Impact of Channel Deepening on Tidal and Gravitational Circulation in a Highly Engineered Estuarine Basin

Deepening of estuarine channels is a common practice to ensure navigation. Here, we investigate whether such deepening impacts physical processes such as the strength of the estuarine exchange flow, the horizontal salinity gradient, and tidal dynamics. We analyze recent and historical hydrodynamic observations in Newark Bay, New Jersey, to assess the effect of channel deepening on tides, circulation, and salinity. The Bay’s navigational channel has undergone significant deepening, from 3 to 10 m in the nineteenth century to ~16 m today. Observations presented here include sea-level data from the nineteenth, twentieth, and twenty-first century, and moored Doppler current data and bottom salinity measurements made over the past 20 years. Results show a doubling of the estuarine exchange flow, a slight increase in salinity and in the horizontal salinity gradient, a decrease in tidal current amplitude, and a spatially variable change in the tidal range. The doubling of the exchange flow is consistent with the Hansen and Rattray scaling provided that the horizontal salinity gradient is unable to fully adjust landward because the dredging is limited to a short reach of the estuary. However, uncertainty in channel depth leaves open the possibility that the exchange flow is also augmented by an increase in the horizontal salinity gradient and/or a reduction in vertical mixing. Nevertheless, results demonstrate that a relatively small (15%) increase in depth appears to have doubled the exchange flow. We believe that this result is relevant to other systems where dredging is limited to a short reach of an estuary.     

Bridging Deep Convolutional Autoencoders and Ensemble Smoothers for Improved Estimation of Channelized Reservoirs

Mathematical Geosciences - One of the main problems associated with applying data assimilation methods for facies models is the lack of geological plausibility in updates. This issue is even more...     

Metamorphic evolution of the Briançonnais units along the ECORS-CROP profile (Western Alps): new data on metasedimentary rocks

Briançonnais units are squeezed between two Mesozoic eclogitic belts (Piemont-Ligurian ocean and Valaisan ocean) along the ECORS-CROP seismic line in the Italian-French Western Alps (France, Italy). The metamorphic evolution of this area plays a key role for understanding the evolution of the Western Alps and is discussed on the basis of detailed petrographic investigations carried out on weathered sediments issued from the erosion of the Hercynian belt, especially on lower Permian to Mesozoic sediments. In the Zone Houillère, as well in the Permo-Triassic cover of the Briançonnais basement, the index metamorphic mineral assemblage is mainly composed of white micas with varying chemical composition, chloritoid and garnet. This same assemblage occurs within different lithologies (metaarkose, metapelite, metasandstone). Consequently, equilibrium phase diagrams were computed for different whole rock compositions using DOMINO software. The results of the P-T investigations clearly show that each unit underwent a different sequence of metamorphic reactions. An increase in metamorphic grade from greenschist facies conditions in the Northwest (Zone Houillère) to the transition between blueschist and eclogite facies conditions in the Southeast (Internal Briançonnais) is observed. A major discontinuity in metamorphic grade is located at the contact between Zone Houillère and Ruitor unit, as documented by a pressure gap of ~ 7 kbar. In general, the observed metamorphic field gradient is inverted and is interpreted to represent different depths of burial during subduction, which correlates with the paleogeographic position of the different units.     

Geodetic methods to determine the relativistic redshift at the level of 10$$^{}$$ in the context of international timescales: a review and practical results

The frequency stability and uncertainty of the latest generation of optical atomic clocks is now approaching the one part in \(10^{18}\) level. Comparisons between earthbound clocks at rest must account for the relativistic redshift of the clock frequencies, which is proportional to the corresponding gravity (gravitational plus centrifugal) potential difference. For contributions to international timescales, the relativistic redshift correction must be computed with respect to a conventional zero potential value in order to be consistent with the definition of Terrestrial Time. To benefit fully from the uncertainty of the optical clocks, the gravity potential must be determined with an accuracy of about \(0.1\,\hbox {m}^{2}\,\hbox {s}^{-2}\), equivalent to about 0.01 m in height. This contribution focuses on the static part of the gravity field, assuming that temporal variations are accounted for separately by appropriate reductions. Two geodetic approaches are investigated for the derivation of gravity potential values: geometric levelling and the Global Navigation Satellite Systems (GNSS)/geoid approach. Geometric levelling gives potential differences with millimetre uncertainty over shorter distances (several kilometres), but is susceptible to systematic errors at the decimetre level over large distances. The GNSS/geoid approach gives absolute gravity potential values, but with an uncertainty corresponding to about 2 cm in height. For large distances, the GNSS/geoid approach should therefore be better than geometric levelling. This is demonstrated by the results from practical investigations related to three clock sites in Germany and one in France. The estimated uncertainty for the relativistic redshift correction at each site is about \(2 \times 10^{-18}\).     

