bluuebunny/crossref_metadata_2025 huggingface dataset:
A Linear Inverse Model of Tropical and South Pacific Seasonal Predictability
Authors: Lou Jiale , O'Kane Terence , Holbrook Neil
Published: March 2020

A multivariate linear inverse model (LIM) is developed to demonstrate the mechanisms and seasonal predictability of the dominant modes of variability from the tropical and South Pacific Oceans. We construct a LIM whose covariance matrix is a combination of principal components derived from tropical and extra-tropical sea surface temperature, and South Pacific Ocean vertically-averaged temperature anomalies. Eigen-decomposition of the linear deterministic system yields stationary and/or propagating eigenmodes, of which the least damped modes resemble the El-Niño Southern Oscillation (ENSO) and the South Pacific Decadal Oscillation (SPDO). We show that although the oscillatory periods of ENSO and SPDO are distinct, they have very close damping time scales, indicating the predictive skill of the surface ENSO and SPDO is comparable. The most damped noise modes occur in the mid-latitude South Pacific Ocean, reflecting atmospheric eastward-propagating Rossby wave train variability. We argue that these ocean wave trains occur due to the atmospheric high-frequency variability of the Pacific South American pattern imprinting onto the surface ocean. The ENSO spring predictability barrier is apparent in LIM predictions initialized in Mar-May (MAM) but nevertheless displays significant correlation skill of up to ~3 months. For the SPDO, the predictability barrier tends to appear in June-September (JAS), indicating remote but delayed influences from the Tropics. We demonstrate that subsurface processes in the South Pacific Ocean are the main source of decadal variability, and further that by characterizing the upper ocean temperature contribution in the LIM the seasonal predictability of both ENSO and the SPDO variability is increased.
Evidence for a Wet Martian Interior from Magnetic Sounding with the InSight Magnetometer
Authors: Yu Yanan , Russell Christopher , Fillingim Matthew , Banerdt William
Published: March 2020

The martian magnetic field oscillates at frequencies from once per day to periods of only 100s of seconds. The interior of Mars is electrically conducting, and the time-varying magnetic fields create induced currents in the electrically conducting subsurface of Mars. The diurnal periods are little affected by the interior conductivity, but at periods shorter than about 1000 sec, the reflection of the magnetic wave energy is strong, and the vertical component of the oscillating magnetic field approaches zero as the frequency increases. Electromagnetic waves at the shorter (<1000s) periods are produced by the nighttime currents such as those flowing on and within the Mars magnetotail. These fluctuations are weak in the vertical component of the waves associated with the restriction of the currents to flow horizontally as the wave period grows shorter. This phenomenon is also seen on Earth and has been well characterized there. The measure of the attenuation of the vertical component is referred to as the skin depth. The attenuation observed at the InSight landing site is consistent with a skin depth of 3.4 km for the expected conductivity of terrestrial seawater. We have not seen any variation of this skin depth with season. These observations are consistent with the many manifestations of the occasional presence of water on or near the surface of Mars and strengthen the case for permanent water in the soil only several kilometers beneath the surface.
Mapping Cretaceous Seafloor Fabric: A Changing View of the Equatorial Ellice Basin
Authors: Wessel Paul , Benyshek Elizabeth , Taylor Brian
Published: March 2020

The plate tectonic revolution and decipherment of magnetic isochrons that followed the pioneering work of Marie Tharp and coworkers in visualizing the seafloor has led to a near-complete understanding of the first-order evolution of global seafloor spreading.  However, lagging behind in exploration and understanding are areas of seafloor formed during the Cretaceous Normal Superchron (CNS, 121-83 Ma) when no magnetic reversals were recorded to guide investigators.  Thus, for such regions tectonic interpretations are largely driven by mapping and identifying seafloor fabric indicators such as fracture zones, abyssal hills, rift propagators, and extinct spreading centers.  Here, we focus on the relict spreading system of the Cretaceous Ellice Basin that was apparently formed by seafloor spreading that split the world’s single largest oceanic plateau Ontong Java Nui, composed of present day Ontong Java, Manihiki and Hikurangi plateaus and other (now subducted) fragments.  We examine what was known about this basin from historical single and multibeam bathymetry, what was revealed by the advent of satellite altimetry, and why bathymetric mapping is still required to infer short-length-scale tectonic fabric.  High-resolution bathymetric data from the central basin were recently acquired by the University of Hawaii’s vessel R/V Kilo Moana. Evolution of the spreading system is characterized by three main stages of spreading based on directional and morphological analyses of the seafloor fabric indicators identified from bathymetry.  Spatially conjugate points symmetric about the spreading central zone were identified at the establishment and cessation of each spreading stage and were assumed to be of the same age to form pseudo-isochrons. Pseudo-isochrons were then utilized in reconstructing the basin through time.  The earliest Stage 1 fracture zones trend E-W and consist of multiple closely spaced, parallel fault strands that were indistinguishable in satellite altimetry.  A clockwise rotation of the spreading direction led to Stage 2 NW-SE trending fracture zones, which splayed from Stage 1 multistrands. An offset between Stage 2 fracture zones indicates a short-lived late Stage 3 that appears to be the result of a counter-clockwise rotation of the spreading direction shortly before spreading ceased.  Seafloor evidence for the initial breakup and rifting between Ontong Java and Manihiki plateaus prior to Stage 1 has yet to be mapped.  Basaltic rocks dredged from selected locations along the survey track promise to provide tighter temporal constraints on the evolution of Ellice Basin.
Deep crustal structure in the Taiwan-Ryukyu arc-trench system junction area: determined from gravity modeling
Authors: Doo Wen-Bin , Wang Hsueh-Fen , Huang Yin-Sheng , Lo Chung-Liang , Wang Shiou-Ya , Kuo-Chen Hao
Published: March 2020

