bluuebunny/crossref_metadata_2025 huggingface dataset:
Sailing meets Science
Authors: Landschützer Peter , Tanhua Toste , Raimund Stefan ,   Team Malizia and Team Newrest
Published: March 2021

The surface partial pressure of carbon dioxide (pCO2) is one of the main quantitates determining the ocean sink strength for CO2 and knowledge of surface ocean pCO2 plays a vital role in monitoring the global carbon budget. However, measuring pCO2 via infrared absorption requires repeated calibration and drift corrections, and therefore ships are still the major platform for these measurements. Given the limited number and availability of pCO2 observations, scientists have fostered collaborations with industrial partners, participating in the Ships of Opportunity (SOOP) program, to collect valuable pCO2 measurements. One fleet, however, has thus far been largely overlooked: sailing yachts. Modern sensor technology to-date allows for low weight and low energy consumption equilibrator systems that can be successfully mounted on recreational and high-performance sailing yachts with good quality data. Here we present the first results from 3 years of autonomous measurements aboard two IMOCA yachts, Seaexplorer -Yacht Club de Monaco (previously Malizia) and Newrest –Art & Fenêtres using a SubCtech flat membrane equilibrator system. First results indicate that sailing yachts provide crucial high frequency measurements to study open and coastal ocean systems, are well suited to study mesoscale variations in the ocean carbon sink and provide measurements beyond industrial shipping routes (e.g. the Southern Ocean). In summary, sail yachts are a promising way forward in order to complement the current observing system for the global ocean carbon cycle in a changing climate.
GeoAI:artificial intelligence for interpretation and processing of complex geomatic data 
Authors: Pierdicca Roberto
Published: March 2021

Nowadays, the exploitation artificial intelligence approached is overwhelming in several domains. As well, geomatic data are becoming more and more complex and heterogeneous, as they are collected with multi-source data collection techniques. Remotely sensed data, point cloud, thermal images and more are just few examples of complex data which requires growing computational capabilities, but, foremost, powerful tools of processing and interpretation.

The applications of modern AI-based algorithms for the processing of geomatics data offer opportunities that wouldn't be affordable up to few years ago. For geospatial domains, fundamental questions include how AI can be specifically applied to or has to be specifically created for geomatics data. This change is also having a significant impact on geospatial data. Machine Learning (ML) has been a core component of spatial analysis for classification, clustering, and prediction. In addition, Deep Learning (DL) is being integrated to automatically extract useful information with the task of classification, object detection, semantic and instance segmentation, etc. The integration of AI, ML, and DL in geomatics has developed into the concept of Geospatial Artificial Intelligence (GeoAI) that is a new paradigm for geographic knowledge discovery and beyond. 

This talk aims at giving a sight on the emergent discipline called GeoAI, a novel research field in which cutting edge learning based methods are applied to enhance the knowledge and improve the ability of humans to manage complex information. Beside providing a picture of the latest achievements in the filed (outlining AI-based techniques for the analysis and the interpretation of complex geomatics data), this lecture will provide several examples of researches and applications, demonstrating opportunities, challenges and limitations with practical examples. 

Bearing in mind that, for the upcoming future, the "man on the loop" will always assess unpredictable outcomes from the automatization process, it will be demonstrated, at different scales of representation and facing research challenges in different domains (e.g. environmental challenges, forestry, cultural heritage, tourism just to mention some), AI outperforms manual operations in terms of both cost effectiveness and reliability. 
Neogene tectonics during granite emplacement in Northern Apennines: the case of the Gavorrano monzogranite (southern Tuscany, Italy)
Authors: Liotta Domenico , Caggianelli Alfredo , Brogi Andrea , Zucchi Martina , Spina Amalia , Capezzuoli Enrico , Casini Alessandra , Buracchi Elena
Published: March 2021

The tectonic setting of Neogene is under debate, being interpreted as a contractional, pulsing or extensional framework. On the key-areas to unravel this issue is the Gavorrano monzogranite, located  nearby the Tyrrhenian seacoast, in the inner zone of the Northern Apennines (southern Tuscany), where a Neogene monzogranite body (estimated in about 3 km long, 1.5 km wide, and 0.7 km thick) emplaced during early Pliocene. This magmatic intrusion is partially exposed in a ridge bounded by regional faults delimiting broad structural depressions. A widespread circulation of geothermal fluids accompanied the cooling of the magmatic body and gave rise to an extensive Fe-ore deposit (mainly pyrite) exploited during the past century. Data from a new fieldwork dataset, integrated with information from the mining activity, have been integrated to refine the geological setting of the whole crustal sector where the Gavorrano monzogranite was emplaced and exhumed. Our review, implemented by new palynological, petrological and structural data pointed out that: i) the age of the Palaeozoic phyllite (hosting rocks) is middle-late Permian, thus resulting younger than previously described (i.e. pre-Carboniferous); ii) the P-T conditions at which the metamorphic aureole developed are estimated at about 660 °C and at a maximum depth of c. 5 km; iii) the tectonic evolution which determined the emplacement and exhumation of the monzogranite is constrained in a transfer zone, in the frame of the extensional tectonics affecting the area continuously since Miocene.
A unified and automated approach to attractor reconstruction
Authors: Kraemer Hauke , Datseris George , Kurths Juergen , Kiss Istvan , Ocampo-Espindola Jorge L. , Marwan Norbert
Published: March 2021

