Vertical crustal motion observed in the BIFROST project

This paper reports from investigations on the robustness of estimated rates of intraplate motion from the continuous GPS project BIFROST (Baseline Inferences from Fennoscandian Rebound Observations, Sealevel and Tectonics). We study loading effects due to ocean, atmosphere and hydrology and their impact on estimated rate parameters. We regularly find the admittance of a modelled perturbation at less than fifty percent of the full effect. We think that the finding relates to a difficult noise situation at all periods, and that a satisfying model for the dominating noise source has not been found yet. An additional reason for low admittance is found in the mapping process of the no-fiducial network solution into a conventional reference frame.     

Nordic Geoscience and the 33rd International Geological Congress： Introduction

Geology has been of profound importance for the Nordic countries since the Middle Ages. Strong economies were built on an understanding of the occurrence in bedrock of minerals containing metals, e.g., silver, copper, zinc and iron, and eventually led to the establishment of the first Geological Surveys in Norway and Sweden in the middle of the nineteenth century. The geology of Norden ranges from the oldest to youngest rocks on the planet. Based on the papers in this special issue, this introduction provides a brief summary of the geological evolution of Norden, from the Archean of Greenland and northern Fennoscandia to the on-going volcanicity in Iceland on the MidAtlantic Ridge. It also refers to aspects of Geoscience that are particularly important for society in Norden, including geo-resources （petroleum, geothermal energy, nuclear energy, metals, industrial minerals and groundwater） and environmental geology （including natural and anthropogenic processes, medical geology, geo-hazards and climate）. Information on the early history of geology in Norden and the geological surveys is also included and, finally, an outline of the 33rd International Geological Congress with its main theme “Earth System Science： Foundation for Sustainable Development”.     

Modelling surface drifting of buoys during a rapidly-moving weather front in the Gulf of Finland, Baltic Sea

The Gulf of Finland is an elongated estuary located in the north-eastern extremity of the Baltic Sea. This semi-enclosed sea-area is subject to heavy sea traffic, and is one of the main risk areas for oil accidents in the Baltic. The continuous development and validation of operational particle drift and oil-spill forecasting systems is thus seen to be essential for this sea-area.Here, the results of a three-day drift experiment in May 2003 are discussed. The field studies were performed using GPS-positioned surface floating buoys. The aim of this paper is to evaluate how well models can reproduce the drift of these buoys. Model simulations, both in forecast and hindcast modes, were carried out by three different 3D hydrodynamic models, the results of which are evaluated by comparing the calculated drifts with observations. These models were forced by HIRLAM (High Resolution Limited Area Model) and ECMWF (European Centre for Medium-Range Weather Forecasts) meteorological forecast fields.The simulated drift of the buoys showed a good agreement with observations even when, during the study period, a rapidly-changing wind situation was observed to affect the investigation area; in this situation the winds turned about 100 degrees in half an hour. In such a case it is a very complicated task to forecast the drifters' routes: there is a need to regularly update the meteorological forcing fields and to use these regularly-updated fields throughout the simulations. It is furthermore recommended that forecasts should be made using several circulation models and several meteorological forecasts, in order to get an overview of the accuracy of the forecasted drifts and related differences in between the forecasts.     

Palaeoenvironment of the Karelian Isthmus, the easternmost part of the Gulf of Finland, during the Litorina Sea stage of the Baltic Sea history

The palaeoenvironment of the Karelian Isthmus area during the Litorina Sea stage of the Baltic Sea history, between 8.0 and 4.5 kyr BP (8.8-5.2 cal. kyr BP), was reconstructed by studying four sites located on the Karelian Isthmus in Russia. Methods included diatom and pollen analyses, sediment lithostratigraphical interpretation and ¹⁴C dating. The brackish-water (Litorina) transgression began c. 7.7 kyr BP (8.45 cal. kyr BP) in the Karelian Isthmus area. The transgression maximum occurred between 6.7 and 5.7 kyr BP (7.6-6.5 cal. kyr BP), depending on the glacio-isostatic land uplift rate. Regarding the vegetation, the maximum occurrence of temperate deciduous trees took place at the same time. The transgression was interrupted by a short-lived sea-level standstill during the middle phase of the main transgression, c. 6.3 kyr BP (7.2 cal. kyr BP), on the eastern part of the isthmus. The highest Litorina shoreline is located between 8 and 13 m above present sea-level and the amplitude of the Litorina transgression has varied between 5 and 7 m. The 8.2-kyr cold event is not evident, but the sea-level standstill around 6.3 kyr BP (7.2 cal. kyr BP) could reflect a cool episode at that time in the Karelian Isthmus area.     