Arc-continent collision and post-orogenic extension are both currently in progress in different parts of the Taiwan mountain belt. In particular, the junction of eastern Taiwan and the southernmost Ryukyu arc-trench system is a complex tectonic region where the Philippine Sea Plate (PSP) changes from overriding the Eurasian Plate (EUP) to subducting beneath the EUP. The Taiwan Integrated Geodynamic Research (TAIGER) program collected two wide-angle and multi-channel seismic transects (T5 and T6) across the Taiwan mountain belt and the western end of the Ryukyu arc-trench system, which provide good constraints on the seismic velocity structure of the crust. However, due to the resolution problems, the detailed deep structures are not fully understood, especially offshore eastern Taiwan and in the southernmost Ryukyu fore-arc area, where seismic activity is frequent. In this study, we perform 2-D gravity modeling along these two P-wave (Vp) transects, which not only helps to reduce the non-unique problem but also provides a possible solution for the deeper structures where the velocity model is not well constrained. Conversion of the P-wave velocity to density allows us to model the gravity anomaly and then provide a likely density model for the study area. Gravity modeling along profile T5 shows relatively high-density (3.10 g/cm3) material beneath eastern Taiwan under the Longitudinal Valley between the Central Range and the Coastal Range. The source of this high-density material could be serpentinized mantle, with serpentinization caused by the dehydration of the subducting Eurasian Plate. Along profile T6, the revised density model indicates that the subducting Gagua Ridge has a deep crustal root and extends northward to the Ryukyu fore-arc area.
Check dam is an effective engineering for soil and water conservation, carbon sequastration on the Loess Plateau of China
Authors: Li Peng , Yu Kunxia , Xiao Lie
Published: March 2020

Check dam is widely used in the soil erosion control in the gully on the Loess Plateau of China. Check dam has significant effects in sedimentation, erosion control, land formation, water storage, and vegetation restoration. This result shows that the main dams and medium-sized dams on the Loess Plateau had deposited 5.12 million tons of sediment by the end of 2011, reducing sediment transportation to the Yellow River. The check dam system decreases the probability of gravity erosion. Check dams increases cropland in the gully-hilly area of the Loess Plateau, thus increases grain production. The check dam project is a carbon pool. On the Loess Plateau, 123 million tons of soil carbon is storaged in the check dam, accounting for 17.08% of the carbon sequestration in afforestation projects in China from 1994 to 1998. Check dam construction increases regional vegetational coverage, and the NDVI in the Dali River watershed increased by 28.4% after the dam project. The results provide a scientific basis for the assessment of the eco-environmental benefit of check dam on the Loess Plateau of China.
Impact of Economic Development Levels and Disaster Types on the Short-Term Macroeconomic Consequences of Natural Hazard-Induced Disasters in China
Authors: Tang Rumei , Wu Jidong , Ye Mengqi , Liu Wenhui
Published: March 2020

The relationship between natural hazard-induced disasters and macroeconomic growth has been examined widely on global and national scales, but little research has been focused on the subnational level, especially in China. We examined the impacts of natural hazard-induced disasters on the regional growth in China based on subnational panel data for the period from 1990 to 2016. First, we used the number of people affected and the direct economic losses as the measures of the scale of disasters. Then, we used the direct damages of meteorological disasters and earthquakes as disaster measures separately to examine the impacts of different disaster types. Finally, we performed intraregional effects regressions to observe the spatial heterogeneity within the regions. The results show that the adverse short-term effects of disasters is most pronounced in the central region, while the direct damage of disasters is a positive stimulus of growth in the whole of China. However, this stimulus is observed in a lagged way and is reflected differently meteorological disasters in central and eastern China and earthquakes in western China are related to regional growth. The results demonstrate that the short-term macroeconomic impacts of these disasters in the three geographical regions of China largely depend on regional economic development levels and the disaster types.
Revisiting the statistical scaling of peak annual discharges with respect to the basin size in the light of rainfall climatology
Authors: Perdios Anastasios , Langousis Andreas
Published: March 2020