Since acquisition costs for sensors and data collection decrease rapidly especially in the geo-scientific fields, researchers often have to deal with a large amount of multivariable data, which they would need to automatically analyze in an appropriate way. In nonlinear time series analysis, phase space reconstruction often makes the very first step of any sophisticated analysis, but the established methods are either unable to reliably automate the process or they can not handle multivariate time series input. Here we present a fully automated method for the optimal state space reconstruction from univariate and multivariate time series. The proposed methodology generalizes the time delay embedding procedure by unifying two promising ideas in a symbiotic fashion. Using non-uniform delays allows the successful reconstruction of systems inheriting different time scales. In contrast to the established methods, the minimization of an appropriate cost function determines the embedding dimension without using a threshold parameter. Moreover, the method is capable of detecting stochastic time series and, thus, can handle noise contaminated input without adjusting parameters. The superiority of the proposed method is shown on some paradigmatic models and experimental data.
Jovian Planets influence on the Earth’s Temperature Variability
Authors: Yndestad Harald
Published: March 2021

Abstract

A possible relation between plants period oscillations and the Earth´s temperature variability reveals deterministic variations in the Earth´s temperature variability. This study is based on a deterministic solar-lunar model, a wavelet spectrum analysis of global temperature data series from 1850 and a wavelet spectrum analysis of Greenland temperature (GISP-2) from 2000BC.

 

The results reveal a period- and phase-relation between the Jovian planets, Total Solar Irradiation variability from 1700, global sea temperature variability from 1850 and Greenland temperature variability from 2000B.C. in a multidecadal spectrum of 4480 years. The results are explained by interference between accumulated solar-forced and lunar-forced periods in oceans. The climate response from solar-lunar forced periods explain Grand Solar minimum periods from 1000A.D. the Little Ice Age from 1640 to 1850, the Deep Freeze minimum at 1710 A.D. and the global temperature growth from 1850 to 2000. The solar-lunar model computes a modern global maximum temperature at 2030A.D. and an upcoming Grand Solar minimum at 2062A.D. and an upcoming deep temperature minimum at 2070A.D.

 

Keywords: Solar-lunar interference; Deep solar minima; Earth’s temperature variability; Global temperature minima.

 
From Point Clouds to Surfaces: Overview on a Case Study
Authors: Pluta Kacper , Domej Gisela
Published: March 2021

The process of transforming point cloud data into high-quality meshes or CAD objects is, in general, not a trivial task. Many problems, such as holes, enclosed pockets, or small tunnels, can occur during the surface reconstruction process, even if the point cloud is of excellent quality. These issues are often difficult to resolve automatically and may require detailed manual adjustments. Nevertheless, in this work, we present a semi-automatic pipeline that requires minimal user-provided input and still allows for high-quality surface reconstruction. Moreover, the presented pipeline can be successfully used by non-specialists and only relies commonly available tools.

Our pipeline consists of the following main steps: First, a normal field over the point cloud is estimated, and Screened Poisson Surface Reconstruction is applied to obtain the initial mesh. At this stage, the reconstructed mesh usually contains holes, small tunnels, and excess parts – i.e., surface parts that do not correspond to the point cloud geometry. In the next step, we apply morphological and geometrical filtering in order to resolve the problems mentioned before. Some fine details are also removed during the filtration process; however, we show how these can be restored – without reintroducing the problems – using a distance guided projection. In the last step, the filtered mesh is re-meshed to obtain a high-quality triangular mesh, which – if needed – can be converted to a CAD object represented by a small number of quadrangular NURBS patches.

Our workflow is designed for a point cloud recorded by a laser scanner inside one of seven artificially carved caves resembling chapels with several niches and passages to the outside of a sandstone hill slope in Georgia. We note that we have not tested the approach for other data. Nevertheless, we believe that a similar pipeline can be applied for other types of point cloud data, – e.g., natural caves or mining shafts, geotechnical constructions, rock cliffs, geo-archeological sites, etc. This workflow was created independently, it is not part of a funded project and does not advertise particular software. The case study's point cloud data was used by courtesy of the Dipartimento di Scienze dell'Ambiente e della Terra of the Università degli Studi di Milano–Bicocca.
West Antarctic archipelago covered by cool-temperate forests during early Oligocene glaciation
Authors: Klages Johann Philipp , Hillenbrand Claus-Dieter , Bohaty Steven M. , Salzmann Ulrich , Bickert Torsten , Lohmann Gerrit , Gohl Karsten , Kuhn Gerhard , Titschack Jürgen , Müller Juliane , Bauersachs Thorsten , Frederichs Thomas , Larter Robert D. , Hochmuth Katharina , Ehrmann Werner , Rodríguez Tovar Francisco J. , Schmiedl Gerhard , van de Flierdt Tina , Spiegel Cornelia , Eisenhauer Anton ,   Science Team of Expedition PS104
Published: March 2021