Stratigraphic and geotechnical characterization of regionally extensive and highly competent shallow sand units in the southern North Sea

A detailed stratigraphic and geotechnical investigation of the uppermost 50 m below the sea floor was carried out for parts of the German North Sea sector using combined information from shallow seismic reflection surveys, 50-m-long sediment cores and cone penetration tests covering an area of ~150 km². While most recent studies concentrate on unusual features such as buried tunnel- or river-valleys, this study focused on the less well understood, regionally dominant sand units deposited after the retreat of the last glaciers in this region. We identified two sandy units which dominate the late- to post-Saalian geology: (i) the Upper Fluvial Member, believed to be derived from deposition of the Weser, Ems and Elbe palaeorivers as well as other tributaries of the Elbe Palaeovalley in the NE during the Saalian; and (ii) the Aeolian Member, which correlates with periglacial deposits of Weichselian age. Additionally, a Saalian Buried Valley Member believed to comprise fluvial deposit was also identified. Key stratigraphic units within the uppermost 50 m below the sea floor were also identified and mapped. Detailed geotechnical properties were obtained for each of the individual stratigraphic units. The regional extent of the Aeolian and Upper Fluvial Members was documented in the region west of the Elbe Palaeovalley and south of the Dogger Bank, where their geotechnical properties are important for foundation design. In conclusion, the study complements the established regional geotechno-stratigraphy and offers new and detailed publically accessible information beneficial for offshore wind farm development within the region.     

A new implementation of narrowband interference detection,characterization, and mitigation technique for a software-defined multi-GNSS receiver

Due to the very low power of satellite signals when reaching the earth’s surface, global navigation satellite system receivers are vulnerable to various types of radio frequency interference, and, therefore, countermeasures are necessary. In the case of a narrowband interference (NBI), the adaptive notch filtering technique has been extensively investigated. However, the research on the topic has focused on the adaptation of the notch frequency, but not of the notch width. We present a fully adaptive solution to counter NBI. The technique is capable of detecting and characterizing any number of narrow interfered bands, and then optimizing the mitigation process based on such characterization, namely the estimates of both interference frequency and width. Its full adaptiveness makes it suitable to cope with the unpredictable and diverse nature of unintentional interfering events. In addition to a thorough performance evaluation of the proposed method, which shows its benefits in terms of signal quality improvement, an analysis of the impact of different NBI profiles on GPS L1 C/A and Galileo E1 is also conducted.     

Synthetic RapidEye data used for the detection of area-based spruce tree mortality induced by bark beetles

Tree mortality caused by outbreaks of the bark beetle Ips typographus (L.) plays an important role in the natural dynamics of Norway spruce (Picea abies L.) stands, which could cause far-reaching changes in the occurrence and duration of vegetation phenology. Field-based early detection of tree disturbances is hampered by logistic, terrain, and technical shortcomings, and by the inability to continuously monitor disturbances over large areas. Despite achievements in remote mapping of bark-beetle-induced tree mortalities, early warning has been mostly unsuccessful mainly because of the lack of spectral sensitivity and discrepancies in definitions of field- and image-based disturbance classes. Here we applied a method based on inter-annual phenology of Norway spruce stands derived from synthetic multispectral data to part of the Bavarian Forest National Park in Germany. We fused temporally continuous Moderate Resolution Imaging Spectroradiometer and discrete RapidEye data using a flexible spatiotemporal data fusion method to achieve validated 8-day RapidEye-like composites of normalized difference vegetation index for 2011. We assumed that the dead trees delineated on 2012 aerial photographs were those in which bark beetle infestations were initiated in 2011. Samples were drawn with variable-sized buffering to represent the areas prone to infestations and their surroundings. We applied a conditional inference random forest to select the best image date among the entire 46 synthetic datasets to best discriminate between the core infestation patches and their surroundings from the subsequent year. Of the discrete time points identified, day 281 of the year represented the highest discrepancy between aerial image-based dead trees and their surroundings. Classification results were significantly correlated with beetle count data obtained using pheromone traps. Our method provided valuable information for management purposes and enabled wall-to-wall mapping of stands prone to infestation and its uncertainty. The results offer potential implications for rapid and cost-effective monitoring of bark beetle outbreaks using satellite data, which would be of great benefit for both management and research tasks.     

Testing Nano-Powder and Fused-Glass Mineral Reference Materials for In Situ Rb-Sr Dating of Glauconite,Phlogopite, Biotite and Feldspar via LA-ICP-MS/MS

Reference materials (RMs) with well-characterised composition are necessary for reliable quantification and quality control of isotopic analyses of geological samples. For in situ Rb-Sr analysis of silicate minerals via laser ablation inductively coupled plasma tandem mass spectrometry (LA-ICP-MS/MS) with a collision/reaction cell, there is a general lack of mineral-specific and matrix-matched RMs, which limits wider application of this new laser-based dating technique to certain minerals. In this work, pressed nano-powder pellets (NP) of four RMs, GL-O (glauconite), Mica-Mg (phlogopite), Mica-Fe (biotite) and FK-N (K-feldspar), were analysed and tested for in situ Rb-Sr dating, complemented by isotope dilution (ID) MC-ICP-MS Rb-Sr analyses of GL-O and Mica-Mg. In addition, we attempted to develop alternative flux-free and fused ‘mineral glasses’ from the above RMs for in situ Rb-Sr dating applications. Overall, the results of this study showed that among the above RMs only two NP (Mica-Mg-NP and GL-O-NP) were suitable and robust for in situ dating applications. These two nano-powder reference materials, Mica-Mg-NP and GL-O-NP, were thus used as primary RMs to normalise and determine Rb-Sr ages for three natural minerals: MDC phlogopite and GL-O glauconite grains, and also Mica-Fe-NP (biotite). Our in situ analyses of the above RMs yielded Rb-Sr ages that are in good agreement (within 8%) of published ages, which suggests that both Mica-Mg-NP and GL-O-NP are suitable RMs for in situ Rb-Sr dating of phlogopite, glauconite and biotite. However, using secondary RMs is recommended to monitor the quality of the obtained ages.