Over the years, several studies have been carried out to investigate how the statistics of peak annual discharges vary with the size of basins, with diverse findings regarding the observed type of scaling (i.e. simple scaling vs multiscaling), especially in cases where the data originated from regions with significantly different hydroclimatic characteristics. In this context, two important questions arise: a) how rainfall climatology affects the scaling of peak annual discharges, and b) how one can effectively conclude on an approximate type of statistical scaling of annual discharge maxima with respect to the basin size. The present study aims at addressing these two questions, using daily discharges from 805 catchments located in different parts of the United Kingdom, with at least 30 years of recordings. In doing so, we isolate the effects of the catchment area and the local rainfall climatology, and examine how the statistics of the standardized discharge maxima vary with the basin scale. The obtained results show that: a) the local rainfall climatology is an important contributor to the observed statistics of annual peak discharges, and b) when the effects of the local rainfall climatology are properly isolated, the scaling of the standardized annual discharge maxima with the area of the catchment closely follows that of the underlying rainfall process, deviating significantly from the simple scaling rule. The aforementioned findings explain to a large extent the diverse results obtained by previous studies in the absence of rainfall information, shedding light to the approximate type of scaling of peak annual discharges with the basin size.
Occurrence of gas hydrate in the Chukchi plateau, Arctic
Authors: Jin Young Keun , Kang Seung-Goo , Jang Ugeun , Kim Sookwan , Choi Yeonjin , Kim Ji-Hoon , Kim Young-Gyun , Lee Dong-Hun , Lee Young-Mi
Published: March 2020

The Arctic MArine Geoscience Expedition (AMAGE) program led by the Korea Polar Research Institute (KOPRI) is a multidisciplinary undertaking to investigate the geological environment and methane release phenomena in the Arctic seas. The icebreaking research vessel (IBRV) Araon has carried out three expeditions in the Chukchi Plateau (CP) and the East Siberian Seas in 2016, 2018 and 2019. In the first 2016 expedition, a chain of topographic mounds (with the height of several tens meters and the width of hundreds meters) was identified by subbottom profiler and multibeam bathymetric survey in the western continental slope of the CP. Gas hydrate samples were first retrieved in the Araon Mound-6 among the mound structures in the CP and ESS areas during the expedition. The detailed morphology and subsurface structures of the mounds were mapped from the subsequent expeditions in 2018 and 2019. More gas hydrate samples were obtained in the Araon Mound-3 and Araon Mound-6 in these expeditions. To examine gas hydrate occurrence conditions, we conducted geophysical surveys including seismic (sparker in 2018 and multi-channel in 2019) and heat flow methods during these expeditions. The seismic profiles obtained using two seismic methods show very well-developed bottom simulating reflectors (BSRs) which are widespread on the western slope of the study area. The BSR depths detected on the seismic profiles are well coincided with the depths of the lower boundary of the gas hydrate stability zone calculated from the geothermal gradient of heat flow measurement.

Arctic gas hydrates are considered to be vulnerable to the ongoing rapid Arctic warming. The AMAGE program will provide comprehensive understanding on poorly-known gas hydrate in the Arctic in the various research fields of geology, geophysics, geochemistry, biogeoscience, and oceanography.
Impact of ship emission controls recorded by cloud properties
Authors: Gryspeerdt Edward , Smith Tristan , O'Keefe Eoin , Christensen Matthew , Goldsworth Fraser
Published: March 2020

The impact of aerosols on cloud properties is one of the largest uncertainties in the anthropogenic forcing of the climate system. As large, isolated sources of aerosol, ships provide the ideal opportunity to investigate aerosol-cloud interactions. However, their use for quantifying the aerosol impact on clouds has been limited by a lack on information on the aerosol perturbation generated by the ship.

In this work, satellite cloud observations are combined with ship emissions estimated from transponder data. Using over 17,000 shiptracks during the implementation of emission controls, the central role of sulphate aerosol in controlling shiptrack properties is demonstrated. Meteorological factors are shown to have a significant impact on shiptrack formation, particularly cloud-top relative humidity. Accounting for this meteorological variation, this work also demonstrates the potential for satellite retrievals of ship sulphate emissions, providing a pathway to the use of cloud observations for monitoring air pollution.
Drivers of water exchange in the ORUST fjord system
Authors: Brunnabend Sandra-Esther , Axell Lars , Garcia-Jove Maximo , Arneborg Lars
Published: March 2020

The Orust fjord system, located on the west coast of Sweden, has openings on both ends and consists of several fjords that are connected by narrow and shallow channels. The fjord system includes the islands Orust and Tjörn as well as various smaller islands. The water exchange between the Kattegat and the different fjords is influenced by different factors, such as winds, tides, and density gradients. However, advection between the open sea and the complex fjord system are not yet well understood as lower resolution ocean models cannot resolve the small scale structures of the fjords and their connections. In addition, observations are rather sparse.

Therefore, the water exchange in the Orust fjord system is simulated using a high resolution (50 meter) NEMO3.6 ocean model setup, forced with the UERRA atmospheric reanalysis dataset. The lateral open boundary conditions for temperature, salinity, sea levels and velocities are provided by a low resolution (1.85 km) NEMO3.6 simulation, which spans the Baltic Sea and North Sea regions.