The Eocene-Oligocene Transition (~34.4–33.7 Ma) marks a major step in the long-term evolution from the greenhouse climate of the Early Palaeogene to the icehouse regime of the Late Neogene and Quaternary. However, it remains uncertain which landmasses were covered by ice sheets during the Early Oligocene Glacial Maximum (~33.7–33.2 Ma), an interval of peak glaciation inferred from deep-sea benthic foraminifera oxygen isotope records that immediately follows the Eocene-Oligocene Transition. The scarcity of Late Eocene and Early Oligocene continental and shallow-marine records in both Arctic and Antarctic regions has prevented the reconstruction of environmental conditions and ice-sheet extent during the Early Oligocene, which is critical for assessing ice–ocean–atmosphere interactions during early stages of the Cenozoic icehouse. Here, we present the first Early Oligocene shallow-marine record from the Pacific margin of West Antarctica, recovered from the central Amundsen Sea Embayment shelf on RV Polarstern expedition PS104 at Site 21. Marine mudstones recovered at this site document the presence of a vegetated archipelago at a palaeo-latitude of 73.5°S. Pollen assemblages and organic biomarker proxies indicate a cool-temperate Nothofagus-dominated forest situated within a productive marine archipelago. No evidence for marine terminating ice was detected in the cores from Site 21, thus indicating that the West Antarctic Ice Sheet was small or entirely absent during the Early Oligocene.
Recent, rapid and profound changes to glacier morphology and dynamics, Juneau Icefield, Alaska
Authors: Davies Bethan , Bendle Jacob , McNabb Robert , Carrivick Jonathan , McNeil Christopher , Campbell Seth , Pelto Mauri
Published: March 2021

The Alaskan region (comprising glaciers in Alaska, British Columbia and Yukon) contains the third largest ice volume outside of the Greenland and Antarctic ice sheets, and contributes more to global sea level rise than any other glacierised region defined by the Randolph Glacier Inventory. However, ice loss in this area is not linear, but in part controlled by glacier hypsometry as valley and outlet glaciers are at risk of becoming detached from their accumulation areas during thinning. Plateau icefields, such as Juneau Icefield in Alaska, are very sensitive to changes in Equilibrium Line Altitude (ELA) as this can result in rapidly shrinking accumulation areas. Here, we present detailed geomorphological mapping around Juneau Icefield and use this data to reconstruct the icefield during the “Little Ice Age”. We use topographic maps, archival aerial photographs, high-resolution satellite imagery and digital elevation models to map glacier lake and glacier area and volume change from the Little Ice Age to the present day (1770, 1948, 1979, 1990, 2005, 2015 and 2019 AD). Structural glaciological mapping (1979 and 2019) highlights structural and topographic controls on non-linear glacier recession.  Our data shows pronounced glacier thinning and recession in response to widespread detachment of outlet glaciers from their plateau accumulation areas. Glacier detachments became common after 2005, and occurred with increasing frequency since then. Total summed rates of area change increased eightfold from 1770-1948 (-6.14 km2 a-1) to 2015-2019 (-45.23 km2 a-1). Total rates of recession were consistent from 1770 to 1990 AD, and grew increasingly rapid after 2005, in line with regional warming.
Carbon cycle response to Dansgaard-Oeschger events in a freely oscillating LGM setup of the Community Earth System Model.
Authors: Jochum Markus , Chase Zanna , Nutermn Roman , Pedro Joel , Rasmussen Sune , Vettoretti Guido
Published: March 2021

We use a LGM setup of the CESM with marine and terrestrial biogeochemistry. This free-running  set-up (i.e., no freshwater hosing) exhibts Dansgaard-Oeschger events and Antarctic Isotope Maxima with time-lags and amplitudes that are consistent with paleo reconstructions. The CO2 signal associated DO events is also consistent with reconstructions: a 10 ppm/kyr increase during stadials, with the increase continuing some 400 years after Antarctica has started to cool again. An analysis of the modelled air-sea/land carbon fluxes reveals that some 3ppm of the stadial increase are due to shifting rain and temperature patterns that reduce growth of land vegetation. This adjustment is largely concluded after 3 centuries. The remainder of the signal is due to reduced ocean uptake. It turns out that reduced subduction of carbon in the Southern Ocean is mostly compensated by reduced upwelling in the equatorial oceans. Thus, as found in previous studies, much of the extra carbon is due to reduced uptake in the North Atlantic, partly directly due to reduced deep convection, and partly due to a reduced biological productivity because much of the North Atlantic nutrients are supplied by the AMOC. A big surprise is the emergence of the North Pacific as a major contributor to the changes in the air-fluxes of carbon. It is the reorganization of its wind-driven circulation that explains why global net-outgassing of carbon continues long after the interstadial has begun.
Tectonic activity of the northern and southern plate boundaries of the Niuafo’ou microplate, Lau Basin, southwest Pacific Ocean
Authors: Beniest Anouk , Schnabel Michael , Dannowski Anke , Schmid Florian , Jegen Anna , Kopp Heidrun
Published: March 2021

The northern Lau Basin in the southwest Pacific Ocean is one of the fastest opening back-arc basins on Earth, resulting in a mosaic of microplates, including the Niuafo’ou and Tongan microplates. The Fonualei Rift and Spreading Center (FRSC) is the eastern plate boundary that separates the Niuafo’ou from the Tongan microplate. The northern part of the FRSC is actively spreading, whereas the southern part is rifting. What is unclear, however, is how extension of the Lau Basin is accommodated north and south of the FRSC.

