-resolution weather data may be necessary to correctly simulate local to regional infrasound propagation, especially within warm-season, convective environments.

(This work was funded by the Assistant Secretary of the Army for Acquisition, Logistics, and Technology [ASA{ALT}] under 0602784/T40/46 and 0602146/AR9/01.) 

Approved for public release: distribution is unlimited.
A 10Be-dated record of glacial retreat in Connemara, Ireland, after the Last Glacial Maximum and implications for North Atlantic climate
Authors: Foreman Adrienne , Bromley Gordon , Hall Brenda , Jackson Margaret
Published: March 2021

Late Pleistocene stadials were global events, associated with weakened Asian monsoons and Atlantic Meridional Overturning Circulation (AMOC), shifts in atmospheric boundaries and precipitation belts, and warming of the Southern Hemisphere and tropics. In the Northern Hemisphere, stadials are traditionally viewed as dramatic cooling events centred on the North Atlantic, with their abrupt onset attributed to meltwater-induced suppression of the AMOC due to melting of large Northern Hemisphere ice sheets. As warmer temperatures are required for sustained meltwater input, however, there is an apparent inconsistency with this model of Northern Hemisphere stadial cooling. To investigate this inconsistency, we reconstructed the timing and nature of glacial fluctuations in Connemara, western Ireland, located within the in the North Atlantic basin, during Heinrich Stadial 1 (HS1). Fifteen internally consistent cosmogenic beryllium-10 ages of erratic boulders indicate rapid and widespread deglaciation of the former Connemara ice centre at ~17.5 ka. The apparent abruptness of ice retreat, coupled with stratigraphic correlation with geomorphic features indicative of meltwater, suggest that HS1 deglaciation was driven by enhanced melting during the summer ablation season. This interpretation supports evidence for enhanced meltwater discharge and summertime warming elsewhere in Europe during HS1 but may conflict with the traditional view of stadials as severe cooling events.
Weathering conditions of Buddhist caves dug in soft rocks and conservation attempting from the deterioration
Authors: Oguchi Chiaki , Ogawa Momoko , Sakane Kaisei , Tamura Yasuhiko
Published: March 2021

The Taya Cave, a sacred Buddhist cave, locates in the precincts of Josenji Temple in Yokohama City, central Japan. The geologic materials of the hills surrounding the cave are soft rocks composed of early Quaternary sedimentary rocks. The cave has a complex three-layer structure with a total length of 570 m. The excavation of the cave is estimated to start in the Kamakura era around A.D. 1200. Since then, the cave became a training place for Buddhists until around 19 C. There are many Buddhist reliefs on the walls and ceiling inside the cave. Because the bedrock is extremely weak, the rocks easily break when they get wet again after drying, namely prone to slaking. Thus, weathering and deterioration have progressed in various parts of the cave. Many valuable Buddhist reliefs have damaged by exfoliation. The walls at several points in the cave have also collapsed on a small scale. Therefore, it is necessary to investigate such deteriorated parts in the cave by simple non-destructive tests of physical and mechanical properties by using Silver Schmidt hammer and ultrasonic velocity test. These measurements clarified the vulnerable points even in the main worship route of the cave. In October 2018, a stainless-steel door installed at the cave entrance to save from deterioration due to slaking. The effect of the door was verified as well by monitoring the environmental conditions inside the cave. Environmental monitoring results revealed that the temperature and humidity near the entrance changed most drastically in this cave. Although the door was closed only at night, the range of maximum and minimum values ​​of temperature and humidity near the entrance became smaller after installation than before. Non-destructive measurements and in situ environmental monitoring are a useful way to assess weathering without damaging geoarchaeological sites. 
Asking questions of data in nonlinear geophysical inversion
Authors: Sambridge Malcolm
Published: March 2021

For more than half a century, geoscientists have sought new ways to solve inverse problems, which occur when observations only indirectly constrain some property of interest. In the case of geophysics this usually means using surface observations to quantify properties of the Earth hidden from us within its interior, or processes which occurred in the past. Both the target is not directly accessible, and measurements which constrain it are not completely under our control. This is a challenging situation, where the search for new efficient and practical methods of solution to inversion problems has received regular attention.

A convenient way to view inverse problems as a way of asking questions of data. A common class of question might be to ask `Which set of model parameters, within a chosent class, fits a subset of the data best?’  How one measures `best fit’ constitutes a fundamental component of the question being asked. Another example might be `Which probability distribution best describes a `state of knowledge’ about a set of representative parameters?’. As the question changes, naturally so does the solution, even if the data does not. This talk will examine this approach to inversion and explore some new forms of question that can be asked of data. In particular, cases will be examined where the same answer can arise from different style of questions, some of which are much easier to solve than others. A focus will be on optimal model generation in nonlinear cases using data questions based on mathematical ideas from the field of Optimal Transport.