The model results are validated by comparison of modelled temperature, salinity, velocities and sea surface height with in-situ measurements. A detailed analysis of the different drivers of modelled water exchange between the Kattegat and the fjord system as well as between the different basins is presented. In general, the modelled water properties of the near surface layer in the fjord system are influenced by the Skagerrak surface water, which is controlled by the prevailing northward flowing Baltic Sea water. However, the residence times of water masses below the sill level are longer than the ones of the surface water masses as dense inflows of Skagerrak water in the basins create a strong stratification leading to weak vertical exchange.
Drought-forced tree morphological changes facilitate trubs in a semiarid region
Authors: Dai Jingyu , Liu Hongyan , Wang Yongcai , Guo Qinghua
Published: March 2020

Semiarid forests characterized by the presence of “trub” species, which have short heights but large canopy sizes, can maintain a high carbon sequestration rate. By integrating terrestrial laser scanning (TLS), we quantified drought-forced tree morphological variation along a precipitation gradient; annual precipitation (MAP) explained 70.3% of variation in tree height (Height) but did not explain the variation in canopy area (CA). Theoretical CA-Height relationships widely adopted by dynamic global vegetation models (DGVMs)  matched only the 5th percentile of our results, which is problematic for simulating carbon sequestration of open forests in semiarid regions. The trend toward “trubs” under a drying climate implies two decoupled functions of stems, mechanical stability and hydraulic efficiency, and can be an important strategy for trees to balance water and carbon. Our results demonstrate the importance of tree morphological studies for both tree environment-acclimation strategies and the improvement of DGVMs.
Continuous components of solar activity oscillation spectrum and forecasting of solar activity
Authors: Sokoloff Dmitry , Frick Peter , Stepanov Rodion , Stefani Frank
Published: March 2020

Spectrum of solar activity oscillations contains apart from the well-known 11-year activity cycle a continuous component, which includes, in particular, quasy-biennual oscillations as well as long-term oscillations including so-called Gleisberg cycle.  We suggest to consider the mid-term solar variability in terms of statistical dynamic of fully turbulent systems, where solid arguments are required to accept an isolated dominant frequency in a continuous (smooth) spectrum. What about the timescales longer than the Schwabe cycle, we consider them as a presence of long-term memory in solar dynamo and discuss statistical test for veryication of this interpretation. Sequences for statistical long-term forecast of solar activity are discussed.
Heavy Metal City-Zen. Exploring the potential risk of heavy metal contamination of food crop plants in urban gardening contexts using a citizen science approach.
Authors: Ziss Elisabeth , Friesl-Hanl Wolfgang , Noller Christoph , Watzinger Andrea , Hood-Nowotny Rebecca
Published: March 2020

Urban Gardening has become increasingly popular globally in the past two decades as urbanites begin to recognise the benefits of growing their own food and the sense of community these gardening activities engender. These activities grow as citizens reclaim derelict land and are increasingly using roof top gardens and novel containers, providing much needed green oases in the city, concepts which are particularly popular with the “share” generation. However, many such sites are in areas of high traffic density, on brown field sites or on sites overlying landfill, as a result of their urban location. The proximity to such sites may lead to worries about the food safety and reduction of the adoption of such healthy urban gardening practices. One of the main concerns is the transfer of urban pollutants into the consumer’s food chain. Trace metals are one of the contaminants frequently found in urban crops and soils. Perceived concerns about the effects of these heavy metal contaminants on human health often outweigh the true risk; part of the problem is the lack of data in the urban production context. Moreover, collection of city-wide data on the health of the soil is often difficult and expensive to collect. In this project we intend to attempt to overcome these issues by recruiting citizens to conduct simple common collaborative experiments in their urban gardens, from these data we will create a city map of soil health status and providing information on potential risk of heavy metal contaminants and ways in which to mitigate those risks in an Urban Gardening context. We chose a citizen science approach in this project, not only as it will allow us to gather a wealth of data but also it will empower us to jointly generate useful information for the greater public good which can contribute towards creating green sustainable cities.

This project will place the citizen at the heart of the experimental process in contrast to more traditional observational data collection. Using an experimental approach really exposes the citizens to the scientific process and enables them to gain tacit knowledge of how scientists overcome variance, bias and arrives at scientifically sound evidence based conclusions. As a result, citizen science can provide reassurance to the public about the rigour and process of scientific enquiry. In doing so it can inspire confidence and understanding of the nuances of political bias; putting contextual knowledge together, in learning by doing.
Identifying buildings at risk and pedestrian travel times to safety areas in a debris flow worst-case scenario
Authors: Melo Raquel , Zêzere José Luís , Oliveira Sérgio , Garcia Ricardo , Oliveira Sandra , Pereira Susana , Piedade Aldina , Santos Pedro , van Asch Theo
Published: March 2020

During the last two centuries, several debris flow events occurred in the upper part of the Zêzere valley, which is located in the Estrela mountain, in Central Portugal. These events were responsible for material damage as well as for the loss of lives. Given the susceptibility of this area to the occurrence of debris flows, a methodology for pedestrian evacuation modelling was implemented, in order to identify buildings at risk and pedestrian travel times to safety areas in a debris flow worst-case scenario. Starting from a dynamic run-out model, developed in previous works, the potential debris flow intensity was estimated (e.g. flow depth, velocity and run-out distance). Sequentially, the buildings potentially affected by the impact of debris flows, as well as the ones where the evacuation would take longer than the debris flows arrival, were identified. In addition, the potentially exposed population was estimated by applying a dasymetric distribution to each residential building. This population distribution took into account the identification of the older residents as the most exposed to debris flows, which is critical to develop reliable pedestrian evacuation travel time scenarios. The pedestrian evacuation modelling was performed using the Pedestrian Evacuation Analyst, a GIS tool developed by the United States Geological Survey. The evacuation modelling was based on an anisotropic approach, which considers the influence of slope direction on travel costs, thus its application is suitable in a mountainous area. The implemented methodology is a critical step towards the implementation of a reliable early warning system to debris flows that can be reproduced elsewhere.