We present the results of six Multi-Channel Seismic profiles acquired during the ARCHIMEDES-I expedition and show an analogue lithosphere-scale model example of our proposed tectonic evolution. Profiles P1 (oriented NW-SE) and P2 (oriented W-E) cover the Mangatolu Triple Junction (MTJ) and the northern part of the FRSC. P3 and P4 (both oriented W-E) cover the southern Niuafo’ou microplate. P5 and P6 (both oriented W-E) cover the area south of the FRSC.

The northern profiles (P1 and P2) reveal a thick package of sediment towards the east, covering a heavily faulted basement over a wide area. Some indication for intrusive material is observed closer to the volcanic arc, but also further towards the western end of P2. Faults cross-cutting the basement but that do not reach the surface are considered inactive today. Faults reach the surface close to the MTJ and the northern tip of the FRSC and are considered active today. This leads to the interpretation that an earlier rift phase accommodated extension in a wide rift tectonic setting, whereas today, the extension is accommodated in a narrow rift or spreading tectonic setting. We will show an analogue model example that demonstrates this wide-to-narrow extensional tectonic evolution.

The profiles that cover the southern extent of the FRSC (P3, P4, P5 and P6), show that active faulting occurs towards the west, close to the Central Lau Spreading Center. Hidden faults that have deformed the basement, but do not affect the surface today anymore are observed in the abyssal parts of P3, P4, P5 and P6. Active faults that reach the surface are also observed towards the east. Recent volcanism is observed, both in the form of intrusive bodies, i.e. sills, as well as volcanoes that pierce through the stratigraphy. The observations lead to the conclusion that south of the FRSC an earlier (wide) rift system affected a larger area in the current abyssal parts of the profiles, whereas extension is currently accommodated through spreading in the CLSC, west of the southern tip of the FRSC.
The use of a 3rd U/S or D/S sensor in Salt Dilution Flow Measurements
Authors: Sentlinger Gabe
Published: March 2021

Salt Dilution flow measurement is relatively accurate and easy way to measure flow in turbulent waterways.  However, it’s accuracy and precision are governed by the Signal to Noise (SNR) Ratio, which can be very low in urban, sub-urban, and rural waterways due to a highly variable BackGround specific Electrical Conductivity (BG ECT) signal.  Conventionally, more salt is added to the waterway to overcome the noise in the BG ECT.  The “noise” is a combination of random noise, which is amplified by the typically high BGECT (>500 uS/cm), but also lower frequency noise that changes on the same time scale as the salt breakthrough curve.  To compensate for the changing BG ECT, we have employed a 3rd UpStream (U/S) probe to track the BG ECT, along with algorithms to transform the signal in 3 domains: magnitude (ECT offset), time (transit time of pulse), and frequency (to compensate for storage in the waterway).  Additionally, we have tested the use of a 3rd DownStream (D/S) probe to measure cross-channel variance when mixing is not complete in order to achieve a reasonable flow estimate.  Results are compared and discussed.
Projections of tropical heat stress constrained by atmospheric dynamics
Authors: Zhang Yi , Held Isaac , Fueglistaler Stephan
Published: March 2021

Extreme heat under global warming is a concerning issue for the growing tropical population. However, model projections of extreme temperatures, a widely used metric for extreme heat, are uncertain on regional scales. In addition, humidity also needs to be taken into account in order to estimate the health impact of extreme heat. Here we show that an integrated temperature-humidity metric for the health impact of heat, namely the extreme wet-bulb temperature (TW), is controlled by established atmospheric dynamics and thus can be robustly projected on regional scales. For each 1°C of tropical mean warming, global climate models project extreme TW (the annual maximum of daily-mean or 3-hourly values) to increase roughly uniformly between 20°S and 20°N latitude by about 1°C. This projection is consistent with theoretical expectations based on tropical atmospheric dynamics, and observations over the past 40 years, which gives confidence to the model projection. For a 1.5°C warmer world, the likely (66 per cent confidence interval) increase of regional extreme TW is projected to be 1.33-1.49°C, whereas the uncertainty of projected extreme temperatures is 3.7 times as large. These results suggest that limiting global warming to 1.5°C will prevent most of the tropics from reaching a TW of 35°C, the limit of human adaptation.
A New Algorithm for the Retrieval of Volcanic Ash Cloud Properties using MSG-SEVIRI and Artificial Neural Networks
Authors: Piontek Dennis , Bugliaro Luca , Voigt Christiane , Hornby Adrian , Gasteiger Josef , Schumann Ulrich , Marenco Franco , Kar Jayanta
Published: March 2021

Artificial neural networks (ANNs) have been successfully applied to various remote sensing problems. Here we use ANNs to detect and analyze volcanic ash clouds pixelwise in MSG-SEVIRI images. Therefore, radiative transfer calculations based on realistic ash properties and atmospheric profiles covering a wide range of possible atmospheric states are performed, and their results are used for the training of the ANNs.