 
Observing and quantifying ocean flow properties using drifters with drogues at different depths
Authors: Rypina Irina I. , Getscher Timothy R. , Pratt Larry J. , Mourre Baptiste
Published: March 2021

We present analyses of drifters with drogues at 1, 10, 30 and 50 m, which were deployed in the Mediterranean Sea to investigate subduction and upwelling processes. Drifter trajectories were used to estimate divergence, vorticity, vertical velocity, and finite-size Lyapunov exponents (FTLEs), and to investigate the magnitudes of terms in the vertical vorticity equation. The divergence and vorticity are O(f) and change sign along trajectories. Vertical velocity is O(1 mm/s), is larger at depth, indicates predominant upwelling with isolated downwelling events, and sometimes changes sign between 1 and 50 m. Vortex stretching is one of, but not the only, significant term in the vertical vorticity balance. 2D FTLEs are 2x10^(-5) 1/s after 1 day, about twice larger than in a 400-m-resolution numerical model. 3D FTLEs are 50% larger than 2D FTLEs and are dominated by the vertical shear of horizontal velocity. Bootstrapping-based uncertainty for both divergence and vorticity is ~10% of the time-mean absolute values. Simulated drifters in a model suggest that drifter-based divergence and vorticity are close to true model values, except when drifters get aligned into long and narrow filaments. Drifter-based vertical velocity is close to true values in the model at 1 m but differs from the true model values at deeper depths. The errors in the vertical velocity are largely due to the lateral separation between drifters at different depths, and partially due to having drifters at only 4 depths. Overall, multi-level drifters provided useful information about the 3D flow structure.
3-D tomographic observations of Rossby wave breaking over the Northern Atlantic during the WISE aircraft campaign in 2017
Authors: Krasauskas Lukas , Ungermann Jörn , Preusse Peter , Friedl-Vallon Felix , Zahn Andreas , Ziereis Helmut , Rolf Christian , Plöger Felix , Konopka Paul , Vogel Bärbel , Riese Martin
Published: March 2021

We present measurements of ozone, water vapour and nitric acid in the upper troposphere/lower stratosphere (UTLS) over North Atlantic and Europe. The measurements were acquired with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the Wave Driven Isentropic Exchange (WISE) campaign in October 2017. GLORIA is an airborne limb imager capable of acquiring both 2-D data sets (curtains along the flight path) and, when the carrier aircraft is flying around the observed air mass, spatially highly resolved 3-D tomographic data. We show a case study of a Rossby wave (RW) breaking event observed during two subsequent flights two days apart. RW breaking is known to steepen tracer gradients and facilitate stratosphere-troposphere exchange (STE). Our measurements reveal complex spatial structures in stratospheric tracers (ozone and nitric acid) with multiple vertically stacked filaments. Backward trajectory analysis is used to demonstrate that these features are related to several previous Rossby wave breaking events and that the small-scale structure of the UTLS in the Rossby wave breaking region, which is otherwise very hard to observe, can be understood as stirring and mixing of air masses of tropospheric and stratospheric origin. It is also shown that a strong nitric acid enhancement observed just above the tropopause is likely a result of NOx production by lightning activity. The measurements showed signatures of enhanced mixing between stratospheric and tropospheric air near the polar jet with some transport of water vapour into the stratosphere. Some of the air masses seen in 3-D data were encountered again two days later, stretched to very thin filament (horizontal thickness down to 30 km at some altitudes) rich in stratospheric tracers. This repeated measurement allowed us to directly observe and analyse the progress of mixing processes in a thin filament over two days. Our results provide direct insight into small-scale dynamics of the UTLS in the Rossby wave breaking region, witch is of great importance to understanding STE and poleward transport in the UTLS.
Identification of hotspots of flood risk in High Mountain Asia region based on geomorphology and climate data
Authors: Khanam Mariam , Sofia Giulia , Nikolopoulos Efthymios I. , Anagnostou Emmanouil N.
Published: March 2021