Funding information: This work was financed by national funds through FCT—Portuguese Foundation for Science and Technology, I.P., under the framework of the project BeSafeSlide—Landslide Early Warning soft technology prototype to improve community resilience and adaptation to environmental change (PTDC/GES-AMB/30052/2017) and by the Research Unit UIDB/00295/2020. Pedro Pinto Santos is funded by FCT through the project with the reference CEEIND/00268/2017.
First direct monitoring and time-lapse mapping starts to reveal how a large submarine fan works
Authors: Talling Peter , de Silva Jacinto Ricardo , Baker Megan , Pope Ed , Heijnen Maarten , Hage Sophie , Heerema Catherina , Simmons Stephen , McGhee Claire , Ruffell Sean , Hasenhündl Martin , Apprioual Ronan , Ferrant Anthony , Urlaub Morelia , Cartigny Matthieu , Clare Michael , Parsons Daniel , Dennielou Bernard , Gaillot Arnaud , Peirce Christine
Published: March 2020

Turbidity currents form many of the largest sediment accumulations, longest channels, and deepest canyons on our planet. These seabed sediment avalanches can be very (> 10 m/s) fast, runout for hundreds of kilometres, and break seabed cables that now form the backbone of the internet and global data transfer. It was once thought that detailed monitoring of turbidity currents in action was impractical, ensuring these flows were relatively poorly understood. However, a series of recent projects have used new approaches and technology to show how these flows can be measured in shallow water (< 2 km) settings, such as Monterey Canyon and Canadian fjords, where flows ran out for < ~50 km and had speeds of up to 8 m/s. Here we present initial results from an ambitious project to measure active flows that runout for >1,000 km to form a major submarine fan in the deep ocean. The project studies the Congo submarine canyon-channel system that extends for ~1,100 km from the mouth of the Congo River, offshore West Africa. Monitoring in 2010 at a single site in the upper Congo Canyon had previously shown that flows are active for ~30% of the time, and reach speeds of up to 3 m/s. In this new project, direct flow monitoring at 11 sites are being combined with detailed time-lapse mapping and coring of flow deposits, through a series of 4 or 5 major research cruises from 2019 to 2023. Here we present initial results from the first of these cruises (JC187) in August-to-October 2019, which placed 11 moorings with sensors at water depths of 1.6 to 5.5 km. The presentation will initially focus on the geomorphology of the channel system, and how it varies down-slope and through time. For example, it is apparent that a landslide partly blocked one location in the upper canyon in the last 20 years, causing meander bend cut-off and sediment ponding. The talk will then discuss models for how submarine channel bends evolve, and the implications for channel deposits. Recent work in sandy submarine channels suggests that they can be dominated by very fast-moving knickpoints (waterfall like features). However, the much muddier Congo channel displays well-developed meander bend bars for which cores are available. We therefore start to show how muddy deep-sea channels may differ in significant ways from their sandier cousins in shallow water. 
Variability and Trends of Surface Solar Radiation in Europe based on satellite- and surface-based data
Authors: Pfeifroth Uwe , Trentmann Jörg
Published: March 2020

The EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF) generates satellite-based  high-quality climate data records, with a focus on the global energy and water cycle. The new concept of Interim Climate Data Records (ICDRs) that extent the fixed-length Climate Data Records (CDRs) into 'near-realtime' in a consistent way, enables climate monitoring at a higher level of accuracy.

It has been found in recent studies based on surface and satellite data that on average SSR has been increasing in the last 3 decades in Europe (e.g. Sanchez-Lorenzo et al. 2017, Pfeifroth et al. 2018) - especially in spring and summer. Here we use the latest SARAH-2.1 TCDR (1983-2017), potentially together with its corresponding ICDR (2018 onwards), to analyze if the found positve trends in SSR are about to continue. In this respect, the satellite-based data record will be compared and validated with surface measurements given by the Baseline Surface Radiation Network (BSRN), the  World Radiation Data Center (WRDC) and the Global Energy Balance Archive (GEBA). A reasonable line of potential reasons for the found spring and summertime brightening in Europe is discussed.
The global extent of artificial light pollution in the marine environment
Authors: Smyth Tim , Davies Thomas , McKee David
Published: March 2020

Coastlines globally are increasingly being illuminated with Artificial Light At Night (ALAN) from various urban infrastructures such as houses, offices, piers, roads, ports and dockyards. Artificial sky glow can now be detected above 22% of the world’s coasts nightly and will dramatically increase as coastal human populations more than double by the year 2060. One of the clearest demonstrations that we have entered another epoch, the urbanocene, is the prevalence of ALAN visible from space.