With respect to the volcanic ash properties the role of the complex refractive index (RI) is highlighted: While it can vary strongly between different eruptions, some models use a limited set of RI measurements. Here we sketch a novel method to calculate the RI of volcanic ashes for wavelengths from 5 to 15 µm from measurements of their individual components (i.e. minerals, glasses, gas bubbles) based on generic petrological ash compositions. A comprehensive data set of RIs for volcanic glasses and bulk volcanic ashes of different chemical compositions is derived and used for the ANNs training data set.

The final ANNs with specific tasks (classification, retrieval of optical depth, cloud top height and particle effective radius) are validated against an unseen simulated test data set. This allows us to systematically investigate strengths and weaknesses of the retrievals with respect to cloud properties (e.g. optical thickness), geographic and meteorological conditions. To prove real-world applicability case studies for volcanic ash clouds produced by Eyjafjallajökull (2010) and Puyehue-Cordón Caulle (2011) are considered, and comparisons with lidar and in situ measurements show overall good agreement. As for the training only homogeneous single layer ash clouds were assumed, a sensitivity study was carried out to investigate the impact of the vertical mass profile, multiple layers and the geometrical extent of the clouds on the retrieval results.

Finally, a comparison with a precursor algorithm running operationally at the German weather service (DWD) since 2015 shows that in the case of the Eyjafjallajökull 2010 eruption the new algorithm detects more as well as higher concentrated volcanic ash clouds.
Decadal Seismicity Prior to Great Earthquakes at Subduction and Transform-Fault Plate Boundaries
Authors: Sykes Lynn
Published: March 2021

Decadal forerunning seismic activity is used to map great asperities that subsequently ruptured in very large, shallow earthquakes at subduction zones and transform faults. The distribution of forerunning shocks of magnitude Mw>5.0 is examined for 50 mainshocks of Mw 7.5 to 9.1 from 1993 to 2020. The zones of large slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Much forerunning activity occurred at smaller asperities along the peripheries of the rupture zones of great and giant mainshocks. Asperities are strong, well-coupled portions of plate interfaces. Sizes of great asperities as ascertained from forerunning activity generally agree with the areas of high seismic slip as determined by others using geodetic and tide-gauge data and finite-source seismic modeling. Different patterns of forerunning activity on time scales of about 5 to 45 years are attributed to the sizes and spacing of asperities. This permits many great asperities to be mapped decades before they rupture in great and giant shocks. Rupture zones of many large earthquakes are bordered either along strike, updip, or downdip by zones of low plate coupling. Several bordering regions were sites of forerunning activity, aftershocks and slow-slip events. Several poorly coupled subduction zones, however, are characterized by few great earthquakes and little forerunning activity. The detection of forerunning and precursory activities of various kinds should be sought on the peripheries of great asperities. The manuscript can be found at http://www.ldeo.columbia.edu/~sykes

 
The role of land-use change and restoration on nitrogen processing in tropical coastal wetlands of Vietnam
Authors: Comer-Warner Sophie , Nguyen Anh , Nguyen Minh , Wang Manlin , Turner Antony , Sgouridis Fotis , Krause Stefan , Le Hue , Kettridge Nicholas , Nguyen Nghia , Ullah Sami
Published: March 2021

Coastal wetlands, including mangrove and melaleuca forests, are globally important due to their capacity in sequestering carbon and nitrogen, and intercepting nutrient pollution from vast, nutrient-rich, tropical riverine networks. Despite this, the environmental drivers controlling soil biogeochemistry in these ecosystems remain poorly understood. Here we conducted a study across gradients of restoration and land-use in the mangrove forest of Xuan Thuy National Park in the Red River Delta, northern Vietnam and the melaleuca forest of U Minh Thuong National Park in the Mekong River Delta, southern Vietnam. We investigated nitrogen transformation processes and greenhouse gas production in mangrove and melaleuca forest soils using a 15N-Gas flux method to determine rates of denitrification, and its relative contribution to soil N2O emissions. We found that denitrification was a more dominant source of N2O in the melaleuca soils, despite higher rates of denitrification in the mangrove soils resulting from more complete denitrification in the mangroves. N2O and CO2 emissions were significantly higher from the melaleuca soils. Disturbance and subsequent recovery or restoration of these forests did not have a significant effect on soil biogeochemistry. The mangrove system, therefore, may remove excess nitrogen and improve water quality while maintaining low emissions of greenhouse gases whereas melaleucas process nutrients at a cost of N2O and CO2 emissions. Melaleucas, however, may act as a significant CH4 sink at least partially balancing these emissions.
Antarctic Slope Current controls warm ocean intrusions towards Totten Glacier
Authors: Nakayama Yoshihiro , Greene Chad , Paolo Fernando , Mensah Vigan , Zhang Hong , Kashiwase Haruhiko , Simizu Daisuke , Greenbaum Jamin , Blankenship Donald , Abe-Ouchi Ayako , Aoki Shigeru
Published: March 2021