Laboratory studies into the effect of regolith on planetary X-ray fluorescence spectroscopy

In the analysis of X-ray fluorescence spectra from planetary surfaces, it is traditionally assumed that the observed surface is a plane-parallel, smooth, and homogeneous medium. The spectral and spatial resolutions of the instruments that have been used to measure X-ray emission from planetary surfaces to date have been such that this has been a reasonable assumption, but a new generation of X-ray spectrometers will provide enhanced spectral and spatial resolutions when compared with previous instrumentation. In light of these improvements in performance, it is important to assess how the requirements on the methodology of analysis of spectra may change when the surface is considered as a regolith. At other wavelengths, varying physical properties of planetary regoliths, such as the packing density, are known to have an effect on the observed signal as a function of viewing geometry. In this paper, the results from laboratory X-ray fluorescence measurements of regolith analogue materials at different viewing geometries are presented. Characteristic properties of the regolith such as particle sizes and packing density are found to affect the measured elemental line ratios. A semiempirical function is introduced as a tool for fitting fluorescent line intensity dependences as a function of viewing geometry. The importance of the results is discussed and recommendations are made for the future analysis of planetary X-ray fluorescence data.     

Evaluation of erosion and surface roughness in peatland forest ditches using pin meter measurements and terrestrial laser scanning

Anthropogenic activities on peatlands, such as drainage, can increase sediment transport and deposition downstream resulting in harmful ecological impacts. The objective of this study was to quantify changes in erosion/deposition quantities and surface roughness in peatland forest ditches by measuring changes in ditch cross‐sections and surface microtopography with two alternative methods: manual pin meter and terrestrial laser scanning (TSL). The methods were applied to a peat ditch and a ditch with a thin peat layer overlaying erosion sensitive mineral soil within a period of two years following ditch cleaning. The results showed that erosion was greater in the ditch with exposed mineral soil than in the peat ditch. The two methods revealed rather similar estimates of erosion and deposition for the ditch with the thin peat layer where cross‐sectional changes were large, whereas the results for smaller scale erosion and deposition at the peat ditch differed. The TLS‐based erosion and deposition quantities depended on the size of the sampling window used in the estimations. Surface roughness was smaller when calculated from the pin meter data than from the TLS data. Both methods indicated that roughness increased in the banks of the ditch with a thin peat layer. TLS data showed increased roughness also in the peat ditch. The increase in surface roughness was attributed to erosion and growth of vegetation. Both methods were suitable for the measurements of surface roughness and microtopography at the ditch cross‐section scale, but the applicability, rigour, and ease of acquisition of TLS data were more evident. The main disadvantage of the TLS instrument (Leica ScanStation 2) compared with pin meter was that even a shallow layer of humic (dark brown) water prevented detection of the ditch bed. The geomorphological potential of the methods was shown to be limited to detection of surface elevation changes >~0.1 m. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of land use on ground water quality in the Anoka Sand Plain Aquifer of Minnesota

We began a study, in 1996, to compare ground water quality under irrigated and nonirrigated agriculture, sewered and nonsewered residential developments, industrial, and nondeveloped land uses. Twenty-three monitoring wells were completed in the upper meter of an unconfined sand aquifer. Between 1997 and 2000, sampling occurred quarterly for major ions, trace inorganic chemicals, volatile organic compounds (VOCs), herbicides, and herbicide degradates. On single occasions, we collected samples for polynuclear aromatic hydrocarbons (PAHs), perchlorate, and coliform bacteria. We observed significant differences in water chemistry beneath different land uses. Concentrations of several trace inorganic chemicals were greatest under sewered urban areas. VOC detection frequencies were 100% in commercial areas, 52% in sewered residential areas, and <10% for other land uses. Median nitrate concentrations were greatest under irrigated agriculture (15,350 microg/L) and nonsewered residential areas (6080 microg/L). Herbicides and degradates of acetanilide and triazine herbicides were detected in 86% of samples from irrigated agricultural areas, 68% of samples from nonirrigated areas, and <10% of samples from other land uses. Degradates accounted for 96% of the reported herbicide mass. We did not observe seasonal differences in water chemistry, but observed trends in water chemistry when land use changes occurred. Our results show land use is the dominant factor affecting shallow ground water quality. Trend monitoring programs should focus on areas where land use is changing, while resource managers and planners must consider potential impacts of land use changes on ground water quality.     

The wake model for azimuthal brightness variations in Saturn's A-ring

A dynamical model offering a possible explanation for azimuthal brightness variations in Saturn's ring A is considered. The orbits of ring particles encountering a massive moonlet (radius～100m) are integrated numerically. It is seen that a density wake is produced if the random velocities of the ring particles are much smaller than 1 cm s^?1.     

Local Winds In A Valley City

Local winds were studied around a valley city, by using a high resolution two-dimensional mesoscale model forced by surface temperatures from a measurement campaign around Lanzhou City, China, during stagnant conditions. In the simulations nighttime winds are purely katabatic downslope winds without urban effects, despite the fact that the city is 6–7°C warmer than its surroundings all night. In contrast, daytime near-surface winds result from upslope flow resisted by an opposing simultaneous urban heat-island circulation (UHIC). Hence winds remain weak and variable around a city in a narrow valley during daytime. These conditions may lead to severe air quality problems day and night.The local circulations are sensitive to the widths of the valley and/or city,and also latitude, as is demonstrated by model experiments. Interestingly, in a flat and calm environment an extratropical daytime UHIC cell may turn into a weak `anti-UHIC' by the morning, due to frictional decoupling after sunset and subsequent inertial oscillation during the night, analogously tothe land breeze and nocturnal low-level jet formation.