High Mountain Asia (HMA) has the most complex terrain with active hydrologic and geomorphologic processes. Climate change has expedited glacial melt and altered monsoon rain intensity. This has increased flood vulnerability across the region. There have been a few initiatives to measure the vulnerability locally. However, to identify hotspots of flood risk across the region, investigation of the entire HMA region is necessary. Unfortunately, in ungauged basins, the use of traditional floodplain mapping techniques is prevented by the lack of the extensive data required. The present work aims to provide a remote sensing-based flood-risk assessment model that maps and quantifies susceptibility in flood-prone areas. We developed a procedure for floodplain delineation based on high-resolution terrain data and a geomorphic classifier, coupled with satellite-derived extreme rainfall quantiles, and records of past flood events. For this work, we used the unique 8-meter Digital Elevation Models (DEMs) for HMA that are available at the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC). The geomorphic classifier is based on the Hydraulic Scaling Function automatically derived from the DEM, which is used to normalize topography according to the ratio between the local elevations along the drainage network and the riverbanks.  We assess the flood risk hot spots for a specific year based on the spatial distribution of flood losses, drainage density, flood-prone areas, and rainfall. This local flood-risk assessment framework, gradually applied across the entire HMA domain, will increase the awareness of flood risk, towards improved measures for flood risk reduction.
Aggravated water deficit in the Loess Plateau of China as indicated by the soil available water content
Authors: Zhang Xiao , Zhao Wenwu , Wang Lixin , Pereira Paulo
Published: March 2021

The soil available water content (AWC) has a strong ability to indicate the soil water conditions under different land cover types. Although the AWC has long been calculated, soil water characteristic curve estimation models and the distribution of AWC, as well as the impact factors, have rarely been evaluated in the Loess Plateau of China. In this study, four typical land cover types were selected: introduced shrubland, introduced grassland, natural restored shrubland and natural restored grassland. Four widely used models were compared with the van Genuchten (VG) model, including the Arya and Paris (AP) model, Mohammadi and Vanclooster (MV) model, Tyler and Wheatcraft (TW) model, and linear fitting (LF) model to estimate the wilting point. The distribution of AWC and the relationships with environmental factors were measured and analyzed. The results showed the following: (1) the MV model was the most suitable model to estimate the soil water characteristic curve in the Loess Plateau; (2) the factors impacting the AWC varied under different precipitation gradients, and the area with a mean annual precipitation of 440-510 mm was the most sensitive zone to environmental and vegetation factors; and (3) the soil water deficit was more severe when considering AWC than when considering soil water content (SWC), and the water deficits were different under introduced grassland and introduced shrubland. Consequently, the construction of vegetation restoration should be more cautious and consider the trade-off between soil conservation and water conservation. During restoration, policy makers should focus on the AWC in addition to the SWC to better assess the soil moisture status.        
Assessing groundwater management sustainability of coastal cities by utilizing the City Blueprint Approach 
Authors: Lee Khawon , Chang Sun Woo , Park Jeryang
Published: March 2021

    Groundwater is the largest freshwater resource available on Earth, and many coastal regions are depending on groundwater as a primary freshwater source. For example, in Busan and Incheon, two of the largest coastal cities in South Korea, 5.7% and 7.0% of freshwater uses are from groundwater while only 1.8% is from groundwater in Seoul, the capital of the country. Globally, groundwater availability is diminishing primarily by population increase, and especially in coastal regions, this problem is exacerbated by overexploitation and seawater intrusion, which causes groundwater contamination and further reduces its availability. Here, we view the groundwater system and its management for sustainability as a complex problem that is associated with various social, economic, and environmental factors. By adopting the City Blueprint Approach (CBA), which has been used extensively for assessing the sustainability of integrated water management of numerous cities on the globe, we identify water management factors that potentially have direct and indirect links and feedbacks with groundwater variables. We selected Busan and Incheon as case studies for coastal cities that are facing the risk of groundwater salinization by seawater intrusion. This study aims to 1) assess City Blueprint (CB) of selected coastal cities, 2) identify major factors for coastal groundwater management through correlation analysis, and 3) suggest management options regarding identified factors for sustainable groundwater management of the study areas. Our results on CB indicate that the groundwater quality and quantity of the selected cities are currently in ‘good’ status. Also, from the correlation analysis, we identified heat risk and freshwater scarcity as the major factors that potentially can affect groundwater quantity. For groundwater quality, the factors of voice and accountability, regulatory quality, and rule of law and control of corruption, most of which had not been explicitly considered for groundwater management, were identified as the major factors. Some of these factors were assessed from ‘little concern’ to ‘very concern’ for both cities. These results indicate that, regarding the linkages between groundwater variables and other factors in concern, more actions beyond environmental factors should be taken for sustainable groundwater management. This study helps to understand how non-conventional factors could contribute to coastal groundwater, and can provide extensive options for sustainable groundwater management.

 

Acknowledgement: This research was supported by the Development program of Minimizing of Climate Change Impact Technology through the National Research Foundation of Korea (NRF), funded by the Korean government (Ministry of Science and ICT) (NRF-2020M3H5A1080775).