The Totten Glacier in East Antarctica has received increasing attention in recent years for its ice loss and warm oceanographic conditions observed at the ice shelf front. Here, we developed satellite estimates of temporally varying Totten Ice Shelf (TIS) melt rates and a high-resolution ocean model. We show that the Antarctic Slope Current (ASC) impedes ocean heat intrusions, and on-shelf intrusions enhance when the ASC weakens. The interannually varying strength of the ASC is primarily controlled by lateral ocean boundary conditions (and thus atmosphere and ocean circulations outside of the model domain) but also likely influenced by local wind stress curl and upstream decent of shelf water. We further show that heat intrusions towards the TIS are enhanced with coastal freshening, suggesting that freshening from ice loss in West Antarcticacould start a chain reaction, leading to increased melt in East Antarctica, and further coastal freshening.
Improving Deep Learning hydrological time series modeling using Gaussian Filter preprocessing
Authors: Barzegar Rahim , Adamowski Jan , Quilty John
Published: March 2021

Hydrological time series modeling is an important task in water resources planning and management. However, time series may include noise, which can result in an inaccurate model. Therefore, removing noise from time series is valuable to obtain accurate predictions. The aims of this study are i) to develop and compare Long-Short Term Memory (LSTM) and Gated Recurring Units (GRU) Deep Learning (DL) models to predict hydrological time series and ii) to integrate a preprocessing method, Gaussian Filter (GF), to smooth out time series and couple it with DL to improve prediction accuracy. Moreover, the DL models are benchmarked against statistical time series models (e.g., Seasonal Autoregressive Integrated Moving Average (SARIMA)) to assess their added value for hydrological time series modeling. To establish predictive models, several monthly hydrological time series including water level (e.g., from the Great Lakes in North America, including Lakes Michigan, Ontario, and Erie (1918-2019)) and streamflow (e.g., gauging stations at Umfreville, along the English River, Ontario, Canada (1921-2019), Rapides Fryers, along the Richelieu River, Quebec, Canada (1937-2020) and near Lethbridge, along the Oldman River, Alberta, Canada (1957-2019)) were explored. For developing non-GF- and GF-DL models, time series were partitioned into training (70% of the data) and testing (the remaining 30% of the data) subsets and the time series’ past measurements up to 12 months (t-1, t-2, ..., t-12) were served to the DL models (LSTM and GRU) to predict the time series at time t. The structure of the DL models was tuned using Bayesian optimization. The SARIMA models (i.e., non-GF- and GF-SARIMA) were also implemented and tuned using pmdarima's auto-arima function. After calibrating the models, the testing step was implemented and the performance of the models was evaluated using statistical indicators including correlation coefficient, root mean square error, mean absolute error, the Nash-Sutcliffe efficiency coefficient, and Willmot’s index. The results of the developed DL models showed that the GRU outperforms the LSTM models. Moreover, both LSTM and GRU have superior performance when compared to the SARIMA models. It is observed that GF preprocessing significantly improves the accuracy of the developed DL and SARIMA models. It is concluded that coupling GF preprocessing with DL, due to capturing both linear and nonlinear features of the time series, represents a promising tool for obtaining accurate hydrological time series predictions.
Underestimated snow density in ERA5-Land as a cause for warm bias of soil temperature over permafrost regions
Authors: Cao Bin , Gruber Stephan , Zheng Donghai , Li Xin
Published: March 2021

ERA5 is the latest generation atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). ERA5-Land (ERA5L) is derived by running the land component of ERA5, Tiled ECMWF Scheme for Surface Exchanges over Land with a revised land surface hydrology (HTESSEL), at an increased resolution of 0.1°. This study evaluates ERA5L soil temperature in permafrost regions based on observations and published permafrost products. We find that ERA5L overestimates soil temperature in northern Canada and Alaska but underestimates it in mid–low latitudes, leading to a near-zero overall bias (−0.08 ˚C). The warm bias of ERA5L soil is more pronounced in winter than in other seasons. As calculated from its soil temperature, ERA5L overestimates active-layer thickness and underestimates near-surface (< 1.89 m) permafrost area.This is thought to be due in part to the shallow soil column and coarse vertical discretization of the land surface model and to warmer simulated soil.

The soil temperature bias in permafrost regions correlates well with the bias in air temperature and with snow height. A review of the ERA5L snow parameterization in the code and a simulation example comparison with permafrost-specific processes rich model (GEOtop) both point to an error in snow metamorphism of HTESSEL leading to a low bias in ERA5L snow density as a possible cause for the warm bias in soil temperature. The apparent disagreement of station-based and areal evaluation techniques highlights challenges in our ability to test permafrost simulation models. While global reanalyses are important drivers for permafrost simulation, we conclude that ERA5L soil data are not well suited for informing permafrost research and decision making directly. To address this, future soil temperature products in reanalyses will require permafrost-specific alterations to their land surface models.
Microbial-driven Impact of the Topmost Bed Sediment Layer on Aquatic Phosphate Fluxes
Authors: Choo Simeon , Dellwig Olaf , Wäge-Recchioni Janine , Schulz-Vogt Heide
Published: March 2021

