Potential impact of climate change on ecosystems of the Barents Sea Region

The EU project BALANCE (Global Change Vulnerabilities in the Barents region: Linking Arctic Natural Resources, Climate Change and Economies) aims to assess vulnerability to climate change in the Barents Sea Region. As a prerequisite the potential impact of climate change on selected ecosystems of the study area has to be quantified, which is the subject of the present paper. A set of ecosystem models was run to generate baseline and future scenarios for 1990, 2020, 2050 and 2080. The models are based on data from the Regional Climate Model (REMO), driven by a GCM which in turn is forced by the IPCC-B2 scenario. The climate change is documented by means of the Köppen climate classification. Since the multitude of models requires the effect of climate change on individual terrestrial and marine systems to be integrated, the paper concentrates on a standardised visualisation of potential impacts by use of a Geographical Information System for the timeslices 2050 and 2080. The resulting maps show that both terrestrial and marine ecosystems of the Barents region will undergo significant changes until both 2050 and 2080.     

Evolution of the oceanic sulfur cycle at the end of the Paleoproterozoic

Here, we present new measurements of ³²S, ³³S, ³⁴S, and ³⁶S in sedimentary sulfides and couple these measurements with modeling treatments to study the sulfur cycle of a late Paleoproterozoic marine basin. We target the transition in ocean chemistry from the deposition of Paleoproterozoic iron formations (Gunflint Formation, Biwabik Formation, Trommald Formation, and Mahnomen iron formations) to the inferred sulfidic ocean conditions recorded by overlying shale (Rove Formation). The data suggest that certain features of the global sulfur cycle, such as a control by sulfate reducing prokaryotes, and low (mM) concentrations of oceanic sulfate, were maintained across this transition. This suggests that the transition was associated with changes in the structure of the basin-scale sulfur cycle during deposition of these sediments. Sulfide data from the iron formations are interpreted to reflect sedimentary sulfides formed from microbial reduction of pore-water sulfate that was supplied through steady-state exchange with an overlying oceanic sulfate reservoir. The sulfide data for the euxinic Rove Formation shales reflect the operation of a sulfur cycle that included the loss of sulfide by a Rayleigh-like process. We suggest that the prevalence of large and variable heavy isotope enrichments observed in Rove Formation sulfide minerals reflect a sustained and significant net loss of sulfide from the euxinic water column, either as a result of a shallow chemocline and degassing to the atmosphere or as a result of a water column pyrite sink. The inclusion of ³⁶S measurements (in addition to ³²S, ³³S, and ³⁴S) illustrates the mass-dependent character of these sedimentary environments, ruling out contributions from the weathering of Archean sulfides and pointing to at least modest levels of sustained atmospheric oxygen (>10⁻⁵ present atmospheric levels of O₂).     

Geological modeling and simulation of CO2 injection in the Johansen formation

The Johansen formation is a candidate site for large-scale CO₂ storage offshore of the south-western coast of Norway. An overview of the geology for the Johansen formation and neighboring geological formations is given, together with a discussion of issues for geological and geophysical modelling and integrated fluid flow modelling. We further describe corresponding simulation models. Major issues to consider are capacity estimation and processes that could potentially cause CO₂ to leak out of the Johansen formation and into the formations above. Currently, these issues can only be investigated through numerical simulation. We consider the effect of different boundary conditions, sensitivity with respect to vertical grid refinement and permeability/transmisibility data, and the effect of residual gas saturations, since these strongly affect the CO₂-plume distribution. The geological study of the Johansen formation is performed based on available seismic and well data. Fluid simulations are performed using a commercial simulator capable of modelling CO₂ flow and transport by simple manipulation of input files and data. We provide details for the data and the model, with a particular focus on geology and geometry for the Johansen formation. The data set is made available for download online.     

Frequency of maxima of non-narrow banded stochastic processes

In many engineering problems one deals with quantities that must be considered to be of a stochastic or random nature. This is true for the natural environment such as wind, waves, and earthquakes, which are the driving mechanism behind the loadings on a wide variety of land-based and offshore structures. From a design perspective it is important to determine the expected highest value of a stochastic process, and structural fatigue life. The relevant procedures are reasonably well established for processes that have narrow band spectra, but it is much less clear how to deal with non-narrow band cases. In this paper it is shown that the extremes of a Gaussian, non-narrow band process are asymptotically equal to the extremes calculated according to the narrow band formula. Also demonstrated is that fatigue estimates may, with good accuracy, be based on the narrow band formula unless the bandwidth becomes extremely large. These statements are illustrated by examples of a process with (1) a low pass box spectrum, and (2) a Pierson–Moskowitz wave amplitude spectrum. It is also shown that the bandwidth parameter may in some cases be counter-intuitive, as the Pierson–Moskowitz spectrum has a larger bandwidth parameter than the box spectrum, even when both cover the same frequency range.     

Mesoscale modeling study of the oceanographic conditions off the southwest coast of India

A high resolution model, using the Miami Isopycnic Coordinate Ocean Model (MICOM), has been implemented for the first time to study the seasonal circulation and coastal upwelling off the southwest Indian coast during 1974. This model is part of a model and data assimilation system capable of describing the ocean circulation and variability in the Indian Ocean and its predictability in response to the monsoon system. Along the southwest coast of India the dominant coastal current is the reversing West Indian Coastal Current which is well simulated and described, in addition to the weaker undercurrent of the opposite direction. Upwelling of cold water, 4‡C lower than offshore temperatures appear in April. The upwelling intensifies with the southwest monsoon and is simulated in accordance within situ observations. Upwelling appears to be strongest off Cochin and Quilon, and the upwelling of cold water is seen together with a decrease in salinity in the model simulation.     