Photobiological life history adaptations to the moon and sun are near ubiquitous in the surface ocean (0-200m), such that cycles and gradients of light intensity and spectra are major structuring factors in marine ecosystems. The potential for ALAN to reshape the ecology of coastal habitats by interfering with natural light cycles and the biological processes they inform is increasingly recognized and is an emergent focus for research.

In this paper we derive a methodology to quantify and map the depths to which biologically relevant ALAN penetrates in the marine environment.  We use two satellite derived global datasets to achieve this: an artificial night sky brightness world atlas (Falchi et al., 2016) and an in-water Inherent Optical Property (Lee et al., 2002) dataset derived from ESA’s Ocean Colour Climate Change Initiative (OC-CCI https://www.oceancolour.org/).  These primary datasets are both used in conjunction with in-situ derived measurements and radiative transfer modelling in order to quantify the critical depth (Zc) to which biologically relevant ALAN penetrates throughout the global ocean’s estuarine, coastal and near shore regions, in particular the area defined by an individual country’s Exclusive Economic Zone. 
Spatial and temporal distribution of polycyclic aromatic hydrocarbons in sediments from the Canadian Arctic Archipelago
Authors: Corminboeuf Anne , Montero-Serrano Jean-Carlos , St-Louis Richard
Published: March 2020

In Arctic, because of the ongoing diminution of the sea ice coverage, it is speculated that anthropogenic activities such as cargo transportation and oil explorations/exploitations could increase in the Canadian Arctic Archipelago (CAA). However, the vast majority of the channels within the CAA, as well as the adjoining continental shelf and slopes, are characterized by a substantial knowledge gap regarding the regional-scale sediment composition and associated contaminants. Overall, knowing that sediments are a sink for pollutants, a wider spatial coverage of sedimentary records across the marine CAA is essential to provide fundamental baseline information on the physical and geochemical sediment properties in this Arctic region. In this context, a total of 118 surface sediment samples were collected over a large area covering the Canadian Beaufort Sea to the Baffin Bay in order to characterize the modern spatial distribution patterns and the temporal trends of polycyclic aromatic hydrocarbons (PAHs) within the CAA. Sampling was performed in 2016, 2017, 2018 and 2019 aboard the CCGS Amundsen as part of the ArticNet program. Extractions were performed using one-step accelerated solvent extraction and clean-up, followed by gas chromatography coupled to a mass spectrometer analysis. To characterize the temporal concentrations of PAHs, the top 10 cm of 8 push-cores distributed across the archipelago were sub-sampled and analyzed just as the surface samples. Sedimentation rates for each core were obtained by 210Pb dating and allow to reconstruct the PAHs inputs from the last century. Results of the surface sediment samples indicate that the sum concentrations of 23 PAHs ranged from 6 ng/g (dry weight basis) in the North Baffin Bay to 437 ng/g in the Canadian Beaufort Shelf, with a mean value of 67 ng/g. PAHs source characterization was investigated through diagnostic ratio: fluoranthene over the sum of fluoranthene and pyrene. This ratio tends to point a profile with mainly petrogenic sources (i.e., igneous rock-derived, petroleum or crude oil spill) for the majority of the CAA. Some samples in the Beaufort Sea have a mixed profile with petrogenic sources and pyrogenic sources from incomplete combustion of fossil fuel that could indicate an anthropogenic input. Along Ellesmere Island, ratios are mainly pyrogenic from biomass combustion. Results of the push-cores suggest that the inputs of PAHs to the sediment in CAA were relatively stable during the last years. Taken as a whole, our study will provide a baseline of PAHs levels in surface sediment within the CAA before an increase in maritime transport in this area and a comparison of the modern concentrations versus the last century tendencies.
On the magnitude of the stratospheric radiative feedback in global warming
Authors: Huang Yi , Wang Yuwei
Published: March 2020

Global warming is amplified by radiative feedbacks. Compared to the feedback in the troposphere, the feedback in the stratosphere is less understood. The stratospheric water vapor (SWV), one of the primary feedbacks in the stratosphere, is argued to be an important contributor to global warming. This, however, is at odds with the finding that the overall stratospheric feedback does not amount to a significant value in global climate models (GCMs). The key to reconciling these seemingly contradictory arguments is to understand the stratospheric temperature (ST) change since the impact of SWV on the top-of-atmosphere (TOA) radiation budget results more from its cooling of the stratosphere than its direct radiative impact on the TOA radiation. Here, we develop a method to decompose the ST change and to quantify the effects of different climate responses associated with SWV on the TOA radiation budget. We find that although the SWV feedback by itself would lead to strong stratospheric cooling, this cooling is strongly offset by the radiative coupling between the stratosphere and troposphere. Such compensation results in an insignificant overall stratospheric feedback. SWV-locking experiments verify that the SWV feedback does not significantly modify the overall climate sensitivity in the GCM global warming simulations.
Size of the atmospheric blocking events: A scaling law and response to climate change
Authors: Hassanzadeh Pedram , Nabizadeh Ebrahim , Yang Da , Barnes Elizabeth , Lubis Sandro
Published: March 2020

Understanding the response of atmospheric blocking events to climate change has been of great interest in recent years. However, potential changes in the area (size) of blocking events, which can affect the spatio-temporal characteristics of the resulting extreme events, have not received much attention. Using two large-ensemble, fully-coupled GCM simulations and two blocking indices, we show that the size of blocking events increases with climate change, particularly in summers of the northern hemisphere (by as much as 17%). Using a two-layer quasi-geostrophic model and the Buckingham-PI dimensional analysis technique, we derive a scaling law for the size of blocking events, which shows that area mostly scales with the width of the jet times the Kuo scale (i.e., the length of stationary Rossby waves). The scaling law is validated in a range of idealized GCM simulations. This scaling's predictions agree well with changes in blocking events' size under climate change in fully-coupled GCMs in winters but not in summers. These results, recently published in Nabizadeh et al. (2019 GRL) suggest that future studies should focus on investigating the consequences of larger blocks on the size, magnitude, and persistence of extreme weather events, and on improving the understanding of summer blocks. Our more recent work using an idealized moist GCM (MiMA) with aquaplanet lower boundaries and seasonal cycle shows that, again, the scaling law works remarkably well in winters but not in summers, which points to diabatic processes as the likely source of discrepancy. Using MiMA to extend the scaling law to account for diabatic processes is currently underway.

 

Nabizadeh, E., Hassanzadeh, P., Yang, D. and Barnes, E.A., 2019. Size of the atmospheric blocking events: Scaling law and response to climate change. Geophysical Research Letters.
Lessons from a high CO2 world: an ocean view from ~3 million years ago
Authors: McClymont Erin , Ford Heather , Ho Sze Ling , Tindall Julia , Haywood Alan , Alonso Garcia Montserrat , Bailey Ian , Berke Melissa , Littler Kate , Patterson Molly , Petrick Benjamin , Peterse Francien , Ravelo Christina , Risebrobakken Bjorg , De Schepper Stijn , Swann George , Thirumalai Kaustubh , Tierney Jessica , van der Weijst Carolien , White Sarah
Published: March 2020

A range of future climate scenarios are projected for high atmospheric CO2 concentrations, given uncertainties over future human actions as well as potential environmental and climatic feedbacks. The geological record offers an opportunity to understand climate system response to a range of forcings and feedbacks which operate over multiple temporal and spatial scales. Here, we examine a single interglacial during the late Pliocene (KM5c, ca. 3.205 +/- 0.01 Ma) when atmospheric CO2 concentrations were higher than pre-industrial, but similar to today and to the lowest emission scenarios for this century. As orbital forcing and continental configurations were almost identical to today, we are able to focus on equilibrium climate system response to modern and near-future CO2. Using proxy data from 32 sites, we demonstrate that global mean sea-surface temperatures were warmer than pre-industrial, by ~2.3 ºC for the combined proxy data (foraminifera Mg/Ca and alkenones), or by ~3.2ºC (alkenones only). Compared to the pre-industrial, reduced meridional gradients and enhanced warming in the North Atlantic are consistently reconstructed. There is broad agreement between data and models at the global scale, with regional differences reflecting ocean circulation and/or proxy signals. An uneven distribution of proxy data in time and space does, however, add uncertainty to our anomaly calculations. The reconstructed global mean sea-surface temperature anomaly for KM5c is warmer than all but three of the PlioMIP2 model outputs, and the reconstructed North Atlantic data tend to align with the warmest KM5c model values.  Our results demonstrate that even under low CO2 emission scenarios, surface ocean warming may be expected to exceed model projections, and will be accentuated in the higher latitudes.
Numerical simulations to study the geodynamic origin of Los Humeros Volcanic Field in Mexico
Authors: Bayona Ordóñez Andrés David , Manea Vlad Constantin
Published: March 2020

Los Humeros Volcanic Field (LHVF) represents one of the key volcanic calderas in Mexico. Nowadays, LHVF is the third largest geothermal field in Mexico in terms of energy output, with an installed capacity of 94 MWe. The caldera is about 21 by 15 km wide and is located in the Serdán Oriental basin, east of the Trans- Mexican Volcanic Belt in the central-eastern part of the country, roughly 440 km away from the Middle American Trench. In this study we show results of numerical simulations of magma intrusion in order to better understand the deep origin of the caldera. For this purpose, we used high-resolution two-dimensional coupled petrological-thermomechanical numerical simulations of magma intrusion where an initial thermal anomaly was placed in the asthenosphere just below the lithospheric mantle. We performed a parametric study where we investigated the influence of several parameters such as the diameter of the thermal anomaly, the excess temperature and the regional tectonic regime. These 2D simulations were carried out using the finite difference method coupled with the cell marker technique and employing the multigrid method. The physical parameters used for the Earth’s layers (asthenosphere, lithospheric mantle, lower crust and upper crust) and for the composition of the magmatic intrusion were taken from literature and previously established models. In addition, we considered a viscoelastoplastic rheology and the simulations included erosion and surface sediment transport. Modeling results showed that only under certain conditions of temperature excess, initial diameter of the deep thermal anomalies that come in a specific chain-type sequence, it is possible to form a volcanic caldera similar with the dimensions of the LHVF. The temperature excess (ΔT = ~150K) suggested a deep origin for the thermal anomaly with an approximate depth of ~380 km, where currently the surface of the Cocos slab is located below the North American Plate. Additionally, we found that several magmatic pulses can reach the surface only if we consider in our models a small horizontal extension rate consistent with the extensional tectonic regime in the region.
Moist static energy solves storm track intensity puzzle for Snowball Earth
Authors: Shaw Tiffany A , Graham Robert J
Published: March 2020

Modern theories of the midlatitude storm tracks connect their intensity to surface baroclinicity (latitudinal surface temperature gradient). However, simulations show storm tracks were weaker during past cold, icy climates relative to the modern climate even though surface baroclinicity was stronger. We revisit this surface baroclinicity-intensity puzzle for Snowball Earth using simulations across the climate model hierarchy. Here we show the Moist Static Energy framework for storm track intensity solves the puzzle for Snowball Earth. It connects the weaker storm track to the increase of surface albedo, decrease of latent heat flux and decrease of latitudinal surface Moist Static Energy gradient. Weaker intensity can be predicted assuming a surface ice albedo and zero latent heat flux (large Bowen ratio) everywhere in Snowball Earth. The weaker storm track is also consistent with weaker Mean Available Potential Energy (weaker upper-tropospheric baroclinicity), however that cannot be predicted. Overall, the exotic Snowball Earth climate reveals storm track intensity follows the surface Moist Static Energy gradient and not surface baroclinicity. Our insights may help resolve the puzzle in other climates such as the Last Glacial Maximum.
Nanoscale Dust Production at 1 Au; Identification and Tracking with 12 Spacecraft
Authors: Lai Hairong , Jia Yingdong , Connors Martin , Russell Christopher
Published: March 2020

Interplanetary Field Enhancements are phenomena in the interplanetary magnetic field, first discovered near Venus, during an extremely long duration (12 hours) and large size (about 0.1 AU) passage across the Pioneer Venus spacecraft. Three and a half hours later and 21 x 106 km farther from the Sun, this structure, somewhat weaker and off to the side of the expected radial path of any solar initiated disturbance, was seen by first Venera 13 and then Venera 14, trailing behind V13. Since this discovery, many smaller such disturbances have been observed and attributed to collisions of small rocks in space at speeds of about 20 km/s at 1 AU and faster, closer to the Sun. All sightings with magnetometers and other space plasma instruments give very precise measurements of the radial structure (of usually the magnetic field), but the scale transverse to the solar radius is poorly defined, as is the temporal evolution of the structure from single spacecraft data.

On January 16, 2018, near Earth, 12 spacecraft equipped with plasma spectrometers and magnetometers observed the passage of a single Interplanetary Field Enhancement. The magnetic field profiles at the four 1 AU spacecraft were very similar. The profiles were obtained at different times appropriate to their locations. The 4 Cluster spacecraft were closer to the Earth and in a region in which the solar wind had slowed down because of the Earth’s bow wave (shock) in the solar wind. The disturbance in the shocked solar wind occurred at the time expected if the IFE structure had not been slowed by the plasma, but rather had proceeded with the momentum it had prior to the shock crossing. If the disturbance causing particles are small bits of rock (not protons), then they should have kept most of their momentum in crossing the bow shock. We view this as a complete test of the dust producing collisional origin of these Interplanetary Field Enhancements, and a clear demonstration of how the solar wind clears out the dust in the inner solar system produced by the continuing destructive collisional process.
The atmospheric water vapor retrieved by OH(8-3) band airglow from astronomical observations
Authors: Liu Weijun , Xu Jiyao , Bian Jianchun , Liu Xiao , Yuan Wei , Wang Chi
Published: March 2020

Water vapor in the atmosphere is an important trace gas, and seriously affects the ground-based astronomical observations due to water vapor attenuation and emission. It is significant to correct the effects of water vapor along the line-of-sight of astronomical target in real time. Here, we discuss a method to retrieve the precipitable water vapor (PWV) from the OH(8-3) band airglow spectrum. The pressure, temperature and water vapor profiles determine the effective absorption cross-section in PWV retrieval, so a simple and effective method of the effective absorption cross-sections using profiles from a standard atmosphere model is discussed. The Monte Carlo simulations are used to estimate the PWV retrieval. Besides, the PWV is calculated using the sky nightglows from UVES and is compared to that from the standard star spectra of UVES observed from 2000 to 2016. The results indicate that The PWV derived from OH(8-3) spectra is in good agreement with that retrieved from UVES standard star equivalent width and the averaged difference between the two is 0.66 mm. The regression result indicates that the slope α=1.06 +/-0.03 and the correlation coefficient is r=0.87. Because the sky emission spectra and the astronomical target are observed at the same time and along the same line-of-sight, the method of PWV retrieved by OH(8-3) band spectra provides a quick and economical means of correcting the effects if water vapor on ground-based astronomical observations locally, in real-time, and along the line-of-sight of astronomical observations.