There is a longstanding principle that the uppermost layer of aquatic sediment is the primary regulator of nutrient loads in the bottom water zone, pertaining to the fact that it is significantly biological in nature and thus the site of a myriad of biota-associated processes. Nevertheless, although this principle is seemingly obvious, there is unusually scant literature corroborating the impact of the uppermost sediment layer on water column nutrient fluxes, in particular soluble reactive phosphorus (SRP). It has also been theorized that in certain environments, large bacteria play a major role in phosphorus cycling in the sediment. This challenges the prevailing dogma that the control of bottom water phosphate (PO43-) is mainly attributed to the SRP flux contribution from iron (Fe) oxide-bound P in sediment or remineralisation under anoxia and warming conditions respectively. In this study, elevated temperature as well as anoxic incubation treatments were set up to demonstrate that in response to an increased level of PO43- being released under stressful conditions, the topmost bed sediment layer (TBSL) has an unmistakable impact on P sequestration and stabilisation of the bottom water PO43- fluxes. Likewise, we also show that large filamentous microorganisms residing in the TBSL were seemingly active in polyphosphate (polyP) accumulation during these stress-inducing conditions. This therefore strongly points to a new and important biological sink for the SRP flux at the benthic layer of an aquatic environment.
Consequences of nutrient load reductions for carbon and alkalinity dynamics within the region of freshwater influence of River Elbe
Authors: Paetsch Johannes , Thomas Helmuth
Published: March 2021

Since the early eighties of the 20th century nitrogen and phosphorus loads of the River Elbe, a river entering the North European Shelf at the southeastern coast, have decreased by a factor of about four. This resulted in a reduction of the eutrophication status in the adjacent German Bight and the coastal waters west of Denmark. In addition, benthic carbon and alkalinity pools have changed due to 1- changed carbon loads and, 2- changed decay pathways of benthic organic carbon.

We investigate the consequences of observed nutrient and organic loads by rivers with a 3D-biogeochemical model including a 3D-early diageneses model within the sediment for the time 1979 - 2014.   

The results show a strong decrease of benthic carbon rather due to decreasing nutrient loads and subsequent autochthonous biological production than changes in organic loads. The export of inorganic carbon from the sediment is related to the magnitude of benthic organic carbon and cannot explain the strong decrease of the benthic POC pool. During the time until the early nineties aerobic degradation increases, whereas denitrification and sulfate reduction as organic matter degradation pathway decreases.

Alkalinity production due to benthic organic matter degradation decreases over the first half of the investigated time interval and keeps constant during the second half. Denitrification and sulfate reduction dominate the mechanisms decreasing the alkalinity export. Benthic nitrification consuming alkalinity strongly increases during the first half of the time dampening the decrease of alkalinity export.
Analyzing 67P’s dusty coma
Authors: Hänni Nora , Altwegg Kathrin , Müller Daniel , Pestoni Boris , Rubin Martin , Wampfler Susanne
Published: March 2021

While the volatile species in comet 67P/Churyumov-Gerasimenko’s coma have been analyzed in great spatial and temporal detail, e.g., Rubin et al. (2019) or Läuter et al. (2020), little is so far known about the less volatile, heavier species. There is growing evidence, however, that less volatile species, such as salts, may play a key role in explaining some of the puzzling properties of comets, as for instance shown by Altwegg et al. (2020). These authors also have demonstrated the unique capability of ROSINA/DFMS (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/ Double Focusing Mass Spectrometer; Balsiger et al. (2007)) to detect exactly such little volatile species in-situ, namely during a dust event on 5 September 2016 (when a dust grain entered the instrument and sublimated inside).

Complementary information on 67P’s dusty coma can be obtained from data collected during time periods of high dust activity. A clear advantage of such data is they also allow for a quantitative interpretation thanks to the much more stable measurement conditions. Moreover, a comparison to data collected during a time period of little dust activity (e.g., to the days around end of May 2015 as in Rubin et al. 2019) also allows to link species to dust.

End of July / beginning of August 2015, the comet was approaching its perihelion and ejecting a lot of dust, as seen by the OSIRIS camera (Vincent et al. 2016). The data from this period are therefore a promising starting point for the search of heavier species (m > 100 Da). Altwegg et al. (2019), for instance, reported on the tentative identifications of the simplest polyaromatic hydrocarbon species naphthalene as well as of benzoic acid, the simplest aromatic carboxylic acid. To confirm these identifications and to achieve a more complete inventory of heavier and chemically more complex species, we are now analyzing these data sets strategically. In our contribution we will share what we have learned from pushing the exploration of 67P’s dusty coma.

 

Altwegg et al., 2020, Nat. Astron., 4, 533-540.
Altwegg et al., 2019, Annu. Rev. Astron. Astrophys., 57, 113-55.
Balsiger H. et al., 2007, Space Sci. Rev., 128, 745-801.
Läuter et al., 2020, MNRAS, 498, 3, 3995-4004.
Rubin et al., 2019, MNRAS, 489, 594-607. Vincent et al., 2016, MNRAS, 462 (Suppl_1), 184-194.
Mantle flow and orography: the effect of basal lithospheric shearing and lateral erosion gradients on continental rifting
Authors: Sternai Pietro
Published: March 2021

Mantle plume-lithosphere interactions modulated by surface processes across extensional tectonic settings give rise to outstanding topographies and sedimentary basins. However, the nature of these interactions and the mechanisms through which they control the evolution of continental rifts are still elusive. Basal lithospheric shearing due to plume-related mantle flow leads to extensional lithospheric rupturing and associated magmatism, rock exhumation, and topographic uplift away from the plume axis by a distance inversely proportional to the lithospheric elastic thickness. When moisturized air encounters a topographic barrier, it rises, decompresses, and saturates, leading to enhanced erosion on the windward side of the uplifted terrain. Orographic precipitation and asymmetric erosional unloading facilitate strain localization and lithospheric rupturing on the wetter and more eroded side of an extensional system. This simple model is validated against petro-thermo-mechanical numerical experiments where a rheologically stratified lithosphere above a mantle plume is subject to fluvial erosion proportional to stream power during extension. These findings are consistent with Eocene mantle upwelling and flood basalts in Ethiopia synchronous with distal initiation of lithospheric stretching in the Red Sea and Gulf of Aden as well as asymmetric topography and slip along extensional structures where orography sets an erosional gradient in the Main Ethiopian Rift (MER). I conclude that, although inherently related to the lithosphere rheology, the evolution of continental rifts is even more seriously conditioned by the mantle and surface dynamics than previously thoughts.
Understanding the impacts of climate change on high mountain practices: the case of the Mont Blanc massif through an interdisciplinary approach
Authors: Salim Emmanuel , Mourey Jacques , Ravanel Ludovic , Duvillard Pierre-Alain , Cathala Maëva , Magnin Florence , Deline Philip , Kaushik Suvrat , Guillet Grégoire , Gallach Xavi , Olhasque Marie
Published: March 2021

The intensity of the current climate change has strong consequences on high mountain tourism activities. Winter activities are currently the most studied (ski industry). However, the consequences of environmental changes are also strong in summer, as geomorphological processes are enhanced at high elevation. The Mont Blanc Massif (Western Alps) is a particularly favourable terrain for the development of research about these processes. Emblematic high summits (28 of the 82 peaks > 4000 m of the Alps), dozens of glaciers, strongly developed tourism with summer/winter equivalence, active mountaineering practice, etc. all contribute to the interest of studying this geographical area. A lot of work has been carried out on glaciological and geomorphological issues. These studies, which deal with "physical" impacts of the climate change on the high mountains, are also supplemented by studies of their consequences on human societies, as its impacts on practices such as mountaineering or glacier tourism. Risk-related issues are also taken into account with, for example, the stability of infrastructure (huts, ski lifts) or the impact of glacial shrinkage on the formation of new and potentially hazardous lakes. Accordingly, the aims of our presentation are to show the extent of the research developed on climate change in the Mont Blanc massif and how social and environmental sciences are interlinked to provide a holistic vision of the issues of this territory. As these experiments are not exactly interdisciplinary experiments, this presentation also aims to discuss the points that need to be further developed in order to promote inter- and trans-disciplinary research.
Diverse manifestations of insolation forcing of environmental changes during the middle Piacenzian
Authors: Gao Peng , Nie Junsheng
Published: March 2021

The middle Piacenzian period is the closest sustained warm interval and a possible analog to the future climate. It is well known that global ice volume exhibits dominant 41-kyr cyclicities. However, high resolution terrestrial paleoenvironmental records are scare. Here we present a 3.6 kyr terrestrial environmental variation record from Teruel Basin of Spain and compare the results with the East Asian monsoon records. The Spain results show dominant 41-kyr cycles during the early Piacenzian (3.3-3.15 Ma) when eccentricity was at minimum, but the 41-kyr cycles weakens during the late Piacenzian 3.15-2.95 Ma when eccentricity got increased, suggesting direct forcing by insolation. This pattern is different from the monsoonal records from China, which demonstrates persistent 20-kyr cycles during the entire middle Piacenzian. The strong 41-kyr cycles in westerly region during the early Piacenzian may originate from its higher latitude and higher sensitivity to insolation gradient forcing.
Model-derived uncertainties in the calculation of geological phase equilibria
Authors: Green Eleanor , Powell Roger
Published: March 2021

Phase equilibrium modelling offers a welcome window onto rock-forming processes. It underpins the principles of geothermobarometry, which today is commonly carried out via pseudosection calculations in software such as THERMOCALC and Perple_X. Increasingly, phase equilibrium modelling is combined with complementary approaches such as diffusion or geodynamical calculations, in order to simulate Earth processes.

However, as anyone with experience of pseudosection calculations will know, it is not always easy to make sense of a rock through phase equilibrium modelling. Problems may relate to: (1) in what way the assumption of thermodynamic equilibrium may, or may not, be applied; (2) uncertainties in compositional analysis; and (3) uncertainties in the composition-dependent equations of state (x-eos). The x-eos are the building blocks of the modelling – one x-eos is needed to represent each of the mineral and fluid phases in the calculation. 

Of the problems listed above, (3) is the most opaque for the user. In this talk I will discuss the uncertainties associated with the x-eos, and the implications of those uncertainties for thermobarometry and the simulation of Earth processes. I will describe two tools, currently in development, for investigating x-eos-derived uncertainty in thermobarometry.