Comparing the adaptive Gaussian mixture filter with the ensemble Kalman filter on synthetic reservoir models

Over the last years, the ensemble Kalman filter (EnKF) has become a very popular tool for history matching petroleum reservoirs. EnKF is an alternative to more traditional history matching techniques as it is computationally fast and easy to implement. Instead of seeking one best model estimate, EnKF is a Monte Carlo method that represents the solution with an ensemble of state vectors. Lately, several ensemble-based methods have been proposed to improve upon the solution produced by EnKF. In this paper, we compare EnKF with one of the most recently proposed methods, the adaptive Gaussian mixture filter (AGM), on a 2D synthetic reservoir and the Punq-S3 test case. AGM was introduced to loosen up the requirement of a Gaussian prior distribution as implicitly formulated in EnKF. By combining ideas from particle filters with EnKF, AGM extends the low-rank kernel particle Kalman filter. The simulation study shows that while both methods match the historical data well, AGM is better at preserving the geostatistics of the prior distribution. Further, AGM also produces estimated fields that have a higher empirical correlation with the reference field than the corresponding fields obtained with EnKF.     

Mesozoic and Cenozoic tectonics of the Møre Trøndelag Fault Complex,central Norway: constraints from new apatite fission track data

The Møre Trøndelag Fault Complex (MTFC) of central Norway is a long-lived structural zone whose tectonic history included dextral strike slip, sinistral strike slip, and vertical offset. Determination of an offset history for the MTFC is complicated by the lack of well preserved stratigraphic markers. However, low temperature apatite fission track (AFT) thermochronology offers important new clues by allowing the determination of exhumation histories for individual fault blocks presently exposed within the MTFC area. Previously published AFT data from crystalline basement in and near the MTFC suggest the region has a complicated pattern of exhumation. We present new AFT data from a NW–SE transect perpendicular to the principal structural grain of the MTFC. FT analyses of 15 apatite samples yielded apparent ages between 90 and 300 Ma, with mean FT length ranging from 11.8 to 13.5 μm. Thermal models based upon the age and track length data show the MTFC is comprised by multiple structural blocks with individual exhumation histories that are discrete at the 2σ confidence level. Thermal modeling of the AFT data indicates exhumation progressed from west to east, and that the final juxtaposition and exhumation of the innermost blocks took place during Cretaceous or Tertiary (possibly Neogene) time. We suggest that least some of the fracture lineaments of central Norway were re-activated during Mesozoic extension and the opening of the Norwegian sea, and may have remained active into the Cenozoic.     

Cloning and developmental expression of kinesin superfamily7 (kif7) in the brackish medaka (Oryzias melastigma), a close relative of the Japanese medaka (Oryzias latipes)

kif7 is a member of the kinesin superfamily members which are molecular motor proteins that move along microtubules in a highly regulated manner through ATP hydrolysis. In this paper, we report on the cloning of the Oryzias melastigma kif7 (omkif7) using primers designed according to the Japanese medaka (Oryzias latipes) database. The cloned omkif7 has an open reading frame of 3762bp and is deduced to encode a polypeptide of 1254 amino acids that possesses the putative ATP-binding and microtubule-binding motifs in its motor domain at the N-terminal region. We characterized the cloned omkif7 by comparison with the zebrafish kif7. Both omkif7 and zebrafish kif7 are shown to be expressed in all embryonic stages and adult tissues examined with higher expression level in the testis and ovary. Whole-mount in situ hybridization revealed that the expression of omkif7 is ubiquitous during the early stages of embryonic development, but became more restrictive and localized to the brain, fin bud and eye at later development. This study suggested that the brackish O.melastigma can serve as a good seawater model organism for developmental studies by utilizing the resources developed from its close relative of the Japanese medaka.     

Geophysical and Hydrochemical Identification of Flow Paths with Implications for Water Quality at an ARR Site

Two key challenges regarding the design and operation of aquifer recharge and recovery (ARR) systems are evaluating aquifer heterogeneity and understanding hydrochemical interactions. Uncertainty in this respect can impact the volume of recoverable water and the improvement in water quality. The objective of this research is to leverage the advantages of geophysical measurements and hydrochemical sampling to reveal the properties of an ARR site to inform current ARR system operations and future design decisions. Electrical resistivity tomography was used to image the subsurface below two key infiltration/extraction areas of an ARR site in Colorado, USA. Hydrochemical measurements on transects intersecting the geophysical measurements resolved bulk parameters (i.e., total organic carbon, nitrate, and major cations and anions) and trace organic chemicals (e.g., pharmaceuticals, personal care products). Conservative tracers were also used to estimate degrees of mixing and water travel times and to better assess the performance of the ARR site regarding water quality changes and water recovery. The electrical resistivity measurements suggest that certain areas of the infiltration basins have hydraulic connections to the extraction wells through preferential flow paths, compared with other infiltration basins that are separated by fine‐grained materials from their respective extraction wells. The hydrochemical results indicate that consistent improvements in water quality can be achieved in these preferential flow paths within relatively short travel times (<5 d) at this